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LC Monitor (12" RGB) Weirdness

Scott Baret

Well-known member
Weird 12" monitor issue (the LC kind). When I move my mouse or press a key, I see some interference. The cables aren't touching each other. I also notice some scan lines when the screen is completely white or mostly white (i.e. a new Word document). I'm guessing this is the result of too much power, especially since with the brightness turned up, the black becomes practically dark gray. Anyone willing to verify this?

 

just.in.time

Well-known member
I have the LC RGB High Res monitor, so different, but have never seen anything like that.  However, my LC 550 used to have an issue when plugged into a specific outlet at my old place where there would be crazy interference every time the A/C ran.  Definitely was annoying.

First thing I would check is to make sure everything is grounded properly, including the power outlet you are plugged into.  Most tool and home improvement stores will sell a device for $10 or less to help you check your outlet's wiring.  You just plug it in, and a series of 3 lights light up to tell you the status of your outlet's electrical wiring.  Try unplugging both power cables, make sure the ground pin within the plug on the devices is still nice and shiny and not corroded or dusty.  Then get some new power cables (or some known good ones from most any modern desktop PC) to see if that resolves the problem.  Finally, try unplugging other devices on that same building circuit, potentially one of them can be introducing oddness.  Last but not least, pop open the LC and monitor and make sure any grounding wires within them are not loose.  Using the SE as an example, the PSU has a green wire that screws onto the frame and I believe the analog board has another ground wire that screws onto one of the four screws holding the picture tube in place.  Not sure exactly what your equipment will have.  None the less, seems like a potential grounding issue somewhere along the way to me.  Best of luck :)  

 
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Scott Baret

Well-known member
All good ideas--thanks!!

Let's see...I first noticed this around the time I put a new lamp on the same power strip. I did try it on another outlet and things seemed better, just not by much. I am currently in an apartment complex so I can't rewire things, but I could take the LC to someone else's house and try it out. I could also start taking stuff off the other outlets if the circuit is an issue.

The cords are a good idea too. The cords are integrated but I do happen to have an extra and have taken these monitors apart before, so a replacement wouldn't be too hard. I know the grounding wire was OK in there but who knows, it could have come loose over time--probably didn't tighten it as well as I could have and I have moved it around a little since then.

If all else fails, I do have a backup set of boards, both with new capacitors on them...but I'm glad you seem to think it's not a huge issue!!

 

just.in.time

Well-known member
Interesting, my old place was also an apartment. The first time I saw my 550's monitor freaking out I thought for sure there was going to be serious issues to deal with.  Took a day or two before I noticed it only had issues when the AC is running.  You can imagine my relief when the issue wasn't internal to the computer (and the air conditioner at my current place has no effect on the 550).

Please post back what your solution ends up being when you get it all figured out :)  Hopefully it isn't anything too difficult.

 

Scott Baret

Well-known member
I haven't gotten a chance to work on anything, but I do have two questions here:

1. Could this explain why the LED bulb in the lamp on the same circuit flickers a bit?

2. Is it harmful to the CRT itself to be used with interference?

(I still have an old CRT television in storage and it doesn't even have a grounding wire on its plug so I'd suspect it has something to do with the analog more than the CRT, but let me know since I have used this LC several times this way)

I'm also thinking it could be several apartments here are on the same overall circuit and it could be something from my neighbors?

Trying to think of some culprits...the speakers on the other side of the wall?

Here's one more tidbit that may prove useful: there was more interference than usual while I was adjusting the contrast knob--during that process, that is. It settled down after that.

 
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cruff

Well-known member
Do you have a UPS unit handy?  They often include noise filtering, you could plug the monitor into the UPS and see if that helps.  I have some high end LED bulbs in some of my lamps, and they will flicker sometimes when on their lowest setting if other large motors are running  in the house, such as the furnace blower or the AC compressor.

 

Scott Baret

Well-known member
Just did some experimenting...

First, I stopped by the storage unit earlier today and picked up another LC--one which I last had on in November and had no problems with. It also has new caps, so it's in top shape.

When I got home, I plugged the monitor, as well as the same power cord and ADB chain, into the other LC, which was set up next to the one with the issue. No monitor problems!! (I refurbed that monitor myself and knew I had tightened the ground wire pretty well, so I was hoping it wasn't my doing!)

I plugged everything back into the original LC. The problems came back. I took the monitor off, opened up the LC, disconnected the PSU from the board, and plugged it back in. After all, I had just fixed an issue with the sound shorting out on this board (which is also re-capped). With the monitor still on the chair next to my desk, I tried it again. Success! If there was any interference, it was likely the product of my imagination.

I put the monitor back on the LC, returning it to its original location. Again, any noise lines were the product of my imagination or very, very faint. I suspect they'll go away completely, if they even existed, once I either move or replace the boards inside the monitor with the newly-recapped ones I have in the closet (I just don't feel like tearing apart a monitor unless I need to). I drew a little on Kid Pix and moved the pointer around a blank screen on a word processor. Again, I feel any lines I saw were a product of my imagination at this point--and if they were there, it's likely just typical CRT behavior that I've grown unaccustomed to after using LCDs as primary displays for the past 19 years.

My guess is that it was indeed an interference issue. Grounding or not, discharging everything seemed to do the trick. The speaker has been working well too.

I'm also happy I didn't have to donate a board from the other LC!

My other guesses? Some sort of buildup caused by the conditions around there. This seemed to start when I moved the LC to carpet temporarily while flipping a mattress in the same room. My guess is there was some static buildup when I moved it--but that's a shock to me because I move LCs all the time with the mobile lab.

 

CC_333

Well-known member
This is probably a stupid little thing, but did you adjust the brightness cutoff on the monitor that was acting up?

Scan lines could indicate that the cutoff is out of adjustment (i.e., set too high). This can happen with compacts as their components age and rift out of spec, and trimming the cutoff down a bit solves it most of the time. It seems logical that the same could happen to the LC Monitor. Especially if it isn't recapped.

So, maybe before you go about replacing all the boards (probably a tedious job), try checking and readjusting the brightness cutoff first?

c

 
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