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advice needed: restoring 47-1230 - FM & AM now works!!!! :D (uncertain about SW)
#22

Thanks a lot Ron!

but I was already aware of that special cap, thanks to you mentionning it on another thread about the exact same radio.

Still, the C419 - the cap section of it - is shorted. The 3 legs would read as ground, leading C102A to read as shorted.


BTW thanks a lot for taking the 47-1230 as an example on how to replace this capacitor; otherwise I would have been lost on how to fix it, being that my own capacitor was now short.


Here's readings I did for all the steps on Riders 19-73

With C419 shorted (C102A shorted to GND):
A to C = 154V. (should be 310)
B to C= -5V. (should be -16)
D to C= 0 (connected to C419 that is shorted to GND - should be 190)
E to C= 134V (should be 240)

That's when I realised the C419 is shorted, so I disconnected it and re-did the same checks before reconnecting it.
With C419-to-C102A connection removed:
A to C=188V
B to C=-6V
D to C=187V
E to C=160V

I will want to replace it and redo the same readings... but I wonder if just the bad C419 would cause the voltages to be so low..?

I guess my next step will be to change C419, C314 and C216.


note: altough it is drawn as being between C103 and C102B in the troubleshooting technical drawings, the resistor R100 is placed between C103 and C102A in the schematics, and was like that prior to me changing the caps, so I replaced it like so.

Also, what I assume to be R214 was reading (with one leg open) 74000 ohm. In the schematics, it talks about 47000 ohm.

here's a close-up picture of the new filter caps. not that we can really see much from there, I'll need to make better ones next time I'm in the chassis.

[Image: http://i146.photobucket.com/albums/r253/...0_9379.jpg]

-Mars


Messages In This Thread
Re: advice needed: new ecaps = 47-1230 no longer receives AM - by Marsupial - 05-03-2011, 11:21 PM



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