DEC VT-101 Flyback Transformer Blues

[beatkamp]

I have settled on the following snubber diode:

2CL2FM 20 kV 100ma 100ns

The 30 kV diodes I have been able to get a look at seem too large to fit. I think 20 kV should be fine given that the VT snubber is running at 15 kV when operating correctly.

The data sheet is attached here.

* this is not yet advice as I have yet to install and proof this diode

[beatkamp]

Ooof... scratch that.

I am getting:

2CL2FP 30 kV 100ma 100ns

- from the data sheet above.

I don't feel too cozy putting a diode in with so little safety margin: 15 kV operating with a 20 kV diode.
30 kV for 15 kV operating feels much better.

Now I wait for the part to arrive in Iceland.

[caseybea]

Wow. So.. This is the diode inside the flyback?

[beatkamp]

I just received the diode and visually, its a perfect match. Now to install it. Very excited!

[beatkamp]

Here it goes! I will insulate temporarily with electrical tape.

[caseybea]

OK,,this is exciting. Keep us (or me, ha) posted!

I have what I **think** is the exact same situation. But sadly, I am not the electronics expert you are, nor do I possess the equiptment you have for testing.

I have a few questions:

(A) Where did you get the diode from? Web link/url/info?

(B) If I shipped you MY flyback would you test it for me? To confirm my suspicions. I of course would pay all postage to and from and throw in a few bucks for your time.

If I have the same situation (after testing), I can do the same thing, I'm super good with my hands and have no problem soldering in a replacement component....

[beatkamp]

So, I just tested and now I have a working flyback. Great. There is also bad news. Still, I have something not right here. The video board starts to heat up terribly and the video is not stable. I must still have a bad driver transistor. The video begins to fade out as quickly as the driver board heats up.

[beatkamp]

The diode I had to get from Ebay. I paid 13 Euros for a single one. I am not in a position to recommend anyone do this as I have not been able to prove success.

[beatkamp]

Another Test:

All video, CRT, driver board disconnected. Composite video only from the motherboard to a Sony monitor.

This works well.

So I have to have a look at what I am trying to accomplish here.

The goal:
- a fully functioning dummy terminal I can use daily

I am now going to look at fully replacing the CRT elements with a LCD panel.
Perhaps this is the best long term solution?

Its times like these I really miss the slide rule generation of engineers.

[beatkamp]

I was quite disappointed yesterday having put so much hope into a bad snubber diode.

Now I am going ahead with an LCD panel install in my VT.

The main issue with this is that the composite video in the VT is very non-standard NTSC.

A Sony PVM monitor will display it but virtually nothing else will work. None of the cheap composite video converters that are readily available will handle this signal. It needs to be somehow conditioned or converted.

Lotharek.pl seems to be making something that may do the trick. I have asked them about it and am waiting to hear back,

The Medusa:
https://lotharek.pl/productdetail.php?id=135

This caught my attention due to the following description:

,, Special modes (unrecognised PAL-like and NTSC-like)
unknown PAL
unknown NTSC