Yaesu FT-101 Repair Adventure

I wired up a bunch of microphones.  The Cobra power mic that I used last time developed a broken wire, so I had to repair that one before I could test it.  The Uniden amplified mic didn't give enough gain. The Cobra Power mic did OK, but not full power. The Yaesu MD-1 gave some output power, but the mic gain on the radio had to be at 10. Finally I wired up the Shure 444T.  Even though it is a Low Z microphone, it worked the best. I could get power output out of the radio on SSB with a reasonable mic gain setting.  Between 2 and 4. Looks like that is the best mic so far. Through testing, It looks like I'm getting between 75 and 95 watts out on 20 meter SSB.  There may be a little drift over several minutes, but it doesn't seem bad.

After I looked up the specs for the Shure 444T, it turns out that it is a low impedance microphone.  1000 ohms or less.  Looks like that won't work.

I tried the mic that worked last time, the Cobra power mic, but it didn't work at all.  For some reason it didn't key the radio.  Then I tried the second mic, a Powered Uniden Desk Mic.  It doesn't want to work either.  I have to run the mic gain up to max to get any little bit of output... So next I'm going to wire up this Sure 444 mic.  But I have to figure out the pinout first...

I took the original FT101 and put it back on the bench.  I put in the known working Power supply board.  Then I swapped out the ALC board with the second one.  Woohoo!  This fixed the ALC maxed out problem.  When looking at the board I did notice that one of the transistors had been replaced.  So maybe the replacement one is the wrong part... Anyway after that I adjusted the bias, adjusted the ALC and did some transmit tests.  I got over 100 watts on 80, 40, 20, and 15.  I think I got 75 watts on 11m.  And only 35 watts on 10 meters.  Also only got 25 or 35 watts on 160 meters. This radio also had a problem with the PO position.  It always read too high/off scale.  I did find the adjustment and was able to adjust this down to the correct level. So it is 95% working.  Next I'll have to work on a microphone.

I pulled out the second FT101E and put it on the bench.  Initial tests are good. But it has a very wobbly RX.  If you tap it or touch it it changes frequency.  If you tap the power supply board it goes off frequency. I ended up pulling out the power supply board from the first FT101E, and swapping it to this one.  That cured the wobbly RX. Then I readjusted the bias and did some power testing. This one the ALC works correctly. However there is no power output on 11 or 10 meters.  Only 1 or 2 watts at full carrier :( I may have to do some more board swapping to get one of these radios running...

Did some more testing on the FT101. The ALC function doesn't seem to be calibrated correctly. So I'll have to figure that part out. Next, I'm going to let the tubes burn in for 8 or 12 hours... then I'm going to hook up a watt meter and see how much power its putting out. After that is wiring a microphone.

Worked some more on the FT101. Looks like I was able to successfully align the transmit and receive frequencies.  I used a procedure shown in this video https://www.youtube.com/watch?v=Q1FE9lnzEhk When reading the manual I saw that it should be able to receive .3uV.  So I set up my service monitor to output that level, and success!  I was able to hear the .3uV signal on all of the bands. I also noticed it had a partially broken knob. So I'm trying to repair that. Superglue gel didn't stick to that type of plastic, so I'm trying an epoxy. Its drying now...

Well it has been quite a while since I last worked on the FT-101s. I've done quite a few projects in the meantime including repairing Hallicrafters, Collins, and National receivers.  I have gained some more and better equipment also. Anyway I still had this FT101 sitting under the workbench, so I finally cleaned the bench off and put this baby on it.  Initial tests weren't too good.  But it turned out that I just needed to Deoxit the volume pot and RF gain pot again.  I also put some on the band switch.  After that, the internal calibrators seemed to be working correctly and I was getting internal signals. So I hooked it up to my Service monitor and gave it a signal.  I'm happy to report that it could hear .5uV signals on 15, 20, 40, 80, and 160 meters.  I didn't play around with 10 meters too much because I don't remember what frequency crystals are in it. So far it is looking pretty good.  I did check the clarifier, and it is off fr...