88-94 Factory Stereo Info

[AK49BWL]

Playing around with these led me to a very interesting discovery.

It is in fact possible to utilize a head with the Bass/Treb buttons with a 5-Band cassette deck (and 5-EQ CDM) and still be able to use all the bands. How?

On some of the heads' wire harness is an extra wire with a connector on the end that seemingly has no use.

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Through tracing the CDM board, I found that it's connected directly to the pin beside it, which is the CDM/Head data supply line. In addition, on the 5-EQ heads, this wire is also connected to the white wire in that extra 2-wire connector that plugs into the back of the cassette deck. So, cue some experimentation.

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I plugged my Bass/Treb head into my 5-EQ CDM, and plugged that extra wire into the 5-EQ cassette's pin 2 (also a white wire internally). Lo and behold, all 5 bands lit up on the cassette deck, and the Bass/Treb buttons actually controlled the EQ display too!

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So I found that pretty cool of course, the middle three bands still have to be controlled from the EQ itself.

I also discovered that the yellow wire in the 2-wire connector is for the EQ display dimming. The button backlighting gets its signal from the actual cassette player's harness, but there's no wire in that harness for LED display dimming. There's a voltage regulator in the head that operates the LED display dimming when the park lights are turned on, and this voltage regulator also runs the EQ display in the cassette deck via the yellow wire. More interesting stuff.

The 5-EQ heads actually have the Bass/Treb buttons internally bussed to work, just no external buttons mounted. And it turns out the two different heads have the exact same circuit boards in them, so guess who now has a Bass/Treb head with the extra 2-wire EQ connector

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Why? Cuz I can

 

[Eveready]

I might have found both an 88 and an 89 with the stereos still in them. They aren't anymore lol.


I agree with the black button/silver face being a really good look for these! Needs a lot of cleaning tho. CDMs are both 16072780, 89's cassette deck is 16084945, 89's head is 16084245. The stickers were ALL missing from the 88's head and cassette deck so dunno if they're the same or not. I'd have to assume not, based on the difference in aesthetics, but the CDM was the same part number so who knows lol

An old radio guy I knew cleaned that sort of stuff up by spraying Windex on a hand towel and just wiping it off. You don't want to spray directly as you don't need liquid getting into the works. The alcohol in the windex will evaporate the small amount of water pretty quickly if it is wiped on with a towel. That gets most of the dust and crud off quickly.

 

[Donald Mitchell]

My 2 cents. The caps last a long time but for most of these time is running out. M hobby is vintage radios and I find later solid state equipment holds up well especially if you use it regularly. I got from a friend of mine who works on these units that all the black round electrolytics should be replaced to to protect the non replaceable chips in it if nothing else. If your experienced at soldering you can probably handle the job. most of these are polarized meaning a pos and neg that has to go back the same way. Best to use good quality but not expensive brands. Nichicon, or Panasonic are great and a lot of others. Each one has the value in microfarads (Mf or Uf) and Voltage rating. The Mf or Uf needs to be as close as possible while one rated with higher voltage is fine as long as the physical size will fit the location. Do not go lower on voltage! Of course if your radio is dead there might be something else wrong. Look for burnt shorted parts, dark aeras on the circuit board and a magnifying glass to see bad cracked solder joints.

 

[AK49BWL]

I was thinking about that last night as I took apart the 88 cassette deck and found a couple melted components (the EQ display doesn't light up, and the biggest burned area looked to be around a current-limiting resistor going to the 5v voltage regulator that feeds the display... The cassette player sounds muted as well as only playing on the left channel so I'm probably just going to harvest that one for mechanical parts).. Some of the caps didn't look so great either. I'm handy with soldering to an extent, but I really need to get a new iron lol.

@Donald Mitchell - would you happen to know a good place to order small quantities of components for agreeable prices? I'd prefer Panasonic if I can get em, I've never had problems with anything Panasonic in my life.

 

[Eveready]

My 2 cents. The caps last a long time but for most of these time is running out. M hobby is vintage radios and I find later solid state equipment holds up well especially if you use it regularly. I got from a friend of mine who works on these units that all the black round electrolytics should be replaced to to protect the non replaceable chips in it if nothing else. If your experienced at soldering you can probably handle the job. most of these are polarized meaning a pos and neg that has to go back the same way. Best to use good quality but not expensive brands. Nichicon, or Panasonic are great and a lot of others. Each one has the value in microfarads (Mf or Uf) and Voltage rating. The Mf or Uf needs to be as close as possible while one rated with higher voltage is fine as long as the physical size will fit the location. Do not go lower on voltage! Of course if your radio is dead there might be something else wrong. Look for burnt shorted parts, dark aeras on the circuit board and a magnifying glass to see bad cracked solder joints.

You give good advice sir. I still have the OEM radio and thought I might recap it at some point. Those end of life caps are the reason i went aftermarket on the radio. My last two restorations were black dial Zeniths . An 8s154 and a 5s127. Both play great.

 

[AK49BWL]

Since we're on the subject of caps now...

CDM 16172125 -- I forgot to take the FM receiver cover off, but there are only two caps under there, both marked.

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Cassette Player/EQ 16156545 -- most of the cassette player boards are similar, however the 88-89 definitely are not! ALL of the EQ driver boards are the same between 88-94 however.

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EQ Driver Board

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Head 16189885 (16189895 identical)

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I don't know why those two caps are two different sizes.... They both have the same markings.

Those two current limiting resistors get HOT AF while the displays are on... IMO they really should be heat sinked like the voltage regulators are. Two of my EQ decks have burn marks under that resistor, one smoked while I was testing the system. Stinks like a *$^%*^#$*&%^*&#&$^%

 

[Donald Mitchell]

I was thinking about that last night as I took apart the 88 cassette deck and found a couple melted components (the EQ display doesn't light up, and the biggest burned area looked to be around a current-limiting resistor going to the 5v voltage regulator that feeds the display... The cassette player sounds muted as well as only playing on the left channel so I'm probably just going to harvest that one for mechanical parts).. Some of the caps didn't look so great either. I'm handy with soldering to an extent, but I really need to get a new iron lol.

@Donald Mitchell - would you happen to know a good place to order small quantities of components for agreeable prices? I'd prefer Panasonic if I can get em, I've never had problems with anything Panasonic in my life.

I use ebay a lot for small quantities and mostly free shipping. For harder to find items I use Mouser and DigiKey, top notch companies.

 

[Donald Mitchell]

Since we're on the subject of caps now...

CDM 16172125 -- I forgot to take the FM receiver cover off, but there are only two caps under there, both marked.

You must be registered for see images attach

Cassette Player/EQ 16156545 -- most of the cassette player boards are similar, however the 88-89 definitely are not! ALL of the EQ driver boards are the same between 88-94 however.

You must be registered for see images attach

You must be registered for see images attach

EQ Driver Board

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Head 16189885 (16189895 identical)

You must be registered for see images attach

I don't know why those two caps are two different sizes.... They both have the same markings.

Those two current limiting resistors get HOT AF while the displays are on... IMO they really should be heat sinked like the voltage regulators are. Two of my EQ decks have burn marks under that resistor, one smoked while I was testing the system. Stinks like a *$^%*^#$*&%^*&#&$^%

Excellent job!

 

[Donald Mitchell]

You give good advice sir. I still have the OEM radio and thought I might recap it at some point. Those end of life caps are the reason i went aftermarket on the radio. My last two restorations were black dial Zeniths . An 8s154 and a 5s127. Both play great.

Cool, I love the older radios. Are you on Antiqueradios.com boards? I'm drmitch on there.

 

[Insert Quarter]

I came across a PDF of a "1990 Delco Auto Radio Service Manual". It has some repair procedures, part numbers, and schematics. I used it to figure out which pins to solder RCA outputs to. Anyways, I can't seem to upload it, I get a "file is too large" message, it's PDF format, 3.15MB, a small booklet only a handful of pages. If there's a way to attach it please let me know, otherwise I can email the PDF if anyone is interested.