Hi everyone, I'm hoping you can help me out with this issue. I have a flourescent interior light from a vintage VW camper van that doesn't work. I have found a small diode (possibly zener) which only has ITT markings and a double line at the cathode end, which i believe is faulty on the driver pcb.
When testing in ohms mode with the multimeter, I get OL with the red probe on the cathode (expected), and 2.1Mohm resistance the other way way round.
This particular board is a single transistor type (which after research, I have found this to be the worst way to drive a flourescent tube, bigclivedotcom explains flourescent tubes in an excellent youtube video).
If the diode is faulty, is there a way I can find the original value? I believe it is quite an important part of the circuit.

 

Welcome to AAC.

I can't help directly much but do you know that Big Clive has a Parteon and for a buck or two you can join and ask him about it directly. Unlike email, he answers messages on the platform. He does answer email but gets so much you are unlikely to be a person that gets an answer via that route.

I strongly encourage you to throw a few dollars his way. He only wants very small subscriptions, and you both win.

 

Hi everyone, I'm hoping you can help me out with this issue. I have a flourescent interior light from a vintage VW camper van that doesn't work. I have found a small diode (possibly zener) which only has ITT markings and a double line at the cathode end, which i believe is faulty on the driver pcb.
When testing in ohms mode with the multimeter, I get OL with the red probe on the cathode (expected), and 2.1Mohm resistance the other way way round.
This particular board is a single transistor type (which after research, I have found this to be the worst way to drive a flourescent tube, bigclivedotcom explains flourescent tubes in an excellent youtube video).
If the diode is faulty, is there a way I can find the original value? I believe it is quite an important part of the circuit.

Does this help? [The link is to a post on a VW Forum which includes a hand drawn schematic specifying the diode a 1N314 —MODERATOR]

 

Does this help? [The link is to a post on a VW Forum which includes a hand drawn schematic specifying the diode a 1N314 —MODERATOR]

That makes some sense. The double band, so far as I know, indicates a germanium device. Not all germanium does are marked with a double cathode band, but in my experience no silicon diodes are.

It didn't seem right that it would be a germanium diode, but given the age of the lamp, it certainly could be.

Here's the datasheet:

​

 

Does this help? [The link is to a post on a VW Forum which includes a hand drawn schematic specifying the diode a 1N314 —MODERATOR]

That is absolutely perfect! My goodness where did you find this??

 

That is absolutely perfect! My goodness where did you find this??

It was buried deep in thesamba.com, but I knew exactly where to look; from your question, I immediately knew that you were asking about a Westfalia conversion in a late Bay. (Not an early Bay Westy like mine, not a Vanagon like my Wife’s).

 

Just to let all of you know, (especially those that helped me) I fixed the light! It was the diode and the transistor that was at fault! I replaced the 2 normal and 1 electrolytic capacitors as they were reading just out of spec.
I really can't thank @seamallowance enough for finding that schematic, I'm pretty sure I wouldn't have fixed it otherwise!