The Pics

Here are some gut shots from my recently acquired Silkyn Super 50.

Silkyn Super 50 update.

I had a chance to drop the chassis out of this bird a couple of days ago and I did a little testing. The sound was a little gritty so I measured voltages, tested tubes, and proceeded to install some good glassware from my collection.

V1 was a JJ ECC83 and the rest were Sovtek 12AX7 long plate 12AX7s. One was pretty weak, and they all had dates of 2003 on them.

I installed V1: JJ ECC83, V2: Philips 6681 V3: JAN 12AX7 (Philips ECG) V4: 12AX7 RCA, V5: Mullard ECC83 and V6: 6201 GE 5  Star.

I'm making a pitch for mobile radio tubes like the 6681 and the 6201 5 star, because they're meant to work in the worst kind of service with wacky voltages. They're great stuff if you can get them.

Here's what I found in the way of voltages.

Vp: 484v dc
Vscr: 483v dc

Cathode current 39.2/38.7 (this was after installing a matched pair of Ruby 6L6GCMSTR power tubes in place of the Sovtek 5881 coin base numbers which were about 7ma mismatched. The Super 50 has a neat adjustable bias which works like a charm.

V1 1: 217v 6: 217v
V2 1: 237v 6: 219v
V3 1: 358v 6: 358v
V4 1: 238v 6: 308v
V5 1: 238v 6: 308v
V6 1: 248v 6: 242v

Following David Bock's postings on youtube and his other mod postings on the Super 50 I changed out R33 from 4.7k to 1k to improve the reverb a little and installed an old Accutronics 4AB tank from my Princeton Reverb. There's plenty enough room.

So far, so good. Pics to follow

Cheap Orphan Tube Amps On A Budget: The Silkyn Super 50

This photo came from Kevin Paul, and I borrowed it-something I usually do not do but it was needed here. If I get the schematic he'll be the first to have it.


I recently became aware of the existence of some ridiculously inexpensive tube amps recently and scored one on fleabay. The cost at $209 shipping included makes this amp worth it for the parts alone. The power, output and reverb transformer and tubes plus the Eminence Legend speaker, purchased online would come to about that so I figure I bought it at salvage prices.

This is not my first expedition into the gray world of orphan guitar amps. I've got a couple of Judybox Revivals-they folded a number of years ago-and a repository of information on the Masters TV30 including the schematic and field mod information. But this one looks especially interesting.

It's the Silkyn 50, it's a two channel 50w item with an Eminence Legend, and it comes equipped with a Ruby short reverb tank and channel switching.

According to Fedex it is slated to arrive here tomorrow, and I'm going to be very interested in seeing what I got.

The story of Silkyn Electronics is yet to be told in full,but from what's left of their website over at the wayback machine, they were a startup that folded in the 2007-2008 financial meltdown, and what's being sold by are amps that are leftovers, probably by a recovery specialist or bought from an auctioneer.  The charge was headed up by a fellow named Mark Ausmus who was a veteran of Fluke and Gibson guitars, If these amps sat in a container in the port while the disposition of them was being fought over, that might explain some of the surface oxidation Jeff Fiske saw.

The original intent was to have graphics applied to the cabinets but nobody seems to have seen one of these.

One person has done a` teardown upon receipt and he notes that the construction was not great but pretty reasonable overall, but the tubes supplied were not top drawer stuff.

What I saw there indicates that the circuit board is not terribly complicated, and the next order of business will be to try and obtain a schematic diagram. That may prove to be a task but it is worth the effort.

The intent is to do a teardown and inspection, measure voltages for further reference and photograph as much as I can.

The Washington  secretary of state tells us that the company filed as an LLC in 2007 and was classified as inactive in 2012, which means these amps have been sitting somewhere for at least four years.

I've written to the proprietor to see about a schematic.

UPDATE: The amp arrived today shipped via Fedex ground (good) in fine shape, with all the accessories in the case. It was shipped Monday and got here to central Iowa about noon today while I was mowing and trimming the back yard. Unlike some this amp had never been out of the carton. I did a quickie power up to make sure all was in order and it was, controls worked fine and the channel switching was good. The reverb is kind of thin, not really what I like but that can be addressed.

It should be noted that you need the foot switch on this amp to enable the clean channel and reverb. Odd but true.

Now to pull the chassis, test the tubes, set the bias and see what I got myself into. But first, lunch.

Tone Sniffer Mark III

Sometimes folks need a signal tracer.and they hunt up an old Eico or Heathkit and retube and recap it but I have found something betterI believe that can be assembled on the cheap.

You should always have a test amp in the shop and preferably something that has a line in/line out function which is helpful if you're trying to isolate a problem to a particular part of your amp. One that filled the bill for me was a cheapish Dean Markley bass amp which ran me fifty bucks and a trip to beautiful downtown metropolitan Lorimor, Iowa.

I happened upon a project on a forum somewhere that consists of assembling a small project box, a 1 meg pot, a .1uf/630v or better capacitor, and a probe with some coax. These can be found in your junk box or hand assembled with the body of a BiC pen, a nail, and a sleeve.

The one I built is pictured above.

The pot is used to attenuate the signal the probe picks up so you don't fry the preamp in your shop mule amp, which is something I did with the two small Radio Shack pocket amps I had at one point. You can start at zero and slowly ramp the volume up.

Now, starting with your signal generator putting a signal in the amp under test with its output into a dummy load, you can take your tone sniffer and following the circuit see where the signal dies. At that point it is pretty easy to substitute or bridge the offending component.

I have used this rig to isolate problems and fix a number of amps with serious volume drops.

It's also of use when you're testing an amp with your scope hooked up and you can see that the volume is way lower than it ought to be.

On the subject of scopes, I'm pretty sure my Hitachi V680 died so I went and bought a Hantek digital scope for about $280, and I'm going to try it out tomorrow and see how it performs.

Stay tuned.

The $105 Bassman Cometh

One of the things that I've wanted for a while is a Bassman head that I could keep and love, but was not so expensive as to compel me to sell it for a profit, or that I might be pilloried by the Vintage Amp Police for having a little fun with it.

Let me back up a bit....there's more to this story.

I was at an auction late last year and I picked up a Teisco Del Rey solid body guitar like this one on the cheap-fifty two dollars to be exact. It was covered in sticky schmutz and looked like a wall hanger in a ginmill or somebody's so called "man cave".

Not that I wanted it, mind you, but I figured it would be a good money maker.  So I cleaned it up a bit and put it on Craigslist with a notation that I would trade it for a dead tube amp.

So a pal of mine calls up and says he's got an amp and let's trade for your guitar. What I ended up with was the Sound City 120 head you see here. It was dead but about fifteen minutes of work got it running well enough. Large and powerful, but not my cup of tea as they say. Then, I posted a pic of it on one of my internet hangouts offering to trade it for a Fender Bassman.

Within ten minutes I had been offered a Bassman 70, which is an ultralinear amp which I did not want, and a Bassman 50, which is pretty much the same as an AB165 Bassman, which I did. An agreement was made.

Shipping the Sound City to San Angelo Texas ran me about fifty three dollars, and the Bassman arrived on the return. So I'd gotten myself a silverface Bassman for a total of $105.

I just started improving it the other day. It needed a good crud cleaning which I am about half finished with, and I ditched all the blue Paktron capacitors for Mojotone Dijons-a great improvement. The power supply capacitors had already been replaced.

Right now it works pretty well and sounds as you would expect a Bassman to sound. I'm thinking a custom cabinet with a single 12 inch speaker or a couple 10s would be.

Power Supplies And All That

Lately I had noticed that the power supply exhaust fan on my desktop HP would make noises like a coffee grinder occasionally. So when it started to get really annoying I figured I'd order a power supply, swap it out and then repair the old one.

No surprises here. The fan in the original was pretty noisy even after a dose of 3 in 1 oil, so I ordered another fan, cost $5. It arrived and it was the same make and model as the one I removed.

A couple of observations are in order. To get a Liteon power supply like the box came with and which you see pictured above you will cost you about a hundred bucks. So I ordered a cheapie "Replace Power" power supply from an online vendor, cost $22.79 and it was a drop in installation. The part number is RP-MPS3-420W, and it replaces the Liteon PS-5301-08HA.

Comparing the outputs reveals some differences. I'll put the Liteon's ratings in parentheses. +3.3v 11a (+3.3v 18a), +5v 12a (+5v 25a) +12v1 8a (+12v 19a) +12v2 8a (none) -12v 0.3a (-12v 0.8a) and +5vsb 2a (+5vsb 2a).

In most areas the Liteon has better capacity to deliver current on its individual legs but is limited to 300w combined.

There are a couple points of interest. The Liteon is much heavier and I believe that it is because of the massive extruded aluminum heat sinks. It is also thermostatically controlled and thus the fan does not run continuously as it does in the Replace Power unit. This is a nice feature because the exhaust fan rarely runs and most of the time doesn't bother me. It also has a small LED that indicates when power's on and it slowly fades as power is bled off after shutdown. The Replace Power does not have this feature.

The Replace Power also does not throw off a lot of RF noise, either. My last cheapie power supply for the Dell desktop that this replaced made a whistling noise that meant when it was running I couldn't listen to AM radio anywhere in the house. It's as good as the original in that respect.

Although they're both rated at 300w, the Liteon power supply seems to be more robust, and I'll either reinstall it or save it for another desktop if one should come my way as seems likely.

The Little Amp That Couldn't: The Egnater Vengeance

An Egnater Vengeance 60/100 head arrived here in the middle of a raft of other rocket science, dark matter, higgs boson amp projects last month so it took a little while to get to it.

The story given was that the owner while playing a gig and watching his power monitor saw a huge power surge at a particular local venue that will not be named. His Egnater died, laid down on the job, quit, gave up the ghost and generally took a dump right then and there. There are dark rumors and mutterings that this was not the first time this happened in this particular place although I haven't seen the proof of it.

If there's anything to take away here, when you've got an amp with no output, measure the voltages fer chrissakes. Often it will tell the story. On the average eight pin octal based tube such as everyone's favorites the 6L6GC, the 6V6, the EL34, and the 6550 you can measure pins 3-plate voltage, 4-screen voltage, and 5-negative bias voltage.

Missing voltages and no output has been the story around here the last couple of months. First there was the Sunn 100S with a defunct choke, then there was the Music Man 2100-65 with an open choke, an open filter capacitor and an open capacitor on the board I sussed out with my tone sniffer. Then there was the Vox AC15 HW with no output, a Marshall MA50 with no output, and a few others with various and sundry ailments. On the other hand it has given me an opportunity to put my scope to good use and take baby steps along the long learning curve to scope competency.


In this particular Egnater, there was no screen voltage present. A little work with the schematic located the correct voltage on the standby switch, and it dived into the power supply circuit board bit didn't come back out. A little more work revealed that one of the 100uf/500v radial snap in capacitors had shorted out, and two of the three 10w ceramic resistors were open.

Then the fun started. Getting the power supply board out to gain access to the back side required: removing the voltage selector switch, the power switch, the standby switch and the foot pedal board, unbolting the power transformer to get enough slack in the leads to push them far enough away so as to pull the circuit board up, clear the nearest 10w resistor to the chassis, and then remove the offending components to replace them. I would say it took a good solid hour and a half to accomplish this task.

While inspecting my nifty silver solder joints I managed to burn a hole through an unopened 12 ounce bottle of Coke and made a mess all over everything.

Here you can see the offending bulged shorted capacitor; some of the mass of wire on top of the PS board; ; more wire spaghetti ; yet more wire spaghetti; the PS board emerging; more wire spaghetti; and the new Ohmite 10w resistors.

In addition I was trying to do a clean install of XP on my library computer because one of its critical files had disappeared overnight.

This morning I expect to finish the XP reinstall and start the burdensome and onerous task of installing a bajillion updates and service packs.

Then, and only then, I may try the registry hack that will convince Microsoft that this old workstation is really a "point of sale" device and get more updates.

Of course the wireless business would not cooperate so things came to a screeching halt on the computer front. 

Somehow the usual abbreviation "P.O.S." seems appropriate.

UPDATE: I think that the long road of XP has come to the end. I knuckled under and bought a copy of Windows 7 and a new wireless adapter. These ought to arrive fairly soon and I can then see how well the box operates with a modern-ish operating system.

UPDATE: I got the Egnater running this morning and on the scope it was putting out a good 90w clean, so I proceeded to put the head in the cabinet and to give it a last road test before it went home. The volume had dropped down to nothing, about 2 or 3 w. What now?

I took it back to the shop and opened it up again and this is what I found. I think I'm pulling the captive nut and spring clip and losing them somewhere. The screw had jammed right into the footswitch board. I'm guessing that the hole in the chassis and the mating hole in the cabinet were mislocated.