OTL Asylum

OTL, Output Transformerless Amplifier User Group.

Return to OTL Asylum


Message Sort: Post Order or Asylum Reverse Threaded

Was playing around with an infrared thermometer...

70.186.155.194

Posted on February 4, 2017 at 12:06:47
acres verde
Audiophile

Posts: 464
Location: Big Easy
Joined: November 13, 2004
the other day and decided to take a few readings of the tubes in my M60s (the long chassis type like the prior style MA-1s). I found that, typically, temps were about 50 degrees higher at the tops of the tubes than just above the base and that the outer bank of tubes away from the transformer cover were also at least 50 degrees cooler. These comments both pertain to the 6AS7s, of course. The "middle" tubes in the two banks of four 6AS7s tended to be as much as 70 degrees hotter than the ones on the ends. 6AS7 temps ranged from about 270 degrees to as much as 340 degrees.

V1 ran about 210 degrees, V2 is shorted, V3 ran about 180ish and V4 about 160 or so.

DC offset and bias were both adjusted immediately prior to the taken readings.

Just thought enquiring minds might want to know.

 

Hide full thread outline!
    ...
Fahrenheit or Centigrade?, posted on February 4, 2017 at 14:55:09
Lew
Audiophile

Posts: 8769
Location: Bethesda, Maryland
Joined: December 11, 2000
I assume you are talking in Fahrenheit. I used the temperature probe on my Fluke meter to measure the glass temperature on the type 7241 output tubes in my MA240s, which originally sported 6C33Cs. At or near the top of the one tube I measured, I got 100 degrees C. I now cannot recall whether the tubes were allowed time to reach a steady state temperature, either. The 7241 draws 7.5A filament current and idles at 400mA in my amplifiers, with plate voltage = ~130VDC; they can easily take 500ma idle current at that plate voltage.

 

RE: Fahrenheit or Centigrade?, posted on February 6, 2017 at 09:38:19
acres verde
Audiophile

Posts: 464
Location: Big Easy
Joined: November 13, 2004
Farenheit

 

So, our temp measurements are in near exact agreement..., posted on February 6, 2017 at 10:31:43
Lew
Audiophile

Posts: 8769
Location: Bethesda, Maryland
Joined: December 11, 2000
100 degrees C = 212 degrees F.

 

Page processed in 0.024 seconds.