IC chip HA12002 "stuck in protect" fix for Sansui AU-D11

PE9ZZ said:
No! NOT on the output because the 78M20 does not like that. No, inject it at the bridge rectifier D12. At the +-side. Set your PSU to 30 V/0.1 A.
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If I read your reply here it always make me smile. NO NO NOT ON THE OUTPUT!!!
 
Just wanted to chime in and say I found this thread while working on a Kenwood KR-6050, which also uses the HA12002. This receiver was also stuck in protect for no obvious reason. I performed the same mod described by the OP, but using a 2N3904. Lo and behold, it worked!

Thank you @PE9ZZ !
 
jglinis said:
After trying just about everything else, I just tried this fix on the HA-12002 in a Sony STR-V6 (but substituting a 2n222 since I don't have any BC547's on hand). Worked like a charm!
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Hi, I have the same isue with my sony strv-5
Where no voltage on pin#8, 22v on pin #1
Where did you attached the transistors?
Thanks
 
Just tried this on a Sansui G-5700 with a 2N3904, and it just caused the relay to rattle. Pin 8 goes to 2.6, which is better than the 0V I was getting prior to attempting this, and pin 7 is at 4.5V. The base of the transistor is at 3.2V.

The service manual states 6.6V on pin 7 and 6.9V on pin 8.

Any thoughts on why this isn't working for me? Or is this a sign my HA12002 has failed completely.
 

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Ray122 said:
Any thoughts on why this isn't working for me?
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Maybe the error you have 'fixed' is not what is causing your unit to not come out of protection? - maybe it has a real DC offset issue and the chip is just doing it's job?

You seem like the sort of person who has checked for this - but I have to ask... ;)
 
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Well after letting it sit for a couple of weeks I did go back tonight to double check that my amp wasn't spitting out something nasty, (which it wasn't) but did find the issue in the process. While letting the relay chatter away and checking voltages on the IC chip, I found that the relay would finally click on and remain stable after touching pin 5 with my meter. After that when I turned the unit off and on again, the relay would chatter at first and then click on. Which tipped me off that it had to be C617 which is between pin 5 and ground. After swapping that out, everything worked great.

Consequently, I had to see if it'd still work after I removed the transistor I added because of this post... and it does!... although, I almost wish it didn't. This was a cool work around. And at least it helped me get to the bottom of the issue. Good learning experience for me, and maybe for the next person who stumbles on this thread, checking the capacitor between pin 5 and ground, might save them some trouble.


Hyperion said:
Maybe the error you have 'fixed' is not what is causing your unit to not come out of protection? - maybe it has a real DC offset issue and the chip is just doing it's job?

You seem like the sort of person who has checked for this - but I have to ask...
Click to expand...
 
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