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More Sf2 dramas


brentos82
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Hi guys a few months ago I posted some pics of my Sf2 champion board with vertical glitch bars. I managed to fix it by swapping out the S92-5M rom and it fixed it. Last night I was attempting to use another working SF2 board and all went well for about 2 minutes until I attempted to turn the volume up and then everything went glitchy. Is it bad to adjust volume while the game is on ? Here are some pics. I'm going insane with these games 😭😭😭😭

any ideas ?

Could it be an external issue to do with storage or the wiring/power supply/screen setup? It just seems weird because

I had another cabinet with a different crt and I used these boards for a long time with no problems and the minute I pull them out of storage and put them in this new machine they get issues.

Any help appreciated

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Yep, start with the 5V measurement at the board, don't measure it at the PSU as you won't see what the board gets after any voltage drop in the wiring and connectors.

 

12V won't matter on this board, it only feeds the audio amplifier.

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Hey guys yeh I'm going to buy a digital multi meter today as Ive been struggling along with a non digital one. Just to double check ?

To test at power supply : Black at ground , Red at 5v both on power supply while turned on.

To test at PCB edge connecter: plug game in and turn on. Black at pin 2 components side , Red at pin 3 components side ? Is there enough of the pins sticking out to do this or is jamma thing in the way?

To test at chips on the board: I'm lost here. Is it the 1st and last pins on the mask ROMs ? The first being to the left of the notch when looking from above?

Cheers lads.

 

 

 

 

 

 

 

 

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Hey bud. Just measure it from the JAMMA edge on the CPS-1 stack to start with. The power section is the smaller section of pins separated before the notch at pin 7 on the JAMMA connector.

 

Pins 1&2: Ground

3&4: 5v

5: -5v

6: 12v

 

You don’t need much room to measure it. Just touch the little gold finger with each probe making sure not to bridge the pins.

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Hey guys I'm just about to test with multi meter. Just before I proceed I've uploaded pics of the jamma harness. Does this look correct ? A few questions.. pins 1 and 2 have the 1 wire bridged across the 2 pins. Is there meant to be a seperate wire for each pin? Same for 3 and 4 with the 5v.

Pin 14 is empty (should be video ground according to diagram)

Pin 28 has two black ground wires and one on the component side. Pin 27 is empty.

I Must add last time this was used (before I bought it) it was running a Pandora and LCD screen. Is this something that I've overlooked?

Cheers 😊

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Hi, the main thing to double check would be to make sure the video ground to the monitor is connected to ground on the PCB so if it is not connected to pin 14 then it should be connected to pin 1, 2 or 28. If it is then it should be OK.

 

Pins 1 and 2 on both sides should all be connected to ground to share the current between all the contacts. It can be done with a single heavy gauge wire bridged to all 4 contacts or 4 lighter gauge wires, one for each or as per your photo, as long as they're all ground. Similarly +5V should connect to all four contacts, pins 3 and 4.

 

Pin 28 is also ground on the JAMMA PCB and control panel grounds are often connected to these pins, possibly also your video ground.

 

Pin 27 is defined as ground in JAMMA but some newer boards put controls (e.g. button 6) on these pins as an alternative to using a separate kick harness. Although it is probably ground on your PCB many harnesses leave it empty to avoid compatibility issues. That is why connections on pin 28 are often doubled up. so that looks OK too.

 

Regards John

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Hi John . Thanks for that. Yes the ground from the power supply seems to be a very thick wire then it goes into a little box an comes out with thinner wire. I do also have a slight screen wobble going on. Any point in taking the video ground and moving it to pin 14? Would that have any effect? It looks like video ground is currently one of the ones on pin 28. Hoping to eliminate wiring issues before I proceed .
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H again, it should be OK to move the video ground wire to pin 14, component side but suspect that pin on your PCB edge connector will just be directly connected to the main ground anyway and is unlikely to make any difference. Regards, John
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This fault has nothing to do with grounding issues or where the video ground connects. All grounds are common on the vast majority of arcade boards, including these ones, by moving the video ground you are still connected to the same part of the circuit, just moving it slightly to the left.

 

It is possible, but highly unlikely to be related to a voltage level either, but that’s always the first thing to check, as borderline low voltage can cause odd effects.

 

I’d bet this is actually a RAM failure or damage to one of the mask ROMs. A failure to the A custom is always a concern on these too.

 

There’s no reason why adjusting the volume should cause damage, unless you were holding a static charge and gave the board a tickle when you reached in.

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Hey legends.

tested voltage at PSU and it's 5.01

Drops down to 4.63 at the edge connector

Should I turn it up?

Got zapped when I used the ground terminal nearest to the top of the PSU. Used the other one and it was fine. Is that normal?

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Ok I have some updates. Board one has been problem solved. Mask ROM 5 and 11 are screwy. I've replaced them with the 5 and 11 from game 2 and we have a working A , B and C combo. I've now taken that working B and C combo and tried it with board A ( the one that glitched after volume change ). It still has the graphics glitch and now no sound effects/announcer /hadouken etc only background music . So I'm thinking I messed something up by touching the volume ?
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Jack your 5v so it’s reading 5v on the JAMMA edge.

 

Touching the volume won’t break the board.

 

It’s good you’ve narrowed down the fault to the A board. As you’ve probably read these are prone to just randomly failing. Womble is right that it’s probably either the RAM or A Custom at this point.

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You may not have a board fault after all.

 

Your voltage is far too low at the board, if that is a valid measurement I am surprised the board works at all. TLL logic based systems expect 5 volts, if the voltage is too low then crazy things will start to happen (like you are seeing), usually anything below 4.75v means it will barely boot at all.

 

You also have major voltage drop in your wiring, if the PSU is putting out 5V and the board is only getting 4.6 then the issue is almost certainly that your power wiring is too thin between the PSU and the JAMMA connector. Can you post a photo of the JAMMA connector.

Edited by Womble
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Listen to Womble. Dudes a certified OG in board repair and having him chime in is worth it’s weight in gold.

 

Custom isn’t “fixable� but with the right skills you can transfer one from a junk board if you have one (the custom is also on a CPS-2 motherboard). RAM is replaceable, but would be good to diagnose it as the fault before shotgunning it and replacing them. Then again, they’re not expensive parts.

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