Carver PM-100 Schematics

N-Channel · 19th July 2003, 04:10 PM

Help!

I'm working on a friend's Carver PM-100 Plate Amp, and can not find any (free) shcematics on the web.

The problem is that there is +12V of offset on the outouts, and I've replaced all the output transistors, but no change. Tried disconnecting both secondaries (+/- high Vac & +/- low Vac), but transformer sti8ll hums LOUD, like it's shorted. +/- measured DC Voltages are +54V and -6V. History is that this amp ran a set of outdoor spkrs, and the spkrs shorted, drastically raising the load on the amp.

Outputs WERE Toshiba 2SA1302 & 2SC3281 pair. Since I had a few rails of Motorola & On Semi MJL1302A & MJL3281As laying around, I upgraded to these instead. (I kept the older Motorola-labeled units for myself & gave him the newer On semi units!

)

Any help here would be appreciated. Thanks!!

'73,

N8XO

moamps · 19th July 2003, 06:38 PM

Hi,

Check driver transistors, high power resistors, PCB, bridges. Repair one channel first. In second channel temporally disconnect (desolder ) drivers and output transistors. (or remove fuses). Check quiescent current true output transistors. If rails are unsymmetrical, then your PS is overloaded.(hum).

Regards

N-Channel · 19th July 2003, 11:09 PM

Thanks for the help. I don't know if I forgot to mention that I don't have a schematic. Kinda makes things a little tougher. Muchas Gracias!

73 N8XO

N-Channel · 19th July 2003, 11:11 PM

also forgot- both channels on same pc board and share same power supplu traces. For an early Carver product (that's before he sold the company and later bought it back), this is not a very robust design.

Undertaker · 20th July 2003, 06:47 PM

Pleas send me schematic for Carver PM-100 if you find...
I need too, and if i find i will send to you!!!

stormcom@ptt.yu

oldmarantz · 21st July 2003, 03:50 PM

I don t know the schem of your amp but I will take a look to the differential amp stage...or perhaps you ve got a ground problem how are the solder?

Dom.

19th July 2003, 04:10 PM	#1
N-Channel diyAudio Member Join Date: Mar 2003 Location: Sol System	Carver PM-100 Schematics Help! I'm working on a friend's Carver PM-100 Plate Amp, and can not find any (free) shcematics on the web. The problem is that there is +12V of offset on the outouts, and I've replaced all the output transistors, but no change. Tried disconnecting both secondaries (+/- high Vac & +/- low Vac), but transformer sti8ll hums LOUD, like it's shorted. +/- measured DC Voltages are +54V and -6V. History is that this amp ran a set of outdoor spkrs, and the spkrs shorted, drastically raising the load on the amp. Outputs WERE Toshiba 2SA1302 & 2SC3281 pair. Since I had a few rails of Motorola & On Semi MJL1302A & MJL3281As laying around, I upgraded to these instead. (I kept the older Motorola-labeled units for myself & gave him the newer On semi units! ) Any help here would be appreciated. Thanks!! '73, N8XO __________________ -. ---.. -..- ---

19th July 2003, 11:09 PM	#3
N-Channel diyAudio Member Join Date: Mar 2003 Location: Sol System	PM-100 Thanks for the help. I don't know if I forgot to mention that I don't have a schematic. Kinda makes things a little tougher. Muchas Gracias! 73 N8XO __________________ -. ---.. -..- ---

19th July 2003, 11:11 PM	#4
N-Channel diyAudio Member Join Date: Mar 2003 Location: Sol System	also forgot- both channels on same pc board and share same power supplu traces. For an early Carver product (that's before he sold the company and later bought it back), this is not a very robust design. __________________ -. ---.. -..- ---

20th July 2003, 06:47 PM	#5
Undertaker diyAudio Member Join Date: Jul 2003 Location: Jupiter	Pleas send me schematic for Carver PM-100 Pleas send me schematic for Carver PM-100 if you find... I need too, and if i find i will send to you!!! stormcom@ptt.yu

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19th July 2003, 06:38 PM	#2
moamps diyAudio Member Join Date: Oct 2002 Location: Croatia	Hi, Check driver transistors, high power resistors, PCB, bridges. Repair one channel first. In second channel temporally disconnect (desolder ) drivers and output transistors. (or remove fuses). Check quiescent current true output transistors. If rails are unsymmetrical, then your PS is overloaded.(hum). Regards

21st July 2003, 03:50 PM	#6
oldmarantz diyAudio Member Join Date: Dec 2002 Location: France - Lyon	I don t know the schem of your amp but I will take a look to the differential amp stage...or perhaps you ve got a ground problem how are the solder? Dom.

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