Mark Tsai's Web page: RX-7 Crackly Radio Repair

RX-7 Radio Repair

Symptoms:

Left front speaker, or all speakers exhibit crackling sound when on, regardless of audio source (tape, radio).
Poor frequency response from some or all speakers
Crackling radio responds inconsistently to 'fine adjustment' (i.e. smacking, hitting, etc.) by either returning shortly thereafter or not making any difference whatsoever.

Solution: Resolder 'cold' solder joints within radio, clean contacts for controls.

Tools Necessary:

Phillips Screwdriver
Soldering iron
Flathead screwdriver or thin prying device
Electronic contact cleaner

Background:

I took my radio out of my car no less than 4 times trying to track this thing down, so hopefully you can benefit from my trial-and-error methods.

I'm writing this from memory, so there may be a few inaccuracies, but I don't think it'll be anything that causes your radio or car to blow up...but if it does, you didn't get this from me.

I happened to do this with the 'Turbo II' factory radio (the one with the EQ and full-logic tape deck, but I also have the original radio which came with my base model car, and the procedure seems to be identical.

It took me several attempts to finally get the radio to where it no longer annoyed me. In the process, I also cured the 'crackly' radio knob problem, whereby I'd get static as I made any adjustments to volume, fader, or balance. I'd suggest doing all of these fixes at the same time.

References to "left" and "right" are as you are looking at the radio as you would normally while driving.

Step 1: Expose radio
On either side of the shifter boot, where the black plastic meets the YIC (your interior color) plastic, insert a THIN screwdriver, gently work it up underneath the black plastic. This should pop each side free. This is a great opportunity to clean out all the junk which accumulates in the crevices in the shifter boot.

Now, remove the ashtray, and remove the two screws under the ashtray. Put them in a safe place.

The tricky part: Insert something wide and flat between the heater vents, and the black frame surrounding them. Carefully pry the heater vents away from the console, and they will pop out. This may take a bit of pry here, move a few centimeters, pry again, etc. There are two screws behind the top of the frame which must be removed to successfully remove the frame intact. (This was not mentioned to me, and now I have a cracked frame. I've seen quite a few of these broken, as these screws are not exactly in an obvious place.) This should leave you with a total of 6 screws in your 'safe place,' and a pair of heater vents, and an ashtray. At this point the frame should lift off of the console, exposing the radio, and logicon.

Now, you'll want to remove the connectors which power the cigarette lighter and the ashtray light. The ashtray light comes out by twisting the brown (in my car) connector slightly counterclockwise as viewed from the back. The cigarette lighter power plug (black) pulls straight off.

Step 2: Remove radio modules from console
Four gold screws hold the radio into the console. Remove these, and the console should slide forward a few inches. In the back, there are an absolute multitude of connectors going into the back of the radio system. Most of these are the standard "push in the tab and remove the connector" type, but one or two have the tab on the radio, not the connector. Be careful, some of these get really wedged in there as they age, and become somewhat brittle.

In addition, there are two mini-jack connectors on the right-hand side of the radio as you sit in the driver's seat. These just pull out, and are very short (and may even come out as you're jiggling the radio around to get at the other connectors). Note: Some of the cables actually go from one module to another. It is not necessary to remove these to get the radio free.

After disconnecting the connectors in the back of the radio which are actually connecting the radio to the innards of the dash, and the two jacks on the right-hand-side, the radio should be free and clear for you to remove (and take into the house or your workshop).

Step 3: Inspect radio
This isn't really a step, but it helps for us to have an understanding of what I am talking about for the rest of this document. The radio is made up of discrete modules, depending on whether you have just the radio, the tape deck, and/or the equalizer (I've never actually seen the factory CD player, but I assume it just takes the place of the tape deck.) These are all patched together with a few thick cables in the back, and these cables are fastened to the modules with zip-ties.
In my case, my problems were centered in the radio unit.

Step 4: Separate radio from rest of modules
There are flush-mount screws on each side holding the mounting brackets to each component that you have (2 per side for radio, 2 for tape deck, and 1 for EQ). Remove all of these. On the right side, you'll have to remove the two smaller round-head Phillips holding the mini-jack connectors onto the brackets before you can gain access to the last flush-mount screw. At this point, the brackets should come off, and the three modules separate. You do not have to completely separate the radio from the cable ties if you don't want to, there is adequate room to maneuver the radio to do what you need to while it's 'leashed' to the other modules.

Step 5: Remove billions of screws
There are about 2 dozen screws in various place on the body of the radio holding the metal shell together. All of these are identical, except for two longer ones. Keep note of where these are, as these were the core of my personal 'crackly radio' problem.

Step 6: Remove metal shell
The metal shell is composed of two halves, one which is primarily flat, the other also has the 'sides' of the radio. The flat one must come off first. It pivots on the faceplate side of the radio. This will expose the back of the PCB, and also the two bent, soldered-tabs which need to be desoldered and bent away from the PCB to remove the other half of the shell.

The knobs simply pull off in two stages, first the 'volume' knob comes off and then the smaller 'ring' comes off behind it. The faceplate of the radio comes off by removing the screws on the side, and pushing the pair of tabs in the center together. Note that the knobs must be off before the faceplate may be removed.

Step 7: Cleaning the radio contacts
The potentiometer contacts for all of the 'dial' controls on the face of the radio are visible through small gaps in the black plastic. I squirted electronic contact cleaner (not saline, har har) through these gaps and worked the appropriate control back and forth thoroughly. Remember that one of the knobs has more than one 'level' (i.e. a different potentiometer is moved if you pull it outwards slightly).

Step 8: Resolder cold solder joints
I found several of these on the circuit board which is at right angles at the back of the radio, most notably the four large ones near the side of the radio, which could be accessed without going through the tedious process of desoldering this 'daughterboard.' Resolder these.

In addition, the two long screws you removed in step 5 screw into a small black plastic module. The solder points on this module have a tendency to develop miniscule cracks in the cold solder joints which either cause crackling noises or noticeably degraded frequency response in your stereo. Resoldering these fixed my problem.

Step 9: Reassemble radio
Hope you have a power screwdriver for those billions of screws.

Step 10: Re-install in car
The only thing of note here is that there is sufficient slack on those two really short mini-jack cables for you to pull them out slightly to get them reconnected to the radio before putting them back in the car.

Step 11: Enjoy crackle-free music (hopefully)

Comments? Questions?Mail me!