41-280 Volume issues - Printable Version
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41-280 Volume issues - JGatewood - 12-25-2010
Hello and thank you for welcoming me into your world. I am new to radio restoration and a Newbie here. I recently purchased a 41-280 for a whopping $20.00. The lady I bought i from had it in a Barn. Brought it home, put it on a Variac, brought it up slowly and Voila, she fired right up and sounded beautifully. Was able to tune stations in without issue. I have a Twin Brother who does this and has for awhile. Under his advice I re-capped the radio, very careful to ensure correct ratings were used and all solder joints were solid. Upon completion, put her back on the Variac, brought her up slowly, got lights but no volume. If I go to the extreme right on the dial, I can hear some static but it is very low. Thinking I had a bad capacitor somewhere, I replaced them all with great care but had the same results. My brother who has been doing this for awhile is stumped. We checked voltage at the speaker connector (360vdc) and Ohmed out the speaker, and it is good at 1k ohms which from reading is normal. I checked all wiring connections for quite a few hours and all is good. This is driving us bonkers so if anybody has had this problem before and has some guidance, I would much appreciate it. Thanks and my apologies for being so long winded.
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Re: 41-280 Volume issues - Steve Davis - 12-25-2010
Jerry, When you have a dead radio, you want to narrow the problem down to a specific area. So first, with the radio turned on, touch the center terminal of the volume control with your finger (be careful not to touch the switch terminals). You should hear a loud hum. If so, the problem is ahead of the volume control. If not, the problem is in the output section (or the power supply). Let us know.
Steve
Re: 41-280 Volume issues - JGatewood - 12-26-2010
Ok, Great advice Steve. I touched the center terminal, I do hear a Hum, which i can adjust with the volume control but it is not real loud, but I can hear it. I did notice it is a little loose. I tried tapping it and I get a little popping. I was curious that when I replaced the Cap on that center lug, could the heat from the Soldering Iron affect the pot there? If so does anyone know the value of it? I have a schematic but no parts list to go with it. Thanks again, I think we are on the right track.
Re: 41-280 Volume issues - JGatewood - 12-27-2010
OK, removed volume pot, nothing of significance noted. Cleaned it while I had it off, ohmed it out and only got about .450 ohms. Not sure if this is correct or not. I assume this should be about 1000k ohms but I am not sure. Still the same problem.
Re: 41-280 Volume issues - Steve Davis - 12-27-2010
Jerry,
When you touch the center terminal of the volume control, you should get a fairly loud hum. Be sure the volume control is turned up or else the center terminal will be nearly shorted to ground. If you get a loud hum the audio section of the radio is working. The next quick test is to check the local oscillator. To do this, tune the radio to the high end of the broadcast band, say about 1300 kc. Now place another radio near the dead radio and tune it 455 kc below the dead radio. Now rock the tuning back and forth. You should hear a squeal come and go. If so, the local oscillator is working. By doing these two quick test, you have eliminated about one half of the circuitry of the radio. Let us know.
Steve