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Yamaha CR-1020 adjust idle current TP1 to TP 0 measures 0 mV on both amp boards but will not adjust

Don't sweat it.. I was going to suggest not using it. If you were.
 
I have never used the C3503. And frankly I have never had any issues with the C458 in this application. Your issue has to be something that you did to both of the amplifier boards.
 
Your going to have to reverify everything that you did to each amplifier board.Check the trimmers for serviceability and correct installation. Transistors,capacitors diodes --whatever you did identical to each board.
What resistance value are the new trimmers ? 5K or 4.7K ?
 
To replace TR611 (2SC1212B) on the amp boards I used a KSC2690A - Y.

Should I have used a KSC2690A without the ‘Y’?
Will the ‘Y’ spec cause a problem?

To replace TR612 2SA743B I used a KSA1220A - Y.

Again, should I have used a KSC2690A without the ‘Y’?
Will the ‘Y’ spec cause a problem?
 
Here are some photos of the same board from every angle.
All diodes were changed, all caps were changed, TR607 TR608 TR611 and TR612 but nothing else.
Anything look wrong?

IMG_5329 copy.jpg IMG_5330 copy.jpg IMG_5331 copy.jpg IMG_5332 copy.jpg IMG_5333 copy.jpg IMG_5334 copy.jpg
 
Hifibythekg said:
Is this trimpot ok? I see that it's 5kohms not 4.7kohms, is this a possible problem?
Click to expand...
The trimpot is ok, no problem. If you look at the track work you will see 2 of the legs connected so it's used as a simple VR rather
than a divide/balance between 2 halves.
 
Test the 2SC458's, note the Vbe, then test a sample of the KSC1815's, again note the Vbe. Problem MAY be that the 1815's Vbe
is significantly higher than the C458's, MAY need a slightly larger VR.
 
mbz said:
Test the 2SC458's, note the Vbe, then test a sample of the KSC1815's, again note the Vbe. Problem MAY be that the 1815's Vbe
is significantly higher than the C458's, MAY need a slightly larger VR.
Click to expand...
Problem may be with TR607, measure Vbe of sample KSA1015's and compare with 2SA844 oem.

Measure dc voltage (mV) between TP1 and chassis/GND, repeat for other channel.
 
Avionic and MBZ thanks you both for your responses and providing me with something to work on,
I'll carry out these checks and report back. Owing to time differences it'll have to be tomorrow.
Thanks again, and speak soon.
 
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