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Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


4 posters

    ST-70 chassis to cage screw sizes?

    Kray
    Kray


    Posts : 36
    Join date : 2019-05-06
    Age : 49
    Location : Denver

    ST-70 chassis to cage screw sizes? Empty ST-70 chassis to cage screw sizes?

    Post by Kray Thu May 09, 2019 1:01 pm

    I have the chassis with 3 holes on each side that hold the cage on. My ST-70 is missing the screws.

    Can someone tell me the size? are they 4-40 1/4"?
    Bob Latino
    Bob Latino
    Admin


    Posts : 3260
    Join date : 2008-11-26
    Location : Massachusetts

    ST-70 chassis to cage screw sizes? Empty Re: ST-70 chassis to cage screw sizes?

    Post by Bob Latino Thu May 09, 2019 2:42 pm

    Kray wrote:I have the chassis with 3 holes on each side that hold the cage on. My ST-70 is missing the screws.

    Can someone tell me the size? are they 4-40 1/4"?

    The holes in the chassis that hold the ST-70 cage on are not for 4-40 screws .. Those holes are for #6 screws. I believe most (if not all) of the original Dynaco ST-70's used self-tapping #6 screws. Try first a 6-32 self tapping screw in your chassis. The modern VTA amp kits use stainless steel 6-32 screws in a tapped hole in the chassis.

    Bob
    Peter W.
    Peter W.


    Posts : 1351
    Join date : 2016-08-07
    Location : Melrose Park, PA

    ST-70 chassis to cage screw sizes? Empty Re: ST-70 chassis to cage screw sizes?

    Post by Peter W. Thu May 09, 2019 3:11 pm

    The OEM Dynaco screws were slotted-head 6-32 wood screws. They were 'self-tapping" only after a manner of speaking given that the chassis was a very mild plated steel.

    The modern equivalent in Philips-head, stainless (an excellent idea and choice!) is:

    https://www.mcmaster.com/90087a143  

    I understand that Bob's chassis uses a heavier steel than OEM - you might consider going to 1/4" for that reason. But OEM was 3/16. And self-tapping screws would also help with a harder steel. Cheap enough to replace them all in a vintage piece if needed.
    Kray
    Kray


    Posts : 36
    Join date : 2019-05-06
    Age : 49
    Location : Denver

    ST-70 chassis to cage screw sizes? Empty Re: ST-70 chassis to cage screw sizes?

    Post by Kray Thu May 09, 2019 3:12 pm

    Bob Latino wrote:
    Kray wrote:I have the chassis with 3 holes on each side that hold the cage on. My ST-70 is missing the screws.

    Can someone tell me the size? are they 4-40 1/4"?

    The holes in the chassis that hold the ST-70 cage on are not for 4-40 screws .. Those holes are for #6 screws. I believe most (if not all) of the original Dynaco ST-70's used self-tapping #6 screws. Try first a 6-32 self tapping screw in your chassis. The modern VTA amp kits use stainless steel 6-32 screws in a tapped hole in the chassis.

    Bob

    Thanks Bob and PeterW
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    Guest
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    ST-70 chassis to cage screw sizes? Empty Re: ST-70 chassis to cage screw sizes?

    Post by Guest Thu May 09, 2019 3:36 pm

    .


    Last edited by PeterCapo on Mon Nov 30, 2020 8:36 pm; edited 1 time in total
    Peter W.
    Peter W.


    Posts : 1351
    Join date : 2016-08-07
    Location : Melrose Park, PA

    ST-70 chassis to cage screw sizes? Empty Re: ST-70 chassis to cage screw sizes?

    Post by Peter W. Thu May 09, 2019 3:50 pm

    PeterCapo wrote:Original Dynaco parts list specified #6 sheet metal screws.

    Here are some that retain the original look, as well: https://www.boltdepot.com/Sheet_metal_screws_Slotted_pan_head_Stainless_steel_18-8_6.aspx

    Should have written "Pan Head" wood screws.

    18-8 would be the material, 18-8 Stainless.
    1/4" is too long for OEM - but not for later (Blackwood) Dynaco products.
    The slotted head, however, is a nice touch.
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    Dale Stevens


    Posts : 201
    Join date : 2014-07-06
    Age : 74
    Location : Loris, SC

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    Post by Dale Stevens Thu May 09, 2019 6:08 pm

    I've found a good source for stainless hardware is FASTENAL OEM fasteners, which can be found locally so as not to have to order . Just a thought. Dale

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