Pioneer GM-D8601 switching frequency

[Jartzz]

Hey all,

Got my hands on Pioneer GM-D8601.
Someone else tried to repair it before me but didnt succeed. Originally it had both psu and output blown. New fets have been fitted along with buffer transistors and drive ic. Psu section runs well but the output is problematic.
When CSD cap is installed it swings back and forth between protection. When i remove the cap amp powers up, output starts switching, draws excessive current and fets heat up, also there's ~2V dc offset on output terminals. I did my best probing all the smd transistors and diodes near the drive ic but cant find anything wrong. Drive wave looks a bit off but for me the switching frequency looks a bit high? Also when i have my rca connected i dont seem to have any signal on pin 3(in) of IRS2092.
Anyone have any ideas of what to check next?

Thanks.

 

[Perry Babin]

did you use exact replacement output transistors?

 

[Jartzz]

Output fets are currently IRFB4227 and buffers are A1023 / KTC1027. Buffers should be original part nr. Dont know what the original fets could have been

 

[Perry Babin]

I don't have that manual but the 9701 uses the 4227.

The offset could be the problem. Does it act the same with a speaker connected?

 

[Jartzz]

Without load it's actually stuck in the same protection loop even when csd cap is removed. It tries to oscillate for a millisecond but fails

 

[Perry Babin]

Are the ±5v supplies present on the supply pins?

Did you (or anyone) replace the 2092?

With the CSD pin low and the output disabled, do you have audio on the input pin?

 

[AllegiantStar]

Turner for the tuning frequency is off base. It's switching frequency because it's off track to receive AM/FM signals from the antenna. Any way of fixing that turner?