I can't be certain what those "resistors" are connected to from that diagram. It would be easier to post a link to the full service manual schematic and assembly diagrams, free here: Technics SU-V505 Manual - Stereo Integrated Amplifier - HiFi Engine
I can faintly make out that those 2 circled items J, J are connected to pins 8&9 of the connector and pins 18 & 10 of the AN7062, respectively. They would have to be jumpers or links for that to be the case. If you confirm what they connect to on the little board, you have your answer.
At least you will be able to read off resistor values from the parts list if they are a part of the voltage amplifier section. It seems IC71 is our old unfavourite AN7062, so there will some experience out there with this easily fried chip.
I can faintly make out that those 2 circled items J, J are connected to pins 8&9 of the connector and pins 18 & 10 of the AN7062, respectively. They would have to be jumpers or links for that to be the case. If you confirm what they connect to on the little board, you have your answer.
At least you will be able to read off resistor values from the parts list if they are a part of the voltage amplifier section. It seems IC71 is our old unfavourite AN7062, so there will some experience out there with this easily fried chip.
I'm attempting repair to one of these with very bad distortion on right channel. Done a lot of component testing.... R205 is a short but resistor itself is ok out of circuit. I don't know if it's the balance pot itself I dont think it is
also diode 720 is giving a reading in the wrong direction but it's an unusual one?
also diode 720 is giving a reading in the wrong direction but it's an unusual one?
0V from ground - should have -1.8
This will certainly cause the distortion (half wave) and no bias controllability
⚠️ Set bias to minimum (fully counter clockwise) to prevent issued after this is repaired.
If 0V at Emitter of Q304, check/replace R312
If -50V is at Emitter of Q304, replace it (2SC2631) it would have open - often I replace these in matched pairs (Q72 on V. Amp and Q304) or Left CH (Q71 and Q303)
Can use 2SA1123/2SC2631 (orig spec) or up it to 2SA1124/2SC2632 (better power/heat dissipation)
⚠️ Use very reliable seller as counterfeit transistors are rife
This will certainly cause the distortion (half wave) and no bias controllability
⚠️ Set bias to minimum (fully counter clockwise) to prevent issued after this is repaired.
If 0V at Emitter of Q304, check/replace R312
If -50V is at Emitter of Q304, replace it (2SC2631) it would have open - often I replace these in matched pairs (Q72 on V. Amp and Q304) or Left CH (Q71 and Q303)
Can use 2SA1123/2SC2631 (orig spec) or up it to 2SA1124/2SC2632 (better power/heat dissipation)
⚠️ Use very reliable seller as counterfeit transistors are rife
All good
Now let’ s check Emitter voltage of Q308, then check voltage at Emitter of Q312
something strange just happened
while I was testing Q308 the probe must have touched two terminals and there was a pop through the speakers and the amp went into protect mode with the amber light flashing. I switched it off then on again and it works! the distortion has gone. Q308 -1.3
Q312 -5v
There is voltage on the bias test points too. But if the speakers are turned off via the rotary control the sound does not come on immediately, you have to turn the volume control perhaps the relay is showing signs of age?
There is a bit of distortion at first but once the volume control is twiddled it goes and it's fine after this.
There is a bit of distortion at first but once the volume control is twiddled it goes and it's fine after this.
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