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Author Topic: 2 Questions 1)Jamma harness CGA cable and 2) PVM RGB monitor size  (Read 446 times)

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ZTylerDurden717

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2 Questions 1)Jamma harness CGA cable and 2) PVM RGB monitor size
« on: September 23, 2018, 05:56:43 pm »
Hi all,

I wanted to use an S-video 15khz CRT to save money since it's close enough to the quality of true RGB to the uninformed arcade go-ers.

If I was buying an original PCB and connected it to this JAMMA harness:

https://www.ebay.com/itm/Jamma-Extender-Harness-for-JAMMA-boards-FULLY-LOADED-ALL-56-PINS/381869729342?epid=531197962&hash=item58e935a63e:g:gfoAAOSwyQtVwqky

What's the cheapest converter for CGA to S-video?  Any cheaper paths I can try if I'm using an original PCB to display video besides VGA LCD?

Separately, PVM monitors seem to look longer in the back than an arcade CRT from photos online.  If I wanted to strip the shell for cabinet placement, will they end up being similar dimensions if they're the same screen size as a CRT TV/Arcade Monitor?  Thank you!
« Last Edit: September 23, 2018, 08:42:34 pm by ZTylerDurden717 »

buttersoft

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Re: 2 Questions 1)Jamma harness CGA cable and 2) PVM RGB monitor size
« Reply #1 on: September 26, 2018, 08:30:44 pm »
I'm not sure why you need the jamma harness, but it would be a convenient way to make a breakout. You don't want the cheapest RGB-to-Svideo converter, you want a j-rok. The J-rok's convert the signal format but don't touch the resolution or refresh.

A PVM isn't much larger, mb one or two cm longer neck on the tube, depending. Different Arcade cabs are different, so it might or might not fit. Most of the time you can find the dimensions of pro monitors online (including the casing, obv.) so get that depth and take about 2cm off and you have a very safe estimate.

Using a PVM might not be ideal. A PVM or BVM has a trinitron tube, and they were never used for Arcade games so the tube itself won't look quite right, and you'd have to make a custom bezel to sit against the tube, etc. Very, Very nice picture though, so you might find it works well. The other thing to note is that while an arcade monitor is usually just a tube (w/neckboard) + chassis, and designed to mount in a cab with all the bits in different spots, a pro monitor will have at least 3 or 4 different major PCB's, and a PVM might have more than that. These boards are all cabled together, and while they can sometimes be spread like wings so you can work on the set while it's running, they're not going to separate far enough for you to mount them neatly. You'll either need to use the PVM in it's case and build a bezel or paint the existing one carefully (and perhaps make some sort of clever flip-up hatch to get to the controls) or you'll be cutting and soldering all the cables to lengthen them. The problems with this might be the HV cable to the flyback, which will just arc all over the place without a serious amount of insulation, and that changing the length of all the other cables might introduce ringing issues of all sorts.

It's been my experience that the higher-end you go, the more PCB's you get and the more complex the cabling. And that goes double for Sony. Something like a low-end panasonic TV monitor might work quite well, but it depends what you can find.

Love to hear how you get on, it's something i've thought about doing myself!
« Last Edit: September 27, 2018, 07:21:17 pm by buttersoft »

Zebidee

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Re: 2 Questions 1)Jamma harness CGA cable and 2) PVM RGB monitor size
« Reply #2 on: September 30, 2018, 03:35:11 pm »
I wanted to use an S-video 15khz CRT to save money since it's close enough to the quality of true RGB to the uninformed arcade go-ers... ...
What's the cheapest converter for CGA to S-video?  Any cheaper paths I can try if I'm using an original PCB to display video besides VGA LCD?

True enough, s-video probably seems OK for the uninformed. But I suspect that once you get to know what true RGB is like, you'll always regret not using it in your cab.

As Buttersoft says, you don't want just any cheap/nasty s-video adapter. Mostly they just rescale the image to 480i, which is fine for video but horrible for most retrogaming. Jrok seems good, but it'll probably cost you more than you paid for your TV so it won't be cheap.

If you want good + cheap, consider RGB modding if you can solder and know the difference between a resistor and a capacitor.

Quote
If I was buying an original PCB and connected it to this JAMMA harness:

You probably don't want a JAMMA extender like what you linked - for a new cab, you want a JAMMA harness like this:
https://www.ebay.com/itm/Jamma-Plus-Board-Full-Cabinet-Wiring-Harness-Loom-for-Jamma-Multicade-PCB-boards/322746899241?epid=1008071263&hash=item4b2536db29:g:bGUAAOSwdl9Zku3R

That one comes with connections labeled and with female crimp connectors already in place, ready to connect to your joysticks/buttons/monitor etc

Quote
Separately, PVM monitors seem to look longer in the back than an arcade CRT from photos online.  If I wanted to strip the shell for cabinet placement, will they end up being similar dimensions if they're the same screen size as a CRT TV/Arcade Monitor?  Thank you!

I have done this with Sony PVM2730s. It wasn't easy but no re-soldering was required. After de-casing the PVM, You want/need to keep the box-like "cage" behind the CRT that supports the PCBs. This might be tricky especially if it is supported/attached to the CRT corner pegs/mounting points (and you want to use those pegs to support the monitor in your cab). There was no going back once started - I had to strip (note that the word "strip" has "rip" in it) a lot of unnecessary "stuff" off the out-sides & front to fit it into the cab. You may need to re-position front control panels.

Actually lifting that Sony PVM beast into the cab to mount it was not easy either - they weigh a lot more than normal monitors/TVs (~45kg vs ~20-25kg for standard TV of same size). Trinitron screens are heavy by nature (thicker glass, and the aperture grill inside is much heavier than a standard shadow mask), and all the extra electronics & metal "cage" to support them weigh a lot too. Luckily I'm big and was regularly working out when I mounted mine in, yet it was still quite hard. I dread having to take it out again to service it as I am now 10 years older and not as buff as I used to be.

However, I am very, very happy with the Sony PVM for a horizontal cab (would not look good in vertical because of the trinitron screen shape).

Finally, you can't assume any dimensions from the sizes advertised online - For example, the Sony PVM2730QM I mentioned before supposedly has a 27 inch screen, yet it has the same dimensions (measured peg-to-peg) as a "29 inch" Nanao monitor. Depth (ie front-to-back) also varies widely from CRT to CRT. Look online for specs, or ask the seller to measure it for you (do you trust their skills with a measuring tape?).


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buttersoft

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Re: 2 Questions 1)Jamma harness CGA cable and 2) PVM RGB monitor size
« Reply #3 on: September 30, 2018, 08:29:41 pm »
I have done this with Sony PVM2730s. It wasn't easy but no re-soldering was required. After de-casing the PVM, You want/need to keep the box-like "cage" behind the CRT that supports the PCBs. This might be tricky especially if it is supported/attached to the CRT corner pegs/mounting points (and you want to use those pegs to support the monitor in your cab). There was no going back once started - I had to strip (note that the word "strip" has "rip" in it) a lot of unnecessary "stuff" off the out-sides & front to fit it into the cab. You may need to re-position front control panels.

Finally, you can't assume any dimensions from the sizes advertised online - For example, the Sony PVM2730QM I mentioned before supposedly has a 27 inch screen, yet it has the same dimensions (measured peg-to-peg) as a "29 inch" Nanao monitor. Depth (ie front-to-back) also varies widely from CRT to CRT. Look online for specs, or ask the seller to measure it for you (do you trust their skills with a measuring tape?).

Good points. For some reason when he said PVM i went straight to the 19"/20" models, even though i have a few PVM-2730's myself. Those and the others with the open cube black frame on the back are the only ones with an internal support cage though, that mounting idea is not going to work with the more common 20" models in metal cases. And the 2730 tubes are also much shorter for their size than the 20" ones. Being Trinitrons I wouldn't take anything for granted about their mounting size though, for sure, you'd really want to measure things first.

I should ask, Zebidee, have you ever had a problem with a PVM-2730 where the colours smear or bleed to the right, particularly red? And it gets worse as you turn the brightness up? - https://www.aussiearcade.com/showthread.php/81404-The-PVM-2730QM-thread-(H-STAT-issue-colour-bleed-convergence-and-more!)?p=1202708#post1202708
« Last Edit: October 02, 2018, 08:14:54 am by buttersoft »

Zebidee

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Re: 2 Questions 1)Jamma harness CGA cable and 2) PVM RGB monitor size
« Reply #4 on: October 01, 2018, 01:05:35 am »
I should ask, Zebidee, have you ever had a problem with a PVM-2730 where the colours smear or bleed to the right, particularly red? And it gets worse as you turn the brightness up? - https://www.aussiearcade.com/showthread.php/81404-The-PVM-2730QM-thread-(H-STAT-issue-colour-bleed-convergence-and-more!)?p=1202708#post1202708

Buttersoft, I've yet to finish reading through that 11-page thread on AA in detail, but I can tell you now that I've definitely had that problem (and only partly solved it). Apologies for a long-ish post, I try to include all relevant details without warbling on too much.

I noticed this problem with my Sony PVM sometime last year, and it seemed to happen quickly/suddenly. I'm not sure what caused it, maybe old age (the Sony, not me!) or maybe when my wife got 4 guys to move/manhandle the cab while I was in the shower one day (despite my warnings for her to never move it without me). When I found out, I asked her "Four guys! Why? I can move it by myself. You know my cab has wheels on the back, because I've told you about 10 times, yes?". To which she responded "Oh! It has wheels! How convenient, if only we knew...". Cab survived an oceanic voyage between hemispheres but is undone from being manhandled a few metres. Hurrrrrr......, anyway, the cab I'm talking about, which has the Sony PVM2730QM in it, is the second last on my sig line below.

Whatever the cause, I found the same problem you have: that the red was bleeding a lot at brightness levels that are  "normal" for everything else. Turning brightness down reduces/eliminates the red bleed, but then the image is too dim.

Using some monitor test images, I discovered was that "vertical" convergence was way out ("vertical" convergence = vertical B|G|R| lines coming together => ||| => |). In particular, red lines were shifted to the right, especially towards the right side of the screen, although there were some other issues there as well (sorry no pic). You need to get a good test image/grid pattern on screen to see how much. I used the Nokia test (Ntest) software (but that is 32 bit, doesn't work on x64 CPUs, so find/use something else for 64 bit OS).

I tried adjusting the "dynamic" convergence (the panel of pots at the back/left) and this helped, but was insufficient. They are only for fine-tuning. The best I could get, with various pots at max/min values, was just barely OK. Note that the "geometric" pots on the left side do nothing to help with convergence, they just control things like screen shape/pincushioning.

Adjusting the "H-stat" pot (which is actually for vertical convergence, despite the name), just a little bit, solved the worst of my vertical convergence problems. H-stat is located on a black box halfway between the neckboard and the anode cap. Further re-tweaking of the "dynamic" convergence pots improved things even more.

With vertical convergence fixed/improved, picture was much clearer, red was bleeding less but still bleeding too easily. This might be because the blue gun wears out faster than the red! Apparently this always happens over time in these Sony's, according to some Sony repair guru I talked to last decade. Using the Nokia test software, it as obvious to see that the blue was coming out weakest and the red strongest (sorry no pic available).

After adjusting gain & brightness, all that is left to adjust is the blue/red cutoffs (there is no green cutoff, as that is the baseline). Unfortunately those pots are on the inside of the neckboard, which is almost impossible to access in my cab! I managed to twist my wrist somehow to adjust the blue cutoff and this improved things somewhat, but I can't get any more blue brightness that way. I can't seem to get to the red cutoff pot because of the way my cab is, there isn't much room in there.

STATUS: This is where I am now with the Sony. I can now adjust brightness so that there is no red bleeding, and most things look good, except for faint blues which just come out black (I don't mean "light blue" or "sky blue", as these actually have a lot of "white"). For example, the first stage of Time Pilot (with WWI biplanes) has a faint blue background and it now looks black on my Sony.

I can make Time Pilot etc look good/blue again by adjusting the gamma levels (ie using the slider controls in MAME), but obviously this is an imperfect work-around.

NOTE: I did these adjustments over about a week, as I don't like spending too much time fiddling at the back of my Sony. I've had some minor dizziness when spending too long there, which reminds me that I could be exposing myself to X-ray emissions! I've already had all the children I need, but don't want to push my luck.

If I can manage somehow to access the red cutoff then I should be able to choke the red levels back, closer to the blue levels, and thus eliminate the red bleed. Then I should be able to raise the gain/brightness a bit so that I can see faint blues better. To access the red cutoff I may need to temporarily remove a vent and fan from my cab. I've postponed that as I recently had hand surgery and, in any case, am in a different city than my cab atm - hopefully I'll get to it in a couple of weeks.

EPILOGUE: It seems that I had/have two issues going on, blue gun getting weaker and convergence. Because of the convergence issues I found, I half expect to find that one of the magnetic strips used to fine-tune CRT convergence has fallen off while the cab has been moved. I'm pretty sure of roughly where is must've fallen from too. I may try placing a mag strip there later to see if I can improve the convergence.
« Last Edit: October 01, 2018, 01:08:21 am by Zebidee »
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buttersoft

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Re: 2 Questions 1)Jamma harness CGA cable and 2) PVM RGB monitor size
« Reply #5 on: October 01, 2018, 02:35:30 am »
Cool man, i'll let you know if i manage to find a fix. And you need a thinner screwdriver - all the pots on the neckboard and those on the primary D board can be accessed through the hole beneath each with a nice electronics screwdriver. The only things you have to get to from the inside are the G and B gain pots on the B board.

Zebidee

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Re: 2 Questions 1)Jamma harness CGA cable and 2) PVM RGB monitor size
« Reply #6 on: October 01, 2018, 03:10:02 am »
Cool man, i'll let you know if i manage to find a fix. And you need a thinner screwdriver - all the pots on the neckboard and those on the primary D board can be accessed through the hole beneath each with a nice electronics screwdriver. The only things you have to get to from the inside are the G and B gain pots on the B board.

Oh really, I can get to the pots from the back? lol, I'm looking forward to checking this out on the weekend when I'm back with my cab.

I haven't touched the B board, colour balance chroma/luma etc as such seems good. Hopefully I just need to adjust the red cutoff and then brightness to bring back the faint blues.
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ZTylerDurden717

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Re: 2 Questions 1)Jamma harness CGA cable and 2) PVM RGB monitor size
« Reply #7 on: October 01, 2018, 10:51:22 am »
Thanks guys!  Really helpful.

  
 

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