Icom ic-725 Vco voltage fault..

Post by **Raverrst** » 17 Dec 2023, 20:55

Hi all..

As in title, iv a Icom Ic 725, The Vco that covers 030hz to 8mhz after 5mins of the radio being switched on is not holding its service manual setting of 6.5volt, it’s jumping to 7.8volts and is unresponsive to any adjustments. When first switched on from cold it’s working 100% with correct stable 6.5volts, any thoughts as to what could be breaking down?

Rest of the radio/bands are 100% fine..

Many thanks for any help you can give..

Post by **ch25** » 17 Dec 2023, 21:33

Replace capacitors in VCO circuit.

Post by **Raverrst** » 18 Dec 2023, 16:57

ch25 wrote: ↑17 Dec 2023, 21:33 Replace capacitors in VCO circuit.

I’m glad you’ve said that as that was my first idea, I’ll get into it and do some testing. Thanks for the come back

Post by **Strawberry** » 28 Dec 2023, 22:05

Hi
electrolitics and tantalums are the worst offenders, mica, ceramics and polys tend to stay stable but that isn't to say they wont go bad.
I'd also suspect any zenner diodes too.
It sounds like it might be heat related, ie. bad component goes bad when it warms up, if you get some freeze spray that can be useful too by spraying individual components while monitoring the voltage or even just touch all the components, see if anything gets unduly warm or hot.
Good luck.

Icom ic-725 Vco voltage fault..

Icom ic-725 Vco voltage fault..

Re: Icom ic-725 Vco voltage fault..

Re: Icom ic-725 Vco voltage fault..

Re: Icom ic-725 Vco voltage fault..