1970s Zenith AM/FM/FM Stereo Clock Radio Issues

[vortalexfan]

Hello everyone, recently I had bought off of Facebook Marketplace a 1970s vintage Zenith AM/FM/FM Stereo Clock Radio Model H480W that has a few issues that need addressing to get it fully functional again.

I had one of these previously that had some similar issues (dead left channel, burned out pilot light for the FM Stereo light, &c.) and this unit has one issue that the one I had previously didn't have, and that is that the time and alarm set buttons on the back of the clock don't work, and I removed the push button panel from the back to reveal the circuit board for that and the contacts for the push-buttons themselves.

The contacts on the push-buttons had some corrosion on them, which I cleaned off and cleaned the circuitboard for the push-buttons but the push-buttons still wouldn't set the clock display.
The clock display set pushbutton circuitboard has 3 resistors and one ceramic disc capacitor on it to control the push-button PC Board.

I wonder if maybe one of those resistors or that Ceramic Disc Capacitor might be bad, and causing the clock set push-button PC Board to be dead?

Also I should mention that this clock looks like it has some moisture damage to some of the metallic parts (the chrome plated knobs and slide switch covers, and the screws were kind of rusty/corroded as well.)

Any ideas as to what might be the issue with my clock radio?

[Electronic M]

Buttons could have dirty contacts. You can try shorting the button terminals and see if it reacts.

[vortalexfan]

Originally Posted by Electronic M

Buttons could have dirty contacts. You can try shorting the button terminals and see if it reacts.

I'll give that a try.

[zeno]

Buttons were trouble so try EM's cure first.
Best to remove all & set switch cause any can go leaky.
If the clock IC plugs in clean the socket or solder it in.
Goes for all Zenth digital clocks of the era like the common R472
series.

73 Zeno
LFOD !

[vortalexfan]

Originally Posted by zeno

Buttons were trouble so try EM's cure first.
Best to remove all & set switch cause any can go leaky.
If the clock IC plugs in clean the socket or solder it in.
Goes for all Zenth digital clocks of the era like the common R472
series.

73 Zeno
LFOD !

I was wondering about that.
The circuitry for the clock (the power switch for the radio and alarm etc) all plug into the main board of the clock radio.
There is an old soldered in Ni-Cd rechargeable battery on the clock board in the clock radio used for battery back-up and I wonder if that battery might of "leaked"?

[zeno]

I would take out the battery for now & replace if you fix it.
Believe it or not my '472 kept its time last black out for about 12 hours
They used too good of a battery.

73 Zeno
LFOD !

[vortalexfan]

Originally Posted by zeno

I would take out the battery for now & replace if you fix it.
Believe it or not my '472 kept its time last black out for about 12 hours
They used too good of a battery.

73 Zeno
LFOD !

Ok, I'll try that out and give and give an update.

[Jeffhs]

I also have a Zenith H480W radio which works very well on AM. However, the FM reception, while it is there, is extremely weak. I can barely hear anything on FM, even with the volume control at maximum, and there is no stereo reception because the FM reception is so weak it is almost nonexistent. This problem began several years ago, when I tried to clean the function switches with contact cleaner; when I turned the radio on after I was finished, the symptoms I just described showed up (AM excellent, FM so weak it isn't funny (!)). One other problem is the dial lights behind the radio dial quit at the same time I lost my FM reception. I wonder if the two problems are related, though I can't for the life of me imagine how they could be, unless there is some connection (!) between the loss of FM reception and the dial lights.

I would like to get this radio working again on FM and stereo FM, as it sounds and works great when everything is right. (Zenith really knew its stuff when they designed this radio, IMHO.) I live in an area some 40+ miles from the local FM stations in Cleveland; every one of my FM radios, with one exception (my Aiwa CX-NA888 bookshelf stereo system) get most of the stations just fine, using only indoor FM antennas (the Zenith radio has a coupling device which connects the line cord, by capacitive coupling, to the AC line cord, and works great, receiving every local FM station as well as any other FM radio I own).

I have a feeling I may have shorted something out on a PC board when I was spraying contact cleaner on the function switches, which may very well explain why the FM reception on my H480W Zenith radio is so weak; that, or else maybe I could have pulled a connection loose on the FM function selector switch. I personally cannot imagine how I could have damaged anything simply by cleaning the contacts on the function selector switches, unless there may have been a connection just hanging on by a thread (!) which was torn loose when I was spraying the cleaner around the switches.

BTW, the clock backup battery in my H480W is still connected inside the radio (and is almost certainly dead as a door nail by now), but I am almost afraid to do anything with it because it may have leaked and may have made the heck of a mess on the radio's PC boards. I don't know how long these NiCd rechargeable batteries are supposed to last, but as old as my H480W radio is (I bought it well over 20 years ago), as I said, the battery may very well be dead by now, and will not take a charge. I may just remove the dead cell and use the radio without it. As I said, this radio worked absolutely great on FM before the problem I described showed up, and I'd like to get it working that well again, if possible.

Zenith is out of business as far as radio and TV are concerned, so I would certainly like to get and keep all my Zenith radios (and my 19-inch Zenith SMS1917SG color TV) working as well as possible, as long as possible. There is no more Zenith Radio Corporation, and no one builds radios and TVs as well as they did. Zenith was always my favorite brand of home entertainment gear; it goes without saying I miss them. There will never be another Zenith Radio Corporation, which is, IMHO, too darn bad. They were one of a kind, and one of the best if not the best manufacturers of radios and television receivers.

[vortalexfan]

Originally Posted by Jeffhs

I also have a Zenith H480W radio which works very well on AM. However, the FM reception, while it is there, is extremely weak. I can barely hear anything on FM, even with the volume control at maximum, and there is no stereo reception because the FM reception is so weak it is almost nonexistent. This problem began several years ago, when I tried to clean the function switches with contact cleaner; when I turned the radio on after I was finished, the symptoms I just described showed up (AM excellent, FM so weak it isn't funny (!)).

I would like to get this radio working again on FM and stereo FM, as it sounds and works great when everything is right. (Zenith really knew its stuff when they designed this radio, IMHO.) I live in an area some 40+ miles from the local FM stations in Cleveland; every one of my FM radios, with one exception (my Aiwa CX-NA888 bookshelf stereo system) get most of the stations just fine, using only indoor FM antennas (the Zenith radio has a coupling device which connects the line cord, by capacitive coupling, to the AC line cord, and works great, receiving every local FM station as well as any other FM radio I own).

I have a feeling I may have shorted something out on a PC board when I was spraying contact cleaner on the function switches, which may very well explain why the FM reception on my H480W Zenith radio is so weak; that, or else maybe I could have pulled a connection loose on the FM function selector switch. I personally cannot imagine how I could have damaged anything simply by cleaning the contacts on the function selector switches, unless there may have been a connection just hanging on by a thread (!) which was torn loose when I was spraying the cleaner around the switches.

BTW, the clock backup battery in my H480W is still connected inside the radio (and is almost certainly dead as a door nail by now), but I am almost afraid to do anything with it because it may have leaked and may have made the heck of a mess on the radio's PC boards. I don't know how long these NiCd rechargeable batteries are supposed to last, but as old as my H480W radio is (I bought it well over 20 years ago), as I said, the battery may very well be dead by now, and will not take a charge. I may just remove the dead cell and use the radio without it. As I said, this radio worked absolutely great on FM before the problem I described showed up, and I'd like to get it working that well again, if possible. Zenith is out of business as far as radio and TV are concerned, so I would certainly like to get and keep all my Zenith radios (and my 19-inch Zenith SMS1917SG color TV) working as well as possible, as long as possible.

I'm with you, I really like Zenith products, plus my dad's family always bought Zenith products for years and my dad had a Zenith "Space Command" TV from 1985 that he bought brand new, and we used it until just shortly after the DTV switchover because that's when the picture started getting "soft" and I tried to fix it and I ended up shorting something out on the TV so we had to get rid of it.

Whenever I see an old Zenith radio or TV on Facebook Marketplace and it's decently priced and it's located nearby I try to pick it up.

[vortalexfan]

Originally Posted by zeno

I would take out the battery for now & replace if you fix it.
Believe it or not my '472 kept its time last black out for about 12 hours
They used too good of a battery.

73 Zeno
LFOD !

i'm trying to replace some of the old electrolytic caps in the power supply and output coupling caps and I only had one 470 uF electrolytic that was slightly higher than the original caps voltage wise, so I popped open an old PC Power supply and they had some 470 uF caps in there but they were slightly lower in voltage rating than the original caps, the original caps were 470 uF 16 V caps, and the ones in the old PC Power supply were 470 uF 10 V, would it be ok to use 470 uF 10 V caps in place of 470 uF 16V caps or should I just stick with caps that are the same or higher voltage than the original?

the battery in my radio says it needs to charge for 15 hours at 45 mA, the only kind of battery charger I have is a charger for NiMH batteries that charges at around 2500 mA, what could I use to test the battery to see if it will still take a charge?