Hello everyone.
I am repairing a Punch P3001 board number PC-4714-B.
It had 47.5 VDC on the output terminals. I found Q120 and Q123 output fets shorted. I clipped them from the circuit and DC is gone.
Question I know if I replace the 2 FQA28N15 output fets the amp will work. Should I replace the corresponding FQA36P15 output fets ( Q118 and Q122 ) as well? Since this is a mono amp will it be reliable only replacing the 2 or should I replace all 4?
I am repairing a Punch P3001 board number PC-4714-B.
It had 47.5 VDC on the output terminals. I found Q120 and Q123 output fets shorted. I clipped them from the circuit and DC is gone.
Question I know if I replace the 2 FQA28N15 output fets the amp will work. Should I replace the corresponding FQA36P15 output fets ( Q118 and Q122 ) as well? Since this is a mono amp will it be reliable only replacing the 2 or should I replace all 4?
Are you sure that both failed?
If so, it would seem like there is damage to the protection circuit and possibly to the 0.1 ohm source resistors.
I'd suggest replacing the 36Ps also.
If so, it would seem like there is damage to the protection circuit and possibly to the 0.1 ohm source resistors.
I'd suggest replacing the 36Ps also.
OK I have 60 of the 28N's on order. I have the 36P's in stock. When I get them I will install them and give you an update. I thought it was strange that only the 28N's shorted and the 36P's didnt.
The source resistors metered ok, I have not tested anything in the protection circuit. I soldered 2 used 28N's to the board for testing purposes but didnt solder them to the mesha.
There was no DC and the amp produced audio. One tested good out of circuit but I think one was leaky but it still worked for testing purposes.
The source resistors metered ok, I have not tested anything in the protection circuit. I soldered 2 used 28N's to the board for testing purposes but didnt solder them to the mesha.
There was no DC and the amp produced audio. One tested good out of circuit but I think one was leaky but it still worked for testing purposes.
I think Perry was saying if both 28's were bad then look into the protection. The protection circuit should shut it down if one fails shorted and possibly save the second one. Either way both 28's should be replaced.
With that era of RF amp I haven't seen to many with both the high side and low side fets fail.
With that era of RF amp I haven't seen to many with both the high side and low side fets fail.
- Status
- Not open for further replies.