1990 240 DL Need a schematic for odometer stepper board

durk80 · Post by **durk80** » 19 Nov 2015, 19:38

Hi all, does anyone know where I can get a schematic for a 1990 Volvo 240 DL Instrument cluster. I went into the cluster and replaced the odometer gear, but in the process, I broke the larger (1/4" long body) glass diode next to the stepper motor. To make matters worse, I lost part of the glass with the rest of the identification numbers on it. The only I could salvage were AA 14. The body has an orange-reddish color with a black band at one end.

Does anyone know: a.) What type of diode this is? b.) Where I could find a replacement to solder in?

c.) What would be an alternative diode I could use?

Thank you for all of your help in advance!

The link below shows the diode I am referring to.

http://imgur.com/EB7uWiP

93Regina · Post by **93Regina** » 20 Nov 2015, 21:16

durk80 wrote:schematic for a 1990 Volvo 240 DL Instrument cluster

Poke around here, on his homepage at bottom of page is his email address, where it says "Email welcome."

Do let us know the rest of this story...thx

5ft24 · Post by **5ft24** » 20 Nov 2015, 22:50

Usually glass diodes like that are either germanium, or zener diodes

durk80 · Post by **durk80** » 01 Dec 2015, 17:35

93Regina, Thank you so much for pointing me in the right direction. Mr. Benstein was very informative about the diode in question. He even offered to send me a diode off a spare parts board, but it broke when trying to extract it. It was pretty easy to find a replacement with the wealth of knowledge kindly provided!
From Mr. Benstein:

the diode is a relic from the past, a germanium diode. They chose this because the forward voltage of a germanium diode is about 0.25V compared with the standard 0.7V across a silicon diode. You may find one at RadioShack, but if I were you, I'd call first.

If you have a silicon diode, and you don't mind experimenting, I think it has a great chance of working. The risk is it won't see the very slow mph, say below 5. At least that is the side effect I can envision.

You can find a proper replacement if you google "diode AA143" those being the numbers on the side of the diode (before it broke). If you see an NTE equivalent, that is a line of parts sold to electronic repair techs, so it might be quickly available in single unit.