Boltar VIII
Q302, Q306 we used 2SA935, now replaced with KTA1023
Q304, Q308 we used 2SC2061, now replaced with KTC1027
Q301, Q305 we used 2SC2389 now replaced with KTC3198
I see that the audio drive boards are missing Do you have them?
Who removed all these parts? I see no power transistors either.
The driver transistors next to the banks of output devices can be replaced with MJE15030 and MJE15031.
I guess the value of the rail voltage at this point does not matter.
Are the MOSFETs missing, are the vari-power pass devices missing?
The Pyramid 40 amp power supply it woefully inadequate to power this amplifier to any reasonable power output.
There are quite a few updates I perform on these amplifiers when I restore/repair them.
Steve Mantz
Zed Audio Corp.
Q302, Q306 we used 2SA935, now replaced with KTA1023
Q304, Q308 we used 2SC2061, now replaced with KTC1027
Q301, Q305 we used 2SC2389 now replaced with KTC3198
I see that the audio drive boards are missing Do you have them?
Who removed all these parts? I see no power transistors either.
The driver transistors next to the banks of output devices can be replaced with MJE15030 and MJE15031.
I guess the value of the rail voltage at this point does not matter.
Are the MOSFETs missing, are the vari-power pass devices missing?
The Pyramid 40 amp power supply it woefully inadequate to power this amplifier to any reasonable power output.
There are quite a few updates I perform on these amplifiers when I restore/repair them.
Steve Mantz
Zed Audio Corp.
Thanks for the reply greatly appreciated .
The vari power parts are still on the board .
I have the boards for the amp .
The missing transistors ect were taken off the board by someone that’s how I bought the amp . I bought it for $20 trying to bring it back to life .
Mr Mantz do you happen to know where these 2 wires solder to ? They come of a resistor network .
The vari power parts are still on the board .
I have the boards for the amp .
The missing transistors ect were taken off the board by someone that’s how I bought the amp . I bought it for $20 trying to bring it back to life .
Mr Mantz do you happen to know where these 2 wires solder to ? They come of a resistor network .
Attachments
Boltar VIII
They go to the hot pins of the RCA socket.
The transistors I mentioned are missing and they are part of the vari-power sensing circuit.
Be aware that testing this amplifier requires two scopes. One for the channels and one to see what the switching supply looks like.
One needs experience to know whether the supply is OK.
I ALWAYS power car amps up through a 2 ohm 50w resistor so that if things are bad you will not see a mushroom cloud.
This is another reason I ALWAYS have a scope on the power supply on every amp I test/repair.
I have never taken down a pwr supply MOSFET this way.
Normally on these 28 year old amps I replace the pot and clean the push switch.
The gate drive circuit for the supply's MOSFETs needs major updating as does the dead time for low current turn on.
Note that Boltar used high current Darlington pass deives in the vari-power circuit being SGSD100 and SGSD200.
PS. The last person who called me "Mr. Mantz" I had to shoot him! Please call me Stephen....I did not really shoot him!!!!!!!!
They go to the hot pins of the RCA socket.
The transistors I mentioned are missing and they are part of the vari-power sensing circuit.
Be aware that testing this amplifier requires two scopes. One for the channels and one to see what the switching supply looks like.
One needs experience to know whether the supply is OK.
I ALWAYS power car amps up through a 2 ohm 50w resistor so that if things are bad you will not see a mushroom cloud.
This is another reason I ALWAYS have a scope on the power supply on every amp I test/repair.
I have never taken down a pwr supply MOSFET this way.
Normally on these 28 year old amps I replace the pot and clean the push switch.
The gate drive circuit for the supply's MOSFETs needs major updating as does the dead time for low current turn on.
Note that Boltar used high current Darlington pass deives in the vari-power circuit being SGSD100 and SGSD200.
PS. The last person who called me "Mr. Mantz" I had to shoot him! Please call me Stephen....I did not really shoot him!!!!!!!!
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