| N-Channel |
Help! :eek:
I'm working on a friend's Carver PM-100 Plate Amp, and can not find any (free) shcematics on the web. :bawling: 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! :D)
Any help here would be appreciated. Thanks!! :D
'73,
N8XO |
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| moamps |
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 |
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| N-Channel |
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 |
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| N-Channel |
| 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. |
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| Undertaker |
:( Pleas send me schematic for Carver PM-100 if you find...
I need too, and if i find i will send to you!!!:nod:
stormcom@ptt.yu |
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| oldmarantz |
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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