I've had my Empeg and it's original tuner installed in my '67 Mustang for probably 4 years now and it's been working fine the whole time. Yesterday however my FM reception started dropping out on the way to work and it doesn't look like it's planning on getting any better on it's own.

When I first turn the car on the FM reception is fine. After a while (15-20 minutes yesterday morning, 5 minutes this afternoon, 1 minute now I've been playing with it today) the FM signal starts cutting in and out. The stereo icon disappears, the RDS info stops scrolling and the sound stops. The reception bars remain at full strength and the red light on the tuner stays lit. Then the sound will just pop back in. Usually with a slight pop like you're putting a needle on a record. There seems to be no set amount of time that it spends on or off, it sometimes stays in whatever state it's in for 10-20 seconds, sometimes it flickers on and off rapidly.

The AM reception and the MP3 playing functions work fine during all of this. When an FM station is cutting out I can switch to an AM station or an MP3 and the tuner resumes it's normal operation. Until I switch back of course.

I've pulled the tuner from the dash and tried reseating the cables. I've also jostled the cables on the back of the sled. Nothing I do with the cables makes any difference to the sound output. Shaking the tuner while it's hanging under the dash and turning it every which way doesn't make it work any better either.

I opened up the tuner case, but I don't see anything obviously wrong. I searched the forums and found a couple references to possible op-amp problems with the original tuners, but I didn't find anything about actually fixing them.

Does anyone know what might be causing my tuner to drop out and how to go about fixing it? Or am I going to have to break down and head over to the For Sale forum and pick up a new PCATS tuner?

thanks

taym has had similar troubles with several factory tuners. I had a look at them, and didn't find anything obviously wrong. Sometimes they would work for up to a minute or so after power-on, and sometimes they just wouldn't work at all.

My guess is that something died inside the RF module. But that's with no schematics to aid in debugging.

Cheers

We've got an ailing one too. I'll let you know if we find anything. Does anyone know if the PCATS modules will work with the factory tuners?

Stu

I was afraid it was going to be fatal as soon as I realized the AM was still working.

Guess it's time to start looking for another one.

thanks
-Dave

Sounds like a good plan to me. If my tuner's death can have the slightest chance of helping determine a fix for someone else's that's a far better fate than sitting around my garage collecting dust.

Let me know where to send it and I'll dig up a box for it and you can hack away.

-Dave

I mailed the tuner off Friday so it's on it's way. Hopefully it does more for you than it's done for me lately.

Enjoy,
-Dave

Yeah, I saw your PM, too, thanks!

Once it gets here, I'll make some time to have a look at it. If it's an easy fix, well then that's good. Otherwise, I owe you postage.

Cheers

Your tuner arrived here yesterday, I'm playing with it right now. I see what you mean about cutting out and in again. Will continue..

I have one here that just plain doesn't receive anything, ever. I suspect the module as well. The regulators work and the PIC oscillates, but beyond that it's a mystery.

Stu

I am having the exact same symptoms! Except my AM stations seem to drop off as well. I have been struggling with it for a couple of weeks now and it seems to be getting worse. I also experienced a signal drift where the station slowly fades away, and after some bumps (I have a very stiff suspension) it seems to get tuned to a different station. When this happens, the station displayed on the empeg remains the same. I recently replaced by HDD with v3 software because my previous HDD stopped spinning up successfully. If I can find a replacement (havn't started looking), I will gladly send mine to you to increase your data points.

Here's an update.

It's not completely dead, but there's definitely a dead component inside the RF module.

I have an ancient "signal tracer", effectively a high-impedance audio amplifier, which can be used to probe circuitry to see where a signal exists and where it doesn't.

Here's a block diagram (and pin-out) for the RF Module in the factory tuner.
Note that pin-1 is nearest the Antenna Jack.

The FM audio is working at the Level pin, but not working at the RDS MPX pin, nor at the FM MPX pin. This indicates a faulty FM Demod stage inside the RF Module.

Next I'll pop off the cover and probe inside the RF Module, to see if the FM Demod is accessible and repairable.

-m

EDIT: fixed wrong part number.

The FM Demod is part of the main tuner chip, a Phillips TEA6848H,
for which Google found this information.

I don't want to replace the chip, but the chip is actually likely to be okay (or not).
So now I'll trace a few signals from it back out onto the PCB.

-ml

Mmm.. no joy isolating it any further than the RF module as a whole. The circuit density is just too tight to be easily traced. But I'm starting to suspect the chip now.

Meanwhile, here's some troubleshooting pr0n for y'all:



Yes, that's a PCATS RF module grafted onto a factory tuner board.
The original factory RF module is on the table below, shell removed.

And a close-up of the PCATS module attached to the factory radio.



I have a temporary extension/header soldered onto the tuner board for easier debugging.
The PCATS RF module is plugged into the extension, with a short adapter in between.

While it has a lot more pins, most of them are no-connects in this situation.
The required pins are (fortunately) in the same order as the original,
with a gap+offset mid-stride.

So far, the PCATS RF module is working flawlessly, grafted onto a factory tuner board.
If it continues to behave (fully expected), then I'll remove the extension headers,
and work out a way to install it permanently much closer to the tuner board.

Doing this doesn't look too bad. All of the pins except the final four should line-up
nicely with the holes on the tuner board, and some short wires can be used to
connect up the final four. All unused pins will just get nipped off with some cutters.

None of the ground tabs will line up, though, so some extra grounding work will
be needed -- just some sturdy solid-core wire soldered from the tuner board holes
to the protective can on the RF module.

The can will also have to be nibbled away a tiny bit where it intersects a tall
component on the tuner board, and overall it won't fit as snugly as the original.

But with luck, it will all go back into the same tuner box.

So.. if anyone else wants to undertake such repairs, all you really need for
parts are some of Patrick's surplus PCATS RF modules, if he has any left..

Cheers

And another photo, illustrating where the metal can required a bit of modification to fit:

Thanks for all your experimentation! Glad it worked out. We have a dead PCA tuner (poorly built by a customer) that may have a good module in it I could use to revive the dead factory tuner we have.

Stu

If you have a dead/dying factory tuner, odds are good that replacing the RF module will cure it.
The original modules don't exist anymore, so the PCATS RF module is the only way.

Here is Patrick's original posting about his excess PCATS RF Modules.

Figure in the cost of the RF module, plus.. say.. $50 for the refit labour,
and two-way postage, and there ya go.

Still cheaper by half compared with a full replacement tuner.

Cheers

My god, what a sexy repair job. You are the man.

I mean that in absolute seriousness. There's nothing I love to see more than a good solid hack like that.

Just for posterity:

I've also tried to get a quotation on just the tuner chip itelf, the gizmo at the heart of the RF module. Those are about half the cost (in tiny quantities) of a full RF module, but are more difficult (for me) to replace, and don't have as good odds of success as a full replacement does.

Cheers

To hijack a post and maybe get Mark some business. I have a broken tuner which is probably a bad RF module. $40 plus shipping and its on its way to you, or directly to Mark if you wish.

Magnus, you have mail.

I can now vouch for this repair, having successfully completed one. A word of warning though. Some of the pictures are a little misleading. It looked to me like the shifted pins plugged right into the factory tuner board with no gap, leaving three holes left at the end. However this is not the case. There should only be two holes leftover at the end with a one pin gap between the shifted pins and the unshifted ones. So basically, to be sure you are doing it right make sure you procure a copy of the pinouts for the PCATS tuner kit module before soldering everything down.

Stu

Yeah, the best reference for correct pin placements is this photo from earlier in this thread.
Note carefully that the far left pin (in the photo) of the tuner module is not inserted at all into the temporary header. This pin should instead be soldered to the nearest ground hole on the tuner board (requires a slight bend).

Cheers