Main > Monitor/Video Forum
Contrast/color issues on universal replacement chassis
snappleman:
From what little info I found the monitors used on these Pentranic boards are supposedly around 2.3ohm horizontal and 14ohm vertical, though there are what looks to be 2 vertical transistors (B861 and D1138). They both were in bad shape and it had no vertical deflection, I swapped out the D1138 and it gave me some picture (what's pictured above), I'll order a B861 and see if that helps at all.
I read someplace that if you use a high impedance chassis on a low impedance yoke you damage some things pretty badly, so far this has been running relatively quietly and smoke-free. But I am super inexperienced and just now trying to learn how to work on these things so I'm sure I have everything wrong and will make tons of stupid (and expensive) mistakes. :lol
jennifer:
Ya you will, wait till you blow up your first logic analyzer (dont ask🙄)...Testing the Kv out of that flyback would be my first thought, not that it is wrong at this point, but I would be more concerned about Xray radiation, ( high frequency on faulty equipment) someting nobody ever talks about mind you especially around here, ...After that I would take a close look at the quality of the components especially the caps, (personally I would match it up to a Wg chassis, and probibally just put new high temp Rubicon on there, but that just me, little eccentric)...And after that I would probibally order a few more of those boards just as a comparison against a bad board a curious assessment and spare parts for other projects ,cause that's kinda cool😜
snappleman:
No need to wait, my work is in the pro-audio field and in my career I have already destroyed tens of thousands of dollars worth of mic pres, guitar amps and all manner of stupidly expensive gear they no longer make transformers for... :cheers:
snappleman:
Update! I took a while to get back to this but out of curiosity I put the original chassis back in and fed it an RGB signal via SCART and the changing contrast and color balance happens still, but only on an RGB signal. The NTSC (composite and SVideo) works fine, and also YUV works fine, it's just when it's taking in an RGB signal that it happens. Whatever color is brighest on the screen will change the tone of the other colors and overall brightness of the screen.
This happens when I use official SCART cables for my consoles and also with RGB output direct from my JAMMA boards. I have a Raspberry Pi running with a Retrotink RGB hat, and I made my own VGA->SCART cable for it, and that displays just fine. Since it happens on any compatible chassis I put on this tube, I'm guessing it's the tube? Maybe the consoles and arcade boards all output RGB that's too much for the guns to handle?
At this point I'm thinking the tube might be damaged, I got it as NOS and it was unused so I figured the tube would be in good health, but maybe firing it up after all those years sitting in some storage room may have damaged it?