Lelle
Active Member
For a couple weeks ago, I bought a preowned Yamaha Natural Stereo Receiver CR-2040. The problem with it from the beginning was a RFI noise, regardless of input and volume it was still there. And wasn't affected by the volume, it was even heard from the pre-out. I have totally recapped the power supply, the pre-amp, pre-drives and the power-amps. And partially recapped the tuner, but the noise was still there. And the tuner dial was often pointing at around 100+. And when I turn up the volume a bit, the right vu-meter points at max in a very short while. I even replaced the little 100uF cap between the huge filter caps. I have totally resoldered everything in the receiver. So that wasn't the problem.
And now to the sad part, while I was measuring the -60 volts on the left amp, I accidentally shorted that pin with the "0" pin right beside on the left main board. (power amp) I powered off the receiver immediately. I know that both left and right amps is sharing the same voltages.
I found out that these transistors where shorted: TR902, TR903 and a small transistor that was placed on a little circuitboard beside the two huge caps. I replaced these three transistors with ones of the same kind. But the protection relay won't click. I can see that the "0" pins on both channels are connected to the relay. I also replaced the TR904 and TR905 without any luck. The fuses are ok, so are all the resistors, diodes and the rest of the transistors aswell. I don't have any oscilloscope, only a DMM. I'm experienced in electronics, and I'm good at soldering.
petehall347 gave me the idea to post this in the Yamaha section instead of the "Vintage Solid State" section. To hopefully get more help and answers to my problem with my Yamaha receiver.
But now i'm out of ideas. And need some advice of what I can do next. I have done anything I could think of.
I have the schematics. (PDF) the parts list is missing.
This receiver is beautiful, and it is worth fixing.
The RFI noise before the accident https://www.youtube.com/watch?v=kNRD...k&feature=plcp
I've measured the voltages on TR902 to TR907, and I got the following numbers:
TR902
Emitter: 87,3
Collector: 7,7 (15 volts when turning of the receiver, before it drops to zero)
Base: 87,2
TR903
Emitter: -82,4
Collector: -83,0
Base: -83,4
TR904
Emitter: -6,0
Base: 7,3
Collector: 87,6
TR905
Emitter: -82,8
Collector: -83,6
Base: -82,8
TR906
Emitter: -9,8
Collector: 8,1
Base: 0,3
TR907
Emitter: -6,0
Collector: -71,0
Base: -6,1
Many of these voltages seems to be incorrect according to the schematic.
And now to the sad part, while I was measuring the -60 volts on the left amp, I accidentally shorted that pin with the "0" pin right beside on the left main board. (power amp) I powered off the receiver immediately. I know that both left and right amps is sharing the same voltages.
I found out that these transistors where shorted: TR902, TR903 and a small transistor that was placed on a little circuitboard beside the two huge caps. I replaced these three transistors with ones of the same kind. But the protection relay won't click. I can see that the "0" pins on both channels are connected to the relay. I also replaced the TR904 and TR905 without any luck. The fuses are ok, so are all the resistors, diodes and the rest of the transistors aswell. I don't have any oscilloscope, only a DMM. I'm experienced in electronics, and I'm good at soldering.
petehall347 gave me the idea to post this in the Yamaha section instead of the "Vintage Solid State" section. To hopefully get more help and answers to my problem with my Yamaha receiver.
But now i'm out of ideas. And need some advice of what I can do next. I have done anything I could think of.
I have the schematics. (PDF) the parts list is missing.
This receiver is beautiful, and it is worth fixing.
The RFI noise before the accident https://www.youtube.com/watch?v=kNRD...k&feature=plcp
I've measured the voltages on TR902 to TR907, and I got the following numbers:
TR902
Emitter: 87,3
Collector: 7,7 (15 volts when turning of the receiver, before it drops to zero)
Base: 87,2
TR903
Emitter: -82,4
Collector: -83,0
Base: -83,4
TR904
Emitter: -6,0
Base: 7,3
Collector: 87,6
TR905
Emitter: -82,8
Collector: -83,6
Base: -82,8
TR906
Emitter: -9,8
Collector: 8,1
Base: 0,3
TR907
Emitter: -6,0
Collector: -71,0
Base: -6,1
Many of these voltages seems to be incorrect according to the schematic.
Last edited: