Brian,
I agree with Jerry K0CQ. This is most likely a bad (open or high ESR)
aluminum electrolytic capacitor. The type of noise you describe could
be from the Microcontroller or the BA618 display driver as well as the
PLL circuit. I would look at C-44,C-48, C-42, C-41, C-87, etc. Perhaps
you could tack solder a known good cap across these one at a time and
see if the problem goes away.
Have you installed the "optional" C-86 4700 ufd filter cap? This may
help also.
I have built several of these kits and they have all worked great. The
receiver has exceptional sensitivity.
Good luck. Please let us know what you find.
73,
Bill - K6WLM
Brian Haren wrote:
>
> Hello All!
>
> I have a 1220 2-meter kit that has an 'issue' I hope someone can help me
> with...
>
> The kit was built by a local ham with a lot of kit-building experience and
> was recently received back from TT where they replaced a few switching
> diodes, checked functionality and gave it a clean bill of health. I bought
> it from the original owner and a good friend. According to him it has less
> than 2 hours operating time on it.
>
> The radio emits a constant low-level high pitched whine. It's not a 60 hz
> 'hum', it's much higher frequency whine. It can be heard by receiving
> stations behind my audio and I also pick it up through the radio speaker
> while receiving other stations. I ran a number of tests today, to include
> turning off all appliances, lights and power supplies in the house and
> running the radio from a battery. The whine persists. The interesting thing
> is that other stations report the whine fades during long transmissions, but
> always returns after unkeying and beginning another transmission. One local
> ham stated that it sounded like some of the capacitors had not yet formed and
> might well go away with time. I'm not so sure.
>
> Does anyone have experience with this radio and perhaps have experienced the
> same problem? I'd love to get this problem solved without having to return
> it to TT. Thanks in advance!
>
> Brian
> W8BYH
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