Noise in Video with Third Party Power Supply

[Nibbler]

Hi Folks.

Today i noticed that i have "noise" in my Video ( A600 RGB SCART ) and i think
it comes from the NON ORGINAL POWERSUPPLY.

I had the Same issue with the Amiga CD32 and the Power Supply from Vesalia.de. The Picture was perfect with the Original CD32 Power Supply.

SO what are youre experience with non original power supplys ?
I use the Mean Well RT-50B and i think its causes the video noise problems in my A600.

[Amiga1992]

USually this is a grounding issue. Have you tried plugging the power supply in another outlet?

[Pat the Cat]

Yeah, can be grounding issue.

Can also be a shielding issue, where an unshielded PSU is picking up cross talk (so even original PSUs can do this if in close proximity to "noisy" equipment).

Shield on those looks VERY naff. More like lace than a solid piece of earthed metal!

https://www.meanwell-web.com/en/prod...product/RT-50B

You might want to try enclosing it with silver foil, as an experiment, to see if that actually improves the picture. Obviously you don't want to permanently use a foil shield, but it might help isolate the problem if you try it.

Obviously, you have to be VERY VERY careful with power supplies. It is very easy to short out and get a shock from them, if you don't know what you are doing, do not attempt modification.

People have died from trying. Typically they had heart conditions, sometimes with pacemakers fitted, but still, if you are trying to "replace" a shield, it makes a lot more sense to just put the whole thing into a new metal case.

[Amiga1992]

The tin foil hat brigade has arrived.

[xArtx]

Tin foil would effectively shield a power supply, and safe if it’s plastic.
The foil should be connected to ground.
That only deals with RF/ capacitively coupled noise, not conducted.

[Kelv]

Could be the PSU, But Meanwell are up there with TracoPower and XP power for the industrial PSU's.
Data sheet suggests its got good regulation and 120mv ripple noise shouldn't cause too many issues, could try putting some extra smoothing caps across the outputs to see if that is the issue.

I've seen some really nasty 'clone' designs one called 'Mega Watt' that looked to be trying to pass its self off as a MeanWell : ) these tend to skimp on decoupling / bypass "gubbin's" ( technical term ) to keep costs down.

A repair shop would be able to check the outputs for noise if you dot have the equipment.

Post a piccy might give us a better idea of other possible causes.

As for that type of PSU you might be better spending a bit more and getting something from Tracopower or XP power, in some cases a bit == lots , but as in all things you get what you pay for.

[grond]

If the PSU is anything like my MeanWell PSU, it has a small pot for setting the output voltage. More than a noise problem I suspect that your 5V voltage is too low.

[Nibbler]

Originally Posted by grond

If the PSU is anything like my MeanWell PSU, it has a small pot for setting the output voltage. More than a noise problem I suspect that your 5V voltage is too low.

I used the Multimeter and it showed 5V. What Modell of the Meanwell do you use ?

Anyway, i try the hints above ( besides opening the Meanwell n stuff )

I will report later and show also some pictures.
Your´e the best guys

[grond]

Originally Posted by Nibbler

I used the Multimeter and it showed 5V. What Modell of the Meanwell do you use ?

I think I have the 80W variant because at the time I purchased it the 50W version wasn't available anymore. Multimeters are usually not very precise. At the very least be sure that the battery is fresh.

[Nibbler]

Hi Guys.
Sorry it took so long but i have made INTENSE tests and the result i VERY ODD.


Its NOT the Power Supply at all, its the Chip-Mem Expandsion in my A600.
No Joke ! . If i remove the Chip Mem Expansion the "very hard to see video noise" is gone. ( video Noise can be best seen with some solid background, like in a Paint programm )



So Guys, is this Odd or what ?
For my Specs.
I use the Amiga 600 rev 1.5 ( its so cute ) with the A600 Furia (the Fpu version ) and with the Chip Mem Expansion it produces "very hard to see video noise".


Hmm, rather stange. That brings me to another Question.
What are those 2MB Chip Mem Good for anyways ? ( i ony had OCS and AGA amigas, so the ECS is rather new to me )

Are there any benefits to have 2MB chipmem in a 16 bit AMIGA ????
I know that some "fake AGA Games" like Jungle Strike and Dungeon Master 2 uses 2MB Chipmem and NOT the AGA chipset but is that all ?

I can live without Jungle Strike ( there is a 1MB version anyway )
Dungeon Master 2 & the adventures of Willy Bemish.

On top of my head i have no other clue for what this expandsion is actually good for. ( maybe loading bigger pictures ??? )

Sorry, but i am new to the world of ECS

Anyway, the title should be renamed in
"Noise in Video with third Party Chip Mem Expansion"


HUGE Thanks to all the lovley people here ( you guys are the best )

Maybe some of you can clear up the "need for 2mb chipmem on a 16 bit amiga" thing.


yourse , Nibbler

[grond]

Originally Posted by Nibbler

Its NOT the Power Supply at all, its the Chip-Mem Expandsion in my A600.

Strange. Perhaps cleaning the contacts will help. The "pixel noise" might be caused by erroneous bitplane DMA reads.

[Amiga1992]

2MB is always good to have, more WHDLoad games will preload to RAM, you can softkick a 1.3 kickstart for greater compatibility, load more samples in Protracker, bigger images in Deluxe Paint... there's plenty of advantages.
To me 2MB Chip RAM is essential! Not all software can use Fast RAM as extra RAM.

As for why the expansion is making noise... if it's actually noise (and not corruption), it might be a grounding issue? But if it's actually random pixels/graphic corruption going around, it could be bad RAM.

Have you tried testing with the RAM expansion connected but the Furia disconnected?

Components inside the machine could cause grounding issues too, or perhaps you are having a power drain (doubt it with your power supply).

[Nibbler]

Did more intense tests, and results are that the noise exists anyway, but with the chipem expansion its more noticeable.

I found a few games that need 2MB chip ( f.e. Worms talk version ) ; i paint & make music on my Amiga, so i keep the Chip Mem expansion.

Maybe i should use the Multimeter on the running amiga but i am a little scared of that.

Anyway, a friend of mine has an A1200 in his basement ( he never uses it, ) but i will ask him for the Power Supply to try.

That will be interresting I report back. ( can take a while, because my friend is now on vacation )

Greetings and HUge Thanks from Me, Nibbler

[Amiga1992]

It could be a capacitor issue, either on the Amiga or the power supply.
Could you try to photograph the noise or make a video of it?

[Daedalus]

I had a problem a while ago with some noise in the audio output and waves of noise dots in the video output. The problem turned out to be the PSU, which was introducing a lot of high frequency noise on the 5V line. The PSU was formed from a PicoPSU and an old Dell laptop supply. When I looked at the noise on a scope, you could see the same noise in the output of the Dell charger, and neither the PicoPSU or the Amiga itself had adequate filtering to remove it. I changed the Dell PSU for a different one and I had perfect audio and video.

The RAM could be providing a little bit more of a load, which further reduces the effectiveness of any smoothing capacitors that aren't doing an adequate job.

[Kelv]

This might help:
https://www.eevblog.com/forum/beginn...ly-on-5v-rail/

Failing that try a faraday cage around the chip ram expansion ( same as the a501 ). Someone made one from a soup can ... and it fixed the noise issue ... awesome

http://elgensrepairs.blogspot.co.uk/...nsion-for.html

[Nibbler]

I found the SOLUTION thanks to Grond !!!!

You know folks, i could not wait until i get a original PSU for my Amiga,so i took a look at the Pot in the MeanWell PSU, like Grond was saying.

Originally Posted by grond

If the PSU is anything like my MeanWell PSU, it has a small pot for setting the output voltage. More than a noise problem I suspect that your 5V voltage is too low.

So i used a Paint programm to get a complete White background, (made the most video noise ) and tuned my TV setup way back down in brightness; all the way down.

Turned off the lights, and with a small screwdriver, ... i gently screwed counterclockwise ( multimeter said 5.15, so i choose to lower the value )

I could see , RIGHT BEFORE MY EYES that the noise changed when i used the POT on the Meanwell. ( thankfully, the meanwell has a LED inside, so i could see the pot in my pitch black room )

So i eye/hand adjusted the Pot and now all is hunky dory

Thats so great !!! HUGE thanks to all of you and a special Thanx goes to Grond for his great Meanwell knowledge and Kelv for the great Post find + Links .
It is always good to have you folks, youre the best !

[grond]

You lowered the voltage? That is surprising.

[Nibbler]

yupp, just a little tiny bit, and now it awesomeeeeeeeeeeeeeee

[Amiga1992]

I think the 5V line on the Amiga usually reads a little bit below 5V, never above, so what Nibbler has done makes sense.
I think it's usually between 4.7 and 4.9V. At least in all PSUs I have checked.

Congrats on fixing it, Nibbler!