Circa 1964 Delco automobile AM radio repair - Page 1
Forum section: electronics / repair

author: Wimberleytech
author_rank: Super Contributor
timestamp: July 15, 2018, 04:33:21 pm
content: I ordered an old radio from Ebay to install in a 64 Chevy C10 I just bought and will refurbish. Most likely the radio will not work. I can probably fix it without schematics, but it would be handy to have them.The specific model is: Delco 986771I have seen some links to places selling schematics/manuals and such but figured somebody here might have a schematic.

author: drussell
author_rank: Super Contributor
timestamp: July 15, 2018, 05:08:23 pm
content: It looks like it is in SAMSset 262 folder 4if anyone has that set or you could buy it from:https://www.samswebsite.com/en/photofact/details/index/id/64812You could also take a look in the Rider's books since they've been scanned and are available online... It should be in volume 24, I would think, if they ever had it, but I can't find an index for volume 24 (should be 1955?), though I don't know how many car radios were in the Rider's manuals.

author: Wimberleytech
author_rank: Super Contributor
timestamp: July 15, 2018, 06:00:10 pm
content: Quote from: drussell on July 15, 2018, 05:08:23 pmWow, well done! I will probably just by the Sams...wow that takes me back to the old TV repair days in high school. Thanks!

author: amyk
author_rank: Super Contributor
timestamp: July 16, 2018, 12:11:05 am
content: http://chevy.oldcarmanualproject.com/radios/index.htmhas a lot of useful information.Here is yours:http://chevy.oldcarmanualproject.com/radios/pdf/6D-853ums.pdf

author: james_s
author_rank: Super Contributor
timestamp: July 16, 2018, 01:14:30 am
content: A lot of the issues you're likely to run into will be the same as with household radios from the era. If it's a tube radio I'd start by checking that all the tubes are present and intact, and check that they are the right tubes and not something random someone stuck in there to make it look complete, 1964 is right around the time where it could be solid state though, I don't know offhand. Then replace any wax paper capacitors and check the carbon comp resistors for anything way out of spec. If it is a tube radio then it will probably have a vibrator to generate the plate voltage, those are mechanical devices that tend to fail due to metal fatigue and/or burned contacts.

author: floobydust
author_rank: Super Contributor
timestamp: July 16, 2018, 01:26:30 am
content: 1964 Chevy C10 had the smaller solid-state radio. Class A output stage so it could draw almost an amp at rest.1954 had the tube radio 986771.

author: james_s
author_rank: Super Contributor
timestamp: July 16, 2018, 01:29:32 am
content: Well that should simplify things then, even the early solid state stuff was reasonably reliable, though it can be hard to find replacements for germanium power transistors if one is bad. One thing I forgot to mention if applicable is to re-string the dial cord, they often break in older radios.

author: Wimberleytech
author_rank: Super Contributor
timestamp: July 16, 2018, 01:43:30 am
content: Well something is off...the schematics posted by amyk is a tube radio and agrees with the model number I provided. Mine is solid state. I guess the Ebay seller gave the wrong model number. Here is the actual radio I expect to receive.When it shows up, I will follow up on this post with the correct model number.When I was in high school (a long time ago), I worked for a car radio install/repair place in Houston. I did not do the repairs--just the installations. The two guys that did the repairs (both Marine Vietnam Vets) could repair radios in nothing flat.Anyway, thanks all for the great comments...stay "tuned"

author: Wimberleytech
author_rank: Super Contributor
timestamp: July 16, 2018, 01:45:42 am
content: Quote from: floobydust on July 16, 2018, 01:26:30 amCorrect. Something awry with the model number provided by ebay seller.

author: james_s
author_rank: Super Contributor
timestamp: July 16, 2018, 01:47:51 am
content: Well let us know what happens. Having never dealt with that specific radio, I'd say there's a 75% chance it will just work straight away, although it looks like it could use a good deep cleaning, probably some Faderlube in the volume pot and Deoxit in the switches.

author: Wimberleytech
author_rank: Super Contributor
timestamp: July 16, 2018, 01:49:12 am
content: Now I am confused. Here is a picture of the model number.

author: Wimberleytech
author_rank: Super Contributor
timestamp: July 16, 2018, 01:51:03 am
content: Quote from: james_s on July 16, 2018, 01:47:51 amYup, there is a lot of cleaning to be done!!!

author: james_s
author_rank: Super Contributor
timestamp: July 16, 2018, 02:03:47 am
content: Wow that thing has seen better days. That is a pretty cool looking truck though, I bet it'll be a nice ride once you get it fixed up. I can't really think of any car on the market today or even in the last 10 years that does anything for me.

author: Wimberleytech
author_rank: Super Contributor
timestamp: July 16, 2018, 12:25:08 pm
content: Quote from: james_s on July 16, 2018, 02:03:47 amShort story:Uncle bought it new 1964My dad inherited it about 1974Gave it to me 1985I sold it 1990 (grrrrr!! was in graduate school and needed the money!!!!!!)--Been kicking myself ever since--Last week, my brother found it on CraigslistNow it is mine.Bought it back from the same guy who bought it from me--28 years later.Rust-wise...it is actually in remarkable shape...I will bring it back to its former glory.

author: Wimberleytech
author_rank: Super Contributor
timestamp: July 17, 2018, 12:23:41 am
content: Quote from: james_s on July 16, 2018, 01:47:51 amPrescient you are! Got it today, powered up...it works.

author: james_s
author_rank: Super Contributor
timestamp: July 17, 2018, 02:30:55 am
content: No abilities to see the future there, just the simple fact that a transistorized AM radio is a simple device without much to go wrong. Glad it turned out to be working.

author: floobydust
author_rank: Super Contributor
timestamp: July 17, 2018, 02:36:10 am
content: A few things about the '64, I drove one a very long time ago. All steel interior and dashboard. 283 CID with three on the tree shifter.It was the last year of the single-reservoir brake master cylinder system. If brake fluid went low, you had no brakes. I would recommend something more modern.I put in power steering to make driving it easier.I changed over to the new style alternator (electronic regulator).Point ignition was actually OK if you set dwell and timing every 6 months.

author: Wimberleytech
author_rank: Super Contributor
timestamp: July 17, 2018, 12:35:25 pm
content: Great input floobydust! As far as power steering...I struggle to balance usability to original restoration. With the huge steering wheel, it is not hard to steer.

author: floobydust
author_rank: Super Contributor
timestamp: July 17, 2018, 04:52:58 pm
content: I learned a lot about engineering from the old Chevy's. The good and the bad.The first time you park the truck, it's a good workout. Teens and very few women can handle manual dry steering on a truck. It's a manly job.As I was parking it and brushed up against the curb, the tire dug in and the steering wheel went crazy spinning.I tried to grab the wheel and it trashed my handVery forceful. Installed power steering right away after the bandages came off. I think it was a '67 steering box and pump brackets that fit.Chevy was smart in keeping parts simple and the same across model years, and I do the same with designs - instead of a new custom part every time.Brakes failed when I was entering a corner, so I slid on ice and nailed a curb. It was winter.There's no dashboard warning light and the reservoir cover is steel so you have to pop the lid to check fluid level.It taught me about engineering, feeling like GM was too cheap to put in a light. Or it's just that era.Anyhow, I spend the extra penny and put lights/e-stop/fuse etc. on all safety-critical stuff where other engineers don't bother.