ghetdjc320

I used satellite. Just told them it's a 97 Cherokee. No issues.

Further testing has revealed something interesting that is my current working theory. While tracing signal flows, you can find the distinct AM, FM and Tape sources all coming to the pre-amp board. They first go through the tone control stages starting with treble, then bass, then volume, then out of the board on that 3 pin jacketed cable to the amp stage. Interestingly though, the balance and fader controls have a separate 6 pin connection that seem to run their logic at the amp stage. So basically, if you want to retain fader and balance controls without heavily modifying the PCB, you'll need to use the speaker level outs. Interestingly enough, when I adjusted the AM gain pot on the main board, I got zero am radio bleed through while using the aux in. Removing (or just disconnecting) the tape deck main plug also accomplishes the same thing. It appears that the AM/FM signal is always present at the preamp stage. But the tape deck logic has a radio mute function when playing a tape, causing the preamp to pickup that signal instead. When we inject audio on those test point pins, we seem to be simply overlaying the radio signal. Quite possible we are tricking a transistor somewhere on the pcb since grounding either of these pins also cuts the signal instantly. Instead of using those test point pins, I'd prefer to desolder them and keep mire wiring shielded as far as possible until it makes it to the board. That should help cut down on a bit of interference I've noticed. The signal to noise ratio seems to be decent but I'm limited in how I can test this. I will say though that I am getting very good audio quality by making some adjustments to the board. And I'm very picky when it comes to audio quality

Of course! Happy to help demystify these things a bit.

Out of curiosity, does this radio have an aux input mod? Take a quick picture of your preamp circuit board. It’s the one with the volume and tone controls potentiometers. If you’re amp is testing ok (which it should) check for a 3 pin jacketed cable (typically grey) that runs from the preamp board to the main circuit board to ward the rear of the radio. Make sure it is plugged in well onto the main board. This line carries the line level audio signals from the preamp stage. The aux input mod uses a pair of factory test points to inject audio into the signal pathways. A simple short to ground here will knock out the audio entirely for the am/fm tuner.

Here’s the beginning of this project. 1/2” birch for the shell which is appropriate for the JL 6.5 subs. Exact dimension tbd but I’m within a narrow range. QTC will be in the .75 range

So I’m reading .15 vac or .21vrms on the preamp audio output. To get this reading I applied a 60hz sine wave input at max volume with tone controls at neutral. This is quite low to run directly into RCA outputs. Given the internal build quality and lack of DSP in this radio, I think the best signal path for amplification will come from the speaker level outputs. I’d be inclined to run a 4 input line output converter to preserve the fader function (in my case I’d use them as a subwoofer bias for my b pillar subs project). I believe someone else noted the outputs as being around .6vrms. Not sure where that reading was taken and with what method.

Audio system under construction at the moment. I’ve long wanted to build enclosures for some compact subs in the b pillars. It’s really an ideal location for them if done right. Started by some careful measuring the other day. Plan is custom enclosures for (2) JL 6.5 W3 subs. Will feed them with either a 3 or 4 channel amp from a customized RX173 head unit with a DSP.

That’s right. Since the case and connections are the same, a parts store alternator would work in a pinch. These mechmans are really nice units. High quality bearings and square copper windings.

Just to confirm, the 3 wire jacketed cable running from the preamp to the back of the board is indeed the line level audio output to the amp stage. This line is volume attenuated and tone adjusted already. A couple of good workable solutions for a clean aux/bluetooth input would be to interrupt the TP371 and TP471 tracers on the board and feed them through a switched input device, or run the preamp output to a DSP with external pots controll. So basically, if you’d like to have RCA pre-outs for an amp, there are a couple of viable options here. The stock amplifier seems like a decent quality unit, but I have not yet determined the frequency response. More to come. I will say, the stock RX-171-173 have some interesting differences but seem very well made.

Ordered up a Mechman alternator. My existing alternator was original to the engine and the regulator was staring to have issues. The mechman amperage at idle is excellent. The goal is to keep alternator voltage at idle vs dipping into battery reserve.

On my MJ I used dynaliner on the firewall since it has an adhesive backing. Dynapad is super nice stuff to work with though. It can be a tight fit near the center co sole to dash area but basically from rocker to rocker and back wall to lower firewall are prime spots for dynapad. Also worth adding some rtv or seam sealer around your floor plugs.

The light grey matches the seats a bit better but the dark gray or charcoal looks significantly better.

The block off plates are part of the gauges cluster bezel piece. If you want to install carling size switches, you need to get the actual mounting base that goes behind the dash. I have piles of them somewhere if I can dig them out.

Time for some updates. I knew I had a small leak on the drivers side but wasn’t sure where it was coming from (still investigating that). Also have a small air gap between the booster and the firewall letting in warm air from the engine bay while running. I also want to improve the audio in the can further and replace the cluster with the new custom Dakota digital system I had made. So out comes the interior. Found a decent amount of mildew under drivers side carpet as expected. Will also be swapping out the seatbelts for some corbeau 3 point harnesses. The Trailcat seats make it a bit difficult to grab the seat belts from the b pillars.

That is one clean floor! I’d check the seam sealer and identify any possible leaks. If it’s all good, do as recommended above. On my last build after I removed and re seam sealed the cab, I por 15d it then raptor lined it. It’s worked great so far. And I did end up using dynapad on the floor with excellent results. I just don’t recommend the mass backed carpet. For me, it started to crumble and our gas horribly after 3 months.

Out of curiosity, have you done cruisers tips? That’s typically the gold standard before firing the parts canon at seemingly mysterious renix issues

Steering play can come from the gearbox itself, the ball joints, the tie rod ends, the track bar, the control arms, the sway bar, the alignment etc. it’s really just a process of elimination. My current and last MJ had super tight steering with zero play. Not quite on par with electrically assisted rack and pinion but very good overall. But it took a lot of work to get it that way. The steering column on the manual does have an accessory position that you can access by pushing down on the key release button typically. At least that’s how my 90 and 91 were.

I’ve never seen one before, but if you still have the wiring harness for it, check and see if one side goes to ground. It’s likely just a simple normally closed or normally open pressure switch that you could harvest off of another vehicle. Does the engine try to stall without it?

What is the switch for? Does it turn on a light or operate another function?

I’d just use the Dorman if you can find the right size.

I saw this on Facebook not long ago. Glad it went otherwise a club member

Interesting, I’m only finding a balance pot on the RX-172 I’m working with. Since the diagram I have is from another member, I’ll leave it to his discretion to post. There are many aspects that are the same as the later models but many that aren’t. The manual I have is of an RX-170. I’ve been trying to dig up the manual for the later 172 or 173 but haven’t found any yet. If I am able to get one, I’ll post up whatever I can. If anyone else has one, please let me know. The signal traces from the AM/FM tuners to the PCB-VF are quite different on the 172/173 than on the 170.

As I’ve been compiling data and studying these radios in some detail, I need to jot down some of the info I’ve found so far. Some of this is my operating theory and I’ll update it with further confirmation. To preface, I have both an RX-172 and RX-173 in hand and a schematic from an earlier RX. Here are some of my findings: 1. TP pins such as TP371 and 471 are “test points”. There are many test points on the board, likely to validate the circuits upon or before assembly. 2. TP371 and 471 seem to just sit on the line level input to the tone controls (starting with treble). They are not specifically the tape or tuner signals but rather combined signal. 3. I do not see that there is necessarily any discreet “input selection” in these units. Currently, I’m thinking it is the presence of the tape that sends a “mute” signal to the radio. Some have reported long ago here in CC that removing the tape deck, inserting a blank tape or disabling the am radio will eliminate the audio bleed through issue. There seems to be some logic here but I’ll have to do some testing to confirm. 4. The preamp is labeled as PCB-VR on the drawings. It looks like there have been a few variations of this over the years but the final output to the amplifier portion of the board is the 3 pin connector with red white and black wires. On my RX-172 that is P304 on the pre-amp board (the one with the tone and volume controls). You should see a cable coming from there going to the main board input P304 near the amplification stage. NOTE: this is where one should be able to get line level aka RCA pre-out signals for an external amp. This is before any amplification takes place. The amplifier in these radios seems to just be a simple 2 channel design, which is further substantiated by the lack of a fader control (front and back biasing) and only a balance control (left and right biasing). 5. The AM tuner is the longer vertically mounted pcb that is against the left side of the radio viewed from the top. 6. the FM tuner is smaller but parallel to the AM tuner and also sits near the left side for eh radio as viewed from the top. 7. The amplifier itself sits on the main PCB board near the antenna input. It is not the vertical board mounted behind the main radio harness connector. 8. The AM/FM radio inputs appear to be coming from the 7 pin connector from the main board near the FM tuner to the pre-amp board. The tape input is separate and comes into the preamp board on a 3 pin ribbon wire. 9. There are adjustable potentiometers all over this board. I’ve heard the rumor about “lowering the AM radio volume” as a work around for the signal bleed through issue. I can see how that could be accomplished. I’ll have to determine which pot that is, but a simple adjustment with a small flat head screwdriver would take care of it. Edit: I think it’s pot 71. You can see it circled in the picture just below the volume and tone controls. Turning it counterclockwise should lower the output. More to come as I delve deeper into these head units.

Looks like excessive current draw.

These are standard GM bulkhead fuse blocks. Holes are a bit bigger and you can repin them as you like with the proper tools. I’ve been running my painless 24circuit universal in my MJ for some time now. Most of the circuits are fairly standard on the MJ column since they are GM with the exception of the wipers and hvac controls.