Laney AOR 50

A few weeks ago I saw this Laney combo on Craigslist not too far from here and by the time I jumped on it, a friend of mine had already snagged it for a very modest price. Well, he emails the other day and says it wasn't him, too heavy, and would I like it for the price he paid?

Of course I said yes. I'd been getting the itch for something new and I'd speculated about acquiring the Peavey Prowler that's on CL here at this very moment. Good thing I saved my dough.

Laney was said to be a downmarket Marshall clone, and that may be somewhat truthful as the schematic bears a certain resemblance to the JCM 800, with a few pull boost features thrown in. Reverb and a nice Fane speaker finishes out this amp that was built in 1986.

The transformers were from makers I'd never heard of on UK built amps. The output transformer was made by Skot, and the power transformer and choke were made by Ariel. Skot is still in business and they seem legitimate enough but no trace of Ariel thus far. Either way they've got to be better than the awful Dagnall crap that Marshall was using. The reverb is reasonably nice but not overly drippy, with an Accutronics tank in the bottom of the cabinet.

I had it on the bench today for some much needed maintenance and inspection. Cleaning and douching the pots and replacing both input jacks took care of business and a new set of Valve Art EL34s properly biased and a pair of new 12AX7s finished things up. The plate voltage is relatively modest at a measured 412v, and bias was accomplished with a nice pot located on the circuit board ala Marshall at 38 ma each. I do not know whether there is a connection between Marshall and Laney but I think it is more than likely.

Schematics are available readily from The Tube Store for free on their website.

It sounds good, and you can do some interesting Telecaster plonking easily enough. I'm not a high gain guy but I may never need it. The background noise level is just a little hissy with the master volume dimed but tolerable if you back it down a little.

These are pretty cheap and you can have a whole lotta fun so if you find one grab it quick.

Biasing the Albion TGT-50

An Albion TGT50 head came my way for some routine service and it occurred to me that it would be worth checking the output tube bias to make sure it was reasonably close to what it should be.

Of course I couldn't find any service information readily to hand. So I opened the small hatch on the rear of the chassis and saw what looked pretty close to something I've seen on Marshalls and on a Randall head I used to own-a pair of potentiometers and three pins. I then removed the chassis for a general lookover and it seemed like a pretty conventional 50w channel switching head. Nothing was remarkable except that the tube sockets are chassis mounted and wired to the board.

A nice touch, and one that makes service people happy, if you followed my adventures with hard wiring a Blackstar 100w head recently because the board had burned up.

After using my bias probes and measuring the plate voltage at about 470v DC I adjusted the pots and got the results I needed. I then went back to the original setup, set my multimeter to millivolts and measured the left and right pins with the ground probe to the center pin.

The results were quite similar which led me to believe that the designer of this amp, Steve Grindrod,  used the same setup that Marshall used-not surprisingly when you figure that he worked for Marshall for a while. I figure I was reading across a 1 ohm resistor in the cathode string for each power tube.

Or, of course, you can take the better path and check bias with a pair of probes and a couple of dedicated multimeters. It'll give you a chance to look around inside while you're visiting.

One Day In 1970 Or, How We Fixed Your Telephone

I was having a discussion at the Other Place with a few fellows on the subject of fixing electronics, namely guitar amplifiers, sans a digital multimeter or a scope. So this was rolling around inside my head and maybe it was the story in the AARP bulletin today on the subject of memory loss that had me casting about for something to prove that I'm not dead yet.

So anyway, back in 1970 I was working for New Jersey Bell Telephone Company, better known as Ma Bell. Mother was very picky about a lot of things and when she'd settled on something she liked, nothing else would ever do and no off the shelf stuff either. Mother loved MacMillan Ring Free motor oil and that's all we ever used. Macmillan's only claim to fame was that they'd sponsored the Skoda racing team in the fifties.  The supply crib was well stocked with goodies like Ma Bell bandaids and aspirin, spray paint (olive drab, safety yellow, and black) and other interesting things. They had the best damn first aid kits you ever saw, complete with ampules of antiseptic. They were packed ten to a box with a glass ampule inside a plastic tube with a cap on one end. Pull off the cap, crush the ampule, squeeze the plastic tube and anoint thy self, brother....where was I? Oh, I remember.

When there weren't any big projects going on the repair crew would be sent out to clear defects. What that meant was, there was a defect on a particular pair of wires that the installers and frame men couldn't fix, so they'd bypass the pair (spare pairs, doncha know?) and sooner or later the splicing gang would have it.

The process consisted of going to the frame (usually Somerville), locating the pair, and blasting it with the breakdown set, which was a zapper that would send a jolt down the wire and maybe dry out the fault, but usually ended up fusing the pair at the site of the problem. So we'd read the resistance which would tell us how many miles away it was, and attach a tone generator to the pair. We knew from the print what bundle it was in in the cable.

Off we'd go in the truck watching the odometer and when we got close, a pole with a probe was stuck out the window. The probe was connected to a small amplifier and when we reached the site of the defect the tone would quit. We'd do a little more walking around until we had it located pretty close and then we'd put the bucket up to the cable and open it up to determine the final location. A slack puller on the wire rope could pull enough slack into it that we could dig around inside the cable with a probe until we found the pair. This took a little bit of doing since a 2,200 pair cable is not an easy thing to wrestle with.

Once the pair was located we'd fix it with a splice, put everything back together and install a splice case. We'd wait for a little bit until the air pressure came up, check the case with soap solution for leaks and then head to the diner for coffee.

Tweed Super On The Cheap

While trolling my usual places on fleabay (the "Why pay more?" store), I ran across a trio of partially built tweed amps that consisted of Weber chasses, pots, knobs, and Mercury Magnetics iron but not much else. There were a 5E7 Pro, a 5F6A Bassman, and a high power tweed twin.

Since I'd already built a couple of 5E7 Bandmaster kits I opted to snag the 5E5 Pro and build it as a 5F4 Super. All three of these amps are pretty much the same with some very minor differences.

Once the partially constructed chassis arrived I made an eyelet board for it and loaded it with F&T electrolytics, Mojo Dijon capacitors and mostly metal film resistors. At about the same time I bargained with Dirk Newton for a pair of Weber Ferromax 10 inch speakers and contracted with J.D. Newell for a lacquered tweed cabinet.

Looking through my stash I came up with a trio of new old stock Cinch shielded 9 pin sockets for the preamp tubes and a trio of new-ish Chinese ceramic top loading sockets. For glassware I used new old stock RCA preamp tubes, blackplate power tubes, and a Mullard 5AR4 rectifier tube.

The chassis went together easily as this was my third one, and everything else went together when the cabinet arrived, and it is a beauty. I mostly wired it with 22 gauge pre tinned cloth pushback wire from Stewart MacDonald.

There's a lot of controversy about  what sort of wire and gauge to use for general hookup and filament service but I think it is a relatively simple matter to determine what the current load is and wire accordingly. For instance the total current draw for the preamp and power tubes is about three amps total once the initial inrush is over. At that point we see that 21 awg chassis mounted wire maximum load is 9 amps so that should be well above the margin of safety. Some folks think that they have to use 18 gauge single strand for the filament wiring and there's simply no need for anything that heavy.



Here's the breakdown on prices which includes shipping:

$375.00 chassis
$260.00 cabinet
$  75.00 speakers

Glassware and other components were from stock

Peavey weirdness now morphing into Blunt Instruments

UPDATE: I think I've found an appropriate name for the amps I build, I checked TESS and nobody's sitting on the trademark, so henceforth and forevermore, anything I build will be yclept a "Blunt Instrument". You heard it here first.



Last week as I considered the state my monster amp project was in I decided to plunge for power and output  transformers for the Super Bee.

There are two potential sources for this class of iron, and a possibility of a third. There is, of course, the ubiquitous offerings from Mercury Magnetics about which more anon, or the offerings from Mojotone which are manufactured by Heyboer. If Classic Tone made these transformers I would have shopped there but alas! they do not.

The net total was $117.42 for the Mojo 753 power transformer, and $109.70 for the Mojo 756 output transformer-which came with multiple taps by the way. Shipping was another $20 or so. Mercury would have run me $425 plus shipping so it was a no brainer.  I suppose I could have used a Twin Reverb power transformer which I have as well as a Twin Reverb output transformer and then had to come up with a 5v filament transformer to run a rectifier tube which would have saved some dough but would not be close to the original setup. This amp has to look and sound like something Fender built. If I wanted to hunt til I'm old and gray I could possibly have turned up an original p/n 7993 Triad power transformer and a 45268 output transformer but that is not a likely proposition. I could die waiting.

The transformers were installed with blue Loctite on the screws. I've seen too many get loosened up with age.

I've selected a new old stock Mullard GZ34  for rectifier duties and RCA black plate 6L6GCs for power section duties. I think Uncle Boris over at Sovtek can do the  rest. There is also a Dynaco socket mod for protecting the rectifier tube which I plan on incorporating- to power 4 6L6GCs is asking a lot of a 5AR4.

With the board built, all I have to do now is build a bias board and a cap board, install some controls and start stitching. The biggest unknown is fitment and speaker selection. That will come later.



On the top you can see my layout. This was possible only because a friend owns a high power tweed twin and I was able to lay out the components in the original way. By comparison there is a shot of a recently built tweed twin replica and the output transformer and cake pan are reversed.

 

Peavey Weirdness, Redux part 2.

After having spent the last couple of months fruitlessly looking for a Peavey all-tube Vintage, a voice in my head said, "Hey you! Yeah you. Glassy eyed lounge lizard. That's right. If you want one of these, why not build it yourself?"

After a little thought and study I realized I could build a 5F8A high powered tweed twin and shoehorn it into an only slightly larger Bassman cabinet and accomplish the objective of creating a ridiculously powerful guitar amp in a 4x10 package. I mean, they're the same as an uprated 5F6A Bassman, right down to the components and eyelet board-which I had already built some time ago. There is only one minor difference between the circuit boards which is a smallish resistor.

Of course this project has to be funded on a pay as you go basis, which means that the iron, the cabinet, and the speakers will have to be ordered and paid for out of the sales of my Vox AC30CC2 and my Bogner Alchemist 2x12. and the amps I already have for sale on craigslist. The chassis arrived here from Mojo, and I have the circuit board, new old stock tube sockets (Amphenol military and Cinch shielded) plenty of fine glassware, small parts, jacks and capacitors so I have some work to do.

The proprietor of the shop where I buy cabinets is working on a similar idea and he says that one of his customers, Sligo amps, has built these in the past but they're very expensive and  do not enjoy a great following. I may sound them out for their opinions.

I haven't thought of a name for it yet and Super Bassman is already taken, so that is also going to need some thought.I've added some snaps from the preliminary buildup.

Film at 11, as they say.

Peavey Weirdness

I've got an itch for a fairly rare Peavey amp built in the early 1970s. They were the "vintage" and they were all tube. The amps came in 2x12, 4x10 and 6x10 configuration and used a pair of the now rare 6C10 compactrons to do the preamp and reverb recovery duties.

The schematic is a lot like a tweed Twin. If you find me one, I'll buy you lunch.

Blackstar HT100 Barbecue: Replacing The Tube Board.

I'd worked on this Blackstar HT100 head a while ago and it has served its owner well for the last few years. I'm not entirely sure how the story goes but it is said that a beer got spilled on/in it but who knows?

Either way it had a major cookout which lunched the tube board. Lucky for me it is a separate piece of hardware AND there was available a schematic for the tube board.

On the other hand, the tube board is made of unobtainium. My first thought had been to get a new tube board but that was out of the question.

Looking at the diagram it seemed that I could hand wire it ala Marshall and then I'd figure out how to connect it to the main board. So I installed four ceramic sockets and started in on the wiring and resistors and hookup wire.

When I got to connecting the tube board to the main board, removing the molex connectors was going to be problematic because they're glued to the board. I decided to make loops in the ends of the hookup wires, and lucky me, there was enough separation so that I wasn't going to have problems with bridging.

I finished the wiring today and it powered up the first time. So tonight I'll let it have a slow simmer and see how it goes.

Bored With Boards: Repurposing an Ampeg SJ12T, Part 4.

As I've been thinking about this project some more-well, let me back up.

I've suddenly got a lot more time on my hands due to the ending of my teaching gig.

It happened in a way that was proof of the existence of chaos theory if you needed it. There is a meeting somewhere, people sitting at a conference table, and with the scratch of a pen, everyone goes home.

Meanwhile a couple of years down the road and a hundred miles away, people lose their jobs.

But nevermind.  Let me continue-this line of thought leads only to frustration and less money in my bank account.

I sourced out some 50A bridge rectifiers, the kind that are potted in a metal case-it seemed the answer to my problem about building a hybrid circuit board of 6G3 derivation, and also made more room under the hood, thanks to a thread posted by J.R. Frondelli of DBM Audio in the Big Apple concerning the age old question of what to do with a torched Blues Junior.

Being in an optimistic mood, I then decided that I would out source a circuit board for a 6G3 so as to save myself some work.

What I got was a board that was warped and off dimension, and half the eyelets were not installed. The ordinary dimensions of the 6G3 board are approximately 2-3/4 x 10-1/2 and the backing board is the same size. On the other hand, here is what the board should look like, populated. It took me a bit of time to make up a drilling mask, drill the board including larger pass through holes, clean up the burrs with a razor blade, stuff it with eyelets, tape them down and clinch them. Then, clean off the tape residue and stuff the board with components and solder them in.

 It should look like this:

 The red marks were for orientation of the components. The lower shot is the comparison.

Now. How did I do it? It's posted elsewhere on this blog but it consists of obtaining 3 inch vulcanized fiberboard, making a drilling mask from a photograph or screen shot of an existing board, sizing it with a freeware program called Irfanview, printing out a drilling mask on 8-1/2 x 17 inch paper, trimming the board to size, taping and drilling the 1/8 holes. Then you can trim the burrs , install the eyelets and clinch them and stuff the board.

To complete a board like this one, stuffed with the components of your choice once you have paid the one time cost of the tooling and eyelets should cost you less than $20 in parts.

And you'll have exactly what you want, when you want, with no waiting and no shipping or paypal fees. The folks on fleabay will charge you upwards of a C-note plus shipping for something you can knock out all day long for pennies on the dollar.

Haste, in my case, surely did make waste, but as always it's a teaching moment. I'm making all my own boards from now on, thank you.

Thanks again to Jeff Gehring for being so generous in sharing his knowledge.

The Evil Pro

I've been jonesing for a certain Fender Pro that was made for a couple of years. This model is an AB763 circuit without reverb, and a 15 inch speaker and I guess it is pretty rare as I never saw one in the fleisch as the Germans say.

For a while I was thinking seriously of taking my Bantam and revising the circuit to add vibrato. But then a guy calls me and I was on my way to Boone, Iowa to look at a drip edge 1968 Dual Showman.

The Showman was all there but it was in rough shape, I bought it on the spot, head and loaded cabinet for $325, and I knew right away what I was gonna do with it.

The JBLs were both defunct so I'm gonna have to do something with it.

Some opinion sampling later and a few emails and I settled on J.D. Newell to build me a custom cabinet that would accept the Dual Showman chassis and a 15 inch speaker. They seemed to be the only people who knew exactly what I wanted and how to make it. Money was exchanged, a delivery date was quoted, and I proceeded to overhaul the chassis and spiff it up with a new blackface panel. The Fender logo I had already.

The cabinet arrived right on time and it is a stunning piece of work. A number of my friends have seen it and exclaimed "That's better than anything Fender built."

For the time being I installed a 4 ohm CTS speaker but I have a higher power Oxford that I may use.

How's it sound? Loud as hell, clean and bright, and with the channels bridged it gets even better and you can soften the vibrato by adjusting the balance between the channels. After about five minutes one of my brand new Ruby 6L6GCMSTR power tubes grenaded, so I slammed a Sylvania in the vacant slot and carried on. I've got a quad of Sylvanias I matched up, and there are plenty of RCA blackplates in the stash box. Preamp chores are being handled by Uncle Boris over at Sovtek.

It's the Pro that Fender never built, and I've named it the Evil Pro.

Repurposing an Ampeg SJ12T, Part 3

.If you've read this far you have a pretty good idea of this project. A brief review, then.

I acquired an Ampeg SJ12T a while ago, it is one of the pre-Loud Technologies Diamond Blue Series amps that SLM turned out in the mid 1990s, In theory it was a good bet-a single 12" Eminence speaker, 50w from 2 6L6 or EL34 power tubes, vibrato, and reverb.

That's where the joy ended. The reverb quit and then shortly after the vibrato left town. Nothing could be done to restore it so it sat.

A few weeks ago I decided that it could be repurposed, but into what?

After some study of schematics of likely suspects and examination of the available real estate , it seemed that a Fender 6G3 Deluxe, suitably modified for the power supply and preamp architecture would fill the bill.

There are. of course, two channels on the 6G3 and only two inputs and five total chassis holes for pots on the SJ12T. I did have a couple of dual pots of the right value for volume and tone so that takes care of the two channels pretty nicely. A couple of vibrato pots were added, and I have a single pot hole left which was formerly occupied by the reverb control, and I think I will add a presence control there.

I already installed a proper pilot light assembly and fuse holder.

I started cooking up a 6G3-ish circuit board that will accommodate the diode bridge in place of the rectifier tube as the SJ12T used a full wave, no center tap design. and at this time I hope to continue with the original SLM power transformer which is the same as that installed in the VC50 Crate and presumably the SJ12R as well. Is it up to the job? Only time will tell,.

Choice of tubes was relatively simple, as I have plenty of new old stock Soviet 6SL7s and found a pair of new original type 5881s in my tube overstock carton. That and the Classictone AB165 Bassman output transformer should take care of the power management chores.

Power supply filtration chores will be handled by the JJ multi cap can, and the output transformer lead through provided a nice pilot hole for my Harbor Freight knockout punch

I've got some more things to add to the board and then start thinking about stitching the wiring together. Stay tuned.

Repurposing an Ampeg SJ12T, part 2

The next project has been constructing a circuit board for the repurposed SJ12T, loosely based on a 6G3 Deluxe.

I had a bunch of circuit boards populated with parts from the Judybox Amps garage sale that was had down in Austin a few years ago, along with some other odds and ends that came from the sale.

Part of the repurposing was figuring out the power supply.

The original Ampeg power transformer delivered about 400v of B+, and that was based on a full wave configuration with no center tap, all solid state rectification. The transformer itself is a St. Louis Music item that I've seen in a couple of Crate VC50 amps, which was punishing 4 EL84s in that application. It looks about the same size as a Deluxe Reverb power transformer, but with the full wave setup and no rectifier winding. It does have a bias winding, and what looks like a 12v center tapped supply which gives filament voltage as well as +/- 7 volts for some sort of solid state dog waste.

Aligned with that task was starting a circuit board. I cleaned off all the crap from

one of the Judybox boards, and installed eyelets along each side. Loading the components-all the tone, volume, phase inversion material from the 6G3 circuit plus the full wave bridge and bias supply pretty much used up all the real estate and identified some center holes that need eyelets plus a couple that need drilling. Power supply capacitor tasks will be taken care of by a JJ 40-20-20-20 can that I have not yet installed. The capacitance is a bit higher than the original 6G3 but not radically so.

What to do with the remaining hole in the panel? A presence control can be added.

The last issue will be figuring out how well or not well the octal preamp tubes will work with this circuit and the changes I've made to it. Some study of a few older Ampegs that use octal preamps like the M12 and M15 may give some clues to the voltages that will be needed.

After the octal sockets were installed I ditched the blue neon pilot light for a regular Fender style pilot light and wired up the sockets. That's where I stopped.

More to come as I do some more work on it later on in the week.

Repurposing an Ampeg SJ12T combo Part 1

A while ago I acquired an Ampeg (SLM) SJ12T combo because it sounded interesting. In a word, it turned out to be a complete dud. The reverb and vibrato went out to lunch and they haven't been seen since then, and no amount of endearment could get them to come back and behave.

I mean, the idea sounded good-an all American made tube amp, 50w, single Eminence speaker, reverb and vibrato. Who wouldn't have loved it? Of course, as I mentioned the reverb and vibrato were dodgy, they went out for lunch and never came back despite all my efforts, not to mention intermittent crackling and pops, and there was absolutely no way this amp could deliver 50w-not now, not ever.

So back in behind the water softener it went, to do its term of incarceration for felonious misconduct while I figured out what on earth I was going to do with the thing.

I pretty soon came up with the idea of repurposing it, and it's turned out into an all out project, which means that this is going to be in several installments. There are a number of reworks that are needed so I've had to figure these out as I went along.

After a lot of study I decided to ditch the cheesy reverb and build something close to a 6G3 Deluxe with octal preamp tubes and vibrato. There was room to broach another socket hole so in it went.

Next, I had to figure out how to get dual volume and tone controls. That was easier than I thought as I had two stacked dual 1 meg audio taper pots. Between that and a couple of switches I could have normal and bright channels and bridge them as well with the existing holes, opened up a little.

Considering that the output transformer seemed stingy on the iron for anything close to 50w, I decided a ClassicTone Bassman output transformer I had was just the thing, and it could be located more or less in the same neighborhood as the old one which can find a home in some other project.