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Amplifier Problems With a Sansui QRX-9001

Ok, so I checked the parts I had on hand not expecting to have it, but it turns out I did. I installed it and, THEY WORK! Well kinda, I got them all biased, but even so if I push any more than a few milliwatts I get a nasty crackling sound. Any ideas of what that could be?
 
There was no buzzing before when you ran off the amplifier input wires to another amp? Please recheck voltages either side of R602 and voltages on the three legs of the transistor you replaced. Buzzing sound usually indicates ac leakage and if not present before and without a scope we may be shotgunning caps in the power supply on the negative rail if the diode pair is good. Might also take an AC voltage reading on the collector of TR602 to ground to see if we can pick up any ripple which would show up as ac voltage.
Making progress yes :)
 
Also try the receiver in two channel mode using tape 2 input volume at zero to start and see if the buzzing is there if you add volume. Trying here to eliminate as much circuitry as we can without pre-main dis-connects.
 
That was weird, but anyway thank you for your help! I very much appreciate it! Thanks to your help she’s working as good as new!
 
One more thing, the relay that goes between 2-4 channel is dead on the 4-channel switch board. I can still get it to go into 2 channel via hall, or cd4, so I haven’t been worried about it. Especially since I would have to remove the face again to replace it. I do still want to replace it eventually though, so I was looking around for the part, but can’t seem to find it, or a suitable replacement. Do you know of a suitable replacement? The part is: MH4P-0
 
That Hitachi reed relay has no readily available direct replacement. There was one by Electrol that was available as surplus a while ago, but between Sansui and Pioneer guys using them on lots of repairs, those got wiped out about a year or two ago.

Best bet is to get a voltage compatible DIP reed relay and make a small adapter PC board to mate the dissimilar pinout to the 4CH switch board.

The other cube relay should be readily replaceable by an Omron part.
 
The Omron relay is the bad one. It has an unusual pin out. It seems Omron discontinued it, and doesn’t make any similar relays. I also am not familiar with its specs. I’m not planning on tearing into it to get to the relay for some time, but would still like to have the part at the ready to replace. Do you have any ideas on one with a similar pin out and spec?
 
And much as I am not a fan of cleaning relay contacts that may be your short term solution. Might also contact the fine folks at QXRestore and see if they have one they would part with used or otherwise. Very hard to source that relay now a days.
 
I popped the cover off of it, switched her into 2-ch and manually engaged the relay, and it passed a signal fine. It just won’t energise. Do you think it could be something other than the relay? If not I’ll probably try QRXRestore.
 
Is that RL-02 on the F2634 board? If so you have pass throughs to check as well as dc voltage to the relay pins. Check voltage on both side of R630 and R632 as well as the D602 diode.
 
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