When It rains it pours! Done in by the obscure.
4 Pin Microphone Plug!
Christmas 2022 I was given a Tech Special Drake TR-7 from my #2 son and his XYL. The repair involved a $0.38 24VDC three terminal regulator. 2023 sucked insofar as ham radio is concerned as my time was devoted to the health issues of the XYL. 2024 so far is a rerun of 2023.
Christmas 2023 I thought I would fire up the Drake TR-7 like a sort of a celebration. It didn't work on Phone but CW was OK. A look at the schematic for the Transmit board indicates the phone portion could be defunct but CW would work. Drake advises --get a replacement board is always a good idea versus trying to troubleshoot a board outside of the radio. I found a reputable eBay supplier that I had purchased other boards from in my initial foray into fixing the TR-7. I went to him.
The 1st thing I did was to pull the microphone out of the short adapter cable (stereo to four pin) and ran it into another rig. It was good so lacking lots of time I just ponied up and after a bit of haggling with the supplier bought a replacement board.
I installed that board which is like wrestling an alligator as the Transmit board sits underneath the display board which is hard to get back into place because of all of the pins that have to align. But I did it and on power up yesterday --same issue.
That is when I thought the one thing I didn't check was the short adapter cable and sure enough the microphone lead was broken at the solder lug inside the 4 pin connector. The reason I didn't look at that initially was that the way that is installed there is no strain on that wire or bending as the cable is literally captive inside the connector body.
A stereo type connector is always suspect and I did check that side of the adapter cable previously and it was good. A bit of lead dress and a re-soldering of the wire to the lug on the 4 pin and we are good to go.
There are two VCO's in the TR-7 with one operating below 15 MHz and the other above. Now we have a VCO problem on the higher bands. When you go to 15M the LCD reads 16MHz and when You got to 10M the LCD reads 23 MHz. The frequency mixing scheme does include a 5 MHz component which is the IF frequency. So the 2nd VCO might be good but the 5 MHz IF signal is missing on the higher bands. More troubleshooting as I may have disconnected something when I pulled several of the boards to swap out the Transmit board.
But there is another key point and that is before you undertake drastic steps like buying a spare board and ripping her open, I should have checked both ends of the adapter cable as this was easy to do and I would have saved a lot of money, grief, time and now having to find and fix a second problem. Shame on me!
When it rains it pours. While good for advertising like Morton Salt does, it is not good for our ham rigs.
73's
Pete N6QW