IC-821H Display and Operational Problems

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WD5HHH
Posts: 2
Joined: Fri Jan 31, 2020 7:38 pm

IC-821H Display and Operational Problems

Post by WD5HHH » Tue Feb 04, 2020 5:53 pm

My IC-821H is having difficulties. When I first turn it on the display shows the stored frequency from the last time it was on for about 3 seconds and then it goes to "dashes" in the frequency display. Other parts of the display seem to work normally when buttons are pushed; when buttons are pushed the frequency displays again for a couple of seconds. With all "dashes", there is no audio output with the squelch turned off for both receivers and the radio will not transmit. After about 30 to 45 minutes the frequency displays start to work, they may flicker while coming on, one band comes on and then the other with the first normally being the 70 cm signal path. The audio comes back at the same time. When I try to transmit into a dummy load the display flickers and the s-meter/power meter flutters at the top end. There are some common components for this. The MCU(CPU), the connectors between the display board/front panel and the main board (with the IFs and other signal paths), the front panel 5 V supply are the major common components. I have reset the CPU and it seems to do no good. The connectors mentioned are "flex board" type connections; I cleaned the contacts as best I could with alcohol. The 5 volt supply indicates 4.98 volts on my cheap digital multi-meter, is there when the radio comes on and does not seem to have issues when transmitting. My troubleshooting is limited since I don't have an oscilloscope.

Has anybody seen a similar problem? Has anyone had an IC-821 repaired recently and by whom? I know parts are limited or non-available for this radio but I suspect that the actual signal paths are still good; it is just control issues. There are some commodity ICs that are still available that might be replaced. Maybe there are sub-assemblies out there from a radio that is broken otherwise that might fix this if I can determine what the problem is.

Thanks,

Bill, WD5HHH

WD5HHH
Posts: 2
Joined: Fri Jan 31, 2020 7:38 pm

Re: IC-821H Display and Operational Problems

Post by WD5HHH » Wed Feb 05, 2020 4:47 pm

An addendum to the above: The radio now does not come back to life. It is stuck in a non-operational mode.

Bill, WD5HHH

k9yli
Posts: 228
Joined: Fri Aug 12, 2005 11:35 pm
Location: northwest wisconsin

Re: IC-821H Display and Operational Problems

Post by k9yli » Wed Feb 05, 2020 6:28 pm

as original problem seemed to be affected by time,, then hair dryer might help to locate what was working after warm up.
Also on multi board radios.. grounds are a common problem. re-plug EVERY cable at least twice, to scratch the pins and remove corrosion. also loosen and re-tighten every board mounting screw, as a lot of them provide ground.
get some shish-ka-bob sticks at the grocery store and use one to put pressure around the boards,
localize as best you can any failure or change, then magnifying glass to eyeball for cold solder job , or possible cracked land pattern. (less likely than bad solder)
I am working on a scope and I have found 3 bugs by using board pressure.
your problem is the PLL is dropping out so no frequency, no rec, no xmit..

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