1980s Sanyo RM 6400 Clock Radio

[jt154]

Hey guys, first time posting here. I’ve recently acquired a Sanyo RM 6400 Clock Radio from a flea market that needs repair.

Everything is working except for alarm 1. When alarm 1 is set to radio, the radio comes on as it should. However, when it is set to buzzer, the radio comes on and instead of the buzzer, a popping sound is emitted from the speaker when the volume for the radio is set on minimum.

When I first got the clock radio the buzzer worked, but after one week of storage it has miraculously died. I suspect the TMS3459BNL chip might be to blame, but I’m hoping the problem might be something less costly as the cheapest chip I could find costs more than what I paid for the clock

Would anyone have any schematics or manuals? I couldn’t find any online. Greatly appreciate any help.

[envisionelec]

When I was young, I would test my repair skills on clock radios. I had one exhibit behavior that was very similar to this. I could never find the problem, but chalked it up to lightning damage - here's why: the FM-band antenna is usually coupled to the AC line cord. A high energy spike generated from a nearby lightning strike can easily induce a current into the antenna and convert to a massive energy pulse across the PCB and damage the microcontroller.

These were generally disposable items, even in the 1980's...

[jt154]

When I was young, I would test my repair skills on clock radios. I had one exhibit behavior that was very similar to this. I could never find the problem, but chalked it up to lightning damage - here's why: the FM-band antenna is usually coupled to the AC line cord. A high energy spike generated from a nearby lightning strike can easily induce a current into the antenna and convert to a massive energy pulse across the PCB and damage the microcontroller.

These were generally disposable items, even in the 1980's...

I desoldered all of the electrolytic caps to measure their values, seems like some are gonna need replacing. Hopefully that will fix the problem.

I have2 radio clocks, one of them is the Sanyo (which is my favorite), the other is a Philips D3200. The Philips units works fine except that someone cut off the antenna wire so I’ll have to solder a new length of wire for that and it should be fine.