Delco Radio Repair - Right-Channel out / static / thumping noise....

[turbokinetic]

I always gather the Delco EQ radios from salvage yards whenever I see them. Lately, more and more of them have suffered from the same exact symptom. The right speaker channels will pop, crackle, thump, be muted, or otherwise not work. It's always the right channels.

The problem, I found, is 3 capacitors on the amplicier board. I don't have very good pictures of where this board is located, but I do have the board repair pictures.

The 3 shortest caps (circled in red) are the problem. They are small to fit underneath the heat-sink for the amplifier power stages. These are the only ones that fail.


Pull them off the board, then de-solder the pins. The board may be corroded from leaked capacitor fluid. Clean it thoroughly so that the new ones will solder.


The only 1uF caps I could find at Radio Shack were standard size. To make them fit, I laid the 2 under the heatsink (circled in red) on their side. The one (circled in blue) on the right is not completely under the heatsink, so it could still stand up.


After that, a little daub of silicone sealant on the caps to support them to the board. Then follow with a shot of clear enamel paint to seal out moisture.

The amp board is on the end of the radio with the aluminum heat sink. You'll need a 1/4" nutdriver and a very small Torx screwdriver to access it.

That will 100% fix the right-channel issues.

If you want to operate the radio with the covers off, to verify the repair don't run it long and don't turn up the volume. The amplifier power stages will quickly overheat without the heatsink. Make sure the white heat transfer paste is still in place on them before the heatsink goes back on, too!

Thanks,
David

Tantalum caps installed:





Update -

Radio Shack sells a different style capacitor which will fit in the place of the original small green capacitors. It is a "tantalum" capacitor. It is a small beige pellet-shaped part which will fit under the heatsink without any modifications at all. Makes for a much quicker and factory-like repair.

Part number: Radio Shack 272-1434
Description: Capacitor, tantalum, 35WVDC, 1.0uF

[mechanizeddeath]

Wow. Not only are you amazing with engines and turbochargers, but your electronics skills exceed my own. Great work, is there anything you can't do?

[billkandi]

Thanks, I needed that!

[turbokinetic]

Wow. Not only are you amazing with engines and turbochargers, but your electronics skills exceed my own. Great work, is there anything you can't do?

Thanks! I have been a technician all my life. During my school age years, I would play with things like old electronics and mechanical stuff, while my peers were into football and finding which stores would sell you beer without a drivers license.

Thanks, I needed that!

Glad it helped you!
David

[billkandi]

Does this work on the lower end radios w/out the EQ? I thought my son's car had it but not the case. Same issues though. Replaced RF dash speaker, still didn't work. RR barely works. Left side mediocre.

[Century7667]

If something goes on old audio equipment, it's usually a capacitor. I'm still trying to figure out how David knew just which capacitors were involved. Must have had a schematic.

Ken T.

[turbokinetic]

Does this work on the lower end radios w/out the EQ? I thought my son's car had it but not the case. Same issues though. Replaced RF dash speaker, still didn't work. RR barely works. Left side mediocre.

Should have same amplifier board!

.... I'm still trying to figure out how David knew just which capacitors were involved. Must have had a schematic.

Ken T.

Nope, no shematic. Just troubleshooting on a component level. The failing caps become temperature sensative, and you can touch them with a hot soldering iron. If the thumping or static changes when you heat one particular cap - then that one is damaged.

I knew the static noise was coming from the amplifier board because I could turn volume down all the way and it continued.

David

[mechanizeddeath]

Well in some cases you can simply follow the traces with your eyes and a multimeter, but yeah a schematic works wonders. And in this case, sometimes just looking for something out of place will do the trick. Those bad caps are different from the others on the board, they're stubby and a different color. With everything else working alright, and knowing caps often go bad, I'd immediately suspect those caps over the other ones.

Bad capacitors are definitely the source of most electronic problems. About 10 years ago there was a deluge of bad capacitors out on the supply side of things, and many of them were used on computer components of the time. I don't think any brand was spared, and it resulted in a period of very mysterious computer problems due to the bad caps. It was mostly a computer problem, but I always suspect these defective caps whenever something from '95-'05 starts behaving oddly.

Here's an interesting read on the issue:
http://en.wikipedia.org/wiki/Capacitor_plague

[Century7667]

Should have same amplifier board!




Nope, no shematic. Just troubleshooting on a component level. The failing caps become temperature sensative, and you can touch them with a hot soldering iron. If the thumping or static changes when you heat one particular cap - then that one is damaged.

I knew the static noise was coming from the amplifier board because I could turn volume down all the way and it continued.

David

That's really good to know! I've never pulled the Buick dash. Is the radio hard to pull out?

Thanks,
Ken T.

[mickstan_VR]

Awsome! I've had that problem in the past with some GM radios.I always just tossed them and went to a junkyard and rolled the dice on another one. David, thats a great fix. Not to change the subject, but.... this needs to be "sticky". Can we do that here?

[mechanizeddeath]

That's really good to know! I've never pulled the Buick dash. Is the radio hard to pull out?

Thanks,
Ken T.

I actually did a Century many years ago, and though I don't recall much about it, I remember it being "about average" as far as installation headaches go. Someone said (on this forum I believe) that 6000 owners had the least screws to remove while Cieras had the most. The Ciera wasn't too bad, I would say slightly above average difficulty, but certainly nothing to freak out about. There were a lot of screws but most were obvious, the worst part was the screws hidden behind the leftmost and rightmost vents, I never would have found those without asking around.

[Century7667]

Someone did a nice vid for the Ciera. Nothing on the Century...yet. Maybe I'll get a camera one day!

Ken T.

[jeffreyclay]

Thanks! I have been a technician all my life. During my school age years, I would play with things like old electronics and mechanical stuff, while my peers were into football and finding which stores would sell you beer without a drivers license.



Glad it helped you!
David

You sound alot like me at that age. I was busy learning Corel Draw so I could make the bogus ID's. Amazing what you can do with quality paper stock and a high-end color laser printer.

[mechanizeddeath]

Ah, the laminated paper license. Here in Michigan there were a fair amount of printing errors with '79 birth year licenses. The top of the 9 was often faint or even missing altogether, and even if it was there, a few careful pokes from the backside with the needle could obscure it enough. A topless digital print 9 looks an awful lot like a 4, and quite a few of my classmates got away with these bogus 1974 birthdates on legitimate 1979 licenses. Getting into bars and clubs didn't usually work, but I actually witnessed at least one foreign liquor store employee get duped by a classmate. I still remember passing licenses around at school to see who had the faintest top of their 9.

Did I participate in this? Heavens no, I was too worried about getting caught. Like David, I was tearing into radios and learning about electronics back then, and some would even say I was abusing caffeine to stay up all night in order to learn more. No alcohol for me.

[SexySilhouette]

Never saw this thread...

I have 4 of them with this problem which will now be fixed soon.