Citroen XM Forum

Thank you very much for all the info. I have declined to buy it obviously but at least he knows which XM's it it for now.

Hi Chris

Will have another search and see what I can find.
Not had or kept many of the simple clock displays.
None I found so far are complete.

I have some of the bulb holders fitted with flat wide angle LED's plus resistor.
Gave up on the plug in ones which were too tall and directional.
These are 5mm square and 2mm thick with multiple devices.

John

Thanks, John.
That was my first result with several basic LEDs....too directional.
Ought to be crackable, so would like to try again in a few weeks' time.
C.

Have had a chance to put a test circuit on the bench this morning, based on the non-relay circuit above.

This was it:
When supplied with +14v and GND, LED operates at normal (high) brightness. Current limited by 400R.
When a voltage is applied to Vctrl, LED goes to reduced brightness.

A few measured figs:
14V (bright), ILED = 25mA
When Vctrl at 10V, ILED = 1.3mA [and Ictrl = 100mA]
When Vctrl at 6V, ILED = 12mA [and Ictrl = 49mA]

LED brightness also stable, at both levels of brightness, when 14V line fluctuated by a few volts.

Very basic, but looks promising. Might help with further experimentation.

Chris, I have a couple of these RH units. One in the car works but the rear illumination has gone, one unit bought unseen and untested and another with a delaminated screen, again un tested.

Happy to supply you with the later two units if we can talk a deal on getting the rear illumination working on my unit in the car!

Rob

Postby Dieselman » Thu Aug 20, 2015 5:17 pm
The liquid doesn't leak, the green tinted glass layer becomes delaminated, so appears cloudy.


Diesel if that's the case then could easy be repaired i have that problem with temp/clock led

As stated earlier, the liquid does not leak but it does move out of position within the sealed LCD unit.
This leaves some outer areas of the LCD clear of liquid and clear to see through.
These then show green because of the separate green (orange in Pug displays) plastic sheet next to the LCD glass.
As far as I can see there is no delamination or clouding involved.
Been looking for the same design of LCD element in electronic junk but it appears to be unique and obsolete.

John

Been testing the bag of RH display bits I could find.
Lots of blown bulbs to replace but running temperature does not seem to be a problem.
Three sets of boards for the simple display all run.
So do the three LCD displays but only one is perfect as the other two have areas clear of liquid.

To test I just coupled pins 1 & 3 to +12 volts and pin 2 to earth.

I repeated the test on a couple of the more complex 15 pin displays.
Both worked.
One was in bits but the other was NOS complete still with the protective plastic cover over the display.
Test method was the same as above with these.
Will have to look out a spare temperature thermistor to add that to the test rig.

John

That's really useful bench test detail, John. Thanks for this.
Interested in your comment about running temperature not being excessive.
In the car, with original lamps (3 x 1.2W), our RH display front runs at what can only be described as "very hot".
In my judgement, this can't be good for the LCD element, and probably doesn't do the contained electronics any favours either.
Similar, but slightly less, hot display in the Philips radio (with 2 x 1.2W wire-ended behind the display).
By contrast, the LH display - which from memory runs on just one lamp - runs just very slightly warm when on continuously.
RH display suffers by being on all the time (while driving) of course.

There is a slotted plastic vent screen separating the bulbs from the LCD display.
It is only the complex RH screen that has 3 bulbs.
The simple one uses only 2 bulbs.
If heat was a major issue then the green plastic screen is between the bulbs and the LCD display.
The one here has no evidence of heat effects nor has the electronics board or the bulb pcb.
There is around 15mm air space between each of these vertical panels and lots of air flow slots.

LH display is 2 bulbs with horizontal pcb's so a lot less effective airflow provision.

John