The Lesmann Amplifier Project

If you've been here before you know of my weakness for orphan amps with fifteen inch speakers, and this one seemed to fill the bill on all counts: 15 inch speaker, about 25 w, made by who knows, and general adaptability to other chores.

Behold the Lesmann amplifier which, I think, was built to accompany Lesmann's other big gun, the Accordio-organ (which seems to be a hybrid accordion with electronic organ features).

All I have been able to dig up on this amplifier is the following. I believe the amps were built in West Allis, Wisconsin, as there was a Lesmann Corporation that existed there for a time. In addition, the Accordio-organ was patented (2,983,178) in 1961 by Fred N. Searles and Ralph G. Studemann and assigned to the Lesmann Corporation of West Allis, Wisconsin.

I did find a tantalizing lead on The Accordionists Forum in which the daughter of Fred Searles states that the company came from the two names, searLES and studeMANN. There was no further information

She also states that her father worked at "The Music Shop", which may be connected to Ralph Hanzel's Music Store in Milwaukee which was a powerhouse in the trade at one time. The proprietor was a steel guitar player I believe, and is credited as the co author of a country song entitled "This Is Honkytonk".

I hope that someone finds this information and  adds to the general fund of knowledge. I've been theorizing that there was an interesting music scene in the Milwaukee area during the fifties and early sixties that was heavily into country and accordion music-Flotatone was doing business at the time in the same area, and they were involved in amplified accordion music.

There's a little more about Flotatone on the internet, and I do know that others made and sold accordion amplifiers-Ampeg, Sano, Danelectro and Magnatone, among others.

Well then. Now, to the amp.

It's about the same size as a narrow panel tweed Pro, but I have not as yet drawn out a schematic or done any circuit analysis. This one's relatively untouched, and has the (mostly) original Aerovox capacitors and  Northlake Engineering transformers. Northlake is in Wisconsin and is still in business. I did not check the chokes for manufacturer's dates and codes.

A casual look inside reveals some strange vibrato stuff going on with a couple of neon bulbs but that's about as far as I've gotten. Here are the pictures so far.

Silkyn Super 50 Schematics.

Some good person uncovered the schematic diagrams for the Silkyn Super 50 and wonder of wonders, it reveals that this amplifier was designed by Michael Soldano, the amp genius extraordinaire from the Pacific Northwest.

That gives me some inspiration as far as the design is concerned. Lends it a little class, y'know?

There's a link to the schematics at

http://music-electronics-forum.com/t42632/

Need For Tweed

This 1952 5B5 wide panel Fender Pro showed up a while ago in the hands of a pal, and it has been making the rounds hereabouts for a while now.

It's reputed to have come from Minnesota which seems logical given that it has an ink stamp inside that says it came from Torp's Music Center in St. Paul, which by the way still exists, so it's said. It went from a seller in Minneapolis in a trade for other  gear to a guitar trader who I know who always has the shorts, and then to a smallish music shop owner, and then to another guitar trader I know, and then to  this pal.

In any event my friend was feeling the pinch as his business-which is schlepping pianos and tuning them-has been kind of slow lately so I figured I had a chance to take it out of circulation more or less permanently and let it be known that if it ever came up for sale again I'd like a shot at it.

It wasn't long in coming. A bit of road testing and hoss trading and I had it, and it cost me a home built 5F4 Super clone-which was quite nice if I do say so myself, a Pro Junior that I had acquired in another trade, $1000 cash, and assumption of a $300 debt which I will pay off next week. If I decide I need another  5F4 clone or a Pro Junior I can always build one or buy one.

I may have paid a little too much but there's no down side to vintage tweed amps, and there just aren't that many around these days especially in this shape. I am pretty sure it was recovered but it was a very good job if that's the case. The chrome panel and graphics are in good shape with little rust, and the innards seem to be all original. The Astron power supply capacitors have a little leakage but I have to think long and hard about changing them.

As usual the 6SC7 preamp tubes are prone to noisiness and general bad behavior, so I did a little plugging and tapping to find some quiet ones in my collection. I ended up with two glass Tung Sol originals rebranded as National Electronics and a RCA commercial metal 6SC7.

Some internal shots will be forthcoming as I have to remove the rear panel and encapsulate the asbestos pad on the upper panel. Here's what one on a tweed Deluxe looks like.

I take this stuff seriously because friable asbestos is hazardous stuff. My method is to mask off the asbestos pad and give it two or three coats of clear matte finish lacquer, which will soak in and stabilize the pad without changing the appearance too awful much.

When I get that done I'll past some more gut shots as I know that tweed enthusiasts will be interested in seeing inside an all original tweed Pro.

Soundwise, it plays well, and has no odd noises. The tone is good and it suits a Telecaster well.

UPDATE:

I had a chance to remove the back panel today and treat the  exposed asbestos with a couple generous coats of clear lacquer, so while I was doing that, I took some voltages. Here they are.

AC 380-0-380
B+ 432 v dc
V5 plate 426 screen 357
V4 plate 426 screen 357

V3 plates 189
V2 plates 69
V1 plates 64

I'm a little surprised at the voltages so I'll be investigating the dropping and plate resistor values when I decide to do a recap job.

Here are the gut shots as advertised.

In the meantime I'll replace the rear panel and think real hard about how much I'm going to do here.

Enter the Tweed, or, How I Learned To Stop Worrying And Love The High Power Twin

You know how sometimes you get a wild hair and decide you want something really outlandish? This is what I ended up with and thereby hangs a tale.

One time I stumbled over some of Hartley Peavey's musings about some of the amps he'd built over the years, one of which was the Peavey "Vintage" series. The very early ones were all tube and they're kind of hard to find. I've only seen pictures of them, and they included a 2x12, a 4x10, and a 6x10 towering monster. All three were 100w of all tube power including the out of production 6C10 triple triodes.

What you had, essentially was a 100w tweed Bassman with reverb. Now who wouldn't like that?

I couldn't find one for love or money so I said to myself "Well, I'll just make one, won't I."

So I got in contact with J.D. Newell and he figured he could cook up a 4x10 cabinet that could house a High Power tweed twin chassis.

Somewhere along in there I acquired a chassis and transformers from Mojotone and started constructing the chassis.

I also acquired two new Eminence  Legend 12 inch speakers on the recommendation of a friend of mine. About then the project became a high power tweed twin. I built the eyelet board and sourced the parts, most of which I had and built about 90 per cent of it, and the cabinet and speakers were sitting in my living room.

I used quality parts throughout, Heyboer  iron, F&T and Mojotone capacitors, and choice power and rectifier tubes from my stash: a Mullard rectifier and RCA black plate 6L6GCs.

I also incorporated some changes to the screen and grid resistors. After the first run I changed the Switchcraft jacks for Cliff jacks with a substantial reduction in noise.

All was assembled including a bracket to support the power transformer. It saves a lot of effort to assemble this amp upside down.

How's it sound? Loud as hell, but the speakers are not broken in at all. It sounds purty bright but will mellow with time.

On to  the next project-reviving my Marshall Club and Country. Stay tuned.

There matters stood until last weekend when I finished the wiring, adjustable bias control, and jacks. The first run was uneventful.

UPDATE: I've found some follow on buzzing that appears to be circuit related so it'll have to come out and get on the scope to locate the source of discomfort. Stay tuned.

Tube matching to the Max: The Maxi Matcher cometh.

I've been hankering after a Maxi Matcher for a while. It's a stand alone tube tester and matching device for certain power tubes and it's fast becoming the standard for the industry, so I thought I'd get one. Keeping up with the competition and all that.

I figured it was also a good bet for matching anything but KT88s and 6550s, as those I will still use Iron Gertrude for. That's my home brew tube matching device, it's completely analog and what's important is it'll put out 650v when called upon without even breathing hard, which is mandatory for high voltage Ampeg productions.

In any event the $695 was coughed up and the tester arrived here today.

Right away I knew something was wrong, and it is either me or the tester.

Doing the setups per the instruction sheet in the lid of the nifty hard plastic case I pulled a set of new Shuguang EL34s off the shelf, set the plate voltage to 400v, set the bias to -36v and proceeded to read the outputs.

The plate current should have been between 21 and 50 ma, and the transconductance should have been  greater than 4.0. What I got was around 6 ma per tube for plate current and the transconductance was between 1.76 and 2.31.

This was not good so I pulled another set of EL34s out of their boxes, this time a new set of JJs. The results were quite similar.

That got me worried. I measured the filament voltage and it was about 3.4vac, not the 6.3v one might expect. The 350v and 400v plate settings yielded  177v and 212v respectively.

I'm not convinced that the transformer output voltage is correct and I suspect that it has a 240v power transformer installed.

I'll keep you posted but until I hear back from the makers it's an expensive piece of eye candy, and I'll be using Iron Gertrude for my matching chores, as fussy as she is.

Stay tuned.

UPDATE:  I got a call from the folks at Maxi Matcher and what they told me was that they use a dual winding power transformer that is suitable for 120 or 240v depending on how it is wired. I got an email detailing how to switch the necessary jumpers.

In the lower left hand corner of the circuit board are  three places for jumpers. Bridge the inner one and you have 230v. Remove that and bridge the outer pair and you have a 120v transformer.

Smooth, Very smooth.

Rather than dismounting the circuit board I sweated out the existing jumper and installed two other jumpers-they look like staples-made from the wire shaft of a resistor.

It was easy enough to do and now it works just as it should, and the socket voltages bear witness to its proper function.

It still can't deliver the plate voltage that Iron Gertrude does, but it is quite a bit more stable and the digital readout is good for us old folks who tend to squint a lot.

I tend to think I'm going to be using this a lot.

UPDATE 2: I recently had a Blackstar HT60 in for a high volume crackling that it exhibited. The first task was to put the TAD EL34s -a/k/a gussied up Shuguang-on the Maxi Matcher and after about a minute of cooking the overcurrent LED illuminated and things shut themselves off as they are supposed to. This was a fault I could not have detected on my Hickok tube tester. A reboot confirmed this. A new set of EL34s from JJ and everything was peachy keen, no more unwanted crackling and distorting.
So score one tough fix for the Maxi Matcher that was worth it alone for what I paid for it.Colleagues have reported similar occurrences so I'm on solid ground here.

This is the second set of TAD EL34s in Blackstar amps that have failed or otherwise exhibited bad behavior recently. As of this moment they are all suspect and I'm not buying any.

Mystery Amp: The Epiphone Kent-or Maybe Asta.

Here's an interesting small amp I acquired recently and it was no stranger to me. I'd been at an auction a number of years ago and bid on it but failed to score it. So I consoled myself with a dolphin head Danelectro guitar. The amp itself showed up on craigslist on Saturday and I made my deal over the phone and picked it up yesterday. It was considerably less than it sold for at auction, plus it had been updated with a grounded power cord.

So then, the question was, what is it?

The unofficial New York Epiphone Registry thinks it is an Epiphone Asta, of which no catalog pictures exist. The amp they show on their site has four tubes-two 6V6s in series no doubt, a 6SL7 preamp, and a 5Y3 handling the rectifier chores.

I have my doubts. It looks awfully similar to the Epiphone Kent shown above from the 1950 Electar catalog, pictured in Epiphone: The House of Stathopoulo  by Fisch and Fred from 1996. This is described as a three tube amp developing 6-1/2 w and a single volume control.

The serial number on this amp is 2136. It's covered in tweed and has a 10 inch Rola PM speaker with a production date of 1949. It also carries a Freed power transformer which suggests that it was made in the New York area.

The extra large sized mud dauber nest is an extra cost option.

Nat Daniel made amps post war for Epiphone but according to him he and Epiphone had parted ways by 1946.

I would respectfully suggest that that is inaccurate, because the redesigned Epiphone amps in the 1955 catalog are quite similar in the panel control placement  and graphics to contemporary Danelectro amps including the placement of the pilot light . Nat Daniel was also known for using Freed transformers.

There is a legend on the later amps that says "distributed by Continental Music Champaign, IL-San Francisco CA-Atlanta GA". In further research, Billboard's list of exhibitors at the NAMM convention for 1951 in Chicago shows Continental Music, a division of C.G. Conn four doors down from Danelectro.

Fisch and Fred go into some detail concerning the relationship between Continental Music and Epiphone. which began in 1952 and continued to the end of the line.

I've yet to examine one of the middle fifties Epiphone amps closely, but I suspect not too many were sold because The House of Stathopoulo indicates that by 1957 Epiphone had become moribund and was acquired by Gibson.

If you have a schematic for an Epiphone Kent you can send it right along.

Debugging The Channel Switching On A Hot Rod Deville

(Note: This probably applies to any other amp in this series that uses a similar switching arrangement-Ed.)
(Note: The numbers refer to the Hot Rod Deville schematic, Fender dwg no. 050384 rev, B)

I've had a Hot Rod Deville here for a while as I was trying to sort out a number of problems. The customer complaint was that it had a sort of a crackle as certain notes trailed away. I concluded that it was one of the usual problems that these amps are prone to-bad solder joints on the tube board where the phase inverter resistors are located, a bad R97 resistor (these get hot), or a problem in the +/-16v supply for the solid state devices  that this amp has some of. Also on the list of possibilities were the usual bad solder joints, dodgy filter capacitors and so on.

After some initial testing I discovered that although the bias supply was appropriate for the pair of power tubes this amp had on board, the bias voltage could not be adjusted. That led to  having to remove the main board again, installing a new 25k bias potentiometer (R82) and ultimately replacing the tube board with another.

Great. That problem was cured and it was only then that I found that the channel switching had  disappeared down a rat hole. Since the owner does not use the dirty channel he'd probably never noticed it, all of which led to me dreaming up an amp checkin and evaluation form  so as to evaluate any and all systems on board before disassembly.

The problem manifested itself as the relays started chattering and a lot of noise was being injected into the signal. The system was unusable. Also the dual LED would not light red as it's supposed to when "more drive" is engaged.

After I'd replaced a bunch of small zeners and diodes with no luck I got suspicious of U3, which is a BA4560 dual op amp.  I installed a socket (good thing when removing ICs) and plugged in a 4558 op amp which is said to be equivalent. It quieted the relays but I still did not have the 'more drive' function (which is a couple of FETs).

So back to the drawing board and I ordered all the small parts I didn't have including some real BA4560s. They arrived today and plugging in a genuine BA4560 cured the problem. I think I'm home free on this one.

Points of information. I'd been informed by someone else that had this same problem that installing  a pair of new diodes D26 and D28 cured the problem for him, but the entire episode leads me to believe that if any of the small solid state components in the switching system fails you're likely to run into the same problem.

Best guess? They're cheap, so take the schematic and buy a few of everything you will need to 'cut and paste' your way through this problem.

And beware of "equivalent part numbers."

In the schematic I've marked out the different areas of the switching circuit. 1 is the +16/-16v power supply, 2 is the the switching circuitry including U3, 3 is the 820 ohm 2w resistor R97 and 4 is the more drive FETs.