Can a computer monitor be used to display arcade boards?

[AwesomeAlbert]

I bought an arcade with no monitor. I can hear the game is on and playing.  Is there a way i can connect it to an old computer monitor to test that it works? A tv?

[SavannahLion]

From what I gather, the short answer is no, not directly.

The long answer is a bit more convoluted I think. To sum up what I worked out.

A regular PC monitor can't be driven any lower than ~30kHz

Your average PCB arcade board expects the monitor to operate down at ~15kHz.

Some monitors can accept and display a 15kHz signal, but these are difficult to find and most I've found are long out of production. Those that can accept 15kHz are too expensive and it might be better to just buy a dedicated arcade monitor at that cost.

A T.V. can display 15kHz but most U.S. T.V.'s have no direct method to display the RGBs signal coming out of the arcade board. If you live in Europe and have a SCART T.V., then you're in luck, SCART is directly compatible with the output and all you really need is the appropriate adapter and the correct pins connected and you're good to go.

Outside Europe, you're basically ---fouled up beyond all recognition---. The cost of a converter for a PC monitor outweights the cost of buying a true arcade monitor anyways.

I didn't look into adapters for U.S. T.V.s since I expect the quality to suck.

If I'm wrong on any of this, please correct it.

I did find a really nice page, that keeps cropping up in my searches that goes into a lot of detail about what I explain above, but now I can't find it. Go figure.

[shardian]

I am not an expert in any matter on this, but I will tell you I've seen test rigs that use a tv, or a small lcd a few different times. How they worked, I have no clue. Just wanted to pass along that tidbit.

[Crax]

You can get an rgb to NTSC converter, but they are expensive.  Alternatively, you can build your own as well.  Check this link out:

http://www.engadget.com/2006/11/28/how-to-consolize-an-arcade-game/

You can buy one here, but I think they are like $65+
http://www.jrok.com/hardware/RGB.html

[Ken Layton]

Here is a link to a list of specific makes & models that can be used:

http://www.ionpool.net/arcade/tech/monitor_test_bench.pdf

Keep in mind these are old monitors long since discontinued by their manufacturers.

[BobA]

Or you can get an adapter from JROK and connect your arcade board to a regular TV.Link to JROK

Sorry CRAX missed your link

[SavannahLion]

Does or has anybody here use the JROK adapter? Or the AD725 mentioned in a different link?

[StephenH]

This looks like it would do the job:

http://www.converters.tv/products/cga_to_vga/77.html

[Crax]

I'm thinking about building my own like in that link above.  Won't be for a week or two though at the earliest.  Would be interested to hear from anyone else that has done it already.

[MonMotha]

Does or has anybody here use the JROK adapter? Or the AD725 mentioned in a different link?

I've used the AD724, which is the same thing but with a (nearly impossible to tune up) built-in oscillator.  With an external oscillator (required by the AD725) it works rather well.  Video quality is comparable for YPbPr component.

Be aware that tuning it up properly requires a frequency counter accurate to the nearest Hz (at 3.6MHz), but you can eyeball it using just a TV if you wish and get acceptable performance.

Also be aware that you really cannot point-to-point wire these things and expect it to work, at least not well.  For one, the devices are only available in surface mount packages to start with.  The bigger issue though is that you're dealing with signals having edges with components in the 100s of MHz range.  At those frequencies, everything's a transmission line, so you have to be a bit careful with PCB layout.  Controlled impedance is not required (though it doesn't hurt), but you can't expect things to work perfectly just because they are electrically connected.

Also, the AD72x does not perform any scan-rate conversion.  You absolutely have to feed it video with timings compatible with your chosen TV standard (the chips support both NTSC and PAL at various subcarrier frequencies).

If there's interest, I have an AD725 design pretty much ready to go.  I can probably sell them to the BYOAC community for a bit cheaper than the J-Rok device (if those are even still available).  It has some additional features (high-impedance input option for paralleling with your cabinet monitor, HD-15 RGB input, onboard voltage regulator), as well.  I'm not sure what the J-Rok device is based on, but I wouldn't be surprised if it's also the AD725.

One of my back burner projects is actually a video scaler (anything to anything provided the frame/field rate is kept constant, interlace/deinterlace can be changed).  I'm guessing it'll end up rather expensive though.  It's being designed for a rather weird application and as such has to do some things that most people probably don't need (like handle medium res).

[Crax]

I have an AD725 design pretty much ready to go.  I can probably sell them to the BYOAC community for a bit cheaper than the J-Rok device (if those are even still available). 

I'm interested if the price is right.

[BobA]

Sounds like an interesting unit.  Nice to have some choice.  It has been very hard to see what JROK uses on his board as it is mounted on the underside and you never get to see it in the pics.  He now has 2 boards the newer one has component output as well.

[SavannahLion]

I'm thinking about building my own like in that link above.  Won't be for a week or two though at the earliest.  Would be interested to hear from anyone else that has done it already.

I'm researching for the components for something pretty darn similar.

The problem is that I simply don't have the resources to obtain some of the more obscure IC's needed in some of the schematics I've tracked down. Based on what needs to be done and what designs I could scrounge up, I think I've found comparable or better replacements. But even the replacements are not readily available for someone with limited resources and I'm not even sure if they're correct replacements. 

[BobA]

All you need is the ad725 and a fixed osc plus a few dollars worth of parts.   If you go to the AD site they used to send you samples of the chips for free.  I scored 2 of each of the popular conv chips a while back and it did not cost anything.

[MonMotha]

The scaler I'm working on will have just about every input/output you could imagine (I'm contemplating DVI/HDMI!).  Of course, that's in the future...

If there's a desire for component, I can do that as well.  I've got the chips laying around waiting for a design.

I'll go ahead and have the prototypes of the RGB->Svid board made. I've got my old one based on the AD724, but it has some issues related to my mentioning that the on-board oscillator is impossible to tune up, so it has an external one on a "daughterboard".  If you're interested in pricing, PM me and I'll see if I can get some sort of idea from the current bill of materials.

When I designed this for a friend, we actually looked at the J-Rok board.  I decided to go ahead and design my own for a few reasons:
1. We weren't sure the j-rok was still available
2. We wanted configurable input impedance options with an input buffer/amp, which the j-rok does not offer
3. The connectors were a bit non-friendly to our application as the cabinet it was designed for (DDR) actually has an HD15 output on the back of it
4. We wanted the option to run it off batteries, which is difficult with the j-rok
5. I desired support for both composite (either polarity) and separate sync
6. I find this stuff fun

I'm not sure if any of that stuff matters to you guys, but I'll go ahead and have the board put on my next prototypes panel so I can work any kinks out.

Analog Devices does give samples of most of their parts (that's how I got the AD724s), but that's just the bare chip.  You'd still need to fabricate a PCB to carry it and you'll also need some support parts (something to build the oscillator, a local voltage regulator is a good idea, and of course all the passives).

EDIT/Additional Note:  Just as a word of warning (not trying to discourage you from doing your own design here, in fact I encourage it), those "crystal in a metal can" type oscillators (not bare crystals, the ones with logic level outputs that self-oscillate) are not stable enough or trimmed accurately enough for color subcarrier usage, despite being available at those frequencies (14.31818MHz for NTSC).  You have to build one yourself using a crystal and use a variable capacitor to tune it.  Some TVs will not tolerate deviation of more than 10Hz!

[AwesomeAlbert]

wow, a simple no would have done. Ok so i can use a tv, will this work?
i think its a good price considering that site that was posted.

http://cgi.ebay.com/Arcade-RGB-CGA-to-TV-and-Video-Composite-converter_W0QQitemZ170097074666QQcategoryZ13718QQrdZ1QQcmdZViewItem

i think an ebay store has it for buy it now 30.

[Harry Potter]

Short answer, yes, that one will work with a TV.

Will it look good? Shouldn't look too bad as long as you use the s-video output.