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Post by oldheadtech on Jun 15, 2009 7:29:58 GMT -5
Hello, Fellows! I need some info on a balanced mod board in a D201 I'm repairing. The board I have has a number 17029-A on it. It is almost exactly like the board shown in my D201 manual, but, not quite the same. There are variations in the circuit traces around some of the transistors that make the placement of the parts different from what the schematic shows, making troubleshooting more difficult. Also, someone has added a transistor not shown on the schematic, for what purpose I don't know. It has a wire coming off of it going to pin D2 on the edge of the board. Somewhere in all this lies a problem that is keeping the mixer transistor from working, no output, no transmit and I suspect the mod may be the root of the problem. Is this board perhaps for a D201A and stuck in my D201 by error? Does it make any difference to use this board? Has anyone seen the added transistor mod before? I surely would like some input from some of the D201 gurus out there! Thank you and best regards! P.S.--- Thank you to Alan of Tubes Plus for his courtesy in offering to send some tuning slugs for another, different board I'm working on. This is a first class gentleman, folks!
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Post by 2600 on Jun 15, 2009 22:57:16 GMT -5
The one with the transistor is from a 40-channel radio. It serves to mute the transmit section during receive mode. For some reason the original 23-channel bal. mod board would fail to totally shut down during receive mode in the 40-channel radio. The result was a weak carrier heard in the receiver. The transistor is a kluge that fixed this problem.
Is the radio 23 channel? Or is it the 40-channel D201A?
73
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Post by oldheadtech on Jun 16, 2009 7:31:55 GMT -5
Thank you, 2600, for your explantion of the added transistor on the board. I actually have two radios, a D201 that I'm trying to fix and a D201A that will never again function as a radio. Both were purchased from the same person and both are true clunkers. I'm guessing that the board in question was taken from the D201A and stuck into the D201 prior to sending the units to me. Will the D201A board work in the D201 without having to do anything to the D201? The mod involves a wire run from the added transistor on the D201A board to pin D2 on the board, but, there's nothing else attached to D2, making it look like it's just waiting for something to be attached there to make everything start working. Any suggestions or further explanation would be much appreciated.
Thank you!
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Post by 2600 on Jun 17, 2009 0:27:25 GMT -5
I'll need to look that up. One of the chassis pins for the BM board is not used in the 23-channel Tram. This pin is connected to the 14-Volts receive-only circuit in the 40-channel radio and feeds the base resistor on the added transistor.
Just don't remember which one. I'll check the manual.
73
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