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Comet 200 amp repair. (Previous failed project of mine.)
- Thread starter doffo
- Start date
The high switch appears to bypass that 47ohm resistor. In low, I would expect it to get warm since it would be eating about half of your input power. I would recommend that resistor be carbon composition, not wirewound or metal film as it is in series with the RF input between the relay and the input xfmr, and adding inductance probably throws off the match.
Are those through holes plated or do they depend on the part lead to connect the two sides? I ask because the blue inductor up against the input xfmr doesn't look like its leads go back through like they originally did.
Are those through holes plated or do they depend on the part lead to connect the two sides? I ask because the blue inductor up against the input xfmr doesn't look like its leads go back through like they originally did.
The through holes are plated on the other side. That part was removed when I did attempt the SSB Biasing circuitry. I soldered it back but just above where it makes a connection.
I thought it was a resistor since it had the color bands on it. But the colors were different than regulator resistors.
All good.. What is weird is that even though you flip it on the high side, bypassing the 47 ohm resistor, it still manages to burn it up and stress it with heat.
Have you tested the switch? If the resistor still gets hot with the switch in high, maybe its contacts are toast. As for it burning up, idk. If we had a schematic...
What I like doing is taking equal sized photos of the board straight down, top and bottom. Then I flip the top image and overlay it with the bottom layer and add transparency to the top. that makes tracing out schematics easy.
If I am following the traces correctly, that 47ohm resistor, from a DC perspective, should go to ground via the input transformer winding (the red wire). Maybe something is putting DC to your RF input line. Something around the relay? Or maybe C156 inside that 146GTL went bad and is passing the radio's final DC through. IDK.
What I like doing is taking equal sized photos of the board straight down, top and bottom. Then I flip the top image and overlay it with the bottom layer and add transparency to the top. that makes tracing out schematics easy.
If I am following the traces correctly, that 47ohm resistor, from a DC perspective, should go to ground via the input transformer winding (the red wire). Maybe something is putting DC to your RF input line. Something around the relay? Or maybe C156 inside that 146GTL went bad and is passing the radio's final DC through. IDK.
Doffo -
Since the amp works when the hi/lo switch is in lo. The trouble lies in the hi portion of the circuitry. Like brandon said, check the switch. In the hi position the switch should show open. It looks like the hi contact it connected directly to the wire of the input transformer, which is the way it should be. My best bet at this point is that the problem lies in the switch itself internally.
- J.J. 399
Since the amp works when the hi/lo switch is in lo. The trouble lies in the hi portion of the circuitry. Like brandon said, check the switch. In the hi position the switch should show open. It looks like the hi contact it connected directly to the wire of the input transformer, which is the way it should be. My best bet at this point is that the problem lies in the switch itself internally.
- J.J. 399
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soldered the wire back, and with it on low, it has 50 ohms, and with it switched on, it zeros out as a direct short. hooked up the leads of the volt meter to each leg off the switch.