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What is this goop. High heat caulk?

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  • What is this goop. High heat caulk?

    What is this goop that's occasionally seen ? It seems to be typically red and is some
    Sort of high heat, non conductive caulk? I'm
    Sure someone must know what it is called .

    Here is a funny picture from some rig. I also usually see this type of goop in sunn coliseum series to goop the big 10w emitter resistors to the chassis. Maybe it is for thermal coupling as well ?

    Click image for larger version

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  • #2
    Originally posted by nsubulysses View Post
    What is this goop that's occasionally seen ? It seems to be typically red and is some
    Sort of high heat, non conductive caulk? I'm
    Sure someone must know what it is called .

    Here is a funny picture from some rig. I also usually see this type of goop in sunn coliseum series to goop the big 10w emitter resistors to the chassis. Maybe it is for thermal coupling as well ?

    [ATTACH=CONFIG]46543[/ATTACH]
    That looks like old fashioned RTV Cement or Corona Dope, it was always that dark red color. An early version of technician caulk. RTV stands for Room Temperature Vulcanizing as in rubber.

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    • #3
      What the heck is going on in there? Somebody has gooped in some rubber grommets to support the smaller heatsink?


      Originally posted by 52 Bill View Post
      That looks like old fashioned RTV Cement or Corona Dope, it was always that dark red color. An early version of technician caulk. RTV stands for Room Temperature Vulcanizing as in rubber.
      I always thought those 2 were different things? The corona dope I'm used to is a brush on liquid that hardens, like a varnish. Maybe there are various types?
      "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

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      • #4
        That is the early version Sunn 1200S (the one made by fender in the 90s) that has a big floating heatsink supported by about 6 transistors only. So it vibrates and cracks the solder connections of the transistors. Fender later changed their Sunn 1200S to have a stabilizing bracket for the heatsink. The previous goop concoction is a picture of one I got in for repair where someone rigged a heat sink stabilizing bracket with high temp goop and some rubber grommets.

        Here is a pic of how fender changed the design
        original with floating heat sink
        Click image for larger version

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        and
        https://www.talkbass.com/attachments...b-jpg.1943449/

        I had a 1200S about 5 years ago and fender would not sell me the bracket since I'm not authorized service center, although they still offered it for free because I guess they basically considered it a bad design choice by them. I took it to an "authorized" shop my friend worked at and it was free to me and they paid the shop $35 to install the bracket. It was a 10 minute job.

        It seems like they now no longer offer this at all since the amp is pretty old. I think it was only made 94-99 or so. The first couple years with no stabilizing bracket

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        • #5
          Originally posted by g1 View Post
          What the heck is going on in there? Somebody has gooped in some rubber grommets to support the smaller heatsink?



          I always thought those 2 were different things? The corona dope I'm used to is a brush on liquid that hardens, like a varnish. Maybe there are various types?
          You're right the corona dope was a liquid, I was remembering some sort of putty that we used to use on the rubber high voltage plug to stop arcing.

          That bracket looks like it could be fabricated in about 10 minutes from alum. bar stock and a vise.

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