I just bought this amp and I need a schematic. Can any one help?
Vintage Silvertone Medalist Stereophonic Amplifier Model EL84 Amp 74051
Tube Layout :
- 4 tube 6BQ5 / EL84
- 2 tube 7199
- 3 tube 20EZ7
Vintage Silvertone Medalist Stereophonic Amplifier Model EL84 Amp 74051
Tube Layout :
- 4 tube 6BQ5 / EL84
- 2 tube 7199
- 3 tube 20EZ7
The 20EZ7 appears to be a series string version of the 6EU7. The triodes inside the bottles are the same as those in a 12AX7.
The 7199 has gone the way of the Dodo. No matter how you twist and turn, some re-engineering to deal with difficult (if not impossible) OEM tube types is going to be necessary. JMO, re-engineer to squeeze everything possible out of the OEM magnetics.
Please post some photos, taken at many angles, of the unit. The "pics" will provide some hints about the circuitry.
Count the number of wires on the O/P transformer primaries. Is it 3 or is it 5?
The 7199 has gone the way of the Dodo. No matter how you twist and turn, some re-engineering to deal with difficult (if not impossible) OEM tube types is going to be necessary. JMO, re-engineer to squeeze everything possible out of the OEM magnetics.
Please post some photos, taken at many angles, of the unit. The "pics" will provide some hints about the circuitry.
Count the number of wires on the O/P transformer primaries. Is it 3 or is it 5?
I don't find that model number in the Sams index, unfortunately.
DC heaters are likely for the 20EZ7s. May be common with a negative bias supply. Unlikely that they used output tubes' cathode current since they would need to drop 60V for three of them.
DC heaters are likely for the 20EZ7s. May be common with a negative bias supply. Unlikely that they used output tubes' cathode current since they would need to drop 60V for three of them.
I powered it up and one large electrolytic got hot. I sut if off and measured it and it's bad of course so I am in the process of recapping it and then I'll bring it up on a variable. I'll post a few pics soon. It's a nice looking amp rated at 17.5 wpc and it is in excellent condition and mostly complete. It has solid state rectifier I believe. Thanks for the great input. I'll post more as I dig in.
I recapped it and found a burnt resistor in the power supply section. It now powers up and plays well over one channel. Ch2 is very weak. Did the usual tube swap but no luck yet. No schematic so I'm drawing as I debug. All tubes light. Any hints would be appreciated.
I know this is an old thread.
I have a Silvertone 7407 with a similar tube compliment in the amplifier. I found several out of spec resistors on the 6bq5's that were causing the tubes on one channel to overheat (the plates were glowing red). I had to replace the 2 tubes on one channel with a matched pair from https://www.tubesandmore.com/
There were some out of spec resistors on the 12ax7 that is in mine, I replaced those. The resistors would measure fine when the amp was cold but the resistors went WAY out of spec when warmed up.
As for a schematic there should be a model number on the chassis with the format xxx.xxxxx, I may be able to help if you can provide that.
https://www.tubesandmore.com/
I have a Silvertone 7407 with a similar tube compliment in the amplifier. I found several out of spec resistors on the 6bq5's that were causing the tubes on one channel to overheat (the plates were glowing red). I had to replace the 2 tubes on one channel with a matched pair from https://www.tubesandmore.com/
There were some out of spec resistors on the 12ax7 that is in mine, I replaced those. The resistors would measure fine when the amp was cold but the resistors went WAY out of spec when warmed up.
As for a schematic there should be a model number on the chassis with the format xxx.xxxxx, I may be able to help if you can provide that.
https://www.tubesandmore.com/
Alright I've made some headway. The problem lies somewhere between the input of the amp and the input of the 7199 grids. Both channels are loud and clear when inputting a sine wave at the grids of the 7199. Service number is 132.7405101 a schematic would be awesome. Thanks for your help flinx!
Fixed it! A broken pcb trace in on the volume control. Sounds great, needs a few more caps replaced.
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