Vectrex jumbled text and vectors

[shoggo147]

Hi All,

Hoping someone can help with a Vectrex I purchased recently, which had the usual white dot problem but had working sound.

I replaced a few of the ICs on the bottom PCB and eventually got Mine Storm to boot up.

However a few seconds into the game the text where the score is shown at the top starts to drop down the screen. At the same tim the vectors start to become miss-aligned. I tried replacing 3 x caps on the bottom PCB that were easily accesible but it did not help.

The system does still sometimes boot to a white dot screen and I found if the 4-pin power connector on the bottom PCB is pulled off and replaced it then works OK again. I cleaned this connector with contact cleaner and re-flowed the pads underneath but it still seems to have the intermittent bootup problem.

Has anyone got any ideas what could be wrong? I have added a video below.

[R.Cade]

Mine does something similar, but everything gets slanted and wiggly instead of folding after a bit- I recapped the whole thing and it still has the issue. I'm guessing it's some power supply ripple issue, but I haven't dug further. Let me know if you figure it out on yours.

Edited June 14, 2013 by R.Cade

[ilovethevectrex]

wow, very odd issue. do other games (actual carts) do this when you plug them in? it might just be the minestorm game and not the whole system, because at the beginning of the video it seems fine, then it starts to glitch out.

[shoggo147]

I have no other carts to try at the moment, didn't really want to spend more if I can't get it working.

I might try replacing caps related to the power supply output (such as C110/111 & C120/121/122) , as it could be psu ripple as the first reply suggested.

[shoggo147]

I have finally got back to trying to sort out my Vectrex with jumbled up vectors. After the suggestion that it may be due to power supply ripple I checked out the Troubleshooting Guide which recommended checking ripple at the input of T503, which should be no more than 50mV. Below is are screenshots taken from +9V & -9V inputs of T503, which both show ripple of over 500mV

Screen shot of ripple on +9V input at T503

 

Screen shot of ripple on -9V input at T503

 

My conclusion is to try replacing 2 x 10,000uF capacitors C117/C118 and 2 x 4,700uF capacitors C109 & C119

[iesposta]

My experience has shown me that A LOT of PROBLEMS are just that stupid cable that attaches the computer boards together (the X, Y, Z one), especially if the bottom computer board is working.

It is hard to believe, but in one machine where I replaced all capacitors and also a heat sinked chip (that's in Q*bert) IC401 "LM379 Dual 6W AMP" and got a working Vectrex, now and then it will go slightly jumbled!

I am about ready to solder the two boards together with wires to rule out that connector cable (the X, Y, Z one, not the power connector).

Didn't see your post earlier, or I would have replied.