Vectrex with problem need advice

[vsl]

Hello,

I bought a Vectrex with a stated problem: a white dot and no sound. When it arrived, I replaced the 2764 EPROM, the two 2114 RAMs, and the 6522 PIA.
The sound came back, and the white dot is no longer just a fixed dot, which is visible in the video.
But I got to this point and I can't find the culprit, please help and advise.

Thanks !

 

[big10p]

Do you have a scope? Hook it up to the XY output from the logic board. This will tell you if the issue is on the logic board or the deflection board.

 

[vsl]

yes, this is output from logic board (probe x1):

 

[Georgian2]

yes :View attachment 64154View attachment 64156

You need XY mode in order to see if you have the same image like on your monitor or something else.

 

[big10p]

yes :View attachment 64154View attachment 64156

Use two probes and put the scope in XY mode. Digital scopes aren't very good at displaying vectors, but you should be able to see a rough version of the game playing. Do you have a test cart or a flash cart you can put the test cart ROM on? It will help to see if vectors are being output correctly from the logic board.

 

[vsl]

 

[vsl]

Guys, thanks for the idea! This is my first real experience with a vector system, so I honestly didn’t know about using the oscilloscope in XY mode for this kind of diagnosis. 🙂

That’s actually a brilliant trick — basically turning the scope into a second vector display and comparing what the logic board is generating with what the Vectrex CRT is showing.

I’m learning a lot from this repair already. The machine started as a silent white dot, and now we have sound and actual vector movement, so at least the patient is definitely alive. 😄

Thanks again for pointing me in the right direction — the hunt continues! 🔧

 

[Georgian2]

That’s actually a brilliant trick — basically turning the scope into a second vector display and comparing what the logic board is generating with what the Vectrex CRT is showing.

Classic CRT oscilloscopes are best for this kind of things. On most of them, one can use the Z input on the back too.

 

[big10p]

Vectrexes are usually very fixable. 🙂