Who in (Germany?) made these? Valve rack units, small power amps and a mystery box

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Disco Volante

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Jun 20, 2021
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Southern Denmark, Fyn
Just got these for a bargain. Bought them for the OPTs, for a small PP power amp project (winter is approaching;-).
BUT they're apparently very good quality, all good German parts and outstanding build quality. So maybe they wouldn't need to be cannibalized...

It's two channels of a fairly straightforward PP pentode output stage, one PSU, with two germanium diode bridges and what looks like a valve regulator circuit?
Valves are EL95, E80CF in the amp section, ECC83 and E130L plus one I can't read in the PSU. Siemens and philips "SQ" tubes all over.
Unfortunately, the big pentode didn't survive shipping, so no testing. Not tonight, at least.
No clue what the third type module is. No manufacturer branding anywhere.

Maybe some of you experienced gents have met these units before?
Cheers, Viggo
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Beautiful, can you show some close ups of the transformer? Any logos or brand names visible there? BV numbers?

These OTs for the pair of EL95 (max. 7 Watt PP) are really huge! 100V ELA technic? This set was not cheap in the early 60ies.
 
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abbey road d enfer said:
You mean the AV118's? I don't see how it could be a push-pull stage, with only one bottle, unless it's an ECLL800, which I seriously doubt.
Could it be a SE stage with an ECL8x?
Click to expand...
We need better photos, but I see two or three tubes on the AV118 unit. On the other Hand, SE operation would explain the big OT.
20220913_074941.jpg
 
My guess is these came out of a tube tape machine , The E130L is a powerful regulator tube , its also used in the Studer C37 .
 
Sorry for the unclear pics. There is two EL95's hidden behind the, yes, enormous OPT. My Quad II has smaller OPTs...
So about 7W PP, according to the EL95 datasheet.
The phase inverter is a E80CF.
The OPTs are marked with what seems to be the number of turns and wire gauge.
On the PT, the word "Schirmwickl." (=shielding coil, I believe) is visible and the volts and amps are stated.
More pics coming up...
 
Actually, the old tape recorder lead would maybe explain the weird third type of module. There are a number of trimmers and some low-noise valves. 3x E88CC, E80CF, ECC83 and another 85A2.
Still find it puzzling how little markings there are.
 
Disco Volante said:
The OPTs are marked with what seems to be the number of turns and wire gauge.
Click to expand...
Not necessarily. Many old schoold engineers used lower-case omega for Ohm. *
Since this character is not commonly available on typewriters and linotypes, the letter "w" was used as a replacement.
3700 turns would result in very large nominal impedance.

* Strangely, they would use lower-case for high values and upper-case for low values. So the cathode resistor used Ω and the anode or grid resistor ω :unsure:

Disco Volante said:
On the PT, the word "Schirmwickl." (=shielding coil, I believe) is visible and the volts and amps are stated.
Click to expand...
That may indicate that it's not destined to drive a typical low-Z load. Shields are almost never seen on loudspeaker output xfmrs.
Maybe some kind of distribution amplifier or a modulator...?
The two 3700w windings may well be the two sections of the CT primary. The two others may probably go to the connector.
 
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abbey road d enfer said:
Not necessarily. Many old schoold engineers used lower-case omega for Ohm. Since this character is not commonly available on typewriters and linotypes, the letter "w" was used as a replacement.
3700 turns would result in very large nominal impedance.
Click to expand...
Possible, but the CuL stands for Cupferlackdraht (old speeling for copper enamelled wire), so I think the W is a number of turns. The diameter of the enameled copper wire is also given, which is indicative of this.
 
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Thanks, the OPT is making more sense now.
The two 1050 ohm secondaries are parallelled at the transformer and bypassed by the 2K2 and 22nF visible on the picture before going to the connector.

It's the Power Transformer that has the "Schirmwicklung"...
 
Disco Volante said:
Actually, the old tape recorder lead would maybe explain the weird third type of module. There are a number of trimmers and some low-noise valves. 3x E88CC, E80CF, ECC83 and another 85A2.
Still find it puzzling how little markings there are.
Click to expand...
For me, the absence of manufacturer branding is an indication that this device was built in an in-house department of a large company. This was not intended for external use or sale, hence the winding instructions on the OPT. Apparently money didn't play the biggest role either, which also points to an inhouse use far from the market.

Abbey is right, that device can be just about anything. Is it apparent anywhere that the OPT should work in 4-16 ohms? It could also be a 100V amplifier, but the unit is a bit too opulent for that. Regulated power supply, component quality and construction are already upper class. But maybe it's something completely different...
 
Since I'm not planning on ever owning or making any 200 ohm speakers, I might as well learn how to rewind the transformers. Also, I'd like some UL taps in the primary and some impedance options on the secondary. This was intended as a low-power amp for testing some high-efficiency speakers...

Anyway, started taking them apart. Interesting lams, they look like EI, but they're only split inside, and wedged together with a piece of Pertinax.

Would it hurt the magnetic properties if I clean off the rust with a stainless wire brush? Don't want to glass-blast them because of the possible warpage...

Thanks

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