PDA

View Full Version : JPAC - help me understand what it does for video signal?



dmworking247
14th September 2012, 05:07 PM
Hi guys,

Maybe its because its Friday and my brain hurts... but can someone please clarify what the JPAC does?

I know it allows me to plug into a cabinet wired for Jamma (ie JPAC plugs into the harness).
I know it functions like the ipac that it allows the controls to go through the keyboard encoder (so instead of a jamma PCB you're running a MAME PC for example)


... but what I'm not clear on is the video... does the JPAC actually act as a conversion from a regular VGA signal on a normal video card, in a PC running windows, to the CGA signal for the arcade monitor? Or do I still need an 'arcade vga' card aswell, or a VGA to CGA board?

gameroom
14th September 2012, 05:29 PM
The jpac will not convert the signal, but will block the wrong signal.

If you run soft15k, this will send 15khz from your video card to match the arcade monitor. Before soft15k kicks in (bios and windows startup screens) the video card will send the video signal using 31khz. the jpac can block the 31khz signal from getting to and harming your monitor. Once soft15k starts, the jpac with left the signal through.

casperthefriendly
14th September 2012, 07:17 PM
It also amplifies the voltage that the PC video card outputs from 1v to 4-5v - apparently 5v is a much better match for arcade monitors than 1v.

http://www.ultimarc.com/vidamp.html

Krondorf
14th September 2012, 07:39 PM
So basically if you are wanting to run Mame on a PC in your cab, you will definitely want a JPAC, and 2 servostiks :)

Mikie
14th September 2012, 08:46 PM
Jpac is for a jamma standard wired cab and adding a pc .

Pc will need arcade VGA too.

1 So you got pc with arcade VGA
2 USB port and VGA plug into Jpac ,
3 Jpac plugs into standard jamma bus ,

Now you get a nice pc setup driving a cab without rewiring or cutting any joystick wires , monitor wires or button wires . Can still get rid of PC and plug jamma board back in as it was originally

Note it will not switch seemlessly between all games

dmworking247
15th September 2012, 12:03 AM
Jpac is for a jamma standard wired cab and adding a pc .

Pc will need arcade VGA too.

1 So you got pc with arcade VGA
2 USB port and VGA plug into Jpac ,
3 Jpac plugs into standard jamma bus ,

Now you get a nice pc setup driving a cab without rewiring or cutting any joystick wires , monitor wires or button wires . Can still get rid of PC and plug jamma board back in as it was originally

Note it will not switch seemlessly between all games

I like the idea of leaving the lowboy that I'm fixing up at the moment as a proper jamma setup to run PCBs as required, but running a MAME setup for most of the time. I've heard of soft15khz before, but hadn't looked much into it.

Can you elaborate on why I should go arcadeVGA over soft15khz, and what you mean by not switching seemlessly? I assume its because of different games wanting to run at different resolutions, in which case what is the user friendly workaround?

Is a seperate VGA to CGA adapter the better option then (+ jpac for the controls into the harness)

Mikie
15th September 2012, 05:16 AM
Yeah I really like it too and like to leave the original pcb in to show what it was

The advantage of arcade VGA is it drives the monitor correctly from power on while soft15khz is a windows driver which supports specific video cards, so that is only going to display after windows loads the driver

Not seemless as a mame player expects with a computer monitor. The original jamma cab has a specific monitor and chassis and is tuned for the original pcb

So when you load different games it can require adjustment on the chassis . Sometimes this doesn't work and may need to instruct mame to run game at different size / freq this may not look / feel right for the specific game

Also not expect to use setup for other than arcade gaming from this low rez era . I used vnc to remote over wireless to make pc changes

Least frustrating setup it to select a series of games that require no monitor adjustment and that fully fill the screen and mame front end those ones per cab , then will get the most enjoyment out of this setup

Gives that true retro feel , quite an effort expense with conditions, could put some x in 1 box instead

Rat
15th September 2012, 06:44 AM
If you like being able to configure mame settings then be careful buying a Chinese xxxin1. I hate mine, it's slightly better after dropping in a new hdd, but I still would prefer a PC in my cab. Having trouble with my jpac on 3 sided cocktail though, I suspect it's not standard jamma. Hoping to get some hands on advice with that at my meet ;)

Sent from my MB526 using Tapatalk 2

Mikie
15th September 2012, 07:14 AM
Yeah I don't like the bootleg xin1s , some of the early ones are vbad

Let's say you want to run dk in a jamma cab with a pc , then Jpac and arcade VGA should give an excellent result. Then can add similar ones from the same era like Juno first and galaga and it will switch these with no problems

gameroom
15th September 2012, 07:30 AM
The advantage of arcade VGA is it drives the monitor correctly from power on while soft15khz is a windows driver which supports specific video cards, so that is only going to display after windows loads the driver

If money is no object then get the AVGA, but if you prefer to spend the money on beers for when you are playing, then soft15k works fine.

Soft15k supports many video cards. The only real disadvantage is you get a black screen for the first 20-30 seconds until the driver kicks in. But there is an advantage with this too though. Original arcade machines don't show the bios screens, or windows load screens. Some take a while for the tubes to warm up. You are emulating the slow warm up. :)

I am a distributor for the AVGA but I think it is over priced. I would rather not make a sale than selling something overpriced.

But the AVGA is a great video card fi you still wish to go this way.

Krondorf
15th September 2012, 11:59 AM
what I've done is got an ati video card, and using windows x64, with the CRT_EmuDriver here: http://mame.3feetunder.com/windows-ati-crt-emudriver/
using groovymame, and everything is running great!
everything looks very authentic.

So as Danny said, if money isn't an issue then get the ArcadeVGA, otherwise i recommend one of the ati cards supported by the emudriver, or if you have Nvidia already, then use Soft15khz.
Either way, you'll be needing a JPAC.
even without using groovymame, you can try MameUIFX, which also gives a very good result on the arcade monitor.
Mine works seamlessly in that everything just works... yes, you get a strange looking screen on startup, but once the drivers kick in, everything is awesome!

gameroom
15th September 2012, 03:35 PM
Careful with that strange looking screen at startup as it can damage your screen with the wrong frequency.

Jpac avoids this problem.

Does anyone know of any other circuits which will block the wrong signal?

Krondorf
15th September 2012, 08:23 PM
Careful with that strange looking screen at startup as it can damage your screen with the wrong frequency.

Jpac avoids this problem.

Does anyone know of any other circuits which will block the wrong signal?
yes, this is running through the Jpac.. i get 2 screens side by side, and the top half is a bit crooked... then once the drivers kick in, it switches to a res that the jpac allows through :)

dmworking247
17th September 2012, 09:07 AM
Thanks for all the info guys. I really like the idea of keeping my cabinet wired for Jamma now that I have a working CRT or two. However the issues with game/resolution switching is turning me off the idea because I don't want to make chassis adjustments for particular games.

I'm intending to run this setup in a lowboy with 3 buttons per player, so I'm ok to lose things like SF etc, but if it meant games like Wonderboy couldn't be played on the same cabinet as moon patrol... hmmm.

There are plenty of CGA>VGA converters around, is there an option of VGA>CGA or other alternatives that work around the limitations of using the arcade CRT? Although not as authentic, I guess I could put a PC Monitor in there and run a CGA to VGA converter between the Jamma harness and the monitor (for arcade PCB), and just hook up the PC directly to the monitor when in "MAME" mode?

Krondorf
17th September 2012, 12:13 PM
However the issues with game/resolution switching is turning me off the idea because I don't want to make chassis adjustments for particular games.

I'm intending to run this setup in a lowboy with 3 buttons per player, so I'm ok to lose things like SF etc, but if it meant games like Wonderboy couldn't be played on the same cabinet as moon patrol... hmmm.
Don't worry about that, you'll be fine with what you have. Especially if you get a compatible ati card!

B.M.O.C.
12th March 2015, 02:09 PM
I realise this is an old thread, but someone asked if there is a way to block 31khz signals without a jpac. I was wondering the same thing. I'm not really sure what signals my monitor is getting (using AVGA) before it gets to windows desktop, I would rather the screen was just blank until the front end loads for aesthetic purposes anyway, but also there are some bootup screens that flicker like crazy. Could this potentially be damaging? And is there a way to block them?

Mikie
12th March 2015, 08:36 PM
try to reduce the boot time, in bios set HDD as first boot device, fast boot, no memory test . no timeout. use a sdd , disable any device not required , disable show boot options

Rat
13th March 2015, 07:51 AM
I realise this is an old thread, but someone asked if there is a way to block 31khz signals without a jpac. I was wondering the same thing. I'm not really sure what signals my monitor is getting (using AVGA) before it gets to windows desktop, I would rather the screen was just blank until the front end loads for aesthetic purposes anyway, but also there are some bootup screens that flicker like crazy. Could this potentially be damaging? And is there a way to block them?

Yes there is a way to send only 15kHz you can use Calamity's Atom-15 video card bios hack if your card is compatible. I assume you are running mame as you mentioned a frontend, IMO you need to install Groovymame and CRT EMUdriver to get the correct resolutions, then look into Atom-15. Yes if your monitor is getting the wrong signal it could be damaging, I use a JPAC and Groovymame but have not flashed Atom-15 yet, I need to get my head round the recovery process first in case it goes wrong. So until I flash Atom-15 I keep my cab off until the PC has fully booted then turn it on, that protects from getting the wrong signal on boot up, yeah Iknow the JPAC protects from that, but not enough on boot up from what I have read.

Atom-15 here http://geedorah.com/eiusdemmodi/forum/viewtopic.php?id=64

Groovymame here http://forum.arcadecontrols.com/index.php?board=52.0

CRTemudriver http://geedorah.com/eiusdemmodi/forum/viewtopic.php?id=65

B.M.O.C.
13th March 2015, 11:54 AM
Interesting, thanks for the info. I am already running groovymame with an arcadevga so the in game resolutions are as correct. I'll also look more into options you've described.

Also will implement the suggestions of Mikie.

lordsnipe
14th March 2015, 09:08 AM
Atom15 is only during bios. Then crt emu driver takes over. There is still the gap between when the operating system is loading.

Arcadevga outputs 15k all the time I believe.

Rat
14th March 2015, 10:19 AM
That's interesting, I was under the impression there would not be a gap of potentially sending the wrong kHz, I think I will just stick to keeping my cab turned off while the PC boots up until windows is fully loaded. Sometimes I plug my PC into an old CRT PC monitor if I need to do work on it, I was wondering how this would go if I flashed the video card bios to 15kHz I would not be able to see it on my old monitor. Yeah too much risk, what I'm doing now works, so I'm not gunna stuff with it, crossed off list :)

B.M.O.C.
14th March 2015, 02:03 PM
Atom15 is only during bios. Then crt emu driver takes over. There is still the gap between when the operating system is loading.

Arcadevga outputs 15k all the time I believe.

Arcadevga has the capacity to output a variety of high resolutions and refresh rates, it's not limited to 15k, just depends on what you are sending out. Whether or not the boot sequence is problematic or not I'm not yet sure.

- - - Updated - - -


That's interesting, I was under the impression there would not be a gap of potentially sending the wrong kHz, I think I will just stick to keeping my cab turned off while the PC boots up until windows is fully loaded. Sometimes I plug my PC into an old CRT PC monitor if I need to do work on it, I was wondering how this would go if I flashed the video card bios to 15kHz I would not be able to see it on my old monitor. Yeah too much risk, what I'm doing now works, so I'm not gunna stuff with it, crossed off list :)

How are you having your screen come on after bootup? Are you using multiple power switches or do you have a tricky way of doing it? Currently I use a smart powerboard to power everything in my cab and have a single power button on the outside for the PC.

Rat
14th March 2015, 07:51 PM
I have my PC bios set to resume on power on so that it boots up when I turn on the power point. But my cabs I just use the main isolator switch on the back. Yeah not very pro and I do have to flick two switches, but it's safer. I figure I'm going to sit there pressing buttons for ages, so two switches to turn it on isn't really an issue :)