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Post by vanlifeson on Jan 16, 2024 12:52:16 GMT -5
Transmit and receive are gone on the vfo side.
All good on the crystal side. I replaced the VFO oscillator tube.
Still no good. Just looking for some insight as to what may have caused the VFO side to go dead. Thanks!
This is a hand wired D201.
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Post by 2600 on Jan 16, 2024 23:04:52 GMT -5
There are two 22k 2 Watt resistors in the VFO tube's plate circuit R319 and R320. They are famous for overheating in the circuit-board radio, where you find them side-by-side.
In the VOX radio, one of them is on a tie strip near the audio tube, and the other one is near V302. Quick check for this failure is to check V302 pin 6 in MAN mode, with the VFO active. Should be between 100 and 120 Volts DC, more or less. If the reading is way low, those resistors are most likely bad. We upgrade them to 5-Watt. Wirewound is okay if you can find them. It's just a DC circuit, so any resistor type is okay.
This is not the only component failure than can shut down the VFO, just the most popular.
73
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Post by vanlifeson on Jan 17, 2024 9:21:47 GMT -5
There are two 22k 2 Watt resistors in the VFO tube's plate circuit R319 and R320. They are famous for overheating in the circuit-board radio, where you find them side-by-side. In the VOX radio, one of them is on a tie strip near the audio tube, and the other one is near V302. Quick check for this failure is to check V302 pin 6 in MAN mode, with the VFO active. Should be between 100 and 120 Volts DC, more or less. If the reading is way low, those resistors are most likely bad. We upgrade them to 5-Watt. Wirewound is okay if you can find them. It's just a DC circuit, so any resistor type is okay. This is not the only component failure than can shut down the VFO, just the most popular. 73 Thank you! I’ll check the resistors when I get home from work. |
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Post by vanlifeson on Mar 15, 2024 13:51:49 GMT -5
VFO is now working. I found a 10k resistor connected to pin 4 of the modulator tube that was reading 1 MEG.
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Post by 2600 on Mar 21, 2024 22:44:23 GMT -5
Rock on!
Gotta love it when a plan comes together.
73
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