DonaldSmith Posted July 7, 2007 Report Share Posted July 7, 2007 I've been getting much help from the guys at the nostalgaair.org forum. I got my schematics off their site, and one of the guys sent me a schematic he annotated with additional voltages to be measured at the tube pins. I flashed the vibrator with 120 v through a 60 w bulb, to vibrate the points and burn the crud off the points. That got me a humming chassis. I replaced the film capacitors and electrolytic (filter) capacitors, but fried the filter capacitors by putting them in with the wrong polarity (negative goes to chassis, even if the car is positive ground!). I replaced the replacements, and measured the voltages at the tube pins. One of the pins was supposed cause the speaker to hum when touched, but it didn't. I found a short in a shielded cable, and turned the radio on. After a brief warmup, some voices started yelling at me from my 60-year-old superhetrodyne receiver! Jump up and down for joy! Quote Link to comment Share on other sites More sharing options...
Ed Griffin Posted July 7, 2007 Report Share Posted July 7, 2007 Great news Donald!, Very happy to hear you were able to get the radio working. I've copied and pasted all that you've presented about this in hopes it will help in the future when I try to tackle this myself. I hope you keep this information handy for those of us who plan on trying our hand at it down the road, Ed Quote Link to comment Share on other sites More sharing options...
DonaldSmith Posted July 7, 2007 Author Report Share Posted July 7, 2007 I owe a large debt of gratitude to the guys on the nosgtalgiaair.org forum for seeing me through this. They seem just like the good folks on this forum. I'm putting all my notes in a "Mopar radio repair" folder, in addition to the computer folder. I should pass on what I found to those who are newly emboldened to climb the mountain. I've been to the other side and it is good. Quote Link to comment Share on other sites More sharing options...
eric wissing Posted July 7, 2007 Report Share Posted July 7, 2007 Donald, Congrats. It is a great feeling getting the first radio going. Ten years ago I bought a little metal Hallicrafter Shortwave radio at a garage sale and when I researched how much someone wanted to repair it. I decided to buy a book and give it a shot. 100's of radios later it still is fun, of course there has been a few that never did work!! Car radios can be the hardest to work on because of the tight space and the vibrator. Nostalgia Air is a great place. Again, Congrats on the fortitude. Eric Quote Link to comment Share on other sites More sharing options...
55 Fargo Posted July 7, 2007 Report Share Posted July 7, 2007 Ain't no feeling, like the one of accomplishment, with a job well done. Keep up the good work.........Fred Quote Link to comment Share on other sites More sharing options...
DonaldSmith Posted July 10, 2007 Author Report Share Posted July 10, 2007 It sure does a beautiful job of filling in that ugly hole in the instrument panel. Oh, did I tell you, the radio works? The dial pointer is off. 760 comes in at more than 1000. I'll measure the difference for a few stations, so I can reset the pointer. (But that means taking the radio out again. But I'm getting good at it.) I figured how to pre-set the pre-set buttons. It's not like the Imperial Club "Automotive Radio Service" booklet for early 50's radios, with the horizontal button arrangement. On my upright button '47, remove the button cover, exposing a shaft with knurled knob with a screwdriver slot. Back out the shaft a few turns, to release a pivoting member that engages the tuning mechanism. Tune in your station, hold the tuning knob, push in the button, and tighten the shaft. That should set that button to rotate the tuner to that station. Manually tune the station and press the button. If the tuner moves off, repeat the button procedure. Quote Link to comment Share on other sites More sharing options...
DonaldSmith Posted July 10, 2007 Author Report Share Posted July 10, 2007 I should have adjusted the dial pointer when I was bench testing the radio! Oh, well, two steps forward, one step back. Quote Link to comment Share on other sites More sharing options...
Dennis_MN Posted July 11, 2007 Report Share Posted July 11, 2007 I'm wondering about the speaker hookup. Which wire will work with a modern 8 ohm speaker. It looks like the schematic shows the shielded wire going to a electro-magnet speaker and I don't have one of those. Dennis Quote Link to comment Share on other sites More sharing options...
DonaldSmith Posted July 11, 2007 Author Report Share Posted July 11, 2007 The old speakers did not have a permanent magnet, so they shot 6 volts to an electromagnet. Modern speakers do not need this power. If you take the back (right side) cover off the cadio, maye you can trace which wire is the 6 volt going to the speaker. Or easier, you could check the wires with the radio switch on. The shielding around the three wires is grounded to the radio chassis. I've read somewhere that a modern speaker will work with the other two wires. Didn't try if with mine. Quote Link to comment Share on other sites More sharing options...
DonaldSmith Posted July 11, 2007 Author Report Share Posted July 11, 2007 The shielding wires are a common ground for the speaker power and signal. Connect the new speaker to the ground and the one of the two insulated wires which is not the 6 volt wire. Quote Link to comment Share on other sites More sharing options...
martybose Posted July 11, 2007 Report Share Posted July 11, 2007 The old speakers did not have a permanent magnet, so they shot 6 volts to an electromagnet. Modern speakers do not need this power. If you take the back (right side) cover off the cadio, maye you can trace which wire is the 6 volt going to the speaker. Or easier, you could check the wires with the radio switch on. The shielding around the three wires is grounded to the radio chassis. I've read somewhere that a modern speaker will work with the other two wires. Didn't try if with mine. Being none the wiser, when I received my rebuilt 802 I just went down to Radio Shack, bought a new permanent magnet speaker, wired it up to the two wires in the OEM connector and it worked just fine! Marty Quote Link to comment Share on other sites More sharing options...
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