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Stable pic on Arcade Monitor


metallimax

Question

Hi Guys,

 

My first mame build is slowly coming together. Finally powered it up today and found that computer (running mame & soft 15k) is working fine as well as the jpac and buttons.

 

Only problem Im having is trying to adjust to get a stable picture on the 29' Monitor (pentranic surv crt). I can get it to clealy make out windows / mame game but it is always moving either Hor or Vertically. There is considerable flickering also.

 

I've spent quite a bit of time adjusting for a 'sweet spot' but cant get anything reasonable. Is it likely that:

 

a) monitor just doesnt handle 15k well

b) video card (Riva tnt2 ) & soft 15k arent putting out the correct signal?

 

At this stage im considering going to a pc monitor (sad considering amount of work to get the 29" to sit in so well).

 

Any advice appreciated!

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See if there's a vertical hold knob, most survelliance monitors I have seen have that. Is the picture 'rolling'? The problem might be that once you get it set right, at a resolution change the picture might start rolling again, you'd have to find some kinda compromise in the middle.
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ok res set to 640x480 (wow can hardly read anything even in mame now) but still no luck.

 

No dry joints from what I can see. all the adjusting doesnt seem to help it is always not usable :-(

 

Haven't got another graphics card to try (and dont want to buy an arcadevga in case it is monitor). dam annoying!!

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if the picture was moving- jumping then i would say a couple of caps had gone on the chassis- however we are not sure whether it is a chassis/ graphic card or mame fault at this stage. This is why i ask whether the monitor work ok before being transplanted. You might want to update your profile so we know where you are- Sydney?

I'm no mame expert, but you could prove the monitor/chassis by plugging in an jamma game if you could borrow one?

Edited by serviceit
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How have you wired the pc output into the monitor? Is the H sync and V-sync separate? Are there switches on the chassis to change sync inputs?

Have you got a sync combiner for comp sync or just connecting both to the same pin?

 

Try 320 x 200 res.

 

Found this is the best to start with on most monitors

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Prof is on the money here , Pentranic monitors don't have a separate V and H sync inputs only H composite .

Your video card will be sending out separate H and V sync so they need to be combined to make H Composite Negative Sync , Just joining the 2 wires together isn't going to work.

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Thanks for the help guys....

 

Mind if i get more info? (I'm totally new to this).

 

basically on the monitor it has a comp sync, ground, R,G,B dont see anything else in terms of connections. I've connected these to the JPAC (12,13,14,N,P) I assumed that the jpac would do everything else required for combining the signal?

 

If not, what should I look at doing?

 

Thanks again.

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When the SYNC OK LED is off, this indicates that no sync signal is being sent to the monitor because it is out of the correct range for the monitor. The effect this has on the monitor varies with different monitor types. Some monitors have an in-built line timebase which will free-run at its natural frequency, hence a jumbled picture will be displayed. This will NOT cause any damage as the monitor is not being driven outside its range. If a 15Khz monitor is being used and both the 15 and 31 jumpers are on, the J-PAC will generate it's own "dummy" 15Khz sync signal if it is not receiving any sync from the PC (for example if the PC is re-booted).
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Prof is on the money here , Pentranic monitors don't have a separate V and H sync inputs only H composite .

Your video card will be sending out separate H and V sync so they need to be combined to make H Composite Negative Sync , Just joining the 2 wires together isn't going to work.

Are you sure? I've heard so many times that it does.

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Are you sure? I've heard so many times that it does.

Never investigated myself because I don't play around with Mame , but I get messages all the time from people with this problem trying to run an arcade monitor directly from the video card .

From a Jpac is fine.

 

With pinball 2000 , pokies , original space invaders etc that have dual sync , none of these work by twisting H and V together , all need a sync combiner IC .

It's very basic , just a 7400 IC .

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ok so given this isn't a prob as using jpac... any other ideas?

 

driving me crazy!!

 

"I can get it to clealy make out windows / mame game but it is always moving either Hor or Vertically. There is considerable flickering also."

 

How can you clearly make out windows / mame game if the picture is always moving? :unsure

 

Matthew

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well with enough playing with the V and H hold i can get it slow enough so that im able to see desktop + desktop items. eg. can see folders on desktop but not really read name.

At no point is the pic 'stable' though it is always scolling and flickering just slow enough ot make out icons.

 

thanks

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well, from the video you are getting a 15khz signal with the sync way out.

 

Try the sync circuit first.

 

I have used the dos mame switches in arcadeos to get the freq right on some monitors before.

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ok after a few hours playing it seems the pic is a bit more stable at a much higher res. left everything at a installation default and was able to adjust so it is slightly better. Vertical hold never seems to stop (though do get it to slow down alot) and h seems to be stable for a few seconds before having to be re-adjusted.

 

Posted another vid - keep in mind that i paused 4 or 5 times to adjust the h-hold whilst recording this.

 

http://www.wikiupload.com/download_page.php?id=116870

 

Anyone seen this before and any other ideas?

 

I'll try the circuit once i have some time and see if it gives a diff result jpac.

 

thanks

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Hi

 

... finally had a bit of time to get back to this.

 

Ok tried circuit, still no luck with the same result.

 

One thing I did try was connecting a newer comp monitor whilst runng soft 15k to see what it would say:

 

Signal Freq Out of Range

FH 15.9kHz

FV 50.4Khz

 

Does this sound right freq for an arcade monitor??

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