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    Transformer Temperature

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    Reid

    Posts : 9
    Join date : 2009-02-05

    Transformer Temperature

    Post by Reid on Sun Dec 27, 2009 9:50 pm

    Happy Holidays to everyone.

    Question: I have a ST120 tube amplifier. Today after running for 5-6 hours I decided to measure the temperature of the transformer. The temp was 135. Is this normal? It was hot but I could touch it for a couple of seconds.

    Great forum and Thanks to Bob for all of your help. Smile

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Transformer Temperature

    Post by Bob Latino on Mon Dec 28, 2009 6:24 am

    Reid wrote:Happy Holidays to everyone.

    Question: I have a ST120 tube amplifier. Today after running for 5-6 hours I decided to measure the temperature of the transformer. The temp was 135. Is this normal? It was hot but I could touch it for a couple of seconds.

    Great forum and Thanks to Bob for all of your help. Smile

    Hi Reid,

    The ST-120 will run a little hotter than an ST-70 because it is drawing about 35% more current than an ST-70. The actual temperature of the power transformer will depend on the amount of air circulation and the ambient room temperature. What you measure is about the same as what I measure here for my ST-120 and is normal for this amp and is no cause for concern.

    To offset somewhat the higher current draw, the lamination stack on the ST-120's power transformer is about 2.7 inches high. On a stock ST-70 it is about 1.5 to 1.6 inches. The ST-120 has about 1.1 inch more "iron" (actually M6 silicon steel) which is about 68% more steel in the stack than a stock ST-70. This larger heat sink keeps temperatures of the ST-120's power transformer within manageable limits.

    Bob

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