Author Topic: Electrohome g07 - advice please (Read 8745 times)

matman · « **on:** March 28, 2009, 10:45:49 pm »

I just picked up a ms. pacman cabinet today that wouldn't power on. When I got it to power on, I was totally excited (still am).

Anyway, the monitor came up pretty dim and the colors were off too, not to mention the focus. It's like someone went crazy on all the adjustments. I did some tuning to get to a better focus and adjusted the brightness a little, but the colors still seem off and the picture isn't as crisp as i was hoping to achieve. I turned them all clockwise and started coming back about 1/4 turn each until i got to a point that was..well..acceptable, but when playing the game, the bananas (for example) are green (maybe just not ripe yet and I should wait longer?

)

Also, there are some lines that run the height of the monitor at a slight angle..not quite 45 degrees...run like this:

/ / /
/ /
/ /

I've read all the g07 docs here:
http://www.lizardlickamusements.com/pages/documents.shtml

My questions are:

1) what are the red and green drive tunings for? I've read the service manual but a lot of it is gibberish to me and I don't have a way to put up the crosshatch/etc.. to tune it like they suggest.

2) There appears to be some discoloration on the monitor in the upper right and lower left portions of the screen (as you can see in the attached picture). Not sure what this is or how to fix it. The monitor appears to have no burn in at all - which I find awesome seeing that this monitor is from 1982. Is this something that is fixable?

3) Any suggestions on fixing the color?

4) According to the flowchart at that link above, the only time to do a cap kit is when the screen is wavy...Is that true?

5) What's up with those lines running down the screen? They don't move at all. (I should get a better pic of them huh?)

Thanks,
Matt

Kevin Mullins · « **Reply #1 on:** March 28, 2009, 11:58:10 pm »

You need to turn the SCREEN control down on the flyback. (bottom pot)
The area outside that grid and the inside of each square should be pure black.

Mauzy · « **Reply #2 on:** March 29, 2009, 12:20:59 am »

Also looks to need a manual degaussing and probably a cap kit. Very easy little fixes that will give great results if done correctly.

matman · « **Reply #3 on:** March 29, 2009, 02:08:47 am »

so the service manual seems to indicate the cap kit is needed if the screen is wavy, but i don't get that. what symptoms indicate a cap kit should be done. I'm up for it, just wondering what to look for so I know when I need to do one.

SirPeale · « **Reply #4 on:** March 29, 2009, 08:56:05 am »

Quote from: matman on March 29, 2009, 02:08:47 am

What symptoms indicate a cap kit should be done? I'm up for it, just wondering what to look for so I know when I need to do one.

Weird geometry, doesn't work at all...there are a ton of things that bad caps can do.

Look at the caps themselves. Do they look old? If they're original, they DEFINITELY need replacing.

And yes, you need to manually degauss your monitor.

matman · « **Reply #5 on:** March 30, 2009, 03:44:40 am »

Thanks. i'll see what i can do next weekend...I'll order a new cap kit and figure a way to degauss the monitor.

matman · « **Reply #6 on:** April 03, 2009, 02:56:07 pm »

I have one question that hasn't been answered yet:

1) what are the red and green drive tunings for?

Sorry if this is such a basic question, i just can't find anything that describes it well.

Kevin Mullins · « **Reply #7 on:** April 03, 2009, 03:31:05 pm »

They are for adjusting the individual color guns in the tube. (red, green, blue)

matman · « **Reply #8 on:** April 08, 2009, 02:34:19 pm »

when i pulled out the pcb for the monitor to perform the cap kit, i failed to note which connector from the degaussing coil goes where. does it matter which wire goes where? they are both white wires that look pretty identical.

Kevin Mullins · « **Reply #9 on:** April 08, 2009, 02:43:06 pm »

Degauss coil - it does not matter which way they go.

ken_cinder · « **Reply #10 on:** April 08, 2009, 03:09:28 pm »

Who needs a manual degaussing coil, when you have a circular saw?

Mauzy · « **Reply #11 on:** April 08, 2009, 03:25:20 pm »

Quote from: IJTF_Cinder on April 08, 2009, 03:09:28 pm

Who needs a manual degaussing coil, when you have a circular saw?

Oooh. never thought of that one. Ive used an electric drill, but never a circular saw...

matman · « **Reply #12 on:** April 08, 2009, 04:51:07 pm »

i was planning to use a portable fan as well..but maybe i'm too particular in that i don't like random wires hanging around

matman · « **Reply #13 on:** April 10, 2009, 10:37:15 pm »

I'm almost done with the cap kit. Its come down to two more caps left and i see something that looks kinda odd. I'm sure its there for a reason, but wanted to see if anyone has seen this before.

I'm on C521 and there is a connection made from positive side of C521 to R514 as in the picture attached using some piece of metal as a bridge and its all covered in solder. is this normal? I plan to just leave it there.

I THINK this was done because it looks like a solder pad is missing, so this poor man's connection is then made. I'm not sure how to replace solder pads..or put one back on..but it also makes me wonder if this connection could result in issues.

any thoughts?

qrz · « **Reply #14 on:** April 10, 2009, 11:10:24 pm »

a not so clean trace repair. looks like the board could use a good cleaning/degreasing,
and some solder touch up

qrz

Kevin Mullins · « **Reply #15 on:** April 10, 2009, 11:26:54 pm »

Quote from: qrz on April 10, 2009, 11:10:24 pm

a not so clean trace repair.

No kidding ...

The solder pad does look to be missing on the capacitor side.
Since you are replacing that cap anyways you have extra long legs to work with.
Scrape the trace clean down to the foil surface, bend the leg of the capacitor over enough to reach across and solder it down directly to the trace. Heck you could probably reach all the way over to that resistor if so desired.

matman · « **Reply #16 on:** April 13, 2009, 02:38:03 am »

I ended up running the cap lead to the resistor. didn't have a chance today to try it out tho..holiday dinner got in the way.

matman · « **Reply #17 on:** April 18, 2009, 03:45:16 pm »

I installed the board back into the monitor today. I replace everything that came in the cap kit - flyback, caps, hot, hwidth coil.

I seem to be getting almost the same results and am having a hell of a time getting the ms. pacman test pattern to be white/grey. For some reason I don't seem to get much green. When i turn up the green drive, i have to turn it all the way up to get much of any green and even then it isn't much.

I swapped the red and green wires to make sure that the board is supplying green (so i would expect to see red on the screen) and it does, so i feel i've eliminated the ms pac board as the root of the problem.

Anyone have any advice on how to get the green working? It isn't that there is NO green, it is just not very strong, making it difficult to have a white balance.

I've followed these directions to try to balance it:

Correct color balancing:
- Adjust the Red/Green/Blue DRIVE controls (on the board) to minimum.
- Adjust the Red/Green/Blue CUTOFF controls (presumably on the neckboard) to center.
- Turn up the SCREEN control on the flyback (next to FOCUS) so you see the image and keep going until you start seeing the retrace lines with an overall "fog" on the screen--especially in the black areas. Then back off until it's *almost* black again

****This part is impossible for me.
- Now adjust each of the DRIVE controls so the level of color is the same in the black areas (e.g. if only blue is lit in the black area, bring up red and green slightly to match the same level to make it grey)
****
- Now turn down the SCREEN control to make black pure black again.
- Now adjust the CUTOFF controls to ensure that you don't have bleeding of colors to the edge of anything.

SirPeale · « **Reply #18 on:** April 18, 2009, 04:37:51 pm »

Lack of a color can be caused by a few things. Most likely the green gun in the tube is weak and should be hooked to a rejuvenator to rule that out.

It could also be caused by a crap connection on the neckboard to the neck. Shift it slightly - does it get better/worse?

Possibly the drive transistor on the neckboard could be faulty, you can swap the green for one of the other colors to rule that out.

matman · « **Reply #19 on:** April 18, 2009, 06:05:40 pm »

I just tested the transistors (albeit still soldered to the board) with my DMM and they all read the same..

I did a little more debugging and this is what i've found.

1. I disconnected the blue.
2. i set the red drive to 0

This showed me green (this is good)

3. I turned up the green drive to max and noted the intensity of the green
4. I turned the green to 0 and red to max and noted the intensity.

the red max intensity is much more than the green max
the green max intensity isn't a bright as the standard blue drive intensity

so its like going into photoshop and using the following RGB values to paint white:

R 175 (2/3 red drive)
G 175 (max green drive)
B 240 (standard blue drive)

The blue cutoff only seems to do so much... I guess if i could get the green intensity greater, i'd be in better shape..otherwise the whole pic just looks dim and slightly blue.

SirPeale · « **Reply #20 on:** April 18, 2009, 06:11:11 pm »

FYI, transistors can be "leaky" - eg they don't do the job they're supposed to. They read okay, but work badly.

matman · « **Reply #21 on:** April 18, 2009, 08:31:08 pm »

maybe i should just replace them? I need to find the specs on them first..i found them in the manual:

2SC1514VC

and mr. bob roberts sells them..although I'll check out the local electronics shop first.

qrz · « **Reply #22 on:** April 18, 2009, 10:39:12 pm »

a quick 1st in circuit test on an xistor :

i use the diode/continuity test on the meter ( fluke ).
check the base /emitter junction fwd biased should be around .5-.7 v higher if darlington
then same for the base /collector junction.
the drop across collector /emitter should be high
do test again with revesed meter leads

>> this test may not detect gain related defects <<

however , a 2n3904 dropping .9v be is defective

fet/mosfets will differ per device construction...

when in doubt , pull and retest / use a xistor testor
preferably one that uses a 1khz or higher drive pulse . sencore tf -46 or similar

semiconductor specs should be available here :

www.alldatasheet.com

qrz

matman · « **Reply #23 on:** May 02, 2009, 04:41:26 pm »

Today i replaced all three transistors and fired it up..unfortunately the green intensity problem still remains.

I guess this leads me to seek rejuvinating the tube...i have no idea where i would go for that

It is playable, just doesn't have the vibrant colors i was hoping for.

aPr0mpt · « **Reply #24 on:** June 30, 2009, 02:50:21 am »

Hows the monitor coming? I have a similar problem with the colors in my electrohome.... maybe we should just replace the monitor.

matman · « **Reply #25 on:** June 30, 2009, 01:57:03 pm »

I have not made any progress. I haven't attempted to get it rejuvinated. I would love to replace it, however I have no idea where i can get a replacement. Seems like all the arcade monitor producers have stopped making CRT arcade monitors..which would lead me to gut some other cabinet somewhere - something i'd rather not do.

SirPeale · « **Reply #26 on:** June 30, 2009, 02:03:43 pm »

Something that MIGHT work...put the monitor face down on a towel. Short the green drive transistor on the neck to ground. That'll make the green come on full. You don't want to do that for long, but while you do that, GENTLY tap the neck. It might dislodge whatever's doing that.

Where are you located? Someone near you might have a rejuvenator. I have one, but it's in unknown working condition and I don't have a proper adapter for it yet.

matman · « **Reply #27 on:** June 30, 2009, 07:59:28 pm »

couple of questions..

"monitor face down on a towel" - can you explain the reasoning behind this?

"Short the green drive transistor to ground" - so take a wire from ground and touch it to which part(s) exactly.

"GENTLY tap the neck" - and by the neck which point are you referring to (see the attached diagram...A,B,C).

(sorry if these questions sound lame, just wanna make sure we are on the same page).

I'm in Los Angeles

SirPeale · « **Reply #28 on:** June 30, 2009, 09:08:15 pm »

1) you don't want to scratch the face of the tube when you lie it face down. That's what the towel is for.

2) A wire from ground to the green drive transistor on the....hm...middle pin. I think. It's been a while since I did that. Someone will chime in shortly if I'm wrong.

3) The neck is the skinny part of the tube.

4) I'm going to recommend you have someone knowledgeable in your area look at this.

StephenH · « **Reply #29 on:** July 01, 2009, 02:18:27 am »

I would try swapping the green with red or blue from the signal you are sending it. If the green gets bright and the red or blue (the one you swapped with) gets dim, you could have a gameboard problem instead of a monitor problem.

matman · « **Reply #30 on:** July 01, 2009, 03:36:36 am »

Quote from: StephenH on July 01, 2009, 02:18:27 am

I would try swapping the green with red or blue from the signal you are sending it. If the green gets bright and the red or blue (the one you swapped with) gets dim, you could have a gameboard problem instead of a monitor problem.

thanks. I actually already tried this. I swapped blue and green but had no effect, the green was still dim and blue was fine.


Main	Restorations	Software	Audio/Jukebox/MP3	Everything Else	Buy/Sell/Trade
Project Announcements	Monitor/Video	GroovyMAME	Merit/JVL Touchscreen	Meet Up	Retail Vendors
Driving & Racing	Woodworking	Software Support Forums	Consoles	Project Arcade	Reviews
Automated Projects	Artwork	Frontend Support Forums	Pinball	Forum Discussion	Old Boards
Raspberry Pi & Dev Board	controls.dat	Linux	Miscellaneous Arcade	Wiki Discussion	Old Archives
Lightguns	Arcade1Up	Try the site in https mode		Site News


Unread posts \| New Replies \| Recent posts \| Rules \| Chatroom \| Wiki \| File Repository \| RSS \| Submit news