What Minuit knows about stock Jeep radios

[Minuit]

This thread got stickied? Hmm, I didn't even notice until now.

 

Anyway - for those who have not been keeping up and are only popping in to ask questions or browse through the pretty pictures: From September until April, I had to suspend working in basically anything having to do with these radios due to a very busy - too busy - work schedule. In April I had a medical event that left me "disabled" and unable to work that job for what might end up being forever, so it's back to radios for now.

 

For my first trick, I have managed to locate another hen's tooth: Remember the Eagle Premier head unit I teased a while back? I found the full unit, and fully working too - down to all of the light bulbs. And there's a lot of light bulbs in this thing.

 

 

Weighing several pounds, fused at 10 amps, and almost maxing out my 3A bench power supply at listening volume, this was essentially the ultimate in Mitsubishi's line of car radios. For 1988, this radio has the best of everything. Featuring a 7-band graphic equalizer, a very fancy (and very effective) AM-FM tuner with some special functions including National Semiconductor's Dynamic Noise Reduction, AM stereo, and station scanning (the only radio of this line to have it). They also managed to shoehorn a fully motorized, computer controlled tape deck with Dolby-B, track searching, and auto reverse into this. It's the same deck as the RX-170 through RX-173. The top unit is not capable of driving speakers on its own - the amplification stage is located in the equalizer.

 

The top unit fits into the same footprint as a standard Jeep radio. The bottom equalizer/amplifier has a special bracket attaching it to the main unit. Power output is modest but typical of the era, rated at 9 watts per channel (36W total) into 8 ohm speakers at 10% THD, and roughly double that into 4 ohm speakers, but heat would likely become a major concern.

 

Construction wise, it's no slouch either. All circuit boards are double-sided with plated through holes, conformally coated, and the typically high quality of components used in all of these Mitsubishi-built radios. I'd compare the older ones to being built like an old home audio receiver. This one is built like a piece of military issue test equipment. It must have cost an absolute fortune to make, and based on some factory pricing information, that cost was definitely passed onto the customer.

 

It actually sounds really good, and the onboard equalizer allows you to dial in the sound you like. It still wouldn't be able to keep up with road and wind noise of your typical Jeep at highway speed though.

 

If you're interested in some gritty details, there's a teardown of a non-working one of these on Allpar here: https://www.allpar.com/stereo/eagle-premier-stereo/default.html

 

The guy doing the teardown calls it the "most sophisticated 1980s head unit combo I have ever seen in any Chrysler product" - I don't know about that, but there are a ton of parts to this. I do have full service documentation for this system if you do happen to own an Eagle Premier with one of these.

 

This isn't the only new thing I have to show off either. More coming later.

 

[jdog]

that looks like it could put out some good sound, awaiting to see what else you can come up with

[Pete M]

1 hour ago, Minuit said:

 

 

 

 

score!    

 

oh man, there are aftermarket double-din dash trims for the Libertys now.  all I gotta do is find the rarest of rare radio and I can go back another decade in radios at the same time as upgrading!    (yes I know it's only a couple years earlier, but 80s are 80s. )

[Minuit]

Side note: the Eagle unit gives you no indication of the volume, balance, or fade. I was expecting there to be a little bar on the equalizer at least telling you what the volume is set to, but nope. I thought this was going to be a problem for my upcoming secret project (tm) but nope, that's working as intended.

[Minuit]

Here are the perfect accessories for the 2.5L AX-4, 2WD, vinyl bench seat without headrests crowd:

 

AR-7600 (86-87; possibly up to 1990)

You wanted a radio, but not the very cheapest AM-only thing in the catalog. Your morning FM talk shows are important to you, but you think this fancy "digital tuning" thing is just a fad. Stereo? Is that the thing the kids like? The AR-7600 is for you. Offered with several different model numbers and even more factory part numbers, this is as basic an AM-FM radio as you can get. The tuning knob is connected to a gear and one of those fancy tuning capacitors. Only one channel of amplification is offered. Station presets are handled mechanically - pull the button out and press it back in to save your station.

 

Under no circumstances would I advise hooking more than two speakers to this radio. That single amplifier chip works hard enough to drive two.

 

Radio reception is excellent thanks to the mechanical tuner. Also, these things are stupid reliable. Mechanical issues with the tuning dial are pretty much the only real problem they suffer from, and even then even a crappy one of these still usually works. If you can bear with only mono sound, maybe one of these isn't such a bad idea.

 

Jeep may have offered these until as late as 1990.

 

 

AR-7550 ('85)

Wait, what's that? You have two ears? You want to hear two different things in your two different ears? Fine, fat cat - here's a damn stereo radio. I bet you want power steering and air conditioning too. And radios don't need two gigantic shafts at either side anymore? Fine, be that way. While you're at it, have a separate bass and treble knob. And one of them fancy "Light emittin' diodes" to tell you when you've got the dial set right. That's a bigger deal than you might think. LEDs of any type in the commercial area was a relatively new thing at the time. Typically, you'd see LED based displays in high end test equipment and calculators, not a mid-level car radio.

 

In a revolutionary step up from less luxurious offerings, there are two whole audio channels. Two amplifiers, a balance and fade knob, and support for four whole speakers! 8 ohm, naturally. And since this is 1985, you only get six wires for your four speakers. The negatives are shared between the front and rear of each channel.

 

Catalogs and anecdotal evidence suggest that this radio was discontinued in 1986, replaced by the digitally tuned AR-7650. As a result, this a fairly rare find.

[OldSch88L]

Hey there Minuit, you seem like the reference when it comes to radios. I've read a couple of pages but I'm kind of confused as to what exact model I have.... Anyways, it worked fine when I got the truck, but nowadays the sound just cuts off after a few seconds even though the other radio functions seems ok. Notice that I never got sound from the rear speaker since I got the truck ( most probably blown), garble only from passenger front and fine from driver front. Always works the next day, but always for less than 10 seconds. Any ideas? Thanks!

[OldSch88L]

Oh and btw, the Power/ VOL/BAL/FAD button seems pretty loose in every direction

[Minuit]

On 7/18/2020 at 4:42 AM, OldSch88L said:

Hey there Minuit, you seem like the reference when it comes to radios. I've read a couple of pages but I'm kind of confused as to what exact model I have.... Anyways, it worked fine when I got the truck, but nowadays the sound just cuts off after a few seconds even though the other radio functions seems ok. Notice that I never got sound from the rear speaker since I got the truck ( most probably blown), garble only from passenger front and fine from driver front. Always works the next day, but always for less than 10 seconds. Any ideas? Thanks!

AR-7750. I'm guessing your truck is an 88? If so, that's very likely the original unit.

 

Your truck might not even have rear speakers. Those were optional, and normally came with the cassette radio.

 

These radios are quite repairable. The repairability of these radios took a steep dive off a cliff after 1990, but these are pretty robust. A repeatable loss of sound after 10 seconds could possibly be an intermittent connection inside the radio, or a thermally failing chip.

 

The loose volume knob is probably a loose nut inside the radio. They were not put on very tight from the factory, and I've seen a few of them get loose.

[fiatslug87]

My '90 had that radio (no cassette) with four speakers from the factory.

[Minuit]

2 hours ago, fiatslug87 said:

My '90 had that radio (no cassette) with four speakers from the factory.

You could of course order rear speakers as a separate option. I'm just saying that a truck with an AM-FM radio is less likely to have rear speakers than one with the cassette radio.

[rustfadesaway]

hey minuit, i was wondering if you had any ideas on why a radio would drop in and out? when i start my car, radio is usually all static, then after about 2 minutes it comes on and is fine for the rest of the drive. any way to fix it?

[Minuit]

15 hours ago, rustfadesaway said:

hey minuit, i was wondering if you had any ideas on why a radio would drop in and out? when i start my car, radio is usually all static, then after about 2 minutes it comes on and is fine for the rest of the drive. any way to fix it?

Depends. If you have a very consistent commute every day, it might just be buildings, trees, or other things you drive around blocking your reception. Of course, it could be a problem with the radio too. I've not heard of a single solid state device that isn't very high precision lab equipment that needs to "warm up" to work in specification, so if it doesn't depend on your surroundings, it is a problem and not at all normal.

 

What kind of vehicle/radio is this?

 

Also: the only thing better than a blue VFD is a green one. This is the familiar AR-7650, but as installed in an Eagle car with green lighting as opposed to the Jeep blue.

[silvertwinkiehobo]

So what's the "XJ" suffix on the model number? Is that to designate it's for an XJ body? Maveric and I found this at the J/Y this morning, in a '93 XJ 2-door. Anyway, Minuit, about how much does a working radio like this sell for used, with no mods?

[Minuit]

The designation pretty much just means what bracket it came with from the factory. You'll see XJ, YJ, SJ, and XR variations most often. There is no difference in the radio itself in almost every case. Even when there's a difference, it's usually very minor internal differences. For all intents and purposes, the 1988-1996 Jeep radios are interchangeable.

 

It's worth what you can get someone to pay for it. The AR-7752 is a common model and has no special features that make it stand out. Condition is everything. Don't expect to retire off it, though.

[silvertwinkiehobo]

Well, no, we don't expect all that much from it. So we're gonna test it first, and if it works, we'll put it up for sale. But thank you for your assessment.

[Minuit]

[ajp]

 

 

Quote

 

AR-7550 ('85)

 

In a revolutionary step up from less luxurious offerings, there are two whole audio channels. Two amplifiers, a balance and fade knob, and support for four whole speakers! 8 ohm, naturally. And since this is 1985, you only get six wires for your four speakers. The negatives are shared between the front and rear of each channel.

 

 

 

 

Does anyone happen to know which speaker wire does what on these?  I have one and am curious.

[Minuit]

On 7/26/2020 at 7:49 PM, ajp said:

 

 

 

 

 

Does anyone happen to know which speaker wire does what on these?  I have one and am curious.

The speaker connector is the six-pin one. On the radio side:

 

White: Right front +

Black / white stripe: Left - (shared between front and rear)

White / black stripe: Right rear +

Green: Left front +

Black: Right - (shared between front and rear)

Green / black stripe: Left rear +

 

Per the RX-758 service manual.

[ajp]

On 7/28/2020 at 9:22 AM, Minuit said:

The speaker connector is the six-pin one. On the radio side:

 

White: Right front +

Black / white stripe: Left - (shared between front and rear)

White / black stripe: Right rear +

Green: Left front +

Black: Right - (shared between front and rear)

Green / black stripe: Left rear +

 

Per the RX-758 service manual.

Thank you Minuit, that saved me the time of trial and error.  It works perfectly!  

 

One more question.  On the faceplate there is a tiny round inset on the bottom right side.  It appears as if it is an adjustment for something.  Do you know what it is?

[Minuit]

Pretty sure that's a trimmer capacitor for the radio tuner used in the alignment process. Best not to mess with it.

[Minuit]

 

https://www.ebay.com/itm/164328461436?ul_noapp=true

 

Please nobody spend $950 on an RX-135. Also, it'll only fit 86 and 87 AMCs.

[Pete M]

   I don't normally poke fun at sellers that put an OBO on their item (at least there's a chance they might have realistic expectations), but daaaaaaaaaaang that's a lot to ask for an old radio. 

[TheDude]

 
https://www.ebay.com/itm/164328461436?ul_noapp=true
 
Please nobody spend $950 on an RX-135. Also, it'll only fit 86 and 87 AMCs.

I thought it was at least going to be NOS or something..

I may have one in the basement, I really need to catalog all those funky amc radios I have.


Founding Member of the Comanche Preservation Society

[Minuit]

I've bought multiple NOS AMC radios for literally a tenth of that.

 

I sent him an offer for $40. We'll see how that goes.

[fiatslug87]

At least shipping is free...???