HW Problem. Please Help: Bad VBXE picture

[twh/f2]

Hi there,

 

OMG!! What a bad day.

 

out of sudden my Atari 130 XE equipped with a VBXE board went from crystal clear picture to something very horrible like this:

 

 

In advance I noticed that switching power to on was "comparibly slow" until the light on the keyboard finally went to red.

So I suspected a problem with the power supply unit. I tried out several replacements but the broken video output remains.

 

I suspect a broken capacitor. But I have no idea where to start and how this problem could be narrowed down.

 

Any ideas?

 

 

 

 

 

 

[twh/f2]

Just tried it with a different TVset/monitor and this terrible "snow" is also there.

 

[Beeblebrox]

I wonder if - given the pic was OK before - there is a possibility of a bad wire connection between the vbxe and video out jack?

 

Can you either detail which connector and cable setup you are using and/or take pics? 

 

I also find with my vbxe setup (DIN13 to Scart) that with the two Scart sockets on my TV, only one has a clear pic. The other has a poor output. 

 

 

Edited October 29, 2022 by Beeblebrox

[TGB1718]

If you suspect capacitors, these are the first ones to check/replace, there's a few lines missing from the diagram between C4 and C5 in this schematic

but all the +5V lines derive from the sane source,

check the electrolytics C22, C1, C3, C10.

 

It's unusual for the other types to fail, but not unknown.

 

There's also a 10uF (C98) across the power supply pins of POKEY (17 and 1)

C79 on the collector of Q7 (22UF).

C50 on across power supply pins of CD4050 which is on the video circuit

 

Edited October 29, 2022 by TGB1718

[Rybags]

Can you try something with actual colour?  Like near component values of R, G, B.

[twh/f2]

1 hour ago, Rybags said:

Can you try something with actual colour?  Like near component values of R, G, B.

the effect is very strong in gray scale and but not so extreme with color. But i.e. the Gr.0 / BASIC prompt with it's light blue the screen is also very distorted / blurred.

[flashjazzcat]

Check RGB switching is active if you're using SCART. Could simply be a broken wire.

[santosp]

The same here on my Atari 1200XL installation! 🥺

Very weird! In the past it  worked right! Now it have the right colors but a very snowy screen! 

I have try the sync from composite video either direct from cd4050, but with the same exact result!

I have right clear screen from the stock composite video, if I remove the VBXE and restore the removed components...

 

This is a PAL 1200XL using the GTIA PAL adapter form Dropcheck.

 

 

 

 

Edited February 25, 2023 by santosp
Pics

[Beeblebrox]

Try using an original Atari main powered power supply if you are using modern equivalent. Sometimes the switching type modern psu or the USB ones add interferance. 

[santosp]

I haven't some fancy psu like usb etc, just the original by Atari.

The only thing which changed is the monitor. I have a Philips tv/monitor with a native 640x480 IPS panel. But I think is incompatible with VBXE.