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    Capcitor heat



    Posts : 20
    Join date : 2011-05-18

    Capcitor heat

    Post by snav on Thu May 19, 2011 7:38 pm

    I am still experimenting with this restoration project of a MK3. One thing I've been doing is running the amp for hours at a time. Since I read that a bad cap will get hot if leaking badly I took the cover off to see how hot it was and it was very hot. But realizing that everything was hot I let it cool and then fashioned a heat shield(210degree high collar)from aluminum which I used a cable tie at the base to fasten. I replaced the cover after making sure there was a 3/16 gap between the shield and the capacitor and fired it up for a few more hours. Checking again found that the capacitor was still hot. But I wasn't sure that I wasn't still getting radiated heat. So today I've been running it for 8hrs with the cover off and the cap is slightly above ambient on the far side gradually getting warmer as I check closer to the shield but still only just warm (80f) even closest to the output tubes. So, the capacitor isn't self warming but it begs the question about whether the radiated heat is killing these parts? Based on this I would want to make a sturdy decorative shield if used without a cover or run a very small fan if using a cover. Of course putting a cap board under the chassis would solve that also. Ideas?

    Nemo Me Impune Lacessit
    j beede

    Posts : 438
    Join date : 2011-02-07
    Location : California

    Re: Capcitor heat

    Post by j beede on Thu May 19, 2011 8:54 pm

    I decided a while ago to "just say no" to quad caps. I built a pair of cap boards using series/balanced modern (small) 47uF, 450WVDC radial caps and have never looked back. I left the old quad caps in place as a memorial. Now I can safely run a silicon bridge rectifier with KT-88s without worrying about boiling the insides of the quad cap can.


    Posts : 45
    Join date : 2011-04-04

    Re: Capcitor heat

    Post by jdm on Sat May 21, 2011 12:52 pm

    I have a new St-120 and noticed the radiated heat on the cap closest to the GZ34 rectifier was considerably warmer than the other 3 caps on top of the board. This is not the quad cap it is the far left 47hf 450v cap. Is the heat from the GZ34 going to considably shorten the life of the cap? What is the servive life of these caps in hours?


    Posts : 53
    Join date : 2009-12-01
    Age : 68
    Location : Wa

    Re: Capcitor heat

    Post by Pooch on Sat May 21, 2011 3:36 pm

    After having a new (6 months old)CE cap fail, I went with the Curcio cap board in my VTA Mk4s. This CE cap is not the one Bob is referring to, but the $35- 80,40,30,20- 525V. The one Bob is talking about is an upgrade from the ones I have.
    Anyway, I went with the Curcio board and used Panasonic ED caps, rated at 105C I believe. If you look a the cap maker's site, they may have temperature info listed, ie hours at temp.


    Posts : 60
    Join date : 2010-02-20

    Re: Capcitor heat

    Post by wolverine on Sat May 21, 2011 8:39 pm

    If your caps are getting up around 100 fahrenheit, then consider that that cap likely is rated 85 celsius, and 100f is only 37 celsius. Even at 125f then it's still about 52c. Don't worry about it, put on an album, sit back, pour an adult beverage, and enjoy.

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    Re: Capcitor heat

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