Pioneer SX-636 - request help for repair

[SA-9100]

Hi everyone. I have a problem with the Pioneer SX-636 receiver. The FM radio has no signs of life. Turning the tuning knob, the indicators of the two V-METERS remain motionless and no tuning signal is heard (only white noise). Power is OK; I changed the electrolytic capacitors and all output voltages are OK as stated in the service manual. Up to a week the radio worked (you could hear only small discharges coming from the power supply or some broken transistor in the amplifier section). Can anyone give me some advice on how to proceed? A thousand thanks

 

[markthefixer]

first be sure that pin 3 of the AWE-046 tuner board has 13 volts on it when FM is selected. Pin 20 has 13 volts on it all of the time - it is the meter driver chip power.

There are some dangerous (to it) transistors in the power amp; 2sa726, 2sc1451.

 

[SA-9100]

Hi markthefixer, I was hoping to get some advice from you (I have read your threads on SX-636 and CT-F9191 and they have been very helpful). I insert the diagrams with the detected voltages (in red). I'll check PIN 3 again tonight because I don't remember if it was selected FM or AUX. Up to now, for the few tests I've done, the only very strange value seems to be on pin 14 of the power supply (13 and not 6 - R9 probably doesn't work correctly), but considering that it is the power supply of the lamps it shouldn't affect the tuner. I am writing from Italy, therefore the mains voltage is 230 volts 50-60 Hz and we are several hours out of phase.

 

[SA-9100]

in the attached photo you can see what happens to the VU-meters when FM is selected. In the other cases (AUX, AM, PHONO) Tuning is the focus.

 

[SA-9100]

I previously replaced the capacitors (circled in red) with new ones of the same capacity, but with a higher voltage. As soon as the 0.1uF and 0.47uF capacitors arrive, I will also replace the other original capacitors with new ones

 

[SA-9100]

There are some dangerous (to it) transistors in the power amp; 2sa726, 2sc1451.[/QUOTE]

I ordered these replacements:
2sa726 >> KSA992FB
2sc1451 >> 2SC3503 - KSC3503
should they fit?

 

[markthefixer]

yes, they have been proven over time. btw I was the first one on here that started recommending the ksa/ksc transistors.

ever see this thread? https://audiokarma.org/forums/index...-lists-sticky-suggestion.457663/#post-5897398

 

[SA-9100]

yes, they have been proven over time. btw I was the first one on here that started recommending the ksa/ksc transistors.

ever see this thread? https://audiokarma.org/forums/index...-lists-sticky-suggestion.457663/#post-5897398

Seen it now. I found matches in another post of yours on SA-XXXX. That's why I wanted to confirm if they were suitable as replacements for SX-636. I ask you to be patient as I am not very familiar with the forum.