Interesting Russian amp

[MarkusBass]

I've got interesting Russian amp to be fixed. It's a combo about 50-80W, abot 20 years old. The power amp is build like a tank. Also the preamp looks interesting.
Take a look:



I'm not going to ask whether anyone has a schematic for this amp

Mark

[Jazz P Bass]

Thanks for sharing this, Markus.

[Gtr_tech]

Where's the pwr transformer?

[MarkusBass]

In the enclosure below the power amp board - perfectly shielded.

[km6xz]

I see a lot of different amps from the 80s and early 90s, not too many from the 70s however. I have not seen this one but generally they came in two general types: Really over built and way underbuilt junk. Nice lacing. All those semiconductors are still available here and are really cheap compared to the imports. I see a lot of units with high voltage Teflon dielectric capacitors that perform beautifully in higher end of the voltage spectrum tube circuits. One came to me, running a pair of 6п3с-е with only 300 volts on the plates but all the caps were 1500 rating. The transformer had a lot of iron in it for a 25 watt amp.
Is there a name on it anywhere? I can probably find a print for it.
By the way, the markings on the preamp are НЧ СЧ ВЧ are LF, MF and HF respectively.
Most people assume that Russian or Soviet technology was way behind but in many areas such as ultra high voltage they were quite ahead of the rest of the world. They had a well developed semiconductor industry and even microprocessors from early on. The heavy industrial and military gear is very sophisticated but the consumer radios, hi-fi and tvs were pretty crude. It was like an alternative universe people in the west did not know really existed. Many cities have permanent outdoor Radio flea markets so builders and experimenters can exchange, buy, sell or just talk about parts.

[MarkusBass]

I see a lot of different amps from the 80s and early 90s, not too many from the 70s however.

This one is from early 90s. Most probably 50W with three universal inputs. Quite heavy.

I have not seen this one but generally they came in two general types: Really over built and way underbuilt junk.

This one is rather of the first type you mention - build in some former military factory.

Is there a name on it anywhere? I can probably find a print for it.

Yes, the name is VENTA UAU 001 (see attachments). I'll check the opamps symbols and ask you whether they are still available.

By the way, the markings on the preamp are НЧ СЧ ВЧ are LF, MF and HF respectively.

I know - I can read and speak Russian.

Most people assume that Russian or Soviet technology was way behind but in many areas such as ultra high voltage they were quite ahead of the rest of the world.

I've seen some very advanced microwave Russian equipment from the 50s. Also analog computer used for military purposes.


Mark

[Prairie Dawg]

Nice lacing of the wire bundles-that's aerospace for sure.

[jmaf]

The speaker says 1990-07(July or 7th week of 1990?) on the label, but it could've been replaced. The 47K potentiometers here look built as a tank: http://music-electronics-forum.com/a...779741-pre.jpg

Awesome stuff, thanks for sharing.

[Steve Conner]

Ah, those are 47k pots, I thought they were Russian military grade op-amps.

Most people assume that Russian or Soviet technology was way behind but in many areas such as ultra high voltage they were quite ahead of the rest of the world.

I'm also involved with another forum for hobby electronics, and there are lots of members from Russia, Poland, Czech Republic, Finland and so on, all building cool projects. They obviously got a good technical education somewhere and lots of surplus Soviet military junk to play with, maybe from those flea markets Stan was talking about.

Here's a particularly scary one, a Tesla coil powered by a GMI-38 radar modulator tube, a Winged-C one no less.

4hv.org: Forums / Tesla Coils / Big Pulsed Vacuum Tube Tesla Coil GMI-38

I heard Russian TVs came supplied with a fire extinguisher.

[Gtr_tech]

There's some interesting Russian analog synths from the 80s as well.
Russian synth's

[MarkusBass]

The speaker has release date 1990-07 60W. Integrated circuits are: UD1A A6 - seems to be single operational amp.



Mark

[jmaf]

Ah, those are 47k pots, I thought they were Russian military grade op-amps.

I saw the lugs before I saw the caps, or I'd surely have confused them for something else

[km6xz]

I do not know what that part is because only part of the number is showing. It could be a version of the КР574УД1А which is a common single channel jFET low noise opamp of the era. It is available here but is similar to the AD513 in the west. A lot of the opamps made here had max rails of 10v but that one is 15v so it would be a good candidate. Any general purpose jFET input opamp would probably work well.
That one is entirely FET topography, not just the input.

[MarkusBass]

Thanks everyone for help (especially to km6xz). Unfortunately the owner of the amp decided not to fix the amp because he can buy a chinesse amp for similar amount of money (~$100). It's a pitty because the amp didn't seem difficult to be fixed. And it looked like fancy "military" version - most probably could be use for many years more after being fixed.

Mark