It could be quite informative to see a full serial port trace (with the stalk/tuner debug/trace options you were using above) showing what happens with the stalk connected, and the vol up/down buttons being used.

I wonder if the in-car stalk somehow damaged the tuner's stalk input? We already know there's more in there than just a resistor array (because most buttons generate a pulse, rather than just a continuous level).

With reference to the attached schematic, I would proceed by first connecting the stalk and measuring the voltage at pin 2 of the PIC, IC4, as the controls were manipulated.

If you don't get any voltage there, or it doesn't change, check the output of IC3 pin 1, the LM258. Also check it actually IS a 258

Thanks Patrick!

I really appreciate your help, I know you're a busy guy. I will try out your steps in the car later hopefully.

While my tuner was right here I had a quick look at it and IC3 is not an LM258, its a KA258.

They are both dual op-amps, are they both compatible/interchangable?

I've just been out to check my sisters tuner and that also gives me no output at all on Hijacks 'Show Button Codes' display when fiddling with the stalk.

I don't have a real stalk - so what I do is short out the collar and tip connections with a piece of cut and stripped cable. Mark shows that it works fine for him (if you were following the thread, he has a picture).

I'm rather puzzled by this. The PIC is the same one, running the same code, as the original empeg tuners. I programmed up a batch of about 200 some years ago, and have been using that stock ever since. I know for a fact that several people who bought the kit are using it with a stalk quite happily, so it seems unlikely there is a hardware fault that has gone unnoticed until now.

The same dual opamp that is used for the stalk voltage buffering is used for the signal-strength amplification, and that works fine. So it's unlikely to be only one half of the LM258/KA258 that has died, although it's not impossible. Also, the PIC code, while it could become corrupted by power surges, is obviously mostly intact as the tuner works as a tuner. I can't see that it's very likely that only part of the code has died, so neatly confining it's effects to the stalk

It might be a construction error, I suppose. Can you check whether the diode D2 definitely has the end with the black band connected to +5v, and the other end connected to one end of R4? Also, check that R4 is really a 1K resistor, R2 is 22K, and R1 is 4.7K. If any of these were wrong you would get funny voltages at the PIC pin 2, which would produce erroneous results.

The stalk interface is a rather crudely generated analog voltage, from a resistor ladder in the stalk, and the PIC is simply reading a calibrated set of voltage ranges. If the source voltage is wrong, or the voltage produced by the stalk is out, you'll get odd/no effects.

I will check for construction errors, but Andy has done a great job and I think these are a little unlikely. I seem to remember he has/had a stalk working fine in his Clio.


I think this is my next point of call, I haven't checked this!

Will let you know how it goes once I've checked things out again sometime soon.

Its alive!

After the tip to collar trick failing I was pretty certain my tuner was dodgy. I confirmed this further when the Sony Stalk I picked up on eBay didn't work either. So, I borrowed an original Empeg tuner. Plugged it in, and it all works straight away. Just like that.

So, turns out that the 'stalk' part of my PCATS tuner and my sisters PCATS tuner is faulty somehow.

Btw: does my PCATS tuner really give me better reception than my original tuner, or is it the case that the signal meter on the original one actually works as opposed to the PCATS one being stuck on max?