In the picture above, ignore the Kenwood TM-261A 2 meter radio on top of the Ten-Tec. I got T-Kit as a Christmas gift in 1998 just after getting my license in October of the same year. I had a ton of fun with it the following summer on sporadic E band openings and I have QSL cards from up in the north eastern and eastern parts of the US to prove it. At some point though it stopped transmitting. Last I checked I could hear it fine on my Dad's handheld Icom IC-T81, but only really, really close by, like within half a block. Hooking it up to a MFJ-864 SWR Wattmeter shows *no* movement in needles when transmitting. I went through the manual and tested all the voltages at the test points and they were mostly within the expected ranges. So I called Gary at Ten Tec T-kit tech support and he said he was 99% sure it was the final and suggested replacing it. Unfortunately the original 2SC1971 is no longer available. The replacement for that is the NTE 342:
I got this and replaced it and tried it out and what I observed was that the needle on the MFJ-865 SWR Wattmeter moved once and then went down immediately. The T-Kit went back to operating the same way it had before I replaced the final.
Originally this kit came with a Supplement and a Tech Bulletin to the Supplment. In the Tech Bulletin it provided an extra capacitor and a resistor to create feedback "to reduce gain at lower frequencies, therby stabilizing the amplifier." I had alway suspected something might be wrong with this circuit that could cause the final to short. First, here is the tech bulletin:
Tech-Bulletin-1260-498-1 (click the arrow at the top for full size).
Now looking closer at the resistor in this circuit today I noticed it looks brown in the middle, like it is shorted out! Here, take a look:
Am I on to something? Before I replaced the 2SC1971 with the NTE342 I wanted to remove that circuit for fear it was at fault, but I didn't.
In addition to that you may have noticed in the tech bulletin from above it added a DC blocking circuit on the SO-239. I thought maybe something could have been wrong there, but I have no "smoking" gun like the browned resistor from above, but here are some pics of that:
Do you think I should be worried about that?
Especially after finding that browned resistor I'm tempted to remove it completely or replace it and buy another NTE342 and try again! Any advice appreciated.
For reference here are some of the relevant documents from the instruction manual: