quaddriver

Yinz may or may-not be in luck...

As some may remember, seeing as I have not been around in over 6 months...I have a 78 98. I had asked how to get the radio out as I am going to restore it, well, because it sounds like ***.

on these old car stereos, this is before fancy gizmotronics so the radios have very low rail voltages and are cap-coupled outputs (all technical terms)

Well as some may remember, I have a side biz/hobby of restoring vintage stereos and today at the store, one of my long term customers dropped in to check out some speakers and left me with the factory radios from his factory perfect 1968 and 1969 442's, wants them spiffed up and returned to top shape AND, he found the schematic/service manual for the one which pretty much makes it a road map for most of the solid state stuff in the 60's/early 70's.

So, the part where you all may or may-not be in luck is I am going to put together a 'how to' for the radios in general, given that I have 3 AMFM examples - identify the sections, which parts to peek at etc, what to put in.

who knows, it may start a new cottage biz for me...I never wanted to be the guy at Carlisle that fixed the car stereos, but he seems to be gone now and I'm remodeling the 'new' house so I need money...

what I could use is a line on any and all sams or dephi schematics for same...

Cincinnati Rick

This sounds like a great idea. Wish I had something to contribute but I got notta.
Good luck and I look forward to the "how to's".
I have a AM radio that needs a little love.

quaddriver

I had threatened to do this earlier this year in april, on my 78 98 AMFM but we got the house, closed, moved, ripped out the kitchen, open scaped the first floor... - you know - satisfy the wife demands! I had to put my stereo restoration biz on a back burner for a couple months and now that I got caught up and he dropped off 2 radios and wanting results...I pop the case tops tomorrow at 5pm...

Yellowstatue

GM put out a manual each and every year since forever. Covers all GM's, all models W/model number and even for Lincoln, Studebaker, Plymouth Dodge Imperial Chrysler and Opel in the '50's and '60's. For instance Bulletin 6D-1977-1 is for 1977 of course. Beginning around 1970 the GM books also have an eight year index with radio model numbers for the previous years. These books contain all the schematics and part numbers and illustrations of the radios and speakers with wiring as well. Reverbs are also covered. So check your literature vendors for these publications.

quaddriver

thanks - I have not seen these online as of yet. I did find the sams catalog...for example the 69 442 radio I decided to jump into last night (already got it working) - it was in sams AR-50 and since they differed generally only by case (chevy vs olds vs buick) just getting in the ballpark can help.

I have been putting the tutorial together as a docx - how would I upload the finished product here?

RetroRanger

I think you could save it as a PDF instead of a docx when you save it then attach it as a file....PDF is generally smaller than docx

quaddriver

ok, not nearly done or proof read, but as a test...I count 275 K with pics so far

quaddriver

now that I have the target radio working (90% cleaning of contacts and controls) I am looking at refurbishing the hard parts.

tip: (which will be included in the writeup) the radios make use of about a dozen 1N34xx germanium diodes, which you can still get for about .99 each. I have a hundred 1N90/99s and 1N60's which are more modern and you can get for about .04 each. I am testing them in the detectors and AGC circuits to make sure they stay sensitive.

the owner got the sams and scanned it and sent it to me, these might be crude by modern standards, but not junk...3IF sections in FM. thats pretty sensitive.

quaddriver

The latest cut, with more in depth tech and tons of pictures. even as a PDF it grows to just over 1MB

35tac

This is great.
Thanks
Wayne

quaddriver

Last cut for now...

did the 1969 first, then the 1968 after. GM reserves the right to make small changes in appearance!

Anyways, attached is latest for your pleasure...save it where-ever. I give his radios back saturday and he says he dug out an 8 track to look at (ugh, I hate 8 track stuff)

I know I will be asked, but the parts I did replace came in about $5 retail and it took me about 3 hours per radio. IF I were to do this commercially on a regular basis, these were $50 jobs so use that as a baseline if you shop around. By no means do I want radios mailed to me! I got a kenwood, pioneer and a marantz on the shelves next to me in the bullpen...

quaddriver

Turned over the AMFM's and got an AM FM with a separate 8 track player and amp module from a 1970 tornado

have not cracked it open, he found the SCM for both amps and is looking for the SCM for the stand alone 8 track player (its in a black plastic housing that looks like it bolts under the dash?)

the freaky fader control is now a righteous pot inside the radio and it appears that the L/R heads of the 8 track are fed to each of the 2 amps. things didnt improve electrically so they could not squeeze BOTH amps in, and it seems the standalone amp is merely a clone, front speaker from the internal amp, rear speaker from the external amp. I guess if you are playing an 8 track tape you get each channel in a different speaker, but an optimum sound field it aint.

IT will take me a week or more (prolly 2) to crack this open, have other victims on the bench right now - and once I do, any findings will get added to the document.

but lets digress back to the previous radio....when I got the the 2nd radio, from the 68, he said it worked, and it did, but it appeared electrically to me as a damn near direct short. (the non working 69 radio was actually an easier fix)

the 'DS-501' out put transistor GM used, is the largest consumer - the radio was listed to draw 1.3 amps of current at 12.6v (they insist that battery or alternator voltage will be that low) which is about 16 watts.

if I read the spec on it correctly, it crosses to the 2N441 GE, NTE 105 (dont use NTE) or the later Delco 2N1970. these are 15 amp, 150watt units.

the fuse they say for the radio is 9 amps in the fuse block (is this true? where do you find an ACC or AGC in 9 amps?????) which means, that even if it was fused for 10 amps, the fuse will blow before the output. I guess thats one way to guarantee longevity.

so if you get into one of these, pay REAL close attention to the R2 bias resistor (600ohms) it corrodes BADLY when exposed to wet and it was allowing like 4-5 volts across the collector, which of course, was well below the threshold of when it would pop. but boy it got hot in a hurry.

since the idle voltage (which produces an idle current) is a whopping 1.5v - in home stereos we typically have 15-30 MILLIvolts - they get hot *anyways*

I will add this info to the doc when I have time. stay tuned.

one last thing, if we cannot find the SCM for the tape player preamp (anyone got one?) and it dont work, we are thinking about yanking the preamp out of a home unit - they run on 12v and have silicone guts which I can replace with common A992/C1845 transistors - and save a crap load of space. the belt is very much likely to be available as a generic replacement. all of your 8track tapes remain junk, but still, at least you will be able to have the tape yanked out of the cartridge for extra fun.

quaddriver

bump.

just got in from the same guy a wonderbar. keee-rap. this is a bad idea from someone. 1968 vintage from a 98.

so I will delve into what it takes to fix one of these. apparently, it uses the discriminator output to drive a motor to tune it. that should be fun with caveman electronics