Vectrex White Dot Problem Help - SOLVED

[vectrexguy]

Hi everyone, 

Recently pulled a Vectrex out that I had in storage several years ago (I remember it working before being stored) only to be hit with the "white dot issue" 

Description of Symptoms:

White dot was initially to the top right of the screen but now it is consistently in the center of the screen
White dot only appears with brightness at the back of the machine turned all the way up
I cannot hear anything out of the speakers aside from the odd crackle if I adjust the volume knob
I can hear a faint hum which I believe is the transformer

What I have done so far: 

-Tried to leave the unit on for 20 minutes so anything would "warm up" - did not work
-Tube is glowing when power switched on
-Plugged in unit and measured the AC voltage coming from the transformer. I got approx. 10.8 VAC at the board before the rectifier, which I think is OK
-Measured the voltages on the power board - get solid good voltages on both sides of the connection (+13v, -5V and 5V)

-Here's where I think I may have an issue, I put one lead to ground and measured the voltages of the X,Y and Z pins and found something odd:
Yellow Wire --> Stable 0.6V
Blue and Orange Wires --> Start off around 0.6V but are not stable and continue to fall, I stopped measuring at -0.8V

If I unplug the XYZ cable from the board and power up the vectrex, nothing happens except for the same white dot. 

I'm having a tough time locating what the voltages at the XYZ are supposed to be online. If there is an issue with the XYZ cable, what chips could I order (shotgun approach??) to try and fix this?

All help and ideas are appreciated, would love to get this unit going again. Thanks again!

[kokovec]

It's been a while since I fixed a white dot issue, but I believe it ended up being either the MUX or the DAC.

[Peer]

If you do not hear any game sound (e.g. Mine Storm tunes), then I rather suspect some other reason than the DAC or MUX.

If it were just the DAC or MUX, then only the graphics should be affected and you should hear the game playing. As you do not hear any sound, it seems that the code is not running properly.

You should check the VIA first. It is socketed. Try removing it carefully, maybe clean all the contacts, and then insert it again. Sometimes this works wonders and it was just a bad or dirty contact.

I had broken VIAs in my consoles. Luckily those are still available and can easily be replaced. Cross testing with a second working console is a great way to check, if you know someone with another console in your area.

Hope this helps.

Many Cheers,

Peer

[vectrexguy]

Mar 14, 2023 7:28:02 GMT -5 Peer said:

If you do not hear any game sound (e.g. Mine Storm tunes), then I rather suspect some other reason than the DAC or MUX.

If it were just the DAC or MUX, then only the graphics should be affected and you should hear the game playing. As you do not hear any sound, it seems that the code is not running properly.

You should check the VIA first. It is socketed. Try removing it carefully, maybe clean all the contacts, and then insert it again. Sometimes this works wonders and it was just a bad or dirty contact.

I had broken VIAs in my consoles. Luckily those are still available and can easily be replaced. Cross testing with a second working console is a great way to check, if you know someone with another console in your area.

Hope this helps.

Many Cheers,

Peer

Understood. I was looking in the circuit diagram and couldn't find a chip called "VIA" I found one called "PIA" that is socketed. Number on the chip is "SY6522" Is this what you were referring to? I will try to remove, clean, and replace when I get home. Is contact cleaner safe to use on these machines? was thinking of spraying it into the socket. 

Thanks,
-Jack

[Peer]

Mar 14, 2023 10:30:25 GMT -5 vectrexguy said:

Mar 14, 2023 7:28:02 GMT -5 Peer said:

Understood. I was looking in the circuit diagram and couldn't find a chip called "VIA" I found one called "PIA" that is socketed. Number on the chip is "SY6522" Is this what you were referring to? I will try to remove, clean, and replace when I get home. Is contact cleaner safe to use on these machines? was thinking of spraying it into the socket. 

Thanks,
-Jack

Yes, that is the one. It is referred to both as "PIA 6522" or "VIA 6522". Sometimes it is enough to simply remove and reinsert it without using additional cleaer. I would try that first. If that does not help, then remove the chip again and carefully use contact cleaner on the pins of the chip only, and reinsert it again. I once had a problem when I sprayed contact cleaner into the socket. The cleaner did not fully evaporize, and there remained some residue liquid in the socket for a long time. The chip worked, and the liquid did not seem to have any effect on its operation, but still, I don't know if that is a good thing.

One more caveat: Use caution when removing the chip. Especially if dirt and/or corrosion are part of the problem, then removal can be a bit difficult. There is some danger of bending or breaking the pins if the chip is not evenly lifted. There are tools small chip-lifting tools available which greatly help here.

Good luck, and many Cheers,
Peer

[VectorX]

There's an adjustments thread on this too but this one has additional info for the problem, so I've added it.

Also, on a side note:

Mar 14, 2023 15:15:37 GMT -5 Peer said:

I once had a problem when I sprayed contact cleaner into the socket. The cleaner did not fully evaporize, and there remained some residue liquid in the socket for a long time. The chip worked, and the liquid did not seem to have any effect on its operation, but still, I don't know if that is a good thing.

This can happen for several things, such as when I used compressed air for cleaning my Wii once. I didn't press the button down to spray the inside of the Wii far enough so I assume it came out somewhat in a liquid form, since the next day the colors were off when I was going through some Wii Fit Plus. After having the Wii unplugged for a while when I was done and it had cooled off I tried using the compressed air again and the display was back to normal after that.

[vectrexguy]

Good News!! 

I replaced the VIA 6522 chip with one I had in my working Commodore Vic-20. The Vectrex WORKS perfectly now!! 

Wondering if I scrub the old chip well it might come back to life, there's some black spots of corrosion on some of the legs. 

Thanks again for all the help everyone!!!

-Jack