Vectrex controller repair - replacement pots?

[tjsynkral]

I am rebuilding a Vectrex controller that had a hard life with a previous owner. I already fixed a bunch of broken traces on the buttons PCB and now those work great, but I also have a 3-legged pot that snapped off near the solder points.

Attaching a picture of the part of the pot that broke. These pots latch onto the joystick.

Has anybody managed to find a general purpose pot on the market (shack, mouser, etc.) that can be used to replace it?

[boxpressed]

I read somewhere that some TRS-80 sticks use the same pot, but I haven't ever verified.

[Rob Mitchell]

The plastic lever from the TRS-80 is the same .. But the pot is different .. Let me see what I have in my Vectrex parts bin.

[Rob Mitchell]

I did not find any spare pots in my parts bin ..

[e5frog]

I fixed one of those lately, even if this is an old post it might be a good idea to post it here.

 

If the carbon trace is worn you can use the original to fix it by cutting off the circular part with the carbon trace and silver paint - it's a separate part in the "sandwich".

Then you can cut off a long enough part with the silver paint and then polish the silver paint off - leaving it with the carbon trace still there.

You now have a piece to replace the damaged one, glue it in place with epoxy and then use conductive silver paint to tie it to terminals again.

 

Here are some images, I'm not sure how long they'll last:

Remove glitchy PCB-part from metal cup, use a screwdriver and pliers to bend the metal grabbers.

 

You can see the carbon layer has been worn down.

 

Cut off the carbon layered part.

 

Carefully polish away the silver paint, use car polish, toothpaste or similar.

You want to keep the carbon layer - don't overdo it!!

 

Cut off a long enough piece to replace the usable area.

 

Glue the fresh carbon layer piece to the proper position, I used a thin layer of epoxy.

Paint with conductive silver paint so you get contact.

 

Use the conductive paint over the edge, several layers, wait until fully dry check measurement about 10kOhm - and you're back in business.

 

 

While experimenting I used a second potentiometer, but it's not necessary to do anything else than what is described here.

[CRTGAMER]

I rewired a couple 3rd party Apple Sticks (pictured below) which fortunately had left and right hand buttons. The extra buttons set for each of the four buttons with a slide switch underneath to change the positions of the pair of buttons. The converted sticks worked though the potentiometers more sensitive with a very narrow centering, a tweak of the slide adjustment per game.

[tjsynkral]

I'm reviving this old thread to provide an update on my findings:

 

The Philmore PC74 fits perfectly into the joystick, but resistance is too high for the range of motion of the joystick. This is a 10K pot, and I think 5K or less would be the correct amount of resistance (possibly combined with removing the +/- 5V resistor and adjustment pots since there is a bit of resistance that will always be present on the replaced pot).

 

I did not have success and in trying it out damaged the joystick too far to continue, so I'm keeping the controller for spare parts now.

 

In other news, I replaced the polystyrene caps for the deflection circuit with MLR472K100 and MLR103K630 and they worked just fine.

[e5frog]

The problem is that the joystick potentiometer only uses about 1/3 of the movement that a usual potentiometer has, so if you put a normal pot in there you'll only be able to change the resistance between something like 3.3k and 6.6k and not between (basically) 0k and 10k. So you either need to find one with the same amount of degrees of turning or hack one so that you have this 0-10k in the used area. If you find a good value it's enough to just paint the ends with some conductive paint to fix it. Probably something in the area of 30k or above could work.

I think cutting the carbon layer already there and glue back a fresh piece is a nice and quick fix if you have the materials, a drop in replacement would be very nice though.

Edited March 8, 2018 by e5frog