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Author Topic: Amplitude/Resolution/Width  (Read 360 times)

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CHRIS-F

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Amplitude/Resolution/Width
« on: May 21, 2019, 06:53:32 pm »
Hi Guys,

I tried to get my monitor image centred today, (not that I know what I'm doing), afaik my monitor is a variant of a Hantarex MTC 9000, I've got a little noise in my image but aside from that I had a little mess with the h/v amplitude and the other pots on the adjustment board, I can shift the image from left to right and up down, the height amplitude is ok, but I can not shrink the image width amplitude enough to fit the whole image on screen, in the attached image the width pot is adjusted full to the smallest amplitude but where it says 1 UP top left corner it's just off screen, I can shift the image right, but then the right hand part of the image goes off screen, the games resolution is I think 240 x 224, so I think it should fit on the monitor ok, am I doing something wrong or does my monitor need some type of repair?

Thanks In Advance,
Chris.

lilshawn

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Re: Amplitude/Resolution/Width
« Reply #1 on: May 23, 2019, 03:56:03 pm »
is this an original game board... a replacement board.... or is this a computer hooked up to the monitor? I ask because some computers have an adjustment in the video settings to compensate for this width issue.

i haven't personally worked with this monitor model, but by a cursory glance at the schematics, there looks to be a couple tuning capacitors on the horizontal yoke inputs... (C36 C37) it might be worth checking into these as they can affect the width if they have been replaced or switched for other values..... (like what people sometimes do if they switch game boards and the width is too wide/narrow)

possibly an issue with the horizontal size pot. does it work at all (you can make it bigger and smaller)or is it stuck at that width (does not change width at all when turned)?

maybe an issue with the IC that controls the horizontal things. (IC2) really hard to say. could be a connection or resistor going off. maybe the small c29 C25 caps getting weird since they are tied to the H-frequency adjust before they go into the IC chip.

not a definitive answer, but something to look towards.

grantspain

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Re: Amplitude/Resolution/Width
« Reply #2 on: May 23, 2019, 04:23:07 pm »
check c42 4.7uf 50v

lilshawn

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Re: Amplitude/Resolution/Width
« Reply #3 on: May 23, 2019, 05:08:51 pm »
check c42 4.7uf 50v

 :laugh: this one too...i didn't scroll far enough down on the schematic... I was actually looking for one of these too  :banghead:

this non polar electrolytic cap is almost always toast on other chassis.

grantspain

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Re: Amplitude/Resolution/Width
« Reply #4 on: May 24, 2019, 07:40:19 am »
i use a polypropylene 4.7uf 63v to replace these and they never fail again

CHRIS-F

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Re: Amplitude/Resolution/Width
« Reply #5 on: May 27, 2019, 10:54:40 am »
is this an original game board... a replacement board.... or is this a computer hooked up to the monitor? I ask because some computers have an adjustment in the video settings to compensate for this width issue.

It's an Jaleco 'City Connection' arcade pcb, I bought it off ebay a few years back, it's most likely a bootleg board, I don't know much about pcb's but there's no Jaleco markings so I assume it a bootleg.

CHRIS-F

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Re: Amplitude/Resolution/Width
« Reply #6 on: May 27, 2019, 10:57:33 am »
possibly an issue with the horizontal size pot. does it work at all (you can make it bigger and smaller)or is it stuck at that width (does not change width at all when turned)?

Yeh the pot turns ok and the amplitude grows and shrinks, it just wont shrink enough :-(

CHRIS-F

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Re: Amplitude/Resolution/Width
« Reply #7 on: May 27, 2019, 11:05:23 am »
Thanks for the answers so far guys, much appreciated, couple of questions though.

Do I need to discharge the monitor to remove any of the mentioned caps especially around the yoke are?

The voltages in these things scare the S*#T out of me, I am only a novice with electronics, I can solder quite good and have a component tester, not sure how to test the pot properly though.

One thing I know about this monitor for sure is, when I bought it, it was in a generic jamma cabinet and it had some kind of frame collapse, there was no gameboard present just the monitor, it's a distant memory now but I think it just had a horizontal line across the screen, I took it to an old tv repair shop along with the isolation transformer and he repaired it for me, could this be related in any way?

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Re: Amplitude/Resolution/Width
« Reply #8 on: May 27, 2019, 02:34:43 pm »
I doubt it. if the image was a line, there would have been an issue with the vertical drive IC system or the HOT and it wouldn't work at all.

a timing capacitor has just gone out of whack... which is why it still basically works.