ghetdjc320

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.

Awesome! That was the missing link. So it looks to me like those pins everyone uses for aux are just test points on the PCB. My current goal is to intercept the am/fm signal pre tone controls, and add a switching input that will pass through am/fm but switch to aux or Bluetooth when signal is present. I want to have this trick the radio into thinking a tape is playing so the radio station display goes away. Then have the play, rw and ff buttons trigger a DSP to skip songs and play/pause. That logic looks simple enough. I’ll add a transistor to transfer that logic to the DSP to trigger this functions. I’m liking the tinysine DSP boards with Bluetooth. I can have a clean aux input for my DAC and a Bluetooth for regular wireless pairing

Did a bit of signal tracing on the preamp board. Also desoldered the mounting plate for the volume and tone pots. I hadn’t noticed before that there are several adjustable potentiometers on the board. Two of them attenuate the tape deck input. How I would love a good diagram of the board lol

I was staring at the disassembled radio for a bit… Really wish I had the diagram or schematic for the RX series of radios. However, I’m wondering if, when the cassette is inserted into the deck it mutes or shuts down the radio tuner entirely, thus preventing the bleed through. I wonder if there is a way to emulate the tape being present when an aux input is applied. I’d assume there is some simple 12v or 5v logic commands that trigger the display to show tape commands. And since there isn’t really any input change command, I’m assuming this is just a logic curt unit that mutes the tuner or puts it in standby. I’ll either have to dig up a schematic somewhere or just get the multimeter out and test away. In a nutshell, here is what I’d like to accomplish on a mostly stock radio: 1. Eliminate the tuner bleed through without disabling the radio or attenuating the gain. For this I’m thinking simply intercepting the radio input to the preamp board in some fashion. A switched input jack would do the trick nicely. But an automatic method would also be nice. 2. Get the display to show different information other than radio station while playing aux input. Emulating tape deck display functions seems like the go to option here. 3. Get the stock play, rr and ff buttons to control the aux source. This one is a bit tougher with stock components.

Ive used those in the past. But those still use the FM radio tuner to carry the signal. I'm wanting to run the DAC signal direct to the pre-amp board and disconnect the tuner output altogether.

Just ordered up an RX-173 that seemed to be in good shape from eBay. will be tearing that one apart as well. There is one glaringly obvious solution that occurred to me for the am/fm radio bleed through when adding an aux input, a switched 3.5mm socket. It's a super simple device that passes through signal on normally closed contacts when there is no plug inserted in the jack and automatically switches inputs when plugging in a jack. Instead of using those two pin connection on the pre-amp board, why not just intercept the am-fm radio signal to the board? I do like bluetooth options as well but unfortunately apple still does not support any real HD bluetooth options such as Aptx HD. Therefore the best solutions tends to be a USB C DAC. Installing the DAC close to the head unit 3.5mm port would shorten the signal path. The connection would be USB to the DAC then switch to analog and go to the RX series radio pre-amp board where the am/fm radio would normally plug in. It's just a 3 pin JST connection for the stereo signal. If done properly with quality components, that would be the best audio signal one could get to the stock RX series internals. The DAC analog output may have to be attenuated down to the appropriate line level voltage to match the am/fm radio levels when switching. On the output side, a nice DSP would work great to not just make up for the stock amplifier limitations, but also to tune the cab acoustics. I'll post up how this works out. I think the current RX-172 I have I'll just gut entirely for a future raspberry pi setup with an OLED screen but the RX-173 I'll use to optimize a factory component system.

Notch flares are truly a horrible fit. They look great once finished but the fit is ridiculous. If you really wanted to, you could restore the factory spots by grabbing the key parts bedside repair panels and trimming out the fender mounting portion and welding it to your bedsides.