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Author Topic: 15kHz passthrough CRT protection dongle - sale thread  (Read 764 times)

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buttersoft

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15kHz passthrough CRT protection dongle - sale thread
« on: June 06, 2023, 09:40:14 pm »
I have built a small batch of 15kHz CRT monitor protection passthrough dongles for sale. These are based on @Gambamanís excellent Ultimate VGA-to-SCART design.http://forum.arcadecontrols.com/index.php/topic,160869 They plug into a VGA socket, and pass 15kHz RGBHV as RGBS (C-sync on pin 13). Any video modes with a higher scan rate get blocked.

One dongle is US$50 shipped anywhere outside Australia. Or AU$50 shipped inside Aus.



Can anyone interested please PM me saying you've read and understood this entire post :)

This dongle has three primary uses:
1.   To give CRT arcade monitors some protection.
2.   To generate clean composite sync in certain situations.
3.   As a testing tool to prove a VGA port is/isnít outputting 15kHz.

1.  Most old CRT arcade monitors work at 15kHz and their sync circuitry needs protection from video modes with higher scan rates. (Remembering that arcade monitors were designed to sync to two or three closely-related video modes in their lifetime, not to switch six times whenever you boot up Windows at low res.) Consumer CRTís from the 90ís onwards donít strictly need protecting. Same with PVMís. That said, nothing lasts forever, and the dongle will help you treat their aging electronics a bit more gently.

2.  When a 15kHz video mode is detected, the green LED is lit. The dongle then outputs RGBS via a female DB15HD (VGA) plug, pushing composite sync on pin 13. Most cheap VGA-to-SCART cables will be fine if they also pass 5V from pin 9 (if needed) as will any VGA-to-BNC cable, but you should determine how your setup will work before purchasing.

No c-sync signal is perfect, and operation cannot be guaranteed with any other devices that modify or recreate sync (strippers, positional adjust, signal converters, or any other device without 5V over VGA pin 9) nor with any monitors that have sync issues or interlaced flicker issues. All the PVMís, arcade monitors, and consumer CRTs I own work fine, except the PVM-2730 (which flickers in general, and anyway still works fine at 240p.)

When a video mode with a scan rate above 17kHz or below 15kHz is detected (say, when Windows defaults to 480p sometimes) sync is blocked and the red LED comes on. R, G & B are still passed, so you may see something harmless on screen.

This dongle does nothing to framerate, so if the signal going in was at 50Hz, it will remain at 50Hz (unless blocked). It passes 5V on pin 9, but does not pass EDID, and pin 5 is floating.

3.  The dongle makes an excellent diagnostic tool. With or without a cable you can prove your PC is or isnít outputting video correctly. This would be really handy for anyone jumping into GroovyMAME for the first time. Or anyone with a 15kHz PC connected to windows updates like mine. That said, general support for crt_emudriver should be politely requested in the GM forum, as i don't know everything :)


EDIT: reply #7 contains testing info about compatibility with other devices - http://forum.arcadecontrols.com/index.php/topic,167729.msg1766145.html#msg1766145
« Last Edit: July 20, 2023, 06:37:03 pm by buttersoft »

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Re: 15kHz passthrough protection dongle - sale thread
« Reply #1 on: June 07, 2023, 01:53:13 am »
Looks like a very useful product.   :cheers:

Hope this is ok to post here!
I moved the thread to "Retail Vendors" since it is offering "a small batch" of an item for sale.
- Selling 3 or more of an item with the possibility of acquiring/making more for resale ==>"Retail Vendors" sub-forum.
- Selling items that you won't be acquiring/making more of for resale ==> "Buy/Sell/Trade" sub-forum.

I also put a redirect topic in the "Monitors" sub-forum with a link to this thread so people can easily find it in either sub-forum.

GLWTS.   ;D


Scott

Zebidee

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Re: 15kHz passthrough protection dongle - sale thread
« Reply #2 on: June 07, 2023, 10:36:41 am »
Glad you're offering these for sale. Very handy little dongles.

Thanks also for making the LEDs different sizes. Otherwise, people with red-green colour blindness would weep.
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buttersoft

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Re: 15kHz passthrough protection dongle - sale thread
« Reply #3 on: June 07, 2023, 06:48:58 pm »
Thanks, Scott. I wasn't sure where to post :)

And Zeb, i hadn't thought of the colourblind issue! (I accidentally bought shorter red LED's, i didn't mean to :/) It's not easy modifying the dongles when already built, but I could make new ones with red, green, yellow, blue or white LED's on request.
« Last Edit: June 07, 2023, 07:00:30 pm by buttersoft »

Zebidee

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Re: 15kHz passthrough protection dongle - sale thread
« Reply #4 on: June 07, 2023, 11:30:43 pm »
Is OK, no need to retrofit for me, I'm kinda used to it :D

Yes I am "red-green colourblind", despite designing and building colour space transcoders. It's all maths anyway. FWIW the "blind" part is a misnomer - I still see the colours just fine, is just the way retina cone frequency sensitivities are tweaked.

Some colour shades that are different to most people may look similar to me. OTOH often I see colours or differences where other don't. I see the world slightly differently, but then we all do to some extent.

We have a big green tree with bright red flowers that my wife describes as "outstanding", yet I hardly notice them until I look closely. Stuff like resistor colour-coding is also a nightmare (small as well), I usually have fun guessing then just grab the DMM (like most normal people probably!).

I love your dongle but distinguishing LED colours is hard. Certain things, like old-school red/green/orange LEDs, especially diffused ones, are horrible to distinguish. Guess it doesn't really matter, it is either one or two LEDs on. Colour is irrelevant.

The newer LEDs like the "bright" or "superbright" "clear" ones seem much better (guess it depends on exactly what you get). Many colours to choose from. They can be very bright if run at ~20mA - you can reduce the brightness to suit your needs by using a larger resistor to limit current. 

BTW your dongle works great with GreenAntz! Am testing it as I write. You must use the dongle directly at the video card VGA head though. It won't work attached via a VGA male-male cable, the sync doesn't pass through. Red LED lights up but not the other one (whatever colour it is). Not sure why as all 15 pins are present and accounted for.

I may pull it apart and have another look later :D
« Last Edit: June 07, 2023, 11:32:44 pm by Zebidee »
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buttersoft

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Re: 15kHz passthrough protection dongle - sale thread
« Reply #5 on: June 08, 2023, 02:04:55 am »
Only one LED at a time should be lit! Either the green one (15Khz ok) or the red one (sync blocked).

The dongle only works one way, so the male VGA side is the input. Or did you mean you were using a normal male-male VGA cable, and then a female-female adapter, then into the male VGA of the dongle?
« Last Edit: June 08, 2023, 08:10:44 am by buttersoft »

Zebidee

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Re: 15kHz passthrough protection dongle - sale thread
« Reply #6 on: June 08, 2023, 08:51:49 am »
Only one LED at a time should be lit! Either the green one (15Khz ok) or the red one (sync blocked).


I looked a bit closer - because the LEDs point downwards on my PCs, and the cards are near the bottom already, it is actually hard to get a good look without craning my neck about. So I turned the PC upside-down!

Turns out you are right, of course - but it LOOKS like the red LED is lit at the same time as the other one (yellow?) if you view it from the side. The light from the yellow LED shines through the dome of the red LED, making it look like it is lit.

I've attached pics to demonstrate. I changed nothing between the pics except my viewing angle. The red LED seems lit and seems to get redder as you move around to see the yellow light shining directly through it

I wrapped the dongle in some paper tape because the 3D printed housing was starting to come apart a bit too easily.

Quote
It only works one way, so the male VGA side of the dongle is the input. Or did you mean you were using a normal male-male VGA cable, and then a female-female adapter, then into the male VGA of the dongle?


Oh gosh you are right - I was using a VGA male-male cable and turning the dongle around without even realising it. I think I need to write IN / OUT on it  :laugh2:

One reason why I wanted to use a cable was to see the LEDs better.

Will see if I can find my VGA gender-benders and give that a go :D
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buttersoft

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Re: 15kHz passthrough protection dongle - sale thread
« Reply #7 on: June 11, 2023, 10:12:13 pm »
I'll dedicate this post to the dongle's compatibility with other devices.

Extron 190F
Downstream there's no 5V, though you could probably break it out and try.
Upstream - the specs of the 190F say it takes RGBS input. I think this must mean with c-sync at 5V? Lowering the 1k resistor on the c-sync output to ~950k everything works. HOWEVER, the extron must have DDSP sync processing ON. With sync processing off, i think the Extron is trying to grab sync from the colour lines (it also takes RGsB/RsGsBs input). Which means that at 31kHz, while the c-sync line itself is effectively set to ground (with some MHz hum) the Extron is outputting an unclean 31kHz-ish signal that is half noise, which i wouldn't count as protecting your monitor properly.
I can modify a dongle if you are interested, probably with an 820R resistor. But you MUST remember to set DDSP on (dipswitch off). Most monitors should not be affected by this change, saving that sync processing causes a tiny in itself, but it's not going to fix pre-existing issues.

Other Extron devices
Untested. See above on the 190F, though there are no guarantees your device will work the same.

 
« Last Edit: June 12, 2023, 08:11:29 am by buttersoft »