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48-482 no FM
#5

Quote:for those who might want a clearer schematic and troubleshooting page to help answer, see Audiophool's page (you need the DjVu plug in to read the schematic)

Thanks for the tip.  I was working with the ones from Nostalgia Air and Radio Museum - poor resolution and different layout.

With the better schematic I was able to go back and measure the resistances for the IF coils, rather than test just for continuity, and came up with some interesting results.  I've not attempted an alignment yet.  

Attached are screen shots of my results.  It seems there are some problems, specifically Z400 and Z401 with resistances too low.  Yes, I checked the switch positions with Z400.  Z 300, 402 and 403 appear ok to me.   I just realized that I erred in stating in my original post that I replaced Z300.  It was in fact Z402 that was replaced.

It isn't exactly clear to me what path the FM signal takes, but with the BC/FM switching going on with Z400, that looks suspicious.  Is it possible that this would kill the FM and leave BC/SW functional?

This begs the next question.  If this is possibly the problem, would it be caused by contamination or a failed part (cap)?

Your thoughts?
reb


Attached Files
.docx Z400, 401.docx Size: 185.32 KB  Downloads: 134
.docx Z402, 403.docx Size: 218.27 KB  Downloads: 159


Messages In This Thread
48-482 no FM - by rebrands - 09-10-2017, 07:18 PM
RE: 48-482 no FM - by klondike98 - 09-10-2017, 07:57 PM
RE: 48-482 no FM - by Mondial - 09-10-2017, 08:41 PM
RE: 48-482 no FM - by rebrands - 09-10-2017, 09:50 PM
RE: 48-482 no FM - by rebrands - 09-12-2017, 01:35 PM
RE: 48-482 no FM - by robsradioactive - 09-14-2017, 07:23 PM
RE: 48-482 no FM - by rebrands - 09-14-2017, 10:19 PM
RE: 48-482 no FM - by Mondial - 09-15-2017, 12:35 AM
RE: 48-482 no FM - by rebrands - 09-15-2017, 04:28 PM
RE: 48-482 no FM - by Mondial - 09-15-2017, 09:22 PM
RE: 48-482 no FM - by rebrands - 09-15-2017, 10:44 PM
RE: 48-482 no FM - by rebrands - 09-16-2017, 11:06 PM
RE: 48-482 no FM - by robsradioactive - 09-17-2017, 06:38 PM
RE: 48-482 no FM - by rebrands - 09-19-2017, 12:37 AM
RE: 48-482 no FM - by klondike98 - 09-19-2017, 11:01 AM
RE: 48-482 no FM - by robsradioactive - 09-21-2017, 11:36 PM
RE: 48-482 no FM - by rebrands - 09-22-2017, 10:51 AM



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