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Old 8th Oct 2018, 10:56 pm   #1
Phil G4SPZ
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Default Yaesu FT290R Mk I (1983) - squelch fault repaired

I've been working on this old amateur radio 2-metre band transceiver, which I've owned since new, for the best part of a week and have finally fixed the fault.

Most of the process has been debated here so I won't repeat all that's been said in that thread. However these radios were very popular in their day and there must be many still around, so I'm attaching a couple of images which might prove helpful to other members faced with the same fault. Despite much searching on the web and asking Yaesu main dealers in the UK and the USA, I found it impossible to find a service manual, or any form of component layout or PCB print layout. On the positive side, the fold-out full circuit diagram supplied with the user's handbook is clear and legible. I downloaded a copy of the datasheet for the demodulator chip which enabled me to identify the pin-out and start tracing the printed tracks.

C104 is a miniature 10uF 16V electrolytic which decouples the 6 volt supply to pin 4 of the MC3357P FM demodulator I.C. Q1019. In my case the capacitor had become electrically and physically leaky, depositing electrolyte on the PCB and intermittently dragging down the 6 volt rail to about 2.5 volts, at which point the squelch kept opening at random.

C104 itself is physically adjacent to T1013, the discriminator inductor. The location of C104 on the board and its connections on the print side are shown below. The glass-fibre PCB has plated-through holes, and these required rather more heat than would be expected before they would release the leadout wires. Even so, C104 left one of its legs behind as it came away from the board.

This PCB is right on the limit of my eyesight and dexterity, so I'm pleased to have got it working again.

Phil
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Name:	Yaesu FT290 PCB print side showing C104.jpg
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Name:	Yaesu FT290 PCB zoomed showing C104.jpg
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Old 9th Oct 2018, 10:37 pm   #2
Jon_G4MDC
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Default Re: Yaesu FT290R Mk I (1983) - squelch fault repaired

Well done Phil, you have beaten the nay-sayers who reckon that radio is just crap build quality.
It is of its time - may you have many more years enjoyment from it - and we hope your post saves another one soon.
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Old 9th Oct 2018, 11:20 pm   #3
Phil G4SPZ
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Default Re: Yaesu FT290R Mk I (1983) - squelch fault repaired

Hi Jon. Many thanks. I actually think the build quality is perfectly good; cramped and awkward to work on, true, but definitely not poor quality. These sets must have sold in their millions and a lot of them have survived, so they can't be that bad!

As a postscript to this saga, I have discovered today that the 'Electric Handbag FT290 Group' on Yahoo has some good quality images of the component and print sides of the PCB that will hopefully save someone a lot of time in future repairs:

https://groups.yahoo.com/neo/groups/...bag/info?tab=s
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Last edited by Phil G4SPZ; 9th Oct 2018 at 11:24 pm. Reason: Hyperlink added
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