Vectrex Display Problems PICS

[Rolo]

It turns on, the sound works, I can even see the graphics. However all of the graphics are connected to a dot in the center of the screen with extra lines. Also the text is unreadable. Everything still moves on screen as it should its just those extra lines that all go to the center of the screen.

Well, you clearly have a z-axis problem, as stated above. I once hooked up an oscilloscope to the deflection circuits of the CRT of my Vectrex and got exactly the same picture on the scope. Did you check, if you have any signal coming out of IC207 PIA6522A Pin19 (!Blank)? Do you have Z-AXIS-DRIVE? How about transistors Q303, Q304, Q305? Especially Q305 which drives the cathode up and down (switching on/off the electron gun). And the series resistors nearby. The values of those sometimes change to "infinite" resistance after countless temperature cycles. The transistor would switch, with no effect.

The schematics can be found in the internet. With the help of those, I think, any television repair shop can fix the problem.

[Swainy]

Sadly Rolo most of that goes right over my head. I haven't done any soldering/electrics since I was 15 which was 25 years ago

 

I haven't even got the equipment to be checking. As I said, it's already been to a repair store the vectors were displaying very dim. The cap change did not fix the problem.

 

My problem now is, I've spend £76 on repairs plus the cost of the cap kit and I haven't really got the cash to send it to another repair shop.

[Rolo]

Well that's a shame, of course.

 

What can I say? Well, without some electronic skills and equipment, this will be a hard one. Hm, don't you have a friend nearby, who does? A hobbyist who does not charge you for everything? You could try to sell it on ebay as "not working" for a few bugs. Or maybe there is a retro group somewhere around? Did you try to find one? You could go to one of their meetings and ask for help. Most of those guys normally are willing to help!

 

You can send it to me. I could give it a try. But then again, there would be shipping costs.

 

Blindly changing caps is kind of fashionable those days. Sure, they are aging and loosing capacitance, but frankly: I did not have to change them in any of my 15 or so consoles/8-bit-computers. And even then, I'd have a look first, which ones to change.

[Swainy]

Thanks for the offer Rolo but I should imagine that the shipping costs to & from Germany back to the UK will be a bit too expensive. I really do appreciate the offer though!

 

Unfortunately there doesn't seem to be any retro groups that deal with electronics that I know of in my area. If anyone in Essex/South East region of the UK knows any different then please do let me know.

 

Cheers!

[BigO]

You might check your area for an amateur/"ham" radio group. Some of those guys really know their electronics. You might find a willing and very capable person among them to do the troubleshooting that Rolo describes.

[Swainy]

Good news guys!

 

 

I replaced the M8320-LF347N chip with a new one and it's working fine

[Rolo]

Congratulations! Did you get some electronic equipment or did you guess? Did you have the QuadOPAmp in the drawer?

[Swainy]

It was just a guess. I ordered the spare chip and it arrived the next day.