What CC knows about stock Jeep radios

[ghetdjc320]

So I’ve deciphered the led lighting upgrade and the foam button backing. Took several attempts with different types of foam to figure out what works, but you’re basically looking for a medium density open cell foam about 1/8” thick. It is nice not to have the buttons rattling around and standing as they should. The led upgrade involves using a T1 or 7219 bulb. The bases are a twist lock but the actual bulbs are a wire wrap design around the base. If you switch to led, make sure you get your polarity correct. Also, when soldering, I’d stick with maybe a 20ish watt iron. I have to cycle my 60w iron on and off to keep the right temp. The 7219 bulbs are also correct for the display backlighting. Changing the display bulbs is a tedious and delicate job. I’ve also sourced switched 12v and 5v reference cables on the casette deck connector. I’m about to build my final configuration radio as I want it for my truck. New button foam, refinished face and buttons, all new incandescent bulbs with a slightly higher wattage than stock, Bluetooth receiver with custom DSP. It will have am/fm and Bluetooth. Could also have an aux input but I don’t feel like fishing down more wires through the dash for that. This radio will look like a NOS unit on the outside with completely custom internals.

 

Here are some pics I took while playing around with different bulb setups and restoring the button backing.

 

 

 

[A-man930]

That looks amazing. 

Wouldn't LEDs be poor at dimming on the factory rheostat? 

[ghetdjc320]

29 minutes ago, A-man930 said:

That looks amazing. 

Wouldn't LEDs be poor at dimming on the factory rheostat? 

Thanks! Yep, LED’s don’t dim in a nice linear scale like incandescent as they use pulse width modulation to dim. I’d be inclined to add a filter to them to lower the overall brightness down to a somewhat stock level. You could also switch the hvac panel to led but it required some additional reflective work to have the led look correct. If the hvac panel and other radio lighting matches, it should look good in the dash. And there’s enough separation between the instrument panel and the center of the dash it should look good. 

[A-man930]

9 hours ago, ghetdjc320 said:

Thanks! Yep, LED’s don’t dim in a nice linear scale like incandescent as they use pulse width modulation to dim. I’d be inclined to add a filter to them to lower the overall brightness down to a somewhat stock level. You could also switch the hvac panel to led but it required some additional reflective work to have the led look correct. If the hvac panel and other radio lighting matches, it should look good in the dash. And there’s enough separation between the instrument panel and the center of the dash it should look good. 

 

Yeah that sounds like a bunch of work just so you get to use an LED... sticking with incandescent sounds like a better path.  

What if I want to make all dash backlighting red like a 90s Pontiac? 

[ghetdjc320]

27 minutes ago, A-man930 said:

 

Yeah that sounds like a bunch of work just so you get to use an LED... sticking with incandescent sounds like a better path.  

What if I want to make all dash backlighting red like a 90s Pontiac? 

A light filter should accomplish that. The factory uses a blue filter. Coupled with the yellowish tint of the incandescent bulb, it gives off a pale green glow. 

[ghetdjc320]

So one last note on the signal flow I sure found interesting and this will probably be my final tech entry on these radios. In typical 80’s fashion, there is a lot of circuit back and forth reminiscent of the main wiring harness on the XJ/MJ. Here is a bit of signal flow logic that should prove extremely helpful for future mods:

 

The tape input comes to the preamp board first for attentuation by two potentiometers (one for left and one for right channels) before leaving the preamp board and returning to the main board via the 7 pin connector between the preamp and main board. The main board is the one that selects the tape input or tuner input and typically mutes the other inputs automatically. Until the exact mechanism of switching can be determined along with some type of system hack, there is no point in trying to use the tape input as a selectable source. This may change if I get some spare time someday to create a work around. 

 

The main board then send the main L and R audio channels for the radio or casette over two pins that end up connecting to TP471 and TP371 which are where everyone inserts their aux input mod. The signal then goes to the treble tone control, the bass tone control then the volume control.
 

At this point, the line level signal then exits the preamp over the 3 pin jacketed wire to the main board amp section. This is where it gets interesting. 
 

Contrary to popular opinion, the amplifier does not have 4 discreet channels, it is a 2 Chanel amplifier only. The amplified two channels now go to the power board where the main relay, main connector and other items are sitting vertically on their own board near the rear. 
 

From that board, there is a 6 pin connector that goes back up to the preamp near the volume control. Two of those 6 pins carry, you guessed it, the amplified L and R positive signals. Those two amplified channels then get fed to the balance and fader control which account for the remaining 4 pins on that ribbon connector: RR, FR, FL, RL. These go directly to the main connector speaker outputs. 
 

So that pretty much sums it up. With that info, you can mod away to your hearts content. There are so many different options here. It would be relatively simple to convert the internal amplifier to something more powerful and modern. DSP tuning, aux input, Bluetooth input, anything you can imagine is possible. 
 

And a note on the bulbs, there are two behind the display (pictured below) and 3 on neo-wedge bases for the front panel illumination. There is another that ilumanetes the tape door. They are all T1 bulbs. The 7219 bulb from VCC (available at Mouser) is a great quality replacement. If you’re changing them all, you’ll need 6 bulb. But I’d grab an extra one or two in case you break or misplace one as they are tiny. Swapping out the bulbs behind the display is a bit tedious but well worth it. Just don’t burn the ribbon cable with your soldering iron or that’s pretty much the end of your radio u less you are a micro-soldering master
 

I also removed a good LCD display from the front panel as a spare. 
 

 

[A-man930]

On 8/9/2026 at 8:44 AM, ghetdjc320 said:

A light filter should accomplish that. The factory uses a blue filter. Coupled with the yellowish tint of the incandescent bulb, it gives off a pale green glow. 

I guess this blue filter is in the panel face vs a boot/condom over the bulb?  

[ghetdjc320]

8 hours ago, A-man930 said:

I guess this blue filter is in the panel face vs a boot/condom over the bulb?  

Nope, it’s just on the bulb itself. You’d need a color filter for a t1 bulb. Or you could run an led

[A-man930]

14 minutes ago, ghetdjc320 said:

Nope, it’s just on the bulb itself. You’d need a color filter for a t1 bulb. Or you could run an led

That's relatively easy then. Cool!

I've always wanted red backlight in the MJ just like my old Firebird.  

[ghetdjc320]

45 minutes ago, A-man930 said:

That's relatively easy then. Cool!

I've always wanted red backlight in the MJ just like my old Firebird.  

Technically you could also use a red light filter behind the lcd if you wanted to. That wouldn’t be a bulb filter though. It would be a red semi-transparent plastic filter material. 

[A-man930]

27 minutes ago, ghetdjc320 said:

Technically you could also use a red light filter behind the lcd if you wanted to. That wouldn’t be a bulb filter though. It would be a red semi-transparent plastic filter material. 

Yes, would definitely need the LCD to match the rest of the backlighting.

[A-man930]

14 hours ago, ghetdjc320 said:

Technically you could also use a red light filter behind the lcd if you wanted to. That wouldn’t be a bulb filter though. It would be a red semi-transparent plastic filter material. 

 

Something like this? 

https://www.amazon.com/Rosco-Roscolux-Scarlet-Gel-Filter/dp/B00BAXU4TS

[ghetdjc320]

Little teaser for my personal radio build

 

[ghetdjc320]

The new DSP and bluetooth module has been programmed. These things are too cool in what they can do. With the Analog Devices DSP chip, you can create endless automatic signal routing pathways, EQs, ducking settings and so much more. So I wrote the program to do the following: 

 

Receive the analog stereo AM/FM signal and pass it through unless there is bluetooth signal present. If bluetooth signal is present (which is an I2S signal for a clean digital pathway and astounding audio quality) the am/fm is digitally muted from the system. The sensitivity for the ducker. is -80db (line level signal) and the dwell time is 5 seconds. I will adjust further if needed. Now we have a digital "relay" that wholly eliminates any tuner bleed-through without disabling anything on the original radio. Then I added a multi band eq system in the mix and will use it to tune the Comanche cab to perfection with my new audio setup. Really neat to inject this modern tech into these old radios and provide so much functionality along with sound quality that would rival most all aftermarket units. And just for kicks, I renamed the Bluetooth friendly name to "Tomahawk"

 

At some point I may also install a nice mosfet amp board in one of these. That would eliminate the need for a separate amp in many installations. I can fit about 400w of class D amp into these units with the tape mechanism removed. With the right combo, I think I could setup a radio that would handle a perfect Comanche 2.1 audio system with the two main door speakers and a sub, all powered through what looks like a factory radio. It would likely have a little cooling fan on it and would have a connector for an 8awg power wire. 

 

Fun stuff 

 

[ghetdjc320]

Pleased to report that this system is working great now. Just need to source a switched power supply on the board and finish refurbing the radio. The sound quality is superb in both the tuner and Bluetooth sources and there is now zero tuner bleedthrough as I created a digital audio relay system with Bluetooth priority. And the DSP is a tuning dream with endless routing configurations and functionality.

 

I’ll use right angle 3.5mm trs plugs going forward for better clearance. Will also play around with installing a nice amp board at some point. 

Here is how it laid it out for this demo radio: