Posts: 73
Threads: 23
Joined: Aug 2008
I'm trying to trouble shot a problem in the front end of my Model 41-250 and am finding that the schematic and actual wiring don't seem to agree. The radio works well on the two broadcast and highest shortwave band but has a hum on all signals in the 2.5 to 7 Mc band. I suspect maybe an open ground when the bandswitch is in that position. Since the radio works well on three of the four bands, I can't figure out why I can not get the schematic and actual wiring to match up. I've been in electronics for over 50 years and once in a while you come up with a strange situation like this. Any suggestions.
Harv
Posts: 909
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Joined: Jun 2007
Hello Harv. If the set has been previously "hacked", perhaps there is a missing bypass cap previously removed and not replaced? You mentioned the schemat doesnt match. Ive had luck in the past locating orig missing caps by taking a .05/600v , clip a wire with alligator clips to ground one end of the cap to chassis. Then by probing around with the other end of the capacitor lead-wire "point to point" on different connections one at a time can find missing bypass locations and rid hum. Just remember to discharge the cap "probing lead" back to chassis before touching it to all your different test points one test at a time!
Posts: 234
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City: Mission Viejo, CA
Can you take photos of your chassis? if so, I will compare it to mine.
I completely rewired mine, and it worked the first time! I do not yet have a working analog volt meter and RF signal generator, so have not yet aligned it.
Posts: 73
Threads: 23
Joined: Aug 2008
Thanks for your offer, but I have solved my problem and the radio is working. My issue was with the way the antenna coil was wired, but since the radio works OK I guess it was just the way I was looking at things. Thanks again.
Harv
