Interference/Noise on Blue channel

[christian776]

Hi guys,

I'm seeing blue dots and waves in the blue channel, sort of like interference or noise, I've created this short to showcase the effect,

View: https://youtube.com/shorts/4JL_Ir4vjDs?feature=share
and here's a couple of pictures

 

[notsonic]

Are you sure it's only on blue and not in the middle of the monitor? What does an all blue screen look like? What is your source?

 

[christian776]

Oh you're right, it;s not just the blue, it's all over the place. I'm using the 240p test suite and using the IRE 020 , I can see it takes way more space than that. any idea what could this be? A bad cap maybe or some diodes not workking ?

 

[notsonic]

What device are you using to run the 240p test suite?

I have seen this type of interference before from cheap switching power supplies.

 

[christian776]

Oh, I'm using a Mister FPGA using the SNES core. This is the power supply I have in my Astro City

 

[notsonic]

Is the mister actually powered by that PSU (are you using like a Mistercade)?

If it is powered by that psu then, do you have any other jamma board to try, just to rule out the mister being the problem?

 

[christian776]

Yeah, the Mister FPGA is powered by a Jamma adapter and yes I have a bootleg Strikers 1945 board, and upon closer inspection I can see the same dots (while hard to spot) in the screen. Could the PSU be introducing some high frequency noise or something through the video cables?

 

[nem]

The Astro PSU is a quality one, but it's also old. Recapping it would be sound idea.

The interference could also be due to some ground issue.

 

[Mukuro_W]

Wich chassis is this? Nanao ms9 o ms8?

 

[tika]

Looks the same as the audio amp/PSU in my Sega Vs City cab

 

[christian776]

Hi Mukuro_W, this is a MS8-29FSG chassis. Do you mind to give more details Tika ?