Jamma/MVS - monitor adjustment query

[L00b]

Hi guys,

Two quick Q's if I may, hopefully a simple matter:

(i) Is it normal to have to re-adjust the CRT (vert/horiz/etc.) when swapping a Jamma board for an MVS mobo + cart?

(ii) Can there be 'incompatibilities' (of hardware) in a standard Jamma cab? As in 50 Hz vs 60 Hz or stuff like that?

Very broad (and n00bie) Q's I know, but I've received an FZ1 1-slot MVS mobo and, having taken out a Jamma game PCB (fine pix/no problems) from the cab, plugged the MVS mobo in (via Jamma loom, also fine/no probs), I can't seem to be able to get a good picture using the screen adjustment pots - best I get is a stable (horiz/vert) pic, but still with random "horizontal distorts" in places (having used the entire range of adjust pots).

Any ideas (before I have to take pix/vids of the pblm)?

[The Enigmatic Form]

Yes, it´s very common that you have to adjust the screen when you change the hardware.
It´s not a problem of the monitor, it´s just that there is no definitely set standard in screen size, contrast etc. like with consoles or so.

[grantspain]

also important to note that the snk boards prefer a composite sync as opposed to negative horizontal-therefore to achieve this you should link the vertical and horizontal syncs together at the video input plug of the monitor
another important thing to note is that earlier well gardner 7000 series would run snk on standard negative horizontal sync but needed a tweek of the 50/60khz adjustment

[L00b]

Much thanks for your replies and input

therefore to achieve this you should link the vertical and horizontal syncs together at the video input plug of the monitor

Only problem is, I can't make heads or tails of what this involves (spot the software guy, not to be trusted with even a screwdriver! )

Tell you what, I'll post pix of the setup and screen shortly, then you can educate me (if I've still not found out, after searching in here and with Google first, of course).

another important thing to note is that earlier well gardner 7000 series would run snk on standard negative horizontal sync but needed a tweek of the 50/60khz adjustment

I don't think it's a Well Gardner 7000 series, although I've noticed a difference (for the better, but still not right) when flicking a switch by the side of the CRT, from ''Nega" to "Posi''. after checking, the CRT is a Samsung K (E65775-K LR29831 ?)

Right - this is the pinout (std Jamma loom, as best I know/can tell):


These are the monitor pots I haven't tried yet (red, green and blue - there are 6 white ones mounted vertically, visible either side of the spaghetti junction in the first pix below, all of which I've tried):

(Above, the 'nega' to 'posi' switch is the black switch on the left, 'south' the green pot)


And this is the problem, best I manage to get:

[grantspain]

hmm,sounds like a kortek ktm chassis

[L00b]

Updated my query with pix of symptoms.

[grantspain]

you have 2 sync switches on that chassis,if all combinations do not help then if you look to the video input plug you will see a yellow and white wire on pins 5 and 6-all you need to do is link these together

[L00b]

Much thanks for your patience and input

I shall give that a try this week, but can I first put some further gloss on my uber-n00biness, and ask: how do you "put the wires together"?

Do you mean crimp'em together at the J-loom end? or at the CRT input end? (which I suppose is the greenish-coloured molex-looking plug underneath the two sync switches)? And, in either case, in which pin: 5 or 6?

[grantspain]

yes super noob i think,
yes the green molex plug thingy with the 6 wires is the video input,if you look you will see that 5 and 6 are the sync lines-all you need to do is bridge these 2 wires,you can do it at either end on the video loom or shove a wire link across 5 and 6 on the video plug,you can cut both wires half way down the loom and join them with connector block or insulated crimps
whatever you want really
try the switch combinations first though

[L00b]

yes super noob i think,

I have no shame. Didn't you know ?

Thanks for your patience and trouble grantspain, you're a star

[grantspain]

btw those kortek were always a **** with odd ball sync inputs-i never got world rally to work on one back many millions of years ago,but there again i was a noob at that point as well

the patience bit comes from training techs,especially 18 year old snot gobblers

[L00b]

Sorted through the sync switches - left down on 'Posi' (-tive), right up on (can't see writing). Didn't realise I had to switch the cab off, then power it back up between each "combinations attempt"

Thanks all, for your contributions