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andynumbers

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Has anyone else noticed this with their Irem boards? I have a Bomberman, Bomberman World and Major Title 2 boards. When I run them on my Egret II the picture is super dim compared to other JAMMA boards. I have to turn the contrast adjustment all the way to max on the monitor adjustment board to get adequate brightness.

Is there something about Irem hardware where they just didn't amplify the video as much as other boards? Is there anything that can be modded on the boards to produce a stronger video signal?
 
Yep, Irem boards are just darker than others, although replacing the caps sometimes brightens them up a bit. If your Irem boards have brown caps, definitely replace them ASAP because they are known for leaking and causing damage. If they have green caps, those are higher-quality and are less likely to have issues.
 
Is there something about Irem hardware where they just didn't amplify the video as much as other boards? Is there anything that can be modded on the boards to produce a stronger video signal?
If something like that would be incorporated in a Jamma passthrough adapter for it, sign me up!
 
If the resistors in the DAC are reduced to lower values but kept in proportion it should alleviate the problem. However making a little QSB solution that solders on to the PCB should be pretty easy too.
 
Attached are closeups of my Major Title 2 and Bomberman PCBs.

They appear to have 4x 470 ohm resistors, R1 through R4. Are these the resistors that go to R,G,B and sync? Maybe try lowering these values down to 220 ohm? What do you think?
 

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IIRC those are just one component of the DAC. I changed those out, and found that only one bit in the signal changed, which isn't suitable.

A cheapo hack could be to duplicate the DAC resistors in parallel with the current ones, to halve all of them :P
 
So the resistor arrays probably needed to be changed. Not sure how easy it would be to find a suitable replacement SIP. Maybe just do it the quick and dirty way where you stick a bunch of resistors up and tie them together.

Probably not a great solution for collectors that have several Irem boards. I'm starting to think that a JAMMA passthrough with a small RGB amp may be a better solution after all.
 
Finding a SIP package for resistors shouldn't be too hard, they are very common items. But seriously, you can buy the exact same one, wire it invisibly in parallel on the underside, and the video level should double, without having to remove the original.

As someone who makes and uses JAMMA passthroughs, they stink if they aren't necessary, and JAMMA centipede isn't a great thing to have happen!
 
Isn't that some kind of R-2R network? Somewhere I read a repair log where someone replaced it with a small custom PCB.
You do get them off-the-shelf, but I just looked and you don't get a particularly large range of values.
 
If you use a OSSC just up your RGB pre-amp settings evenly, that will brighten things up.

The real problem is when you have a board with too high RGB values...
OSSC can't reduce the input, so you need some type of manual/adjustable physical resistance inside the supergun/adapter itself.
 
Attached are closeups of my Major Title 2 and Bomberman PCBs.

They appear to have 4x 470 ohm resistors, R1 through R4. Are these the resistors that go to R,G,B and sync? Maybe try lowering these values down to 220 ohm? What do you think?
CN2 On bomberman world is an alternative monitor out for a '2nd (vs setup) monitor'

Thanks for the pic, it's very useful to me. some of the boards out there are missing the parts for the full 4 player setup :)
 
Isn't that some kind of R-2R network? Somewhere I read a repair log where someone replaced it with a small custom PCB.
You do get them off-the-shelf, but I just looked and you don't get a particularly large range of values.
Caius has made a repro for R-type PCBs. It appears to be a 470ohm resistor network. Don't have the exact schematics but maybe he could make these repros with lower resistor values... if that is a tested viable solution of course.
If you use a OSSC just up your RGB pre-amp settings evenly, that will brighten things up.

The real problem is when you have a board with too high RGB values...
OSSC can't reduce the input, so you need some type of manual/adjustable physical resistance inside the supergun/adapter itself.
I'm running these boards in Egret II cabinets, so the OSSC is not a viable solution to my problem. I could run these games on my HAS supergun just fine, but I really prefer playing on the arcade cab.
Attached are closeups of my Major Title 2 and Bomberman PCBs.

They appear to have 4x 470 ohm resistors, R1 through R4. Are these the resistors that go to R,G,B and sync? Maybe try lowering these values down to 220 ohm? What do you think?
CN2 On bomberman world is an alternative monitor out for a '2nd (vs setup) monitor'
Thanks for the pic, it's very useful to me. some of the boards out there are missing the parts for the full 4 player setup :)
Interesting. Did not know that. The Atomic Punk II US manual makes no mention of this. Good to know so that I don't have to split the already dim signal between two monitors. I have the official Capcom JAMMA splitter cable modified for other 4P connectors, so I use this on occasion.
 
I'm running these boards in Egret II cabinets
So turn up the brightness on the CRT, if you max out the brightness and its still not bright enough carefully turn up the B gain on the flyback.

Not bright enough is never anything more than a inconvenience (aka it can always be adjusted upwards).
Too bright is the real problem, because you can't ever really turn it down without resorting to physical resistance.
 
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If the user adjustable "picture" contrast control is maxed out on my Nanao MS9, and the picture is still dim when every other single JAMMA board I have would be blindingly bright at max contrast the problem is with the board, not the monitor. Adjusting B+, flyback should not have to be done for a single board.

I'd personally rather have a board that's too bright IMO. You can attenuate signals with resistors easily.
 
Adjusting B+, flyback should not have to be done for a single board.
Your right you shouldn't have to do it for a single board... IF you do then you've never actually "centered" the value.
The B should be adjusted to a point where brightness adjustment should be all you need to dial in PCBs.

As I said CENTERED to the range you want to use!
You are obviously riding the low end (not center) because as you stated, maxing out the brightness still isn't enough (and it should be).
 
B+ and flyback shouldn't be touched for this sort of situation, anyway. This is not a problem of offset/brightness/pedestal/bias level, this is a problem of contrast/amplitude/gain.



Please do not casually touch B+ to adjust brightness, ever. That should be done once, with a multimeter, at the correct value.

The flyback's Screen control can be treated as a coarse adjustment for bias, but if an image is dim with low contrast touching this control will never help, unless you like a shitty washed out image with a poor black level.
 
@Hatsune Mike OK you are the pro here... Don't touch the B I guess. *shrug*

See this is why I don't own CRTs (its just packed full of a bunch of shit I can't adjust properly).
angtft.jpg
 
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