Philips VG8235 - Blurry screen

Rookie (23)

20-07-2021, 19:45

Hi,
My VG8235 has some screen problems. When I turn it on, the MSX Logo appears but is very dark. Then after few seconds, on MSX Basic, the luminosity is shiny.
And if I start Multimente, for exemple, or a game, the colors are blurry, bad.
Made a little vidéo here https://youtu.be/MgNNqvrxM5w

Connected by scart cable (Tried other cable, other TV - no change). Changed the fuse too.

Anyone have an advice ?

By Grauw

Ascended (10768)

21-07-2021, 01:30

The smears in MultiMente make me think it is a capacitor problem on the R, G and B output lines… Check if the electrolytic ones have leaked or are bulging. It could also be an issue with the DAC of the VDP itself, but I’ve never seen this failure mode before. I would inspect the video circuitry first.

Which VG8235 model type do you have exactly? E.g. VG8235/20? Look at the bottom of the machine.

Do you have any electronics measuring equipment and soldering experience?

By meits

Scribe (6544)

21-07-2021, 01:45

To philgood1351fr, sorry for not being totally on topic, but I wanted to react only on one line by Grauw:

Grauw wrote:

Which VG8235 model type do you have exactly? E.g. VG8235/20? Look at the bottom of the machine.

There is a difference between the /00 and /20. /00 does not have a white MSX logo during boot and the overall color output is darker.
From left to right /20, /00, /20. It's not a screen or cable thing. I did check that.

edit:
To philgood1351fr. Can you check if the voltages coming from the PSU are what they should be?

By philgood1351fr

Rookie (23)

21-07-2021, 11:21

Hi, thanks for your help.
Mine is a 8235/39 - French
I checked the voltage on the Fuse, it shows only 8.8V.
It seems low no ? shouldn't be 12v or near ?

By meits

Scribe (6544)

21-07-2021, 14:32

That would be the french version of the /20. In the front right of the PSU board the indivicual voltages can be meassured.

Also check if the big STK Voltage Reg chip has a solid connection. As well on the board side as on the chip side. They're not always placed the way they supposed to be placed.
I had a -9.86V on the -12V read just recently and it was allright.