PC Engine Duo RGB video noise related to power adapter used

[kamiboy]

I have two PC Engine Duos. Both fully recapped and RGB modded.

Both are missing their original PSU so I am using generic 9V@1500mA or 10V@1000mA adapters with them.

The RGB video has a lot of noise in the signal in the forms of lines and dots of static scrolling across the screen slowly.

At first I thought the problem was with my RGB amp, so I removed it and routed the HU6260 RGB signals to a SCART with a known working amp inside it. The video signal interference did not go away, so that counts out the amp as the culprit.

I tried to connect the PC Engine using just the composite out, which produced an artifact free picture. So the noise is in the RGB signal coming from the HU6260 chip.

Next I tried to power the Duo's using an original power adapter which removed the noise and made the picture crystal clear.

At first I thought the generic 9V adapter was not providing enough voltage which resulted in the noise, since the original adapter is rated for 10V. So I tried the generic 10V adapter and no dice, the picture was still noisy.

If anyone knows the root cause and a solution to this I would appreciate their comment. I need to make these two units work in RGB with the generic adapters as using an original adapter is not an option, I only have the one you see and it is spoken for.

It might be worth mentioning that my display is a SONY PVM CRT and that other than the noise in RGB the units seem to function perfectly with the generic power adapters.

The adapters in question:

9V

10V

[Hobie-wan]

Might just be shitty components or workmanship in those adapters. Try different ones.

[kamiboy]

What in the power adapter could cause these symptoms? It cannot be insufficient voltage since I have a 9V and 10V version. Any way to fix them or the problem without having to buy other adapters?

I don't want to spend more money and wait weeks for eventual replacements only to be disappointed.

Finding a suitable, cheap and easy to obtain power adapter for the PC Engine Duo is not as easy as it sounds. If anyone know where I can get some for under $10 shipped do let me know.

[ApolloBoy]

Those cheap PSUs are usually of poor construction and don't have proper shielding to prevent interference such as the kind you're experiencing. It also doesn't help that they're switching PSUs, and switching regulators will put out a fair amount of interference if they don't have extra components to deal with that interference.

[Hobie-wan]

If anyone know where I can get some for under $10 shipped do let me know.

This requirement is incompatible with getting a quality brick.

[Teh Lurv]

I had the same exact video issue when I tried using one of those generic NES/SNES/Genesis AC adapters with a Model 1 Genesis I bought. The video interference is caused by poor shielding/filtering by the adapter. Check out this video for additional info: http://www.youtube.com/watch?v=7nTRIxloDcI

At the time I didn't feel like hunting around for a used original model 1 AC adapter, so I picked up an appropriate Enercell AC adapter from Radio Shack. It wasn't cheap at $30, but it resolved the video interference. In addition, it is about half the size of a Sega AC Adapter and doesn't have a phantom power draw.

[kamiboy]

Any cheap way to filter the voltage using some easy to obtain part?

[ApolloBoy]

You could try snapping on a ferrite choke towards the plug, that should cut down on the interference.

[kamiboy]

Lucky for me there is a big box of misc electronics and cables being thrown out here at work. Fished out some VGA cables with ferrite cores on them. Unfortunately they are not of the snap on kind, but I figure I can still salvage them for a test.

I actually found a 12v 1000mA AC adapter in that box that might be usable. But I am afraid 12V might be too much for the Duo to handle.

[kamiboy]

I had the same exact video issue when I tried using one of those generic NES/SNES/Genesis AC adapters with a Model 1 Genesis I bought. The video interference is caused by poor shielding/filtering by the adapter. Check out this video for additional info: http://www.youtube.com/watch?v=7nTRIxloDcI

That video was interesting, especially the bit about parts missing on the power supply to save cost.

I wish I had a working knowledge of electronics so I could figure this out on my own, alas. I know there are parts known as voltage regulators, could something like that be fitted into the Duo or AC Adapter somewhere help reduce or remove the noise?

It do find it a bit strange that only the RGB lines from that chip have noise in them when composite video appears perfectly normal.