Any info/knowledge about this unique german tube guitar amp?

[devilsindetails]

This is getting cooler by the minute! As you've likely figured out, "vibrator" is tremolo, not reverb, and it looks like it was an option since it was built in its own box and added in the right chassis cutout. You can trace what part of the preamp circuit it was designed to modulate. Unfortunately the "connection point for tremolo" is obscured by the goop in Tony's found schematic. That schematic, though, may be close. You have a mic input, so that probably goes to the EF804, the trem likely modulates the ECC83 instrument preamp. Could they have used the EM85 as just a power indicator, or does it do something cooler?

Yes, it's a trem-like circuit...I'll be doing some tracing over the next few days to find out what's what.

My guess on the EM85 is that it's a power indicator...which seems kind of a waste of the tube's capability as a vu or signal indicator...but seeing as the indicator is at the back of the amp it's probably nothing more than just that.

[overtone]

Ahoy Leon,

I had time today to drop by at K.A. Schmitt.
(There is an excellent Italian Mom+Pop Grocery around the corner )

At the counter was very old chap who said your amp would have been made there around the time he started in 1955.
He thought the cabinet may have been refinished and the grille cloth changed.
He also said that there were several Jubilar tube amp models right up into the 1970s, mostly aimed at accordion players.
He was still proud about the speakers, it seems to have been one of their selling points.

I asked about schematics and he said all the old documentation got thrown out when they moved shop around 1957.
But he said "any good tech should be able to fix it, if it is of importance to anyone."

We went on to talk about the amazing last series of tubes that TFK were turning out, like the EL503 or EL156.
That sent him off into another place for a while.
Then we went onto guitar amps in general and he complained that kids keep on brining him these awful Marshalls to repair.
Fender he said was the ultimate, maybe Vox after that.
I asked his opinion of Hohner who had a 60W EL503 AC30/Twin monster and he just said "Nein, nein. Fender, Fender, Fender."

So there you go, no new leads really but I got some very good Coppa di Parma.

Have a good weekend,
Tony

[devilsindetails]

Wow! Thanks for that Tony...although I must admit I am surprised by the owner's lackadaisical response. As my 77-year-old uncle, a machinist trained in Germany said on reading this post, "Er hat keinen Stolz in seinem Handel" (He has no pride in his trade).

While Leo Fender developed lovely sounding guitars and amps he employed a number of less than sterling manufacturing techniques and shortcuts that our German friend surely couldn't (or shouldn't) be envious of. Perhaps he was referring to the "Fender" sound.

In any event, sounds like you had an interesting visit...thanks once again for your efforts on my behalf...I'll sort this beast out somehow...

[overtone]

My pleasure.
He was referring to the sound of Fender, not any manufacturing principles.
The shop does not seem to have manufactured anything since the mid seventies. The focus is on servicing and that, as a trade, has dwindled rapidly over the last years.

I understand what your uncle was reading into it. But he was fully aware that there is no economic sense in repairing these old treasures. With no schematics left, there was not really much he could help us with!

He gets people coming in with really old equipment quite a lot, but the cost of putting it right mostly outweighs the value. That was the point he was trying to make about if the amp "is of importance" - like an heirloom or was used by a well known musician. Maybe I translated it badly, German is not my mother tongue.

Have you checked out that OT. Will it pass AC?

Best, tony

[devilsindetails]

Hi again Tony....well the fact they (K.A. Schmitt) disposed of their old schematics rather than retain them seems a questionable practice for anyone still in the business of servicing IMO.

Sounds like the business has probably worn him down and sounds too much like the stereotypical "North American" business practice of; out with the old and in with the new.

The more I look at this amp the more I am starting to believe it was for vocal and instruments like accordions etc, although use as a guitar amplifier--albeit with a uniquely Euro approach--is not out of the question.

I am still sorting through this puppy but will advise regarding my voltage tests on the OT....and other findings.

Leon

[devilsindetails]

Well slow progress on this amp ( and others ) seems every time I start troubleshooting in walks something more pressing.

But I have managed to discover that their is a very very low audio hum coming out the speakers. However nothing I plug in or no matter what pot I adjust the level of hum remains constant.

I will be checking voltages shortly and see if that tells me anything. All the tubes are lighting up and I can't see any evidence of thermal failure...or any unaccounted loose ends etc.

[ampmike]

Cool amp and backstory,Hope you can get that guy up and running,thanks mikey

[VacuumVoodoo]

But I have managed to discover that their is a very very low audio hum coming out the speakers. However nothing I plug in or no matter what pot I adjust the level of hum remains constant.

This is most probably caused by PT and OT mounted in line. If it's annoying you can try to turn the OT 45-90 degrees.
Or place a piece of iron sheet vertically to the left of OT. Should be taller and wider than OT.

[Masco]

Some experts here in Germany are very rude about those early brown Wimas, but I have never tested them myself. The other light colored caps are Hydra Werk which was in Berlin.


best, tony

Rude about the brown Wima's??? Those caps are notorious for failing, is that what you mean?

[ampdoc1]

This whole episode reminded me of the of old saw:

The best combination is British humor, French cooking and German engineering. The worst is British cooking, French engineering, and German humor.

[devilsindetails]

Well I promised to keep you posted on the progress of this strange amplifier.

As you may recall everything powered up but no signal output on any of the 4 input pots....

Checked the continuity for opens on the OT and it checked out fine.

Replaced all the Wima Mica Caps with Sprague Orange Drops or ceramic caps, replaced electrolytics and replaced all out of spec resistors and tried again.

Voila! It came to life...

I have to say it sounds.....underwhelming to say the least. The amp really is nothing more than a 4 input general purpose PA amp IMO...3 inputs for instruments and one dedicated to a microphone which likely explains the presence of the EF804 Tube in this circuit.

The "Vibrator" section doesn't work at all even after a recap...the mystery tube that I was never able to identify the tube in this stage as all the marking have been rubbed off and no one here could eye-ball it's identity. It may be defective (although the heater filament is live) and without knowing what it is I can't test or substitute either.
My guess is this is something akin to a tremo/vibrato circuit rather than a reverb section. (After all, without a tank that would be impossible...right?)

I am satisfied I could resurrect this strange beast for the owner who seems quite happy with it...but I do wish I could have figured out that strange "Vibrator" section.....would have loved to hear the German take on tremolo/vibratone tone.

PS: The EM85 Tube acts as both a power on indicator and a crude VU meter when the inputs are engaged. Cool looking, but that's about the extent of its utility

Thanks for all your interest and input everyone. Regards. Leon