Found a 37" Mitsubishi CT3703STX in Europe with horizontal sync issues

[TronicG]

Ok, quick story: found this 37" beast of a TV in the middle of a barn in Tenerife (Canary Islands). I suspect this must be one of the if not tied to the biggest consumer CRT sold in Europe? Manufactured in the UK as per the sticker on the back (tube is manufactured in Japan). Anyhow, the TV was brought to my attention by a friend of mine in Tenerife last year. A family member of his worked as a lorry driver dumping stuff from old houses and whatnot during the 80s and 90s. Of course, as a good fellow spaniard, he did indeed go through all the stuff he was supposed to dump and kept what he thought was of use, and this TV was one of those things. Allegedly, this came from John Palmer's house (who was linked with the Brink's-Mat robbery) in southern Tenerife.

Here's a pic of the TV when I found it.


Long story short: the TV had some kind of horizontal sync issue. Either way I brought it home (boat trip included, since I live in the island next door: Gran Canaria) and really did not have the will to troubleshoot it besides the basics until now.

I've, of course, tried all possible inputs on the back with different sources with no different outcome. I've checked for cold joints here and there, specially on horizontal circuit with nothing to report and changed a couple caps that after inspection looked bulged. Doing a complete cap replacement is quite the daunting task since there must be hundreds? It is quite the mess inside:


Symptoms are as follow:

1) When a cold start is performed after maybe a couple hours unplugged from mains I do have horizontal sync (albeit with a lot of noise in the image), here's a vid right after a cold start: https://youtube.com/shorts/tPbgxnZyXEo?feature=share

2) After 30 seconds or so of operation, it completely loses horizontal sync, here's a vid: https://youtube.com/shorts/c2ldc6YVrG4?feature=share

Any ideas on where to start?

[MKL]

Find the horizontal hold pot and adjust it. There will be an IC for horizontal and vertical deflection timebases and the pot will be connected to this IC. As this is a Japan made TV the semiconductors will be Japanese too. The IC in question could be a HA11235 or HA11423 or something similar.

[TronicG]

Find the horizontal hold pot and adjust it. There will be an IC for horizontal and vertical deflection timebases and the pot will be connected to this IC. As this is a Japan made TV the semiconductors will be Japanese too. The IC in question could be a HA11235 or HA11423 or something similar.

Forgot to mention that I fiddled with H Hold pot with no change. The pot serves double duty as an H Frequency pot when shorting two test points on MAIN. Did that too and messed with it with, again, no change. If I crank SCREEN pot on flyback way up I do get the image to stabilise. I'm talking WAY up, so raster lines are visibles and blacks are more like light greys.

[Unseen]

Since the AV overlay looks basically fine while the picture behind is is scrambled I would guess that the signal chain from overlay generation to tube is fine and the fault is somewhere earlier.

Did you try both 50 and 60Hz video sources?

[TronicG]

Since the AV overlay looks basically fine while the picture behind is is scrambled I would guess that the signal chain from overlay generation to tube is fine and the fault is somewhere earlier.

Did you try both 50 and 60Hz video sources?

I indeed tried both. Same result sadly.

Good observation on the OSD, did not think about that. So in theory the fault is happening before the jungle chip? Wouldn't a power supply issue (which was my guess) scramble also the OSD?

[kitty666cats]

Allegedly, this came from John Palmer's house (who was linked with the Brink's-Mat robbery) in southern Tenerife.

Just dropping in to say this is absolutely wild, hahaha