Fisher running too hot?

jstraw

Active Member
I have a totaly rebuilt fisher x 100-c.It's output's run very hot to the touch after about a hour.This scare's me as i have mucho dollar's invested in it.It run's much hotter than stock and hotter than any other amp or receiver i have.It's biased correctly.
Should i be worried?It sound's good.
It's in a wood case now.Before it wasent,it was hot then but it's not much hotter now which i find odd?Case is custom but like a stock case.I'm worried about the output tranni's.
I did replace the 200 uf power caps with 250's.
The pre amp stage is 10 uf higher.
 
What temp is the tranny? how are you measuring??

I asked the same question to Batradio....
He stated anything under 165 F is fine...

My power tranny was ( using a IR/ laser thermometer ) @ 130F and the tube plates were 300 deg!

I was sweating bullets... but Mark sez that's normal
( but I have a small muffin fan anyway... just to be less paranoid )

Mike
 
Are you talking about the output tubes or the output transformers . The tubes can run as high as 200 to 300 degrees ,some 7591's get hot enough to burn the bakelite bases . Check the current draw of the tubes , also turn out the lights to make sure they are not red plating .The output trannsformers should only be geting hot by proximity effect .Discontinue use till you find your heat problem.

The power transformer are good to 165 F , output shouln't get near that hot
 
Hmmm

My outputs are 135 deg F but there's not a lot of room between the 88's and the front bell My measurement is at the top of the core (s)

Mike
 
I don't have a heat measureing device but i can hold my finger on it for 3 second's.Right now after 20 min no heat problem.odd
 
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My rule of thumb is if I can keep my thumb on a transformer for 5 seconds, everything's cool. . . enough.
 
The power transformer on my NOS-Valved 800B gets very hot after running all day. I cannot keep my hand on it for extended periods. Am I worried? Not in the slightest.

If it was so hot I was worried about burning myself from touching it for a second or two, I'd be worried.
 
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