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Author Topic: Bad regulator in FT-101E  (Read 8320 times)
KD5FPO
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Posts: 28




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« Reply #15 on: February 20, 2011, 08:51:56 AM »

The only thing I can find that's amiss on the FT-101 is that the audio has a slightly distorted sound quality, it's present on all bands and all modes, even on WWV at 50db over S-9. Any ideas where I should start looking? Any help is, as always, greatly appreciated. 73 Michael KD5FPO
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KE3WD
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Posts: 5689




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« Reply #16 on: February 20, 2011, 03:08:56 PM »

First step is to clean the earphone jack switch with a bit of Deoxit and inserting of a 1/4" plug a few times, the switch contacts often are the source of audio dropouts and distortion when they aren't used regularly.

Dirty vol pot can also do this as well, and should get a spritz. 

Pull the Audio amp board, wipe off the contacts with deoxit and reinsert.


73
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KD5FPO
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« Reply #17 on: February 21, 2011, 11:21:38 AM »

yup, the headphone switch is new, as is the vol. pot., the audio board contacts will get a good cleaning after work, as will the jack and pot.  too. I'll keep you appraised, thanks some more Clark. I'll tell you right now however, this audio distortion has a very regular "buzzing" sort of quality, almost like a digital circuit might produce. When I tuned WWV 15MHz in AM and went slightly off frequency the time pulses sound more like short buzzes rather than smooth "thumps".  This sort of thing is always hard to describe accurately.  But first things first, I'll clean it up and see. 73 Michael
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KE3WD
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« Reply #18 on: February 21, 2011, 03:42:16 PM »

A leaky or shorted audio signal stage driver transistor can introduce audio clipping of the top of the waveforms...

Another missing or low voltage could also be the culprit, so check the DC voltages on the amp board carefully. 

You be lookin' fer clues at the scene of the crime, man.


73
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KD5FPO
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« Reply #19 on: February 21, 2011, 06:00:30 PM »

Something else I've noticed is a bit too much hum, I didn't notice it at first running through the external speaker, but today I put the headphones on and it's significant, this was after I cleaned the vol. pot and H.P. jack, (haven't pulled the audio board yet) but I remember reading in the Yaesu svc. manual about some FT-101's having a hum that turned out to be a ground loop and was traceable to the regulator board! Hmmm, I thought about the +6V mod. I just made to that board and those unused original components left in place. But the rig is sensitive as all get out right now and is working really well, although the preselector control appears to run out of range on the 160m band, it wasn't that way before. Oh well. I'll start fresh on it tomorrow after work, vy 73 Clark. Michael KD5FPO
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