Icom 720A Stepper relay problem symptoms?

[443]

I have one of these old tanks here. It has the clunky relay in it when you switch bands... I understand it may need cleaning or repairing.

BUT, this radio is having some other problem that I am not sure if it's related to the stepper relay problem or something else. It will switch bands (on the readout, the band changes to a different band/freq), however the big dial (tuning dial) does not work. You can roll it all around all you want and it never changes the frequency. Also the D.Lock button is not working. I tested the light (led) it is good, so the circuit is not working. I am wondering if this is related to the stepper relay problem or something on the logic board is bad/loose? I noticed the ribbon cables and wondering if some pins might be broken on the connectors?

Does anyone repair these? I got it practically for free, it turns on and all the buttons seem to work, just not the tuning dial. I do not know if it receives or transmits, as I do not currently have a microphone for it and have not hooked it up to an antenna or speaker to see if it's receiving, etc.

 

[Captain Kilowatt]

Two things come to mind. You say the D.Lock does not work. That is the Dial Lock switch and with it engaged the dial will not change the frequency. The second thing is that I believe that radio, as is typical of most Icoms from that era and onward, has an optical encoder that shines a light thru the rim of a wheel connected to the VFO dial. This dial has lines in it and the encoder counts light pulses as it is interuppted by rotating the dial. If this optical circuit is bad the radio will not change frequency. If the dial is simp0ly dirty then operation will be erratic and not constant. Probably the best place to have it fixed is Home - Icom America

 

[443]

Thanks for the info. I decided it was too much for me to try to do myself. I sent it to a guy who's been Icom repairing since 1981, he will take care of it for me and for a reasonable price. I figured that was best since I am not up to speed on repairing such complicated rigs, I didn't want to damage something I couldn't replace because of it's age.

The D.Lock is OFF. It will not turn on. He said most likely voltage regulator circuit that powers that tuning knob and other stuff is not working, he will fix that, and clean the stepper relay, apply updates, align/tune etc, all for a real reasonable price so I shipped it off to him....

I am looking for info on what microphone to use with it. I see it requires an amplified (pre-amped) mic. I seen some for $100-$200 that say they work on Icom 8 pin, but does that mean ALL Icom 8 pin? Where can I find a good wiring diagram/info page? Manual? I downloaded it, it's 33 pages, haven't read it all yet. Got my General Class license the other day, didn't have any license before that, waiting on my callsign.