PVM Image Waving Issue Exclusively with Supergun

[SMFK]

Hello!

I have been having image issues when connecting my MiniGun supergun to my Sony PVM. I get an odd wavy image exclusively when using my supergun, all other RGB consoles appear perfectly on this Television. I'm not running it thru a Scart Switcher, but directly into the BNC breakout from the 8 pin min-din to scart cable that shipped with my supergun.

I have some potential thoughts on where the issue is originating, but before making a purchase, I figured I should get some input!

Setup Components:
Sony PVM-1943MD (19in)
Scart Female to BNC Breakout Cable (RetroGamingCables.uk)
Minigun Supergun (Assembled and Shipped from Australia)
8pin Mini-Din Scart Cable (Shipped with Minigun)
Meanwell QP-200-3A Power Supply
CPS1 - A Board 89626A-4 - Fully Recapped / B Board 90629B-3 / C Board 90632C-1
NEO-MVS MV1FS - Fully Recapped

Potential Problems:
1. Poorly Shielded Scart Cable - I had a similar issue with a cheap SNES Scart Cable creating a wavy image that was remedied with a higher quality scart cable.
2. 75 Ohm BNC Terminators to all "Out" lines - I have read these may be important but since I have never had an issue except with arcade boards I wrote it off.
3. Board Proximity to PVM - Rogue RF bombarding the board or the scart cable from the PVM?
4. Minigun Supergun wiring or setup issue - I suppose anything is possible.
5. PVM in need of Recap - Possible, but does not show any issues with any other device.

Images:

 

[hatmoose]

Oooh PVM's and Miniguns - my favorite stuff (I probably have 10 of each!)

Things I have learned that may come in handy
1) Superguns normally have their own mains earth. Most consoles do not. Mains earth at both ends of your video chain often causes a ground loop, ground loop interference can cause all kinds of video artefacts.
To eliminate ground loop interference from your enquiries you could temporarily disconnect mains earth at the meanwell power supply end. A mains isolation transformer (not a common ground stepdown transformer) is a more permanent fix.

2) PVM's didnt auto-terminate until the XX5X models.
I cant see how having unterminated video would cause that kind of video glitch, but you can buy very cheap terminators that work OK for only a few dollars, might be worth checking

3) that cable looks fine to me, especially for a run that short
If you absolutely must buy a new one these are top quality and in stock https://www.retrogamingcables.co.uk...-CDi-Colecovision-Intellivision-Panasonic-3DO

 

[SMFK]

Thank you so much for your response!

I will definitely pick up the terminators because they are cheap insurance!

To eliminate ground loop interference from your enquiries you could temporarily disconnect mains earth at the meanwell power supply end. A mains isolation transformer (not a common ground stepdown transformer) is a more permanent fix.

2) PVM's didnt auto-terminate until the XX5X models.

As for the Mains Isolation Transformer, could you give me a better idea of what this is and how it can be integrated?

Thank you again for all of your help!

 

[SMFK]

Quick update!

I did remove the ground plug from the Meanwell and all of the distortions stopped. Thank you so much for helping me with this!

I feel a little concerned not having the power supply grounded, but it is going into a Furman power conditioner so hypothetically it should be good for now?

 

[Nimmers]

Looks like a ground loop. PVMs ground their video ground on the BNC connectors to frame (mains) ground. See if it goes away when you connect G (COM) and FG (Mains Ground) together on your power supply.

 

[hatmoose]

As for the Mains Isolation Transformer, could you give me a better idea of what this is and how it can be integrated?

Mains isolation transformers are really useful things - basically they decouple DC energy while still allowing AC energy to pass.

You can do fun tricks with Isolation transformers like work on live chassis CRT's without dying*.

In this particular instance we have ground loop interference so we need an isolation transformer that decouples Live, Neutral AND earth.

Sounds simple, not simple
for whatever reason many transformer manufacturers are extremly reluctant to provide an accurate description of what their transformer actually isolates. Sometimes they call them "transformer", sometimes they call them "isolator", sometimes they sell a thing that does neither...

So you dont want a step-down/step-up tranformer
and you dont want an isolation transformer that doesn't isolate earth

Something like this does not isolate from ground - but it does accurately state that that it doesnt isolate ground.
https://www.amazon.com/300-Watts-AC-Isolation-Transformer/dp/B006NG977W/ref=sr_1_21?keywords=isolation+transformer&qid=1647935281&sprefix=isolation+,aps,314&sr=8-21

Something like this would be a better bet
https://www.amazon.com/Tripp-Lite-Isolation-Transformer-Outlet/dp/B00006HPFH/ref=sr_1_3?adgrpid=82205148915&gclid=Cj0KCQjw5-WRBhCKARIsAAId9FlotjwDwAJhe-JQ4o9nvHe2Bip3vBQJ86E59FOs_Cio6LY3qBtpqnAaAjQqEALw_wcB&hvadid=585475090499&hvdev=c&hvlocphy=1011036&hvnetw=g&hvqmt=b&hvrand=3343795080003248813&hvtargid=kwd-14348981&hydadcr=992_1014988925&keywords=isolation+transformer&qid=1647936562&sr=8-3&th=1

But dont buy either of those, you should be able to pick up a perfectly serviceable isolation transformer for about $5 at any electrical junk shop. $200 is just silly...

 

[Nimmers]

You'd still need to somehow get around your PVM having its video ground tied to frame ground though right?

 

[hatmoose]

You'd still need to somehow get around your PVM having its video ground tied to frame ground though right?

Possibly yes - it's been 30 years and I wasnt really paying attention back then because I was young and I knew everything. Now I'm old and I know nothing.

If anyone has some good basic electronics reference guides on why this works I would really value that info.

 

[Mukuro_W]

PVM 1444qm , 1442qm, 1440qm and 2040 series all same issues,
Fe board (psu board) replace c613 4.7uf 250v ASAP
A board (main board) replace
C551 1000uf 16v
C518 470uf 16v
C632 22uf 250v (high ripple)
Check D504 and D505 for cold solder joints, those diodes are near the flyback, on thr bigger 2040 series the flyback is mounted in a separate doutherboard, check all diodes.
Very important: resolder IC 505 on A board, this IC is always ovearheating.