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Author Topic: Odd Yaesu FR-101 problem.  (Read 1632 times)
ZL1BDA
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Posts: 46




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« on: July 26, 2017, 03:36:23 PM »

I've just been fixing up one of these units. Quite good except for the !@##$%$#@! backwards tuning!!!
 However there is one very odd problem which someone else might have experienced.
Sensitivity is fine, BUT while the calibrator signal gives a good strong audio output the received audio, while quite clear is of low volume. This applies even on strong signals. Thus you get the calibrator nice and loud with about 25% AF gain , but the RX on received signals via my antenna system needs almost fully clockwise AF gain setting for a reasonable volume.
BTW it is NOT the antenna. I have my old Kenwood 820S on the same antenna and signal strengths are similar, just the audio is lacking.
I've worked on receivers for over 60 years, but this is a new one on me!
Any bright ideas anyone?
73 Cliff
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N8YX
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Posts: 1083




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« Reply #1 on: July 30, 2017, 07:53:00 AM »

Without knowing the history of your FR: First thing I'd do (having owned a few of those over the years) is to get ahold of a signal generator and make sure that "S-9" really IS S-9 (~50uV generator output.).

Go through the IF alignment process. Verify receiver gain and that any adjustments relating to the IF Board have been performed, and that the receiver is sensitive to weak (1uV) signals. It's easy to give one of those rigs a "generous" S-Meter if the procedure isn't followed.

Should that all be in order, start looking at the AF Amplifier stage. Preferably with an AF signal generator and scope. A low millivolt signal applied to the AF Amp input should give ample output. If it doesn't, suspect all electrolytics associated with the stage - including coupling caps.

Funny you should mention Kenwood 820's. All three of my R-820s are on the bench right now; one to fix a PLL/VCO issue and another to address a muting/recovery problem when being run in VFO Transceive mode. The third is due for a whole-scale rebuild.

When those are done I'll think about rebuilding the VFO drive mechanism in my current FR-101.  Grin  
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HAMHOCK75
Member

Posts: 507




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« Reply #2 on: August 15, 2017, 01:14:09 PM »

Just a guess but the FR101 has three crystals for LSB, USB, CW which drives the product detector. For example, if you are using the CW crystal oscillator for listening to the calibrator, then switching to the LSB or USB crystal for voice, low injection from those oscillators could result in low audio.
« Last Edit: August 15, 2017, 01:19:59 PM by HAMHOCK75 » Logged
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