Mitsubishi HL7965KW-SG twitching!

[Logistics]

Yes, this baby is old, but has served me well for many years. Anyway, the screen is starting to twitch! Meaning I'll see in just a random position a line sort of twitch across the screen, and usually followed by the screen size shrinking horizontally for just a moment and returning to normal size. I guess something is starting to go, eh? Does this sound like something fixable with a recap?

It's also been having a problem, prior to this one, where the screen suddenly gets a tad bit darker and then returns to normal... sometimes, a handful of times in random succession.

When I got this monitor, it was around the time that Voodoo2's running in SLI (yes, the 3Dfx SLI) was the absolute hotness... and even then the monitor was considered to be a little old.

[kc8adu]

Re: Mitsubishi HL7965KW-SG twitching!

bad solder joints.
esp in h-driver and out stages.
fix it now before it kills the hot.

[Logistics]

Re: Mitsubishi HL7965KW-SG twitching!

Is this one of those deals where I need to drain the CRT? Screwdriver tied to ground and slipped under the flyback, right?

[i4004]

Re: Mitsubishi HL7965KW-SG twitching!

no need for that. you won't be removing flyback or tube.

[arneson]

Re: Mitsubishi HL7965KW-SG twitching!

The symptoms could in fact be from a high voltage arking.
If the screen is on in a totally dark room and starts jumping you might see and hear this from the FB or Anode.
Something thats old can build up carbon tracing that needs cleaning and high voltage insulator paint.

[Logistics]

Re: Mitsubishi HL7965KW-SG twitching!

OMG, it was doing it more often then normal so I smacked the side of the monitor and now it doesn't seem to be doing it. Sounds like it really may be solder joints.

I had another problem with this monitor though, where the screen would go slightly dark and then light up again, and I was told when I asked about that that I should replace some caps... somewhere in the monitor. Can someone advise what the solution was for that? I searched, but I didn't see the thread where I asked about that.

[Logistics]

Re: Mitsubishi HL7965KW-SG twitching!

bad solder joints.
esp in h-driver and out stages.
fix it now before it kills the hot.

So the driver board is the one attached to the back of the yoke, right? Can I remove that without getting shocked to death or should I just try rewetting the joints while it's on there? Where are the output stages located? I don't mind dismantling this thing... unless I find a portion I don't think I'll know how to reassemble, but I don't want to get shocked by the flyback or whatever.

[arneson]

Re: Mitsubishi HL7965KW-SG twitching!

Your looking at the wrong area.
Your trying to follow the fat red high voltage wire down to the 'flyback' transformer.
The h-out and driver transistors are close by.
You will flip over or gain access to the bottom of this main board.
Then examine and resolder that area, as well as anywhere else that could be looking burnt or loose.
Clean up carbon deposits around tube being carefull to not get zapped by charge that is on the big suction cup.
If your going to screw with the small board on crt rear socket?
By all means, I clean the tube pins with scotch bright, don't bend, and resolder that as well.
Difficulty level, about four.

[kc8adu]

Re: Mitsubishi HL7965KW-SG twitching!

iirc this unit makes hv independant of h-sweep.follow the red wire on the yoke back to the h-out stage.

[Logistics]

Re: Mitsubishi HL7965KW-SG twitching!

Okay, the way arneson writes, I'm not always sure what he means, but I'm guessing that what he is saying is that I DO want to follow the flyback wire and I will find what I'm looking for nearby. However, on this unit, the flyback transformer is on it's own little PCB next to the one on the back of the yoke. The power, video input and video pass-thru connectors are own their own PCB at the back of the unit. AGH, it's all so intimidating to me. All the caps still "look" good and I believe are all Nichicon and UCC's for the most part. There are alot of 85'c caps, though; I was surprised by that as this thing gets pretty hot.

Anyway, I'll just start rewetting as many joints as possible, minus those on the flyback PCB and hope for the best... I just wish I had a grounded outlet for my grounded soldering iron. Maybe I should take it out in the garage where there are some, just in case. I could drain the CRT while I'm at it. :p

[arneson]

Re: Mitsubishi HL7965KW-SG twitching!

It's true, you should hear me speaking.
With your skill and luck you should get it.
That thing is like 18yrs old.
I wondered if it had this on it:

[Logistics]

Re: Mitsubishi HL7965KW-SG twitching!

No, it doesn't have that. If you take the cover off there is access to four big plastic adjusters, one had something to do with horizontal and the other vertical, didn't pay attention to the other two. This monitor has the H+V size and movement under a cover in the middle of the face and the brightness and contrast are on the left side of the face along with the power button and degauss button. Oh, and under the cover in the middle it also has the Mode Select for 3 different presets + a preset recall button. Pretty loaded; I bet this was THE HOTNESS when it first came out. lol!

Anyway, I just got done slapping this thing back together. I'll let you know if the twitch comes back, guys. I guess it's not so intimidating so long as you try to remember which type of screws went where. I'd love to recap the entire thing, but right now I just want to use it, and I don't have a station setup where an actual ground is, (in the garage) yet. Probably time to just invest in an LCD. ;_;