Putting Life Back Into A Silvertone 1335

One of my old pals from Metuchen, the Bench, and Port Jervis runs on the Beezer has reinvented himself three or four times and now holds sway as an auctioneer in the Easton, Pennsylvania area.

He's a grand fellow and a superior auctioneer.

Anyway, he alerted me that this amplifier was coming up in a large estate he sold. As the story goes the estate belonged to two spinsters who'd decided to liquidate their late parents' estate, part of which included a wood shop that had been closed up eighteen years ago. The Silvertone was found under a pile of junk in the back of the shop. Between the purchase price and the shipping I was out about four hundred bucks. The shipping was a little pricey but the people who packed it did a good job so it got here in good nick.

It's an interesting circuit, mostly because of the use of the filaments of the two 12AX7 tubes as the power tube cathodes for biasing purposes. I don't know if anyone else has tried it but Nat Daniel always had some interesting ideas for circuitry.

As it happens I know this circuit pretty well, having worked on a number of old Airline amps that had the same or similar setups. It's good and clean for a while and the low headroom makes for pleasing tone.

I spent the better part of today replacing every capacitor in the lower chassis, and I'd previously redone the upper. They're all wax paper of varying makes and they were all likely to be bad. The folks at Danelectro didn't go cheap on the transformers-the power transformer is a Freed and the output is a Utah made transformer. The fifteen inch speaker is from the House of Rola.

The tubes were all pretty much garbage but I've got a good stock of glassware for these applications.

A good cleanup with lots of spit and polish got most of the musty smell out of it, and I'll give it a road test tomorrow or the next day.

I expect magic.

The fake wood grain shelf paper doesn't look too bad, although the original tweed is underneath. It's tempting.

UPDATE: It lives, but one channel has a lot of white noise-but since that's detachable I'll only have to pull the upper chassis. The vibrato didn't work until I remembered something and started switching tubes for similarly based numbers. It had had a 6AC7 which I pitched thinking it was a hole stuffer but maybe the last person in there installed it for a reason. A 6SH7 got the job done where the 6SJ7 on the chart would not. I may play around with power tubes as well. It still smells kind of musty but that's to be expected.

Reviving an AIMS Producer

AIMS was a maker of amps that was around for a short time in the seventies. It is said that it was started by a couple of refugees from Fender but I have no way of verifying that.

That said the VTB-120 is quite similar to a Fender Bassman with massive transformers and a pair of 6550s running at about 530 volts on the plates. I may have mentioned this amp before but it was recently acquired by a friend of mine and brought in for some needed maintenance.

Here are some pictures of what I found plus a shop sketch detailing what it was, what it was supposed to be and what it ended up being.

20 uf 600v capacitors are pretty hard to find and expensive to boot-the last one I bought was a Sprague and it ran me thirty dollars.

So what I ended up doing was some math and some research, and a liberal borrowing of  news from Fender schematics, and I ended up with two pairs of 100uf 350v caps in series with appropriate balance resistors-much better than the bodged 220uf axial snap-ins that are in the picture.

Calculating capacitor value is the opposite of calculating resistances.

With capacitors in parallel the capacitance is C1 + C2  and so on and the voltage rating does not change. When you place two capacitors in series as I did the sum is half the capacitance and twice the voltage rating-and you should have balance resistors. So, two 100uf 350v capacitors in series is equal to 50uf at 700v. You can calculate this by using this formula:

 Ct=C1xC2/C1+C2

He'd said it was making strange noises and that proved to be a loose phase inverter socket which I plan on repairing tomorrow. That and a bit of bias tweakage to get the level down a bit will be helpful as it is drawing slightly too much current for my taste..

More pics tomorrow.

New power supply configuration.

More Blackstar Stuff

I've been wondering about the subject of Blackstar amps and their nonrepairability. In doing so I found this post on TGP by a fellow from southern Indiana and it sums up my thinking on the matter.

I recently bailed on two of them, and we've been talking about the right to repair. Also, my right to make a living saving things from the landfill.

Take it away, member Thorny64.

I have played a few of these in the store, and they didn't sound badly. Marshally, with a LOT of gain. Clean channels. Seemed to be nice for the money.

Who am I? I repair amps, and have for MANY MANY years. I also have built amps as well. I work primarily with tube amps. I have been an authorized repair person for Marshall, Fender, Ampeg, Crate, Kustom, Peavey, Mesa, and others - but right now I work independently. I have built and repaired for a few big names too. I get a lot of referrals. I get a lot of amps that people have taken to one or two other techs first. And I know enough to say I certainly don't know everything. I know and recommend other techs too.

I knew it was a matter of time before one of these came into the shop for repair. I see most everything eventually. I have a poor customer's HT soloist 60 head in for repair, and I traced down a problem that is keeping it from working, but can't trace it to a component and I get NO support from blackstar on anything. Even if I could, I could not likely replace it. (I fear there might be a short inside the board, but I can't afford to take the time and charge to trace this down, it is not readily apparent). They do no not respond to requests for information. I can't even buy another board and put in this thing. They apparently only have guys that sell amps and are not concerned about people after the sale. And definitely not concerned about people who currently own their amps (or future owners).

This has two preamp tubes (one each channel), and a whole bunch of solidstate preamp and phase inverter components. Construction wise, it is very much like looking at your computer mother board and throwing in a few tube sockets mounted directly to it (bad idea). Maybe some models might have a tube phase inverter (I haven't seen them all), but this one certainly does not.

This is made with a LOT of surface mount technology. This has high voltages running through it. When there is a problem (if it is not under warranty) you basically throw it away. If it is under warranty I bet they rarely fix them, they probably just replace them most the time. Most amps will eventually have a problem, and when this one does, you toss it. I imagine the cabinet and speaker are worth something, maybe the transformers (not sure about that since I don't know if the power transformer has enough specs to drive more than the two preamp tubes. An amp that is built like this is simply disposable. It is sad too, because it sounded decent to me (well the ones that work in the stores did). I would not buy them. I would steer clear of them. I recommend avoiding them.

Compare them to a another cheap amp, lets say a bugera - bugeras are built MUCH better and cost the same or less. Bugeras are usually all tube (except reverb in some, and some may have a diode or two depending on which amp they are copying the circuit from). I can fix Bugeras - I have, and I have played some that with a little tweaking sound fantastic. This one certainly turned out to be a black turd. I thought they had a lot of promise too.

Compare it to a car - if the blackstar were a car it would be a good running car with a lot of features at a pretty good price. It would handle pretty well and may be great if you are very lucky and don't drive it much, bump into anyone, or hit a chuck hole. But if you ever need to do anything besides change the spark plugs, you have to replace the whole motor. And if you try to reach the dealer, you don't get a response from the support department. So you can't even buy a motor. Your car has one thing wrong with it, well, you are left trying to take the wheels off of it and stereo and get whatever you can get out of it and buy another car. And guess what? It WON"T BE THAT BRAND EITHER. They are doomed.

All these guys that love theirs, well, they haven't had a problem yet. Because when they do (they likely eventually will) and it is out of warranty they will wind up throwing away their amp. I bet they are not OK with that. I wouldn't be. Blackstar's are way too expensive to do that. If you already have one, I am sorry. I hope you never have a problem with it. The guy that bought this one says it was $700 - and it was absolutely wasted on this amp.

And trust me guys - there is NOTHING I would want to copy on this amp (technology wise). In fact, it is a lesson in what to avoid as far as what I am concerned. In these cheaper and feature filled amps, they pack a lot into a little package for not much money, but even those usually can be worked on. These can't. If they would sell the board to replace in the amp, MAYBE the customer will do that - but they don't even offer to do that.

I never post opinions this strongly, but this time I do. I hate putting time in to repair a product and can't because of the company won't support it. It almost never happens. Usually with tube amps I just fix them, but this one can't be economically fixed and blackstar has not helped.

I say if you like yours and it works, GOOD FOR YOU. I am glad. You may feel guilty selling it if you ever do. But if you don't own one I say
AVOID. AVOID. AVOID.

And this:

I will preface this by saying these opinions I express are my own, and not reflective of those that operate this forum. This is based upon my hands on with ONE amp. The rest I base on corroborating information found by doing google searches. I bet there are those that would like to know how their amp is put together and what they may be dealing with if it breaks from someone that knows (not a casual player that unbolted his amp and looked inside). Half of what you read on the internet is a bunch of bull, the other is not and it is hard to tell which is which. I have NOTHING to gain other than I'd love to get this one customer's amp fixed. And if I can't, I'd love to make sure that everyone knows. There is NOTHING in it for me. I don't even own one (and I wouldn't).

No comparison between the quality of a Diezel to a Blackstar. Diezels are built like a tank.

On Blackstar's website is a link to UK repair centers. There wasn't a direct link to US repair sites as stated. Plus to do this, you have to be sign up for an account - why? Just to find out who to talk to to get parts or a repair? Trying to find it for the US eventually routes you to Korg. Then you have to email Korg and hopefully they get back to you. Still no repair sites. I went on Korg's site and checked theirs. Theirs is who I called and got no answer from. That is a little different than a single click on a website.

The differences between Blackstars and Bugeras is that Bugeras can be repaired - I know - I have repaired many of them. They have been sold here a lot longer than Blackstars and there are a lot more of them around here. I think they are a little less expensive than Blackstar too. This is despite being fairly inexpensive tube amps, they really are not that bad. They are no cheaper built than the Blackstars. They aren't more or less reliable really that I can say, but I can say they are generally *repairable*. I never had to replace a board in one, not saying that couldn't happen. Most of the problems I found were normal things, usually blown tubes. I don't have to go back to Bugera and ask for anything to support them unless maybe channel switching or similar. Most amp techs wouldn't for most things.

As far as links to information, do your own homework! Google it! Search "Blackstar Amp Repair", or "Blackstar Amp Problem" and see for yourself. They are all over the place. Just because I don't supply you links that you can find yourself does not imply that I am making this up. See for yourself, I am not. Most say they like the tone and features, but don't like the problems they have to deal with when something breaks. I looked things up before I post such things - there is always the chance that when you encounter something like this that it is a "one off" event. But I found others that already ran into this. In fact I have never slammed any company like this before. I don't intend to start flame wars. I feel I need to warn people about this. I have also read accounts of people having problems with boards shorting - no fix for that except another board. I presume most of those didn't last past warranty and were replaced. But that is a design issue.

It is not a question of being able to repair one, it is whether it makes economical sense to do so. Given enough time I could reverse engineer this *stuff* (chosen word edited so as not to offend sensitive ears) and figure it out but life is too short and no one will pay for it. I shouldn't have to reverse engineer it just to fix the darned thing. I am pretty sure the solution for this is another main board but the real offense is Blackstar doesn't even answer the *mail* - so a more appropriate name may be blackhole amplification.

Most people don't have an "authorized repair center" for korg in their back yard. Korg is the distributor in the US. Limiting repair info AND PARTS is a tactic that forces some buyers to trash their amps when they die, or pay HUGE bucks and ship off to a service center that will only REPLACE THE WHOLE BOARD anyway. Korg want to sell amps they don't want to fix them. These guys don't fix problems like this, they REPLACE them. I know, I HAVE BEEN a service center for the huge list of equipment providers I listed in the previous listing. As far as being a repair center - it is a losing proposition with a company like Korg to most shops. I have worked on repairs for them in the past when I was doing authorized repairs for Marshall. But their current policy is you wind up having to repair anything Korg sends your way - keyboards, blackstar amps, and *used to be Marshalls*. Repairing amps for warranty you are imposed a LOT of restrictions. I choose not to work on synthesizers, FX pedals, things like that I will lose money trying to support. It *might* make sense if there were a large enough volume, but there isn't in this market area. Not everyone has a nearby Korg authorized service center, and not every center will work on a blackstar amp either (although they are supposed to do so). So if you get one, you may be traveling 150 miles like the guy I recently looked up did to get his amp fixed (google it).

So, I get to tear down this guys amp, find the problem, and try many different ways to find a way to get what I need to fix this amp (economically) and am unsuccessful. I still charge him a bench fee because I have spent hours on this. I have spent well more time trying it track down and get a part than I would have fixing it if I had the part. The part? The whole main board! That is what a repair center would do. Either of us could do otherwise, but it would take too long and cost too much.

You are right in that this is how Blackstar chooses to support their products (it is NOT a good way - doing this to your customers or even to those they sell their amps to).

I am right in this is what happens when Blackstar chooses to support their products in this manner.

I don't really say they are less reliable - all amps eventually have problems. I haven't had many of them come through for repair. But this one can't be repaired without replacing a whole board. They are difficult to find a repair center in the US, and when I try I still get no answer. Their actions show that they are more interested in selling product and not so much in supporting the product. If you get in this situation you are out of luck unless you have a good authorized repair facility very close to you and one that won't charge you a lot to replace the entire main board of the amp. This is not a problem they would likely troubleshoot to a component on the board - they simply don't do that if it is something that takes much time.

Now - take another company - Mesa. You call them, you get help. It is not that Mesas don't have problems, they do and so do most amps eventually. But they have the attitude they want to see their amps fixed and working. They know that seeing someone playing a Mesa is some of their best advertisement. And from what I have heard, Mesa is VERY protective of their designs without resorting to the support non-sense Blackstar puts you through. Blackstar does not have that commitment at all here in the US. They didn't respond at all to me, not even referring me to their US distributor Korg when I tried to contact them directly. Not that that would actually help either any longer.

So - no offense to you - I don't say anything about you. I only say professional comments about the amp, its sound and features (generally good) and its build quality and repair-ability. But you imply I don't know how to fix it, when I certainly DO. It is a commodity product that is much like any TV set. You narrow it down to the board and swap the board. That is the way it is done. And my efforts to get info or a part to do this from Blackstar amps has not been responded to by them. Since Blackhole amplification chooses to support it this way, I will recommend the user buy an amp that is supported better and that can be fixed - so his money will not be wasted. Other amps in this price range you can generally fix - unless it is a line6 or something. Then you just throw it away and get another. I guess blackstar tube amps are that way too now. It is OK, as long as the customer knows what he is getting into.

Your analogy is all wrong. We are not talking mercedes and lawn mowers. We are not talking even apples and oranges. Serviceability on these amps is extrememly limited. And they have made it difficult to get service limiting your options (if you can even find your options) if you are not the original owner. So you can make light of it. This guy isn't happy and it has nothing to do with me. Blackstar's actions show they couldn't care less for people that buy their amps used and they make them so it is more economical to dispose of them rather than fix them should they have a problem like this. I don't know for certain how prevalent these problems are, but any problem like this will result in the need for a new board, and that is just poor design or build quality. If you want to keep buying disposable amps good for you. But I think they cost too much for that, and it is their actions that make it this way.

The problem may the Korg/Blackstar relationship, but Blackstar hasn't even gotten that far. On my own, I searched and found the Korg listed authorized repair center (the closest one nearby) and got an answering machine. I left a message. I never heard back. It was an outfit I have never heard of and I have been here about 15 years in the business. Kind of makes you wonder if they still are a Korg Authorized repair center or if they work will work on tube amps. I have hours of going round and round in circles and getting nowhere. I just want the guy to get his amp fixed, if not by me then by someone else or someone that can sell me the part or will fix it for him without sending him to hours away to Nashville. Blackstars are not really that special to warrant that kind of treatment.

I WANT THIS fixed for my customer. I know the amp can be fixed. I don't know if the new board will have the same problem as the old one or not, but we are not even getting that far. This guy would like to get his amp working. I am sure he will sell it as soon as he gets it working because of these problems. I am trying to get it fixed. Blackstar so far is zero help. I didn't expect this at all. Maybe he can drive it to Nashville, Indianapolis, or St. Louis and get it to an authorized repair facility if they have one there that will work on it. The one I called didn't call back. But that would cost hundreds in shipping, and/or a whole days worth of driving. And they don't fix them while you wait nor do they typically stock boards. It will take weeks. It may take me weeks to get a part from a distributor, but generally they will sell me one and the customer does not have to travel hours or ship large combo amps long distances.

But mistake or not, the buyer of this blackstar amp is out of luck no matter what option he chooses. What are his options?
1) He can ship and wait, and not know if it is worth repairing after it has shipped. This is a very heavy combo amp.

2) He can drive it, equally unappealing - expect two trips too and from - over 100 miles and X4 (to and from twice).

3) He can dump it and sell broken/for parts *huge loss of money - 90-95% and get something else - that guy won't buy a Blackstar again for certain

What would you do? Would you buy a Blackstar again if this happened to you? The old adage is "it is easier to keep a customer than to win one" - so blackstar expects to win one each and every time? I hope you have some other amp line to move them to, if they even want to talk to the place that sold them this again! It would be a really hard sell to get them to choose blackstar after this experience. Is it time to rethink this strategy? Or are you banking that you won't offend enough of your customers that you still will get by? Customers that deal with this kind of stuff are very unhappy and usually let others know. It grows like a very bad virus. The right thing is for Blackstar to do is to send me a board for this customer's amp. It isn't a big deal to me, I only get paid to put the thing in.

I just feel terrible for the guy. It isn't mine. I didn't buy it. I have no reason to bash blackstar even if it means there will be an amp that I may refuse to work on - it will only likely be a very tiny amount of what comes across my bench. Who knows - you MAY BE the worlds best tech out there. Maybe you have greater than a bachelor's degree and 20+ years of experience with more service center responsibilities And if so, please fix this amp - because in my working on them over 20 years now I tend to know what I am doing, but I can't fix things without parts (in this case proprietary parts). Can you? Does that make me stupid? Frankly I know I am not so it really does not matter what you say.

Although, I design and have built my own amps. I can repair for 20 years, including for professional acts. I have built amps that toured with them and/or are on their albums. I could be touring with some acts if I really wanted to go that direction (but I have a family and a home and don't want to be on the road)

Would I be your amp tech? Not likely if you had a Blackstar and needed anything more than tubes or a bias - or something very simple. I could even be a board swapper for you if they would sell me the board. But as it is it is generally un-repairable. If they want to you send it to a regional board swapper, then go ahead. Don't expect me to recommend a Blackstar though. It is all about what is cheaper to them, and I suppose this is the cheapest way to do things in the short run. Blackstars really sound good for the money in the short run. But it will cost them in the long run. I won't lose any sleep telling my customers they should look at something else - for all the reasons I state. I can't decide for them. If you think it is the greatest thing and that is a smart business model (as a consumer) then go on and vote with your dollars and keep on buying them. You can tell a person over and over again NOT to hit their thumb with that hammer, but regardless of what they think it is going to hurt all the same if they choose to believe you or not.

Also, I know a dealer that has chosen not to continue to sell Blackstar amps as well. If I were a dealer, I'd change too. I did not ask them if this was the reason or not. There are lots of potential reasons. I went to this dealer in order to try to see if they could buy me parts. I won't name names either, but I have no reason to say otherwise. Dealers wouldn't want to discuss a business decision like this publicly.

I have been disappointed by lots of amps in terms of quality, but most you can get fixed. Customers still expect that for one that costs like these do. I use the Bugera brand as an example that is probably cheaper and better overall from a guitar player and experienced amp tech's view. It may break just as often but I have been able to fix them. I think the only problem one of them has ever given me was for intermittent channel switching problem - the rest is all standard stuff. You can gig with them. They generally sound great with a little tweaking. I have not played or repaired every model of both product lines. I have owned several bugeras, tweaked them out and sold them. I wouldn't buy a Blackstar despite them sounding pretty good unless it were VERY cheap. I'd have to be willing to toss it if it broke. I am not saying it will break more often than anything else. I'd almost feel guilty to ever try to sell one used. They have this consistent design from what others have reported throughout this product line. So I make that assumption having only had the one in the shop. If you can report to me that the design is significantly different and more reliable with the other models than the soloist 60 then I will certainly listen. But what others (again, google is your friend) have said, they seem to be very similar.

What prompted me to respond is this current experience and looking online to see if others have had this issue besides me. So far, I have not heard anything inconsistent with what I have stated here.

The Blackstar way seems to be:
- Surface mount technology - not the most reliable/serviceable in a guitar amp.
- most guitar amp techs cannot work on it, not cost effective
- most repair shops simply must swap out boards - not cost effective otherwise
- this winds up costing more to fix and usually means longer times to get fixed
- make it worse by restricting access to information or parts
- this discourages amps from getting fixed

Why might they do this?
- probably easiest way to do things for them
- probably cheaper to not support hardware (short sighted)
- feel it offers some level of control (it really does not)
- encourage obsolescence - old amps out of warranty quit working
- non-original owners are not important to Blackstar

It might be supported a lot better in UK since they are a UK company. I cannot comment on there. But I can hope. 

Repeating Myself With Seaidea

This is a little off the beaten tube amp and antique radio track but it is worthy of some interest here.

Recently my wireless system in the house got pretty tired and it appeared that my repeater had died. Another problem was that a wireless network I'd never heard of before has been stepping all over my somewhat weak wireless-it's OK here but very tired at the other end of the house-which is where I do my amp work and I depend on a computer there to host my library of schematics and answer a few questions.

In a way we should have expected this.

In the 1920s and 1930s many radios were regenerative or had a regenerative feature that would rebroadcast whatever they were tuned to. Remember all that movie schtick with the nazis locating clandestine radio sets via a loop antenna on top of a bread van? That was because of regeneration. It was fine if you lived out on the farm but in an apartment house with multiple families listening to different stations the problem was real.

In the 1930s Philco developed the first remote control for radios that they made-premium sets to be sure. You could sit in your favorite chair and dial in whatever station you liked, but if your upstairs neighbors in the apartment had a similar radio with remote you might be changing their station as well as your own.

The operative principle here is competing signals swamping each other-stepping on them as the CB radio aficionados called it.

Until the other day the downstairs shop computer chores were being handled by an elderly Dell workstation that had been built up out of junk parts, cheap crap from Newegg and the deceased CompUSA chain, and the carcass which I acquired complete with a Pentium 4 processor for fifty bucks at the Iowa State University surplus outlet. It did the job if you didn't ask too much of it at one time.

A friend of mine offered a relatively more advanced HP  tower in exchange for some amp work and we made the swap-kinda like Francis Gary Powers and the bridge more or less, exchanging prisoners at midnight.

I spent today getting it up to date but I still had the problem with a weak signal and my seven dollar Chinese wireless LAN card newly housed in the new-ish computer wasn't liking dealing with a weak signal. Sorting out the audio and video were relatively simple as the new tower had both functions built in.

The computer is the newer SATA format pinout so I could not use my nifty 500gb hard drive, DVD drives and my floppy disk drive. I guess the era of the 3.5 inch floppy diskette is finished around here more's the pity. I think I may be able to repurpose the power supply as the connections look similar.

To continue the thread, I'd purchased a Seaidea repeater on fleabay for about twelve dollars and it was this one. What it is is a simple receiver-transmitter that detects and amplifies weak signals before rebroadcasting them.

But you have to tell it what to detect and rebroadcast first.

So I still had it but it became apparent that the repeater had to be configured to work properly. This unit came with a good set of instructions and I won't bore you with the gory details.

What's required is to use your computer to address the repeater via a LAN cable, configure it, and you're done. I simply connected the device to my wireless router via the short LAN cable that the fine folks from Seaidea, the people who made this device provided.

Then, you take your newly recognized and configured repeater and put it somewhere about half the distance to the place where you want to connect.

It worked terrifically well. I now have five bars throughout the house and with any luck I am stomping all over my neighbor's wireless even as we speak.

If this is you, it's easy and all you have to do is make sure that your computer is set to recognize the wi fi repeater rather than your original network when logging on.

UPDATE:

Nothing's ever as simple as it appears on the surface. Because we were making such fine progress on the home network front we decided to secure our wireless system from freeloaders and moochers of all kinds.

After properly addressing the router to institute a security protocol, not only could I not log onto anything but my nifty Seaidea repeater quit working.

Several hours of bodging revealed that I had to first reset my new cable modem that Mediascam foisted off on me. In order to do that I had to wipe our whatever it had as settings and reestablish that. When that was done the same process had to be repeated with the elderly Cisco wireless router . Then, and only then, could I get the repeater configured to work properly.

Of course there was a benefit in all this because all that time the cable modem had been trying to establish a phone connection because I'd plugged the LAN cable into the phone port. That slowed things to a crawl until I got that figured out in the process of all this other silly shit.

All this took a good part of the day. It's knowledge I had no interest in learning and my spouse does not understand that at nearly seventy I do not want to waste time mastering knowledge that is of no earthly profit to me.

Of course it was after all that that the Tivo decided it did not like the new security settings and I'll have to contact Mediascam on Monday for the proper MoCA encryption key to make the search feature work properly. That means another morning shot doing battle with dunces and morons to acquire knowledge that is of no interest to me.

I mean, who gives a flying f**k what MoCA is or does?

Thanks, everyone. No one ever said.

Of course I missed the opportunity to rename our wireless network FBIvan3.

Ancient Peavey Goodness

The Peavey Artist 240 arrived here Monday and I must say, $200 can take you a long way in this world.

The power tubes were pretty much wasted, and they were never very good in the first place-Mesa branded Chinese coke bottle items and one came apart and left the base behind.

Without further ado, a quartet of JJ 6L6GCs was installed and powering the amp up and letting things settle down a bit got me some nice clean tone from the.....wait for it....fifteen inch JBL that this amp came with.

Unlike the later amps this has an adjustable bias, and I have a set of Rubys I'm going to install mostly because I can sell the JJs to someone and I'm getting out of using Rubys. I've had a couple of them take early retirement.

Going by the serial number this amp was built in 1977, the year after it came out and won the Guitar Player best amp of the year award. No lie.

Looking at the schematic shows an earlier configuration, and this amp does not have the dual pairs of 100uf-350 v capacitors but only one pair which makes me think it was cribbed from the Fender Twin schematic-no bad thing-a single 20uf 600v capacitor with some serious leakage, and a 20-350v number to handle the third node.

For this part of the circuit the later amps use a pair of 100uf 350v numbers back to back with balancing resistors-I guess it was a lot cheaper to build.  There are 20uf 600v Spragues to be had but just one cost me about thirty dollars-ouch!

A good overhaul and some TLC and this will be a peach.

It also predates the use of Basler Electric transformers, as this came with Electrical Windings iron. It's also got the discrete transistors in the preamp which seem to be doing fine.

I had everything in hand except some 25uf 100v  numbers and the aforementioned spendy Sprague Atom. I guess it's there to handle the surge when the standby switch is thrown.

A fair amount of cleaning all the old flux off the board with a cut down acid brush and some 100 per cent isopropyl did the job nicely. Also, some straightening of the chassis was in order as this amp may have fallen over at one time, and the chassis is aluminum. It's not really necessary but I like everything to be at right angles.

Here are some gut shots. The parts were ordered from Mouser and with any luck they'll be here tomorrow or Saturday.

Then, the fun will start.

Vox AC15 Custom Classic spitzen und geschparken und der flammengeschutzen

Ok, enough with the comic German, shall we?

It's been a little slow in the repair business from the shop lately so it has given me a chance to get caught up on a lot of projects that have been hanging fire for one reason or another.

Last week, I managed to get four of them out the door. I got my Fender Bassman knockoff in reasonably serviceable condition, finished up a long term Super Reverb, a Vox AC15CC with a blown screen resistor and something else that I can't remember.

So this AC15 Custom Classic-you know, the first series of Chinese reissues from Vox that were made in the IAG factory under the aegis of Steve Grindrod?

Anyway it had open dropping resistors and a scorched board, so it sat for a while until I was ready to tackle it and fight it to a finish. Because I'd sort of forgotten where I was when I put it down I started by rebuilding the power supply yesterday.

When I threw the switch this morning it was more or less the same thing-a flash of light from under the circuit board and some smells.

This time I jury rigged it so I could observe the underside of the board when powering it up, turned off all the lights, and threw the switch.

And there it was. One of the traces that runs between one of the dropping resistors and the power supply diode was sparking because the substrate of the circuit board became conductive when it got carbonized.

I removed everything that was in the way and commenced drilling out the damaged substrate until I got to solid unburned material. I slotted it out, cleaned it up with a file, painted it with clear nail polish, and laid in a bead of silicone. The dropping resistor was already there with a sleeve of spaghetti tubing around the trailing end.

The silicone will cure overnight and I expect it to be pretty solid by tomorrow, when I will take some images, reassemble everything and road test the amp. If it succeeds it will mean another long term project off the waiting list.

One issue has been the particularly nasty lead free solder that was used in this amp. Cleaning it up required a lot of flux, desoldering braid, and the liberal use of the ZD915 desoldering pump.

In retrospect it was the best $125 purchase I've made in the last year or two and I wouldn't attempt a repair like this without it. Marlin P. Jones has them now and then, but similar devices can be found on the internet. You can read about it here and there is also a great video on youtube on the EEV blog. https://www.youtube.com/watch?v=Ft50m8UU5WQ

UPDATE: The stunt where you turn off the lights and power it up? I used that again on a Crate BX100 solid state bass amp. It's as simple a solid state amp as you can get so I arranged to contribute the labor so as to get some signal tracing in. The first thing I noticed was a crackle from the circuit board and some bad solder joints on one of the power transistors. Turning the lights out and the power on showed me exactly what was happening.

As I was working signal tracing I noticed the briefest wisp of vapor coming off one of the resistors that couples the amp to the drain gates. It was open, and I did the pinky test and found an op amp I think was bad because it got hot. So I shall find out tomorrow if my instincts were correct.

Pro Reverb blowing fuses.

A later model 70w CBS Fender Pro Reverb came in that would blow fuses regularly. Initially it had a bad rectifier tube which indicated something was amiss, as the 5U4 GB that was fitted is a very rugged and reliable rectifier tube. They rarely fail.

I replaced the fuse and plugged it into my spiffy new Chinese monster variac, running through a Kill-a-Watt monitor

The Kill-a-watt is sold with the idea that you can police the appliances in your house and see what maybe is drawing a little current when it's supposed to be switched off.

The Kill-a-watt will cost you about twenty bucks and you can read line voltage, amps, watts and frequency. It's a handy piece of kit and it plugs right into the front panel of my variac. I got mine for free from my old pal from the neighborhood Willy Robertson.

Here are some details. http://www.p3international.com/products/p4400.html

So when the amp was powered up, it would run about .4 amps, but when the standby switch was thrown and the power supply was coupled to the load the current went up to over 3 amps-plenty enough to blow fuses.

It had to have new power supply capacitors so they went in, and I went about eliminating sources of excessive current draw one by one by substitution. Output transformer, choke, power transformer. And I still had the problem of excessive current draw.

After thinking about it overnight and considering that this is one of the waxed boards that are known to be conductive at times, I rebuilt the bias system on a new board and made a new insulator board to slide under the main circuit board.

This is a good reason here to buy vulcanized fiberboard material from Mojotone, and the eyelets and staking tools from Mouser Electronics. You can make your own Fender style eyelet boards in any configuration you like, or you can design your own circuits and build them as you wish.

I know, I know, you can buy them off the internet from a couple of vendors who are pretty well known although I am not going to name them, and if that's your thing that's fine.

My experience was not so nice. I got a bias board from one vendor that was not well made and the other big name sent me a 6G3  board that was missing half the eyelets. Even though I sent pictures of it I still don't think they believed me and it cost me a couple of bucks to send it back. All in all the contretemps cost me too much money and a couple of weeks of f**cking around.

That convinced me that the ONLY way to go was making my own, as taught to me by Jeff Gehring. I have detailed the process elsewhere in this blog, it's simple and with a few common tools-a drill press and a Seymour Iron Co. number 1 arbor press-you can make professional grade boards in any way you like.

Don't waste your hard earned money on junky benchtop drill presses from China. They're not worth the bother.

I had one. It was a piece of crap even if it did only cost me five bucks at a yard sale.

One day at an auction I got a nice Walker Turner drill press from 1936 for forty bucks, it needed only a new belt and some grease, and the arbor press cost me five dollars at a yard sale. So don't complain about how much you gotta spend and it's too much trouble...as Stacy David of Gearz says, "Quit talking and get out in your garage and build something."

A smallish Chinese made arbor press from Harbor Fright would be OK if you can mount the staking tool in the press shaft. If you can't, save your money. You can always stake the eyelets with a hammer and an anvil, or some folks just use their drill press as a press of sorts. Whatever. Do something.

So this morning I made a new bias board-which I do frequently-and a new insulator board for the main circuit board. These were installed and the amp powered up nicely and biased properly, current draw about an amp.

Job done, as Edd China says.

Pics to come.

UPDATE: Here's a waxed insulator board which I replaced, the original bias board and the replacement board installed.

The ground connection looks pretty sloppy but that was before I went over to Hobby Lobby for a proper soldering iron for doing chassis grounds.

I'm still not entirely sure whether it was a conductive board going to ground or something dodgy with one or both of the existing bias caps. I did see a bit of red plating so I suspect the bias network was shot. Either way, cutting drilling and sliding an insulator board under the main board was pretty simple and easy.

Further Peavey Artist Notes.

After I'd gotten the dodgy tube socket thing sorted out, I started looking around for a DIN plug foot switch and didn't find one but I did find out something rather interesting.

The footswitch controls the reverb and the "automix" feature and thereby hangs a tale.

There are two channels, the bright and the normal. The bright has one input and the normal channel has two. In addition there is the automix jack. What I found out was that the automix feature uses one preamp channel to overdrive the other. Not my cup of tea, thanks,

But what I did find is that you can jumper the channels and get a lot more chunky clean tone than you can get out of either channel. It's a simple matter of running a jumper cable between input two of the normal channel and the single bright channel input.

Then, you can plug your guitar into the number one input of the normal channel and be happy.

A simple on-off foot switch may be just the thing to turn the reverb on and off, too.

UPDATE: I located an earlier Artist 240 which is the earlier version and...yep...I bought it, only this one has a 15" JBL. For a mere $200 which is nearly what the speaker's worth if it survives the trip.

Folks, these amps are the greatest thing since sliced bread and one hell of a bargain.

Should be here later this week. Film at 11 as they say.

Peavey Artist Gut Shots

Some before and after shots. Note that I elevated the new replacement zener diodes, as they had done a pretty good job of frying the associated electrolytic capacitors on both amps.

Installing a Bias Control On A Peavey Artist

I got the commission to freshen up an oldish Peavey Artist circa 1980 or thereabouts. This is a single channel very basic amp with a solid state front end, reverb and a master volume, pumping out 100w or thereabouts into a single 12 inch speaker.

The idea sounds so good that I went and acquired one from Music Go Round and it should be here tomorrow if UPS doesn't ruin it.

Overall it's a nice idea well executed. The preamp integrated circuits are all socketed for easy changeouts and it's modular with a preamp board, a power supply board and a tube board. It was built with all Nichicon electrolytics-good material for durability and initial quality. The traces are easy to manage and it doesn't have any of that confounded no lead solder mucking everything up.

The only thing I don't like much is the fact that the  power tube sockets are riveted to the chassis and soldered through the tube board. It could be an issue if a tube socket ever had to be changed.

These are the amps that Hartley Peavey made his fortune on, and it's a shame that Peavey has lost their way and become just another importer of Chinese made stuff of indifferent quality.  You may have read my earlier missive on the Peavey Valve King 100 and what a steaming pile of crap it is.

With rare exceptions that is what Peavey became. I understand that the 5150 and 6505 heads are liked by fans of heavy metal but that's about where it stops. I've had my eye out for an early Peavey Vintage for some time but not a one has surfaced-that's the all tube 100w Fender Bassman with reverb-what a great idea.

I am of the opinion that at some point people will recognize that there is a lot of value in these amps.
They are rock solid and durable, and all it will take for people to start snatching them up is some big name displaying them and talking about what a bargain they are-kinda what Jack White did for all those Silvertone cardboard amps languishing in garages and basements all over the continent.

Until that day arrives, however, they can be had for a song. The one that is on its way here cost me a cool $229 plus $45 for shipping-not a lot of money for a 100w combo that's built like a Pershing tank. The going rate seems to be about a couple hundred dollars give or take so stock up while they're cheap. If I'm correct they won't stay that way forever.

After doing some basic freshening up with new electrolytics-I am waiting for the 2.2 uf 50 volt numbers and some new zener diodes to put things back together-I thought an adjustable bias control would be nice.

The earlier iterations of the Artist had this feature, but later ones did not-bias is set with a 68k resistor.

I took a 100k 25 turn trimmer pot from my stash, adjusted it to 68k  and installed it where the original resistor was placed. As the legs are a little short to stretch comfortably I installed a chunk of solid wire bent into a dog leg shape so that the one leg of the pot could be comfortably wrapped around it and soldered and the other leg dropped right in.

Job done, as Edd China says.

UPDATE: I reassembled this amp today and found something interesting. I had set the trim pot to 68k so as to get the amp in the same configuration as before. It only showed about 12ma on each tube which is ridiculously cold bias. At a plate voltage of 490v, this was far too low. After adjusting the bias upward to about 37ma each on a new set of 6L6GCs from the house of JJ, the outcome was well worth the gamble. Lots of volume and good tone. I've got a set of Ruby 6L6GCs that are going into my amp tomorrow.

It also gave me a chance to download and view the owner's manual which explains the function of the automix input. The idea is when it is activated it uses the bright channel to overdrive the normal channel-I think- or maybe it was the other way around. Either way I'll skip it. My amp awaits a similar tuneup on the workbench.

The take home from it is if you have an old Peavey it is well worth the effort to install an adjustable bias control at the next trip to the amp tech. It will improve things a plenty.

UPDATE 2:I completed the overhaul on my Artist and all appeared in order, after I'd replaced the 100 ohm screen resistors with 470 ohm 5w resistors. Two of the originals were open.

After it went in the cabinet and I powered it up, all was good until it started spitting and humming and two of the power tubes red plated. Something had happened and it wasn't good. Careful inspection revealed that wiggling one of the power tubes around produced a crackling and the usual blue glow was interruptible. The sockets did seem awfully loose.

As I was watching the Giants take a dump tonight I took the time to tighten the tube pins-there are two types of pin receptacles. One is a round type and the other looks like a potato fork with the middle tine missing. These were the latter type-easier to tighten.  So, 16x4 = 52 pins later the problem was solved, and I got myself a sweet quad of STR387s by knocking twenty five bucks off of the bill for the other amp. So, between the quad of oldish Groove Tubes made by Sylvania and the STR387s I'm in good shape with the glassware.

Studiomaster Leadmaster

UPDATE 2-4-18: This thing finally went home a week ago-late January of 2018-after I fought it to a standstill.

The customer complained that the XLR out wasn't working and a trip to Kevin's recording studio proved that the owner wasn't using it properly, or it was not properly wired or both. Kevin tells me that there is no consistency or standard to how XLR plugs are wired.

So that solved one problem. A lot of parts are made of unobtainium, and the ones that are installed are not maintenance friendly.

The LED for the standby switch is one example. To service it the choke and power transformer must be removed. I'm not going to spend a couple of hours fooling around with this to fix a LED.

The pots are hard to come by, the pull switches are unavailable and obsolete, and making them work reasonably well consumed about half a can of Deoxit.

The plate load resistors were making a popping noise so I looked at it. The preamp board is backed up by a metal plate and the entire thing including the preamp tube sockets is riveted together, the gap between the two being maybe a quarter inch-plenty of potential there for shorts.

I was able to install one plate load and lucky me, that was the noisemaker.

Also, selectively dialing back the gain in a few places made the amp much more tractable.

All the preamp and power tubes needed replacement for noise, and I selected the preamps for lowest noise. I think there is a 5751 and a 12AU7 in there somewhere. The amp was full of ancient Chinese junk for tubes, and they all went in the trash.

The reverb was also on the fritz but a new tank took care of that. Luckily it is transformer driven ala Fender and uses a similar tank. It uses a stereo cable so I made do with what was there.

Every once in a while somebody brings in an amp that you've never heard of at all and wants some small thing taken care of. It usually turns into a shit show and this was no different.

Enter the Studiomaster, which looks something like a home made Boogie clone with the extra special unventilated tube section.

After going for a test drive, itemizing its many flaws and opening it up later I decided the owner may not know it but the first thing that was going to get done was a comprehensive power supply overhaul.

It's like a house. If you do not have a solid foundation, nothing else you do will be of lasting value.

Luckily enough the major components are on a board that's easily removed.

Here's what I've found so far. The schematic is courtesy of Nic Grabien, who was involved in the Studiomaster project as a consultant. Thanks brother.

The pics are of the power supply board and the raft of dodgy IC capacitors poorly installed, a/k/a Instant Crap.

Here's the after, with new diodes and balance resistors. The diodes were upgraded with 1N5062 2a .8kv genuine Telefunken diodes for the bias supply, and 1N5399 1A 1.5 kv in the power supply.

Much nicer with F&Ts, don't you think?