electronics

Please can somebody help me!

I'm stuck, the screen inside my car is blank, all the audio works but just no picture.

I have been led to believe its the ribbon cable.

How do I do a continuity test? to check everything before just swapping the ribbon cable out?

Also where could I buy a new ribbon cable from should it be that part that is faulty?

I am struggling with this now

The headunit is a pioneer AVH-P5700

Any help much appreciated.

I have done a few of these in the past, though not this particular model.

The ribbon cable will be a thin film cable - like this


It gets wound and unwound from a "spool" each time the display moves into place and retracts. Over time this movement weaks the very thin cable and causes a break.

Most of the time the break is not in the main cable (as pictured) but in the little conductive tracks within the cable (the black lines). You usually can't see these breaks by eye.

To check continuity, open the unit and remove the cable at both ends they usually just push into connectors on the screen board and the main unit.

Stick the cable down to a flat surface with Cellotape and using a multimeter in continuity mode check each trace (one by one) by putting each of the probes to either end of the trace. This is fiddly as they are very small. Each track should show full continuity or zero resistance.

If the thought of opening the unit makes you feel uneasy, this might not be a job you want to undertake. There's a fair amount of disassembly involved and the screen retraction mechanism can be fairly complex.

Ah brilliant, I will take the thing apart now to remove the ribbon cable. I will use the multimeter and report my findings.

What would you do next if this part appears to be ok?

Originally Posted by sv_rory

What would you do next if this part appears to be ok?

I would say that 90% of the time it'll be at least one broken trace on the ribbon cable.

However check that the backlight is OK on the panel before you take everything apart.

Can you see anything on the screen, however faint under direct sunlight?

How about when shining a bright torch directly at the screen? Can you see any image "under the surface"?

If you can see something, it may still be the ribbon. Check it. If there are no broken traces that you may have to replace the backlight or invertor.

I have stripped the headunit to discover that there was 2 tiny little breaks in the ribbon cable to the screen.

I have ordered the part, and was less than £30 so I'm happy about that.

Only question left now, what is the safest way to install the new ribbon cable, I know there delicate so wouldn't want to damage it.

Can't really give a definitive answer on that as all models are slightly different. But you've removed the old one so that half the battle.

As Haynes says, installation is reverse of removal. Just be careful and try not the bend or twist the cable sharply.

There should be a rewind mechanism to take the slack off the cable when the screen retracts. If there is my advice would be try to find a way to carefully jam it (matchstick, etc) in the fully extended position. This will take the tension off the cable. This way you can work at getting the cable in place without any pressure from the mechanism.

cheers mate,

The ribbon cables in the two headunits I have got dont have any rewind mechanisms, they are just loose, i thought it was a bit weird to be honest