Hello, my amplifier right channel stopped working. I decided to fix it myself, I don't know if this will be possible, but I want to try it. If someone is willing to help me I will be very grateful.
I got the service manual, and I checked the power amplifier components. Result: Two transistors shorted (Q715, 2SC3284 and Q716, 2SA1303), 4 bad resistors (R735, R737 R738, 68 Ohm, and R741, 0.22Ohm x 2, this adjust the bias).
I have the amplifier with the good channel mounted and I have measured the voltage at the inputs of the bad channel (I use a protection bulb(60W)) . And these were the results:
-J702( +43v, -43v, Out R)-----+36v, -36v
-J703( J703 (PROT, GND, +60v, -60v)_____+36v, -36v
Why does such low values?, according to the diagram should be: +43v, -43v, +60v, -60v. Before ordering components I would like to know if I should change more parts. I must check if there is a short somewhere else.
I'm doing things right?, what parts should I continue checking?. I have basic knowledge, but I want to try it. Very grateful, thank you.(sorry for my English)
I got the service manual, and I checked the power amplifier components. Result: Two transistors shorted (Q715, 2SC3284 and Q716, 2SA1303), 4 bad resistors (R735, R737 R738, 68 Ohm, and R741, 0.22Ohm x 2, this adjust the bias).
I have the amplifier with the good channel mounted and I have measured the voltage at the inputs of the bad channel (I use a protection bulb(60W)) . And these were the results:
-J702( +43v, -43v, Out R)-----+36v, -36v
-J703( J703 (PROT, GND, +60v, -60v)_____+36v, -36v
Why does such low values?, according to the diagram should be: +43v, -43v, +60v, -60v. Before ordering components I would like to know if I should change more parts. I must check if there is a short somewhere else.
I'm doing things right?, what parts should I continue checking?. I have basic knowledge, but I want to try it. Very grateful, thank you.(sorry for my English)
I have measured the voltage at the inputs of the bad channel (I use a protection
bulb(60W)) .Why does such low values?
The bulb tester could be causing the low readings.
So, do I do the tests now without the bulb?
There's always some risk in any repair, but if you have checked all the parts for defects,
that's probably the next thing, maybe using a fast blow, smaller line fuse than normal,
and a fused Variac if you have one. Do the capacitors all look ok?
Last edited:
If the input voltage to the power stage measures well, can we think that the problem is in the power stage?
Could you post the power supply schematic?
I have removed the bulb, the readings are: + 45v, -45v. They are correct?.
That seems ok.
I lit with the bulb, the bulb goes off and the relay jumps. But there is a problem,
the bias is 0Mv. I upload the variable resistance and it does not move from 0Mv.
The dual 0.1 ohm emitter resistor unit could be open circuit. See if there is continuity
in both halves. This is either part # R641 or R741.
Checked, it's correct, there's continuity in R741.
Both halves measure 0.1 ohm? Also do you measure 0.2 ohm total between the two outside terminals?
If so, then there may be a problem in the bias or driver circuit. Did you test the other semiconductors?
Yes, , I have measured the two terminals
Ok, then test and replace semiconductors where necessary, avoiding ebay.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
- Home
- Amplifiers
- Solid State
- Marantz PM17 Repair