1 more cap and some adjustments

I replaced the capacitor between the 12BY7 and the finals. This one is an old molded mica capacitor that is known to fail.
I then attempted to do a cold neutralization of the final tubes.
Not having done that before, I followed the guide and adjusted the trimmer according to the directions.




Comments

Post a Comment

Popular posts from this blog

Mic wiring #3

Image
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.
Read more

Alignment of RX/TX and broken knob

Image
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...
Read more

Board swapping

Image
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.
Read more