Repairing a VGA to Composite Converter with a Pico PSU

Repairing a 23 year old Extron VSC-200 VGA to analog scan converter. I’m going to use this rack-mounted scan converter in my homelab to pass VGA video into some RF modulators for internally-hosted TV channels.
Pico PSU: amzn.to/3LRyBPa
BNC Adapters: amzn.to/3p1k4XZ
JST Connectors: amzn.to/42ijqUh
Data sheets I referenced:
7905CT: pdf1.alldatasheet.com/datashe...
HC574: www.ti.com/lit/ds/symlink/sn7...
Astec: datasheet.octopart.com/LPT42-...
Rack stuff:
- StarTech 25U Rack: amzn.to/3mEB7hS
- Tripp Lite SMART1500LCD UPS: amzn.to/3KZW3Jw
- 1U 24 Port Patch Panel: amzn.to/3Nm0bFa
- 1U Brush Panel: amzn.to/3mExAA3
- 1U Rack Shelf: amzn.to/3oaDclT
Note: The above are Amazon affiliate links. It doesn't cost you extra, but I'll receive a commission which will help keep the content coming. I only link to things I've personally ordered.

[@tekvax01]

The LM7905 is a -5volt DC regulator. The LM7805 is a +5 volt DC regulator.

[@umm.gineering2519]

Man, I watch your videos religiously. You make me want to make impulsive and foolhardy eBay tech purchases that would make me very happy, and drive my partner mad. ❤️ I can’t speak for the exact firmware chip without a model, but from my experience of many, MANY other ICs, it will likely be that the pin needs to be set high to disable a certain feature. Given the nature of the chip, it’s probably something like a clear/reset function. [Meaning to say that it won’t be a matter of the IC requiring two different voltages.]

[@DiversityGames]

Nice video! I don't know if you realized, but at 13:22 you can see a sticker on the capacitor with the model number and the output rating, but this video was really informative in case you get one of those weird chinese PSU with no labels at all.

[@clabretro]

Good call out! I almost went down the route of what was on that capacitor alone but didn't want to risk frying the board, ha.

[@SamMcWhannel]

One of the reasons you might have a 5v regulator even though there's already 5v is that the regulator may provide a tighter voltage tolerance than the power supply. Many times power supply voltages can vary slightly depending on the load and this slight variation may not be acceptable for some of the digital ICs in the circuit.

[@clabretro]

Oh cool, that makes sense

[@WooShell]

You *really* shouldn't assume the heatsinks to be ground.. there's a reason why one of them has a lightning sticker on it: they can be *anything* depending on the construction of the power supply. I've seen them at any level from ground to 300V DC behind the input rectifiers. Nothing except the black output pins and/or any ground lug around the mounting screws should be expected to be at ground level.

[@clabretro]

good call out

[@aRndBelgianGuy]

Very, very interesting. Interested by these kinds of niche toys, and learned a lot with the process of debugging the board. Thanks !

[@butlergames]

If anyone here is looking to use this method to replace the PSU in a VSC 500, the voltages are different. It's -5v, 5v, 5v, GND, GND, -5v. You'll need to buy a LM7905 to convert the -12v to -5v.

[@ahmedboutayeb3285]

Thanks for the information.

[@taldmd]

VGA is already analog - a more accurate description of the device for the title would be "VGA to component/composite/RGB converter"

[@clabretro]

lol right you are, very good point. I probably should've just called it a scan converter like it does right on the front of the case, ha.

[@clabretro]

updated to "VGA to composite" since that's all I'll use it for. thanks for pointing that out!

[@tekvax01]

However, it’s worth mentioning that there are two very different versions of a component video signal; RGB and differential RGB. Differential component is actually R-Y, B-Y, and Y. The Y signal is the luminance channel. Some older colour systems would also include a G-Y component as well.

[@thecriss88]

Dude, that power adapter is probably one MOSFET or a diode away from being fully functional.

[@clabretro]

oh yeah I'll get that thing fixed eventually, it's super high quality.

[@mcleodautomation]

The mouth noises in this video make it unwatchable. Thank god your new videos dont have it! Big improvement... A lot of youtubers fail to realize that having your mic too close does not equal good sound quality. Cudos!!

[@clabretro]

Haha I know. The audio improvement has been a journey, hard to watch the old ones.