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Old 23rd Sep 2022, 1:16 pm   #1
Iangebbie
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Default Yaesu FRG7

Yaesu FRG7 Issues
Well folks for once I am looking for some help on this radio,
The following basic conditions are as below,
1. No O/P on any band
2. All supplies present and correct
3. When measuring the first FET (Q101) on Gate 1 with a meter lead, full activity occurs on all bands, Can be tuned and peaked using the related Pre-set and MHz front controls, Main tuning dial works as well.
4. S meter works and + 10 reading on some MW stations (Local Cambridge station at 1.32 MHz)
5. From the service information I have / DC voltage low by about 2V on Drain of Q101,
6. Under the receive conditions (Meter Probe) AGC voltage on G2 of (Q101) voltage reduces as signal level increases by tuning.
7. Frequency readout near correct / comparing TX listing of station
8. The Lock unlock LED, does go out when the MHz pre-set is set correctly (This was also checked across all bands) again using the main MHz adjuster) But I had at one point to adjust VR102 (Within Q110). To fully extinguish the LED.
9. Have checked activity Pre Q101 (No luck)
10. All Switches back to the aerial checked using Meter on Ohms / this also includes the Local + DX positions (note someone was in at this switch before, two resistors changed out, can confirm correct values and correct locations as per circuit diagram.
11. FET Q101 looks like it was changed out before, I have since ordered a replacement (Not the original type but a substituted with a fancy diode protection built in)
12. At this time I donít have access to a Scope / Only a basic signal generator and DVM
Would appreciate any pointers or if I have missed any basics, Regards Ian G
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Old 23rd Sep 2022, 4:44 pm   #2
frsimen
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Default Re: Yaesu FRG7

Your measurement of the drain voltage is what you would expect to measure if Q101 were acting like a near short circuit. While that could be an indication of a faulty Q101, there the possibility of another cause as the radio starts working when a test meter is connected.

Check that that R101 hasn't gone open circuit and that there are no breaks in the PCB traces between R101 and Q101's Gate 1 and Source connections.

Paula
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Old 23rd Sep 2022, 4:58 pm   #3
Jon_G4MDC
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Default Re: Yaesu FRG7

Doesn't the FRG7 have some tricky switching of external and telescopic antennas. This sounds like a fault there.
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Old 23rd Sep 2022, 5:29 pm   #4
Restoration73
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Default Re: Yaesu FRG7

I would tend to view the rx as individual functional blocks and check accordingly.

Like the 7700 the antenna BC terminal is for <2MHz and SW term/SO-239 for>2MHz.

Worth checking this thread-
https://www.vintage-radio.net/forum/...d.php?t=177853
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Old 23rd Sep 2022, 5:54 pm   #5
Iangebbie
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Default Re: Yaesu FRG7

Many thanks Folks will check further / many thanks for the advice and the link, Regards Ian G
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Old 23rd Sep 2022, 9:04 pm   #6
Jon_G4MDC
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Default Re: Yaesu FRG7

I have some diagrams of SW1, the Local-OFF-DX Switch, which I drew in response to a similar thread some time ago. I can't make them out now.

Maybe I can find that thread.
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Old 24th Sep 2022, 7:14 am   #7
vu2nan-nandu
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Default Re: Yaesu FRG7

Hi Ian,

Have you checked with the meter lead on the other side of C101?

C101 open?

VC1 plates shorting?

Nandu.
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Old 24th Sep 2022, 8:44 am   #8
G3PIJpeter
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Default Re: Yaesu FRG7

Quote:
Originally Posted by Jon_G4MDC View Post
Doesn't the FRG7 have some tricky switching of external and telescopic antennas. This sounds like a fault there.
Is this the part of the circuit you need?

Peter G3PIJ
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Old 24th Sep 2022, 8:10 pm   #9
majoconz
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Default Re: Yaesu FRG7

Quote:
3. When measuring the first FET (Q101) on Gate 1 with a meter lead, full activity occurs on all bands, Can be tuned and peaked using the related Pre-set and MHz front controls, Main tuning dial works as well.
As Paula says - check R101 and R102. Your voltmeter connected from Gate1 to ground is providing the current path.

I'm still looking for the telescopic antenna on my FRG7.
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Old 24th Sep 2022, 10:14 pm   #10
Radio Wrangler
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Default Re: Yaesu FRG7

Easily confused with the FT290.... If you're into Yaesu, you spend equal amounts of time guddling about in both sets.

David
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Old 7th Oct 2022, 2:20 pm   #11
Iangebbie
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Default Re: Yaesu FRG7

Thanks for all the input folks, New FET fitted (Full ESD wrist strap worn) Radio now working, picked up Shanwick ATC on 3.4 mHz with a 2 m piece of wire in the living room.

Will have to do something about a reasonable antenna (Dual long wire and Cloths line?)
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