New Scores - Looking for Manuals....other stuff...

[Mad-Mike]

So I'm back, 2 weekends ago I picked up my first CRT Televisions in awhile for a game room rebuild I was doing. This guy had them both for free.

1989 Mitsubishi CS-2720R
1993 Magnavox CML192C109

The Magnavox works great, needed a little focus adjustment but otherwise no problems there. Did not even need to open it up. Just cleaned it up and it powered on.

The Mitsubishi on the other hand is a bit of a mess......

- Power cord was frayed so I tried a temporary bodge wire to test

- Does not power on, not even a click from the relay

- Opened it up last weekend and found out the insides of the poor thing look extremely dirty. RF Sheilds look rusted, the board I assume for the Audio looks like a mudslide landed on it, the other part of the insides are pretty dusty/dirty but not that bad. So obviously some exposure to the elements.

Thinking about trying to revive this Mitsubishi before I decide to recycle it and/or use it for some other art project or something. The capacitors look good inside - something I checked out of research where I read that the Mistubishis of this era had some Cap Problems.

Anyway, starting up this thread mostly for opinions and maybe any input. I may eventually want the Schematic/SAMS.

I'll provide pictures I've taken once I'm in a place I can do that.

[zeno]

Before spending $$ post a few good chassis pictures & the
exact symptoms.

73 Zeno
LFOD !

[Mad-Mike]

Originally Posted by zeno

Before spending $$ post a few good chassis pictures & the
exact symptoms.

73 Zeno
LFOD !

Actually, update, tonight I got the Mitsubishi working. Turns out it was a cold solder joint on a transformer near the power-on relay - used method of deduction to figure it out. Also touched up some other cold solder joints and badly done joints while I was in there. Actually, the cracked solder joint that likely was the culprit is very visible in the "Mitsubishi Chassis Underside" picture.

The Mitsubishi now powers on. I need to replace the power cord (frayed on one wire - did a bodge job just to test), the screen looks like it could use a good degaussing (or maybe I knocked something on/near the deflection yoke off kilter). Only real worrying thing is I did get a static-E type shock when turned off and even unplugged, very mild shock, but apparently able to leap quite a distance....so might be a bad discharge cap somewhere. May also need some final setup (focus methinks). I also cleaned it up real good while I was in there, the circuit boards were HORRIBLE - must have been the original dust from the original owner, lol.

The Magnavox is working great and not really having any issues. Did a mild focus adjustment and it's dead on crisp and nice despite the fact I have my NES and Atari 2600 going through it via RF as that's all It has. Gave a picture of it here just to show it off, lol.

[Electronic M]

Caps job isn't to discharge, but to store charge. But if a capacitor has a resistor in parallel it is the resistors job to discharge the capacitor.

[Mad-Mike]

Did a little more digging....i think the problem may be a loose yolk (hear buzzing, not whine, from that area when on now after moving it). May also need a degauss because of the colors being all jacked up....which is my fault, we put it next to my guitar cab (big ol 4x12 with celestion speakers).

Does seem unplugging it for awhile and then plugging back in and powering it up periofically is starting to very slowly resolve the color issue. Does this look like a degauss issue? Can a loose yolk Affect degauss?

[old_tv_nut]

If the yoke is out of position, it will mess up the purity, in general around the edges more than the center, which looks like what you have.

If the degaussing is not working, it will affect the purity after the set is moved. It could be corrected with a manual degaussing pass, but will recur when the set is moved.

The two basically do not interact - but both need to be right.

A hard drop that distorts the shadow mask will be uncorrectable - hope that's not the case here.

[Mad-Mike]

Originally Posted by old_tv_nut

If the yoke is out of position, it will mess up the purity, in general around the edges more than the center, which looks like what you have.

If the degaussing is not working, it will affect the purity after the set is moved. It could be corrected with a manual degaussing pass, but will recur when the set is moved.

The two basically do not interact - but both need to be right.

A hard drop that distorts the shadow mask will be uncorrectable - hope that's not the case here.

I've been messing with it off/on throughout the day. Yoke is good and looks like a non purity/convergence ring setup. I managed to make considerable correction using old Hard Disk magnets. Put in some pics....now wondering if I should consider getting a manual degausser, seems the hdd magnets are tricky. Turning it off and resetting (unplug), nor does moving mess with convergence so i think this is just the tube being jacked by guitar speakers. The giy i got it from had them stacked near some bass cabinets (even bigger magnets) so that could have messed things as well.

As for the buzzing issue still not sure. I did find the anode cap was loose, reattached after a discharge, no change. Now thinking it could be the loose ferrite core of the flyback. No arcing or sparking inside though, and the buzzing goes down or away with a darker.
Screens that are black with little other colors like Pac-Man seem normal. It seems related to screen power usage. Currently putting together a youtube vid for this fix-it-up. Ill post it once done to show the buzzing issue.

[Electronic M]

If you have a junk parts set you can make your own manual degaussing coil.

Those HDD magnets may be a bit much.

[zeno]

Your MGA uses an RCA bonded yoke CRT. Yoke is glued on
& the neck magnets are a piece of grey tape. Do NOT remove the tape !
Three possable problems with purity.
1) CRT is heavily magnetized & the DGS circuit cant handle it.
It will improve with time ( cold restarts).
2) There is a cold joint in the DGS or a bad DGS thermistor.
& the DGS circuit is not working right. Thermistor usually abt a
1/2" black square part made by TDK. Either 2 or 3 legs.
3) The set fell & the shadow mask broke loose. Nothing you can do
about that. Usually if you hit the set hard the purity problem will shift.
Beyond that the RCA CRT was a common jug. Many Japan & US
set used them & you can swap one out in minutes.

Buzz most likely from the yoke vert winding. NAP sets were a big problem with it. We sprayed it with something it a rattle can but I dont remember what ! Someone here will.
To track down buzzes & screams use a paper towel tube as a stethiscope or a plastic rod to poke at things.

good luck
73 Zeno
LFOD !

[Mad-Mike]

Originally Posted by zeno

Your MGA uses an RCA bonded yoke CRT. Yoke is glued on
& the neck magnets are a piece of grey tape. Do NOT remove the tape !
Three possable problems with purity.
1) CRT is heavily magnetized & the DGS circuit cant handle it.
It will improve with time ( cold restarts).
2) There is a cold joint in the DGS or a bad DGS thermistor.
& the DGS circuit is not working right. Thermistor usually abt a
1/2" black square part made by TDK. Either 2 or 3 legs.
3) The set fell & the shadow mask broke loose. Nothing you can do
about that. Usually if you hit the set hard the purity problem will shift.
Beyond that the RCA CRT was a common jug. Many Japan & US
set used them & you can swap one out in minutes.

Buzz most likely from the yoke vert winding. NAP sets were a big problem with it. We sprayed it with something it a rattle can but I dont remember what ! Someone here will.
To track down buzzes & screams use a paper towel tube as a stethiscope or a plastic rod to poke at things.

good luck
73 Zeno
LFOD !

It looks like mine has a Mitsubishi Tube though, not an RCA. Or did RCA make Tubes for Mitsubishi?

The label is

MITSUBISHI Color Picture Tube
Tube Type: A68AEG20X01

I don't think the Apreture Grill is bad at this point, after more mild distanced HDD magnet waving I managed to get almost the entire center save for 1-2" of the corners of the screen cleared up, right now I'm giving it time to degauss from cold starts periodically and it seems to be slowly improving.

I did not see any magnets with tape inside the case anywhere either, nor rings for Purity or Convergence (a bit odd).

I figured out the buzzing issue occurs more when there's more bright colors on screen. Games like Pac-Man and Ice Climber, or an unused Composite or S-Video input cause it to buzz very little, or not at all, while games like Super Mario Bros or the Wii Menu or the static from analog channels causes it to get rather noisy.

I posted a video talking a bit of what I've done and showing the noise toward the end, though it's not as easily audible in video than it is in real life (sounds more like a hiss in the video, in real life it sounds more like buzzing hornets). - https://youtu.be/255gzdDT2ZE

[old_tv_nut]

The CRT label should have an EIA number, which decodes to the actual manufacturer.

[JohnCT]

Originally Posted by zeno

3) The set fell & the shadow mask broke loose. Nothing you can do
about that.
73 Zeno
LFOD !

Heheh.. reminds me of a story... Probably 20 years ago, a buddy took a large Sony CRT TV on trade that had been bumped and had a shadow mask warp. Now, big Sony's were a handful to get good purity, geometry, and convergence anyway, and bumping them did no good whatsoever.

He couldn't sell it as is and wanted to take it home, so I had him go home with a compass and find the exact direction that the CRT would face in his game room. Back at his shop, we turned the TV in the same compass direction as he was going to use it at home, degaussed it, and I stuck about 20 of the "tweak" magnets that RCA used to put on their big tubes to tweak edge convergence onto that Sony tube. The trick is to not only move them in and away from the yoke, but to rotate them and watch the effect of each one. I got it pretty good, and he brought it home and used it for many years with no further trouble. As long as he didn't rotate it, it had a good picture.

John

[Mad-Mike]

So, update, I may have the noise figured out, though I'm not sure, maybe an expert can chime in here...

The Mitsubishi still makes a buzzing noise congruent with the screen brightness, screens with bright content such as the Wii menu or static are louder, black screens like old Arcade or Atari games don't generate nearly as much racket. Been chasing that demon around a bit for awhile off/on. I also noticed if it runs for awhile I hear a louder SNAP where the screen flickers - it tends to do this on a bright screen, darker screens I don't see it happen as much. This has me believing it's the Anode Cap where the issue is coming from.....a bit hard to tell though as I see no arcing even with the lights off (maybe micro sized arc?). Also, is it possible this is because there's no dialectric left on the back of the screen (thusly a bad seal). Also, when I turn it off, a white dot appears on the middle of the screen for a short bit if it's on awhile (if running for 20+ min, and the dot lasts about 1-3 seconds at most).

I'm going to bite the bullet and buy a Degausser when I get around to it, will be handy to have as I own 4 CRTs anyway and I'm starting to enjoy this so might be worth it anyway, esp if any other CRTs come along. I've recovered the tube a LONG way and it looks beautiful except the corners (bright, sharp, crisp colors).

The Magnavox is still working great. I have Roku, Atari 2600, NES and a Second Wii I built running through it in RF and it's looking rather snazzy with little to no interference.

[zeno]

First be sure its not coming from the speakers. Just turn them
off ( if you can ) or turn the volume all the way down & try it.
If its a HV ark it almost has to be at the anode connector,

You need a clip lead & thin screwdriver thats well insulated.
Hook one end of the lead to the driver & one to the CRT ground.
Usually there is a long bare wire across the CRT bell. Thats
the best way to grab the CRT ground. Slide the driver under the center
of the cap & move it around. That discharges it. It may make a
snap but most solid state sets bleed off in seconds anyhows.

The cap is held in by 2 claws. Fold up the rubber & push one to the side
& it will pop off. Look for carbon tracks on the cap & CRT glass. Clean
all with 91% isopropyl alkahol. There is a black coating on most
of the CRT. Do NOT clean that ! Just within abt 4" of the cap.

Reassemble, let dry & try.

73 Zeno
LFOD !