Hantrarex MTC9000 picture troubles

[remoteboy]

Hi,

I'm repairing an old arcade cab at the moment. It's a generic Electrocoin cab with a 25" Hantarex MTC9000. By the time I retrieved it it had been standing out in the rain for about 6 weeks (typical Irish summer!). I've been working on it with some friends for a couple of weeks and luckily most of it is in pretty good working order, with the exception of the monitor. Initially we thought the monitor was completely dead, but by tweaking the horizontal and vertical sync we managed to get a picture up on the screen. The picture was completely washed out, so we kept twisting things (contrast, screen voltage, red, green and blue, focus, etc. until we got the best picture we could - which was still rubbish. I recently installed a street fighter II board in the machine and while playing it noticed that after each round as the screen fades out and just before it gets to black, the picture looks absolutely perfect. This leads me to believe that the brightness is set way too high and is whiting out all the detail in the picture. Also, the screen voltage is turned up to full at the moment - if i lower it by more than a couple of percent, the screen disappears.

I found this diagram on a Swedish website which seems to indicate that item number 1 is the brightness preset, but I can't figure out how to adjust it. I've tried using one of the pots from the back attached to a long chopstick (there's a big scary monitor attached to the board that i'm anxious not to tip against) but i can't get any purchase. Is there a special tool i need to adjust this, or am i barking up the wrong tree entirely?

All help much appreciated.

R

[Ken Layton]

Hantarex are well known for many bad capacitors so I'd install a capkit first then see how it looks/works.

[grantspain]

the reason your picture was poor/dark is because the tube had sat in the damp,always you leave the machine 24 hours at room temp then switch on and wait about 8 hours for the tube to readjust,then if your picture is poor use the screen volts and focus on the flyback transformer(the big lump of black plastic with the red lead) and the contrast pot which is on the left hand side as you look at the monitor from the back(its 3 pots with a white adjuster,don't adjust the preset brightness pot-the mtc9000 were not as bad as polo with cap faults as they tended to be placed away from heat producing area's(the only execption being the width cap which as you can see on your chassis someone has replaced and mounted it with cable ties on the flyback shield

[remoteboy]

always you leave the machine 24 hours at room temp then switch on and wait about 8 hours for the tube to readjust

Grant,

I left the machine at room temperature for a couple of days before I turned it on, but as yet I haven't left it running for more than three or four hours at a time - although I've done this about 5 or 6 times. Do you think it still needs a full 8 hours to warm up?

Thanks.

R

[grantspain]

you did the correct thing,its warmed up enough now-i think you now just have an adjustment issue,there are the focus and screen volts(brightness) on the flyback,the contrast,and on the neck card you have drive pots for red green blue,also i think there are some background pots on that neck card aswell,you need to adjust this the correct way;
1-make sure your 5volts on the edge connector is 5.05 to 5.15
2-turn down contrast,foreground and background colours
3-adjust brightness so you can only just make out a picture and then focus
4-turn up your background colour a touch,then your foreground colour a little(on the neck card,you will need a watchmakers flat head type screwdriver)
5-turn up your contast to give depth
6-then its a case of tweeking the odd pot here and there to get a perfect picture
happy adjusting,a picture of your picture would help but try this first and remember that 5 volts is extremely important

[remoteboy]

1-make sure your 5volts on the edge connector is 5.05 to 5.15

Hi,

Sorry for the delay - been off on holidays, then had to go buy a multimeter, figure out how to use it etc. 

Anyhow, I've checked my voltage and I'm getting 4.94v on pins 3 & 4, -5.03v on pin 5 and 11.08v on pin 6. Given that these are outside the range mentioned by grantspain, I'm guessing this might be the problem. I hate to be a complete n00b here but does this mean I need a new power supply, or is this an easy fix?

Cheers

R

[grantspain]

the +5 volts is a little low,you should find a adjustment pot on the front of the power supply to bring that up to the correct amount(one thing to be aware of though,a power supply of that age is likely to have a dirty pot and when you adjust up it may sky the 5v so be careful)-one other thing depending on the power supply when you turn up the +5 its possible the +12v will decrease even further and if you have a coin controls electronic mech in your machine its possible it will cease to function(coin controls mechs like 11.5v to 14v to function perfect).
try this first and if you get no joy then post a pic of the screen,it may be just a set up fault