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A client brought a small truck load of amps to me a couple days ago, from their large rehearsal hall. As an afterthought, they unloaded an heavy boxy amp that I assumed was a 70s or 80s solid-state amp, weighing about 60-80lbs, 19" rack mount. They said I probably would not want to work on an old Soviet era amp. They were right, I had learned my lesson on taking in solid state gear made in the period.
They said if it was not interesting to me, I could just keep it for parts. After everything else was repaired, I decided to peek inside . I was surprised it was a tube 2 channel power amp with 8 6П45С power tetrodes with plate caps and a big box fan. I had never seen one before, MAKO brand. I have a big box full of new 6П45с tubes but never played with them. They look beefy inside so I looked them up and found their max rated plate voltage is 800 but home builders are claiming a pair generates 200 watts. Each of the 8 output tubes heaters pulls 2.6amps at 6.3 volts. The official plate dissipation is only 35 watts but Soviet ear tubes have very conservative specs. The 6П3с-е that is what most 6L6's are has ratings of only 250 plate volts and they run reliably at 500.
Firing it up I can see the dozen trim pots are all out of adjustment for balance and bias even for driver stages but with a little blind tweaking and lubing the fan, it is putting 194 watts on 1 channel and 203 on the other with 4, or 8 ohm switch selected output Z. Each amp channel as its own standby switch. The darn thing works, all the tubes are fine. Not sure what I am going to do with it but a preamp ahead of it and it would make a great 400 watt total, stereo guitar amp.
An interesting note is they have somewhat cruse mu-metal shields over both output transformers. That stuff is too expensive to put into hi-fi or pro audio gear nowadays.
They said if it was not interesting to me, I could just keep it for parts. After everything else was repaired, I decided to peek inside . I was surprised it was a tube 2 channel power amp with 8 6П45С power tetrodes with plate caps and a big box fan. I had never seen one before, MAKO brand. I have a big box full of new 6П45с tubes but never played with them. They look beefy inside so I looked them up and found their max rated plate voltage is 800 but home builders are claiming a pair generates 200 watts. Each of the 8 output tubes heaters pulls 2.6amps at 6.3 volts. The official plate dissipation is only 35 watts but Soviet ear tubes have very conservative specs. The 6П3с-е that is what most 6L6's are has ratings of only 250 plate volts and they run reliably at 500.
Firing it up I can see the dozen trim pots are all out of adjustment for balance and bias even for driver stages but with a little blind tweaking and lubing the fan, it is putting 194 watts on 1 channel and 203 on the other with 4, or 8 ohm switch selected output Z. Each amp channel as its own standby switch. The darn thing works, all the tubes are fine. Not sure what I am going to do with it but a preamp ahead of it and it would make a great 400 watt total, stereo guitar amp.
An interesting note is they have somewhat cruse mu-metal shields over both output transformers. That stuff is too expensive to put into hi-fi or pro audio gear nowadays.
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