Yaesu FT-101 Repair Adventure

I played with wiring mics up to the radio a little more, not having much luck.  Seems the Cobra power mic had the best response. I got the radio working today.  I first tried it on 40 meters AM.  Band conditions were bad, so I switched to 80 meters.  It sounded decent on my SDR, and my friend was able to copy me.  However the receive on AM wasn't very good.  I noticed that the narrow CW filter appears to be operating in the AM mode.  So audio was really pinched. I started to see the proper IC movement.  When I switched over to ALC, it was indicating as it should.  This was the first time I've seen the ALC action working in SSB mode. I proceeded to LSB and was able to have a good QSO with my friend on 75 Meters  LSB . I played with the mic gain and power mic gain, and it was sounding real good.  Setting 6 on the mic and setting 8 on the radio. I'll call that a success.  Looks like I'm getting at least 100 watts SSB out o...

I wired up 3 or 4 different Mics.  None of them had enough drive to get any usable power out of the radio.  Will have to get the other FT-101E going to see if it is a Mic problem or a radio problem.

I worked on the FT-101E for a little bit this evening.  I reset the bias to 60mA.  I recalibrated the S Meter.  I recalibrated the ALC meter.  I was able to get 110 watts out on tune mode.  I'm still only getting 10 or 20 watts on SSB though.  It looks like even the Cobra Power mic doesn't have enough gain (or is the improper impedance) to drive it to full power on SSB.  I'll have to start looking for a High impedance mic.

I switched back to the other FT-101E that I had neutralized the finals on. I hooked up an old Cobra CB microphone, and tested the audio on USB. I couldn't really get much out of it unless the mic gain was near 10. So I found a Cobra CB power mic. I hooked that up and saw way better ALC deflection. I was seeing 10 to 20 watts into the dummy load. With the mic a normal distance away, the power mic set at 6, and the mic gain at 9. Next I fired up my SDR and checked the receive audio and Frequency. I had set the radio to 14.250Mhz and the SDR said I was on 14.249.88. So really close. The audio sounded decent to me. So I'll call that a success. More testing will be needed to get more power out and test AM.

Got some more work done on the second FT-101E today.  I installed one of my new 12BY7A tubes that I got.  It tested 7000/6500, so it is really strong.  I dug out the matched pair of the Silvania tubes that I had gotten with the radio and installed them.  I also changed out the neutralization capacitor.  I also recapped the noise blanker board and RF board.  I also replaced a bad capacitor on the back of the mic jack. I let it warm up for a while, then did a test of the transmitter.  I set the bias current to around 60mA.  And tuned it up into a dummy load.  I saw right at 100 watts on 20 meters. I call that a success! The radio has a very hot receiver.

Well, to start with I had only 1 working 12BY7.  So I ordered 4 off of eBay.  While waiting for those to arrive, one of my friends let me borrow one.  Then I went over to my other friends house, and he gave me 4 of the tubes.  The next day, 6 tubes arrived in the mail.  The one seller included 2 extra tubes that were untested.  Out of the entire lot, only 1 tube was bad, with a short between pins 1 and 2.  I've now sorted them and graded them using my Hickok tube tester.  Now I have plenty of driver tubes.  If I were only so lucky on the final tubes...  They run about $125 for a pair on eBay :( Anyway, I replaced a few more capacitors, and set the bias to 60mA on the FT-101E that I've been working on. Next will be wiring up some microphones, and doing some output power tests.

Mystery solved. Turns out that the ground for the crystal calibrator circuit comes from the screw that holds the circuit board to the chassis. So once I took out the screws it didn't work. Put them back in, and they are both working now.

Still trying to figure out the crystal calibrator issue.  I fired up the FT-101, and its calibrator was working.  I pulled the regulator board out to look at it, then put it back in.  Now the crystal calibrator doesn't work.  Same as the other two FT-101Es.  Getting quite frustrated...

Checked the voltages on the rectifier board.  They seem normal.  I set the bias voltage, and the 6.0 volt voltage on the regulator board.  I cleaned the relay in the PA section. Looks like my problem is a voltage problem.  The crystal calibrator chip is seeing 9 volts.  I think its supposed to see 4 to 5 volts.  I'll need to look into it a little more.