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PA1002A workaround / replacement

Going to be placing an order for some of my own projects, Is there still demand for PCB's? i can just add more on. I know someone said the KB4438's are back but who know how long it will last. the boards will only cost me a couple bucks to add them to my order. and yes its the fixed version and not the one with the backwards silkscreen :)
 
KB4438's are OUT... I just checked. So, YES....

I might as well just get 6. PM me with details of how to get $ to you (my memory fails me as to the last time, I think paypal was involved)
 
Order placed for 20 boards. among other projects like a pure class A headphone amp i found online, excited for that one
 
I found some KB4438's, so I won't be needing the work around boards anymore. Many thanks for the help in the past though.
 
Really snoozed or got sidetracked with this entire thread.. Missed out on getting some of the boards. Anyone got some extra boards?
 
I am also looking for some boards. If any are still available please let me know. PM sent to Bassblaster.
 
If you have a bad PA1002A, you will have signals at pins 3 and 14, but no output from pins 5 and 12. You should check to be sure that pin 8 is below about 1.2 volts, as that is the muting input, and mutes when high. You should also check the power on and power off muting inputs at pins 10 and 11 (see internal block diagram). I have attached the (top secret) pioneer internals of the PA1002A. If you can find any, the KB4438 from Harmon Kardon is an exact substitute for the PA1002A. You should also be aware that the current "work around" PC board does not have any of the muting functions. I have a couple KB4438's, but I will not sell them, I am saving them for my own customers if they have an SX-1980 with a bad one (have seen 2 bad in SX-1980's in the past).
 

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AE Bob said:
If you have a bad PA1002A, you will have signals at pins 3 and 14, but no output from pins 5 and 12. You should check to be sure that pin 8 is below about 1.2 volts, as that is the muting input, and mutes when high. You should also check the power on and power off muting inputs at pins 10 and 11 (see internal block diagram). I have attached the (top secret) pioneer internals of the PA1002A. If you can find any, the KB4438 from Harmon Kardon is an exact substitute for the PA1002A. You should also be aware that the current "work around" PC board does not have any of the muting functions. I have a couple KB4438's, but I will not sell them, I am saving them for my own customers if they have an SX-1980 with a bad one (have seen 2 bad in SX-1980's in the past).
Click to expand...
I believe the PA1002A might be ok. I don't get signal at pins 3 and 14 but I don't even get signal at the input of HA1201 pin 2. Further testing Q1 Q2 Q3 I have discovered Q3 Base voltage is off by over 1 volt. Is it correct to think that I must first have signal at HA1201 to have signal to PA1002A?
Q3 2sc535 schematic voltages then my voltages
E ? - 7.1v
C 12.4v - 11.8v
B 9.0v - 7.8v
 
The off voltage in the local oscillator could be an issue, but if that is the issue, then you would have no indication on the tuning meters. The HA1201 is a 10.7 mHz amplifier (you will not see any audio there). There will be no audio until after the FM demodulator PA3001 output pin 6. You should see audio at pin 2 of the PA1001 multiplex decoder input, when you are tuned to a station.
 
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AE Bob said:
The off voltage in the local oscillator could be an issue, but if that is the issue, then you would have no indication on the tuning meters. The HA1201 is a 10.7 mHz amplifier (you will not see any audio there). There will be no audio until after the FM demodulator PA1003 output pin 6. You should see audio at pin 2 of the PA1001 multiplex decoder input, when you are tuned to a station.
Click to expand...
No audio on pin 2 of the PA1001
However with the oscilloscope in the tape out I can see the 400hz modulated tone from the FM signal generator.
I can tune to a station and the signal meter pegs but the volume is very faint. I can turn up the volume knob all the way. Then when I tune just off the station left or right I get the regular audio level (volume knob turned max will make my ears bleed) with a lot of distortion. When I am just off the station left or right the signal is distorted on the oscilloscope. When I tune directly on a station the meter pegs the signal on the oscilloscope is cleaner but barley any sound is coming out.
With muting button out it mutes everything no sound at all. Also no FM light even when feeding pilot signal from signal generator.
 
From what you are describing, I would expect an issue with the PA3001 FM demodulator IC. You can tune an fm station, and you should see a good amount of audio at pin 6 (the output). If the audio at pin 6 is weak, but becomes strong when tuned slightly off the station, it also makes the PA3001 suspect. The Pioneer PA3001's are readily available from many sources.

By the way, In my last post I referred to the PA3001 as PA1003. I have edited the post to correct it.
 
I ordered a PA3001 from china back in April. It might be awhile. Thanks for your help. I will let you know the outcome.
 
Installed the new PA3001 it did clean up some of the distortion but the fm is still not getting through. No stereo light and I can still turn the volume knob all the way up which is not right. So far I have replaced PA3001, HA1201, and PA1001. All that's left is the PA1002A. I am going to replace PA1002A with the board on this thread and see what happens.
 
Hi Kingbleu, I had a TX-9800 a couple of years back that showed similar symptoms to your SX-980 with very low and distorted output. It actually had a bad PA1001A (KB4437) and PA1002A (KB4438). I can only assume the failure of one led to the failure of the second.
 
The PA1002A would have no effect on the stereo indicator lamp. It is just the de-emphasis and muting IC. I does provide a good amount of gain to the audio signal, but has nothing to do with multiplex decoding (except setting up the audio de-emphasis).
 
AE Bob said:
The PA1002A would have no effect on the stereo indicator lamp. It is just the de-emphasis and muting IC. I does provide a good amount of gain to the audio signal, but has nothing to do with multiplex decoding (except setting up the audio de-emphasis).
Click to expand...

Very true AE Bob, if l remember correctly in my case this IC was the cause of the low and distorted output only.
 
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