Pots for a Tempest main PCB

Trakkur

New member
Joined
Jan 13, 2016
Messages
144
Reaction score
1
Location
Bridgewater, New Jersey
While fixing a separate issue on a Tempest main PCB last week it would seem that I managed to damage the small blue pots on the board - the ones that control Y-size and Y-center. The unit was producing an image earlier, but no sound...and now has no image either.

When I looked closer I saw that the legs on those 2 pots were snapped off - which is PROBABLY why the spot killer is on and there is no video. :(

I've been doing some searching but I cant find the pots I need.

A close up of them shows "CTS 375 10K B 8132" printed on them.

Does anyone know where I can find a place to purchase these pots?

Thanks!
 
The original pots are garbage. If you replace them with the same ones, they'll just break off again eventually (and/or get dirt inside them, as they're the open type).

I use type 3386 sealed pots. They aren't an exact fit, but you can bend the legs to get them to fit, however you need to put a piece of Kapton tape under them, to prevent the legs from shorting out against the ground plane underneath. You want to use Kapton tape, as it's thin and high-temp resistant, so it won't melt when you solder the pots in.

The results are worth it though, as they look nice, sit low profile (so they won't get bent over), and are sealed, so dirt won't contaminate them. Plus, you adjust them with a screwdriver, so once they are set, they stay put, and can't get knocked out of adjustment accidentally.

The four XY size pots are 10K each, the two linearity ones are 2K, and the two BIP ones are 500.

Here's a pic of a Tempest board with all of them replaced:

attachment.php
 
Nice...and where would you recommend getting those pots and the tape?'

If you have a URL to the exact ones that you used in Tempest that would be best.

Thanks!
 
Last edited:
Please pardon my ignorance and newbness...but what exactly am I looking for? I checked digikey and there are a lot of different 3386 pots there...I want to be sure that we order the correct ones. I looked at the Tempest documentation, but it is sorely lacking as you can imagine.

Any specific guidance would be greatly appreciated.

Thanks
 
CTS doesn't make that 375 pot but bourns makes the exact fitting replacement and if you don't want to have to tape off the ground mask than you can use the ones i stock which match the originals. they are not sealed but the non-sealed pots have lasted almost 40 years so whether you replace them with sealed or non-sealed you should be fine and the non-sealed are exact replacements of the originals which means install is much easier for someone who doesn't do this daily and no tape needed.
 
https://www.digikey.com/product-detail/en/bourns-inc/3386P-1-103LF/3386P-103LF-ND/1088523

https://www.digikey.com/product-detail/en/bourns-inc/3386P-1-202LF/3386P-202LF-ND/1088527

https://www.digikey.com/product-detail/en/bourns-inc/3386P-1-501LF/3386P-501LF-ND/1088534


When you install them, temporarily push them into the holes first, to bend the legs into the right shape, before you put the Kapton tape down. Else you can potentially rip the tape if you put it down first, then press the pot into the hole to bend the legs.

Also, it helps to solder one leg of the pot first (I typically do the back leg), just to tack it in the hole. Then adjust the pot so it's level and even before soldering the other two legs. It's ok if the pot isn't completely flush against the board, as it helps prevent shorting if it's elevated a tiny bit, even with the tape installed, for extra insurance.

Security0001 is right, it is easier to use different pots that match the pin spacing of the holes in the board, if you don't do regular board repair or soldering work. I just like the additional benefits of the 3386's (e.g., the fact that they're sealed, are low profile, and don't have knobs), so I don't mind taking the extra work to install them.
 
The original pots are garbage. If you replace them with the same ones, they'll just break off again eventually (and/or get dirt inside them, as they're the open type).

I use type 3386 sealed pots. They aren't an exact fit, but you can bend the legs to get them to fit, however you need to put a piece of Kapton tape under them, to prevent the legs from shorting out against the ground plane underneath. You want to use Kapton tape, as it's thin and high-temp resistant, so it won't melt when you solder the pots in.

The results are worth it though, as they look nice, sit low profile (so they won't get bent over), and are sealed, so dirt won't contaminate them. Plus, you adjust them with a screwdriver, so once they are set, they stay put, and can't get knocked out of adjustment accidentally.

The four XY size pots are 10K each, the two linearity ones are 2K, and the two BIP ones are 500.

Here's a pic of a Tempest board with all of them replaced:

attachment.php
https://www.digikey.com/product-detail/en/bourns-inc/3386P-1-103LF/3386P-103LF-ND/1088523

https://www.digikey.com/product-detail/en/bourns-inc/3386P-1-202LF/3386P-202LF-ND/1088527

https://www.digikey.com/product-detail/en/bourns-inc/3386P-1-501LF/3386P-501LF-ND/1088534


When you install them, temporarily push them into the holes first, to bend the legs into the right shape, before you put the Kapton tape down. Else you can potentially rip the tape if you put it down first, then press the pot into the hole to bend the legs.

Also, it helps to solder one leg of the pot first (I typically do the back leg), just to tack it in the hole. Then adjust the pot so it's level and even before soldering the other two legs. It's ok if the pot isn't completely flush against the board, as it helps prevent shorting if it's elevated a tiny bit, even with the tape installed, for extra insurance.

Security0001 is right, it is easier to use different pots that match the pin spacing of the holes in the board, if you don't do regular board repair or soldering work. I just like the additional benefits of the 3386's (e.g., the fact that they're sealed, are low profile, and don't have knobs), so I don't mind taking the extra work to install them.
Are the BIP Pots 500 or 200? The original ones appear to be 200. Is this a recommended change?
 
Are the BIP Pots 500 or 200? The original ones appear to be 200. Is this a recommended change?
I recently did this on my spare Tempest boards, and the 500s work fine. I remember asking this question too, but at the end of the day it didn't matter.

- Jon
 
Hey, sorry I've been traveling the last few weeks and not around here much.

For Tempests, the factory value is actually 200. However 200 or 500 will equally work. This thread is super old, so I don't know if me saying 500 above was a noob error on my part, or just a brain fart.

The video sections of Atari color vector games are almost identical, and they did actually use 500 on some games (like Gravitar/BW). Ultimately it doesn't make much difference, as the pot will always be set below 200 ohms either way. But the correct value per the Tempest schematics is 200 (and if you look at the Gravitar schematics and actual boards, you'll see they say 500). But 500's on a Tempest will work fine.
 
Hey, sorry I've been traveling the last few weeks and not around here much.

For Tempests, the factory value is actually 200. However 200 or 500 will equally work. This thread is super old, so I don't know if me saying 500 above was a noob error on my part, or just a brain fart.

The video sections of Atari color vector games are almost identical, and they did actually use 500 on some games (like Gravitar/BW). Ultimately it doesn't make much difference, as the pot will always be set below 200 ohms either way. But the correct value per the Tempest schematics is 200 (and if you look at the Gravitar schematics and actual boards, you'll see they say 500). But 500's on a Tempest will work fine.

Hey @andrewb,

Are the Bourns 3386 pots you linked above still your preference for a Tempest board? My board still has all original pots. less one now... I just bumped the R168 y-size pot and it fell right off the board.

I'm good with bending the legs and using the kapton tape, just wondering if you have found other solutions since then.


9940.jpg 9941.jpg
 
Hey @andrewb,

Are the Bourns 3386 pots you linked above still your preference for a Tempest board? My board still has all original pots. less one now... I just bumped the R168 y-size pot and it fell right off the board.

I'm good with bending the legs and using the kapton tape, just wondering if you have found other solutions since then.


Yep, I still use the 3386's.

(And yes, Kapton tape and leg bending is still required. But that's easy.)

There are ones out there that are a better fit for the footprint. But they aren't the style I like, as they have the thumbwheels, and are bigger, so they sit higher on the board, and just don't look as good. I like the low profile of the 3386's, and the fact that once you set them, they can't get knocked out of adjustment.
 
Yep, I still use the 3386's.

(And yes, Kapton tape and leg bending is still required. But that's easy.)

There are ones out there that are a better fit for the footprint. But they aren't the style I like, as they have the thumbwheels, and are bigger, so they sit higher on the board, and just don't look as good. I like the low profile of the 3386's, and the fact that once you set them, they can't get knocked out of adjustment.

Much appreciated, Andy, as always!
 
Back
Top Bottom