Pioneer sx-980 with a bad pa1002a chip :(

creeve

Active Member
So as the title says I have an unfortunate problem. The pa1002a chip on the tuner has good signal going in but nothing coming out of pin 5, thus no right channel in FM stereo. This receiver had one foot in the grave when I got it and I’m not gonna give up on it yet. I have read some threads on possible replacement modules made from discrete components but can’t find anything definitive. Does anyone have any suggestions on where to go from here?

Thanks
 
Look at the sx-580 design, it does not use the PA-1002A or the better multi-pole LPF. It uses a passive de-emphasis, a pnp buffer and a LPF. You can put that on a perf board if all else fails.
 
Look at the sx-580 design, it does not use the PA-1002A or the better multi-pole LPF. It uses a passive de-emphasis, a pnp buffer and a LPF. You can put that on a perf board if all else fails.
So if I went a route like this I would lose muting functionality I assume, which is no big deal. Do you have a schematic? I am not very well versed in tuners beyond basic troubleshooting.
 
UA3089PC Equivalent to NTE788, LM3089P
This is the IF amp/limiter/quad detector.

I do not think you need the buffer as done in the SX-580. This is easier.
You can take the o/p from F4 as your L/R and use that.
Lift the +ve lead from c44,45 to isolate it from Q7(PA1002A)
Remove R60,73(3k3) (or just lift the legs that are connected to R59,61) since you do not need more loading. LPF(F4) required loading is done by R46,47
Lift legs of R59,61 (or remove) connected to R60,73(3k3) to isolate from Q7(PA1002A)
Connect lifted +ve legs of C44,45 to terminals 19,21 or pads where R60,73 were soldered to.
make sense?
 
haven't time to study this so i might be wrong in thinking this may do the job
NTE788
Nope thought the same thing yesterday. Not even the same pinout. Gonna try Rcs16 suggestion and see how it goes. At least then it will be usable until a chip or donor unit pops up.
 
UA3089PC Equivalent to NTE788, LM3089P
This is the IF amp/limiter/quad detector.

I do not think you need the buffer as done in the SX-580. This is easier.
You can take the o/p from F4 as your L/R and use that.
Lift the +ve lead from c44,45 to isolate it from Q7(PA1002A)
Remove R60,73(3k3) (or just lift the legs that are connected to R59,61) since you do not need more loading. LPF(F4) required loading is done by R46,47
Lift legs of R59,61 (or remove) connected to R60,73(3k3) to isolate from Q7(PA1002A)
Connect lifted +ve legs of C44,45 to terminals 19,21 or pads where R60,73 were soldered to.
make sense?
Thanks so much. I think I got it. One question though, if I remove R59,61 then I don’t have to remove R60,73 correct?
 
Remove R60,73(3k3) (or just lift the legs that are connected to R59,61) since you do not need more loading.
 
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