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SX-939 tuner issues

Stink Bear

Active Member
I've got an SX-939 that had intermittent FM tuning problems, it eventually went dead. I used to be able to touch the HA1201 and get the signal back, not any more.
I checked voltages, I'm not sure what I should get but things looked normal except for pin 6 (Vcc). I assumed I should have a supply voltage there, I figured out later that was not the case.
I pulled the IC and did some checking with a DVM set to diode check. I have posted a pic of the IC schematic and the measurements I got.
I'm pretty sure I've determined that I have an open between pin 7 and pins 6 & 4. Applying 13V to pin 6 makes the tuner work.
My question is should I just order an IC and install it or should I look for potential related problems?
I think that if 13V is applied to pin 6 and it works that should indicate that there are no other problems, but with my limited electronics knowledge I'm not sure and would lie to hear from someone much more knowledgeable than I.
Thanks
 

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I guess it will work if you supply Vcc to pin 6, so short pin 6 to 7 and you maybe okay without changing the part.
 
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It reads open between pins 6 & 7.
I've been running it shorted for a while now, I finally decided to fix it correctly.
 
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You can replace the DIP, or try to solder in a very small 75Ω resistor (SMD?). :D
 
Watthour: Thanks for confirming the DIP is bad, I will replace it.
Is there any reason for further troubleshooting? Any possibility that related components could be bad? Filters for example?
 
If it is working when you short pins 6 & 7 then I doubt that any other comps, like ceramic filters are damaged.
 
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