Amstrad 6128 and 1804S-P - Possible Sync Issue?

[mbliss11]

Hey everyone! I have been trying to standardize my retro computing cabling and hook things up to my NTSC Commodore 1084S-P. When I hook up my cpc6128 to analog rgb I get weird jitters.

See video:

IMG_3037.MOV

drive.google.com

I scoped out the sync signal from 40007 pin 11 and it looks like there is some noise on the top of the signal. See picture attached. Could this be an indication of a failing gate array or is this normal? Maybe my 1084s is just more sensitive to the sync? I have 2 PVM’s that it works great with.

Any ideas? Any insight or knowledge would be greatly appreciated!

 

[konc]

The 6128 does no internal regulation, voltages need to be regulated at the power supply and it's very sensitive to "bad" power. Since you are not powering it from the original monitor, how are you powering it? The same way like when you used the other 2 PVMs that it's working fine with? I'm not saying that power is the issue, but to rule it out before considering more complex troubleshooting. An easy way to do so is to quickly make an adapter for the 5V (you don't need 12V as they are only used for the floppy), use a good PC PSU and turn it on just to see if anything changes.

 

[mbliss11]

I had purchased a external 5v 2amp center positive power supply online for it. I hooked it up to my bench power supply and sure enough the signal is so much better not nearly as jittery. It does jitter a bit when accessing the gotek drive but nothing like it used to be. I had used the same power supply on the PVM’s and it didn’t experience the jitter but perhaps it has more forgiving tolerances. Don’t know but that seems to be the culprit I’ll put it under the scope again connected to the bench and see if the sync signal is anymore cleaned up.

Thank you so much!!! Now I need to invest in a better power supply for it….