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"Richard Knoppow" wrote in message
m... "tchrme" wrote in message ... Partial success on this stubborn problem and it would have to be my favorite rcvr too. I traced the thunderstorm crashing sounds down to the 2nd converter subchassis. After I pulled it again, I replaced all the caps and the resistors since it is such a pain to access. I powered it up on test leads to the main chassis and still heard the frying thunderstorms. A 22k resistor that I replaced was starting to overheat and turned brown. I checked the one I took out and it too was burned looking. So.... I need help on what would cause the overheated resistor (R24). I can email a schematic to anyone who can help me out on this. I double checked all wiring and parts were replaced one at a time. Help. Thanks ahead of time. 73 Mike KF6KXG Have you made tube socket voltage and resistance measurements? This is a first step and will often point at problems. I've downloaded the schematics for both versions of the RX, you appear to have the earlier one (the 22K resistor is a different value in the later version). I can't see an immediate suspect but any capacitor in a position to draw current through the resistor is a suspect. While paper caps fail mostly by developing a low series resistance I have encountered shorted ones. Both the Mark 1 and Mark 2 models have the 22K resistor in the Bama schematics. I would check both C24 and C26 but a leaky C24 is the most likely cause of overheating in the 22K resistor. A quick check on the plate and screen voltages of V5 should point you in the right direction. A tube socket extender is handy here, but carefully pulling the tube out and carefully wrapping a fine wire around the appropriate pins and plugging it back in will work. C28, C29, and C30 should also be checked. Silver migration in C28 and C29 could conceivably case the noise too. 73, Barry WA4VZQ |
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