Hantarex MTC900/E Jailbars and Color Problems

[mailman-zero]

The Hantarex MTC900/E that I just got in a Real Ghostbusters cab has some problems.  I was wondering what might cause a large portion of the image to be missing the blue, but the top shows it.  What would be the best way to go about fixing it (if it's even possible).  Would it be worth it to replace the caps?  Can bad caps cause these kinds of color problems as well as wavy jailbars?  Thanks for your help!

This gallery is full of larger versions of the pictures below.
http://www.walkingtowel.org/gallery/folder/Arcade/The%20Real%20Ghostbusters

[grantspain]

a monitor of that age would benefit greatly from a full electrolitic cap change,also check for bad solder joints
the colour problem could also be down to gaussing issues

[mailman-zero]

I suppose I could replace the caps and clean up the monitor first, then see what problems still need to be cleared up.  I was especially wondering if bad caps can cause color problems like that, though.

[grantspain]

i think you colour issue is being caused by a faulty degauss or a magnet close to the screen(i.e a speaker),some mtc900 chassis had a push button degauss-does yours?

[mailman-zero]

I can't find a button anywhere on the chassis.  I have looked, but I might be missing it if it is there.  Where would it be located?  I googled for it but didn't find any mention of it anywhere.  Thanks for your help, by the way!

[grantspain]

not all the 900 had a manual degauss.
try turning the cab with it switched on,if the colours get better when you turn the cab or change somewhat then you def have a degauss issue(this could be component failure)
the lines on the pic could be a ground/earth issue

[mailman-zero]

The image did indeed change colors when I rotated the cab.  I had it facing west when I took the photos in the first post, when I rotated it so the front of the cab faced south-east it looked the best, though it was still flawed.

The jailbars are sometimes not moving, ant the picture looks clear except for the light and dark banding, but usually most of the screen "jiggles" left and right with each line on the screen moving left and right very quickly independent of the lines above and below.  I don't know if that makes any sense.

Anyhow, where do I go from here.  I don't want to recap the monitor if I can't fix the color, which is a degaussing issue.  Is there anything else I can try without getting a degaussing coil?  How can I tell if the jailbars are a ground/earth issue, and where would I go from here to diagnose and correct it?

UPDATE: I just realized that the ground prong on the plug has been ripped out.  This doesn't seem like a very good idea, but I'm not sure if that would affect anything like what I'm seeing.

Thanks for helping me with my very first arcade cab!

[grantspain]

earths are an very important thing

[mailman-zero]

I bought a new plug and attached it to the power cord.  I tested continuity from the Chassis to the ground in the plug, and the chassis is now properly grounded.  Are there other grounding issues I need to check for?  How whould I go about doing that?

Thanks!

[mailman-zero]

The color issue from before was not entirely caused by a bad degaussing coil.  I fashioned a VGA plug to a Molex connector that I can plug into the existing cable that runs from the Monitor to the Jamma connector.  After I removed the game and plugged in the VGA cable, the colors were fixed (except for a tiny spot in the corner).  But now I have another question.

My monitor specs say they can support a 1v connection at the minimum.  I think the VGA standard is 0.7v.  I notice that when the original game board is plugged into the monitor there is a lot of leeway about the horizontal and vertical frequencies.  I can move these knobs all over the place and it stays synchronized.  When I plug in the monitor cable and try to test it with Advancemame's advcfg utility, I can't get it to sync.  I accidentally drove the monitor at 31kHz, and I was just barely able to get that to sync (the controls were VERY touchy), but of course, there were two narrow versions of the screen next to each other.

Would an amplifier help so the connection from the computer VGA might work and sync better (more like the arcade game when it's plugged in)?  Thanks for your help!

[mailman-zero]

The yellow monitor problem is back.  I've narrowed it down to a problem with the blue signal.  Adjusting the B gain and B cutoff does nothing at all, whereas adjusting the R and G gain and cutoff knobs changes the picture.

I don't know how I made the blue signal work, and I don't know how it stopped working again.  I have seen it in both states from two different inputs.

My question: which connections on the board should I check to see if they are loose?  I have played around a little bit at the point where the RGB and Sync connect, and I have wiggled the blue wire around where it connects to the neckboard.  Any other ideas?

Anything would be welcome at this point!

[Ken Layton]

Get out a good work light and a magnifier. Look carefully for bad solder joints on all the monitor boards.

[grantspain]

a common problem on hantarex are leaky drive transistors on the neck card,these can give all sorts of problems with the colours including loss of colour or bleeding

[mailman-zero]

Thanks for your help.  I'm going to be changing out the caps pretty soon here, anyway, so I'll just go ahead and replace the drive transistors and examine the board for any other problems when I have it out for that.  I hope to post my success story here once that's taken care of.

This is an awesome community you've got going here, by the way.

[mailman-zero]

It's been a while, but I finally got the money and the time to continue this project.

I replaced the capacitors using a Bob Roberts cap kit and I replaced the blue transistors on the neckboard, and this is what I am left with:


At least the jailbars are gone    The smudge in the upper left is on the plastic, not the monitor. Different inputs cause the monitor to "whine" at different frequencies, but the image looks the same the whole time.  It looks that way with no input, too.

Also: adjusting the pots on the neckboard doesn't change the output AT ALL (not brighter, not darker, nothing) and the brightness and contrast controls on the main board don't seem to affect the picture either.  The vertical hold pot seems to make a difference and the screen and convergence still affect the image, as well.

I only come back here because you have been so helpful in the past. I'm not sure what else to do short of reflowing all the solder joints on the entire board!

Thanks for your help.

[grantspain]

looks like the green drive transistor is full on

[SirPeale]

Actually, that last picture looks exactly what is wrong with my MTC-900. 

http://forum.arcadecontrols.com/index.php?topic=80194.0

I have not yet determined what's causing this.  I'm 99% certain it's in the brightness circuit.

[mailman-zero]

The picture is actually yellow, not green. Unfortunately, I think (after reading Peale's thread: http://forum.arcadecontrols.com/index.php?topic=80194.0) that my problem and his are similar.

I saw this FULL ON thing happening before sometimes when adjusting pots, but it would go away if I wasn't pushing on them. I still have no idea about the intermittent blue. I don't have access to original drive transistors, I used NTE171s and twisted the legs (I was lucky to note the difference before inserting them).

[grantspain]

be bloody funny if it turned those nte transistors are no way similar

[SirPeale]

You're lucky you saw the difference.  I didn't and toasted some resistors on my neckboard.