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Author Topic: R390A IF section now  (Read 3401 times)
KC4MOP
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Posts: 731




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« Reply #15 on: February 07, 2013, 03:17:42 AM »

I'm writing W6OU's response down in my manual for a service tip the next time. We know there's a next time. Very nice approach. Eliminate and conquer!
That's how I fixed my problems with the radio. There was a dedicated time for 2-3 days of staring and troubleshooting and all of a sudden I find my problem(s). Usually involves several components that have been changing value.
Keep us posted pls.
Fred
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N3DT
Member

Posts: 514




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« Reply #16 on: February 08, 2013, 07:01:18 PM »

I inserted 455 into the last 2 IF amps grids and no drifting issues.  Into grid of 2nd IF amp and there the trouble starts.  Found some bad solder joints in the filter area (between 1st and 2nd IF amp), cleaned that up and it's better, but it still looses sens after a while but comes back up in a while.  Guess I'll have to start replacing things, it appears to be in the grid circuit of V502.  It's almost like the grid of V502 is loosing it's grid leak, but that's the filters into the AGC line which is not used in MGC.  Dunno yet but I feel I'm getting closer.  It may be one of the bypass caps in that area.
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