Destroyed my Arcade CRT.. again

[chrisg]

Hello,

I am looking for a meter, tool or possibly a usb device that hooks to a pc that can give me specific details on a video signal (ie frequency and resolution) before I ruin any more of my arcade crts. All classic arcade games (ie pacman, street fighter) output a video signal in different resolutions and the crt needs to match or it can do damage to the electronics.

CGA 15khz
EGA 25khz
VGA 31khz

I know there are some crts that are multimode but most crts hate when you send the wrong signal through them. I am unsure why, but I have blown out the electronics of several arcade crts in the past and I need a solution.

Thanks

[Cornucopia]

Don't know of any USB tool. The traditional pro tool for this would be a vectorscope/oscilloscope/waveform monitor.

Many of the very early vid specs used interlacing, and that is something that often wreaks havok on a monitor. Good monitors that could handle many scan frequencies, including interlacing, were often the better lines from ViewSonic and NEC.

Scott

[chrisg]

I have the following video output format:

Red
Green
Blue
Gnd
Horizontal Sync
Vertical Sync

What I am most interested in measuring is the Horizontal Sync Frequency. Is it as simple as hooking up an Oscilloscope between the Hsync and Gnd ?

[jagabo]

I have the following video output format:

Red
Green
Blue
Gnd
Horizontal Sync
Vertical Sync

What I am most interested in measuring is the Horizontal Sync Frequency.

Horizontal and vertical sync.

Is it as simple as hooking up an Oscilloscope between the Hsync and Gnd ?

Yes. You can probably get away with something as cheap as this:

https://www.amazon.com/DSO138-Oscilloscope-Digital-Handheld-Version/dp/B088FWHKZG/

There's even a $21 version if you can solder it together yourself.

https://www.amazon.com/ICQUANZX-Oscilloscope-Handheld-Pocket-Size-Electronic/dp/B07V67LYXF/

Rigol makes some good scopes. I use one of these:

https://www.amazon.com/Rigol-DS1054Z-Digital-Oscilloscopes-Bandwidth/dp/B012938E76/

But that's overkill if you only need to check VGA and lower sync frequencies.

[jagabo]

Note that some devices place the sync pulses on the green pin rather than the dedicated sync pins.

[chrisg]

Thanks for the help!

I think I will go with this one.

https://www.amazon.com/gp/product/B07QML4LJL/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Its inexpensive and looks like it may work for what i need.

[chrisg]

It worked!

Thank you.

[chrisg]

Verified 25Khz Vsync before hooking up to my arcade crt.



[Attachment 64139 - Click to enlarge]


[Attachment 64140 - Click to enlarge]


[Attachment 64141 - Click to enlarge]


Here is vga output measured at pins for gnd and vsync at 25khz on the oscilloscope.

In case anyone needs their MisterFpga to output to an EGA crt here is the setting to change in the settings.ini file.

video_mode=640,16,64,80,400,3,6,8,20000

[jagabo]

Glad it worked out. The pictures may help the next person. In case one has a scope which doesn't report the stats:

The scope is set to 10 microseconds (10uS) per major division. The pulses repeat every 4 divisions, so every 40 microseconds, or 0.000040 seconds. 1 / 0.000040 is 25,000, or 25 KHz.