(Topic ID: 296916)

Bally/Stern Trimmer Pots

By oldschoolbob

3 months ago

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  • 12 posts
  • 6 Pinsiders participating
  • Latest reply 3 months ago by oldschoolbob
  • Topic is favorited by 1 Pinsider


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    bally stern 1 (resized).jpg

    #1 3 months ago

    There’s a 25K trimmer potentiometer on the high voltage section of Bally/Stern solenoid driver boards. Sometimes these go bad or just fall apart. GPE carries the trimmers for the Bally boards but the Stern boards are a little different. See diagram below.

    I’ve looked at Digi-key and Mouser but I get overwhelmed and confused with all they offer.
    Where do you get your trimmer pots? Which ones do you use?



    bally stern 1 (resized).jpg
    #2 3 months ago

    I think they are the same. Any 20k to 30k trimpot will be ok

    #3 3 months ago

    They are the same resistance but NOT the same size.

    IMG_7567 (resized).JPGIMG_7570 (resized).JPG
    #4 3 months ago

    GPE has a couple different sizes. Did you try the 9.5mm?

    pasted_image (resized).png

    If that one still doesn't quite fit, bending the legs sometimes helps.

    #5 3 months ago

    I've rebuilt many Bally solenoid boards and I always replace the 25K pot. You can find replacements at electronic
    suppliers. Look for Bourns #3352 25K pots. It is exactly the same as the original pot except the thumb wheel is black
    instead of blue.

    #6 3 months ago

    Thanks ForceFlow, I've have some of the 9.9mm on order from GPE, but he's off his feet right now. The hole size seems the same as the 6.6mm - only difference I see is the size of the housing. I tried bending the legs on the original style but they broke off. I may have better success with these from GPE.

    Candyman, I looked at the Bourns 3352. It looks like the 3352P will fit the Bally but I don't see anything to fit the Stern. Also I prefer the enclosed type like the Cermet Trimmer from GPE.

    Thanks for all the help.


    #7 3 months ago

    The 3362 and 3386 trimmers both have the "P" foot print which matches that of Bally foot print in image one of post #1. The only difference between the 3362 and 3386 trimmers is the body and element size. 3386 has larger element (and body) which allows easier adjustment to a finer granularity.
    The 3352P will also have the "P" foot print.

    I checked Vishay, Bourns, TE, Piher and CTS and nobody has anything close to the dimensions you want. You might be stuck with something similar to the "P" foot print dimensions.

    #8 3 months ago

    Thanks Ed for checking your sources.

    Do you think the 3386 trimmer leads could be bent enough to fit the Stern boards? It's only about 0.05 offset. It wouldn't be as secure as the straight thru hole but you usually don't need to adjust it that much.


    #9 3 months ago

    I think these were the original Piher ones Stern used, but Stern had the thumb-wheel included:

    The thumb-wheel clips in so if you still have the original trimmer you can transfer the thumb-wheel across.

    Otherwise there's the screwdriver type - consider whether you'll find screwdriver access difficult since the pot is vertical mount.

    Mousers product pictures don't show the exact unit - you have to look at the datasheet.

    However, I think it's safe to say most people just retrofit something else.

    #10 3 months ago

    Good catch.
    Yeah, I looked at that Piher series but I only looked at the horizontal mount parts.
    Vertical part with "B" spacing looks about right. About 8.8mm between two resistive element connections and 4mm from resistive element to the wiper connection. That's nearly dead on with his stern measurements above.

    #11 3 months ago

    Example from the next rev Stern board - note they also included the footprint for smaller trimmer pots.


    #12 3 months ago
    Quoted from G-P-E:

    That's nearly dead on with his stern measurements above.

    My measurements are probably a little off.

    I ordered the one's Quench showed above. I'll order some of the 3386's as soon as you're on your feet. Thanks

    Quoted from Quench:

    Example from the next rev Stern board - note they included the footprint for smaller trimmer pots.

    Now that's how they should have done it. Unfortunately mine must be the earlier version.



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