Tubes to hot?

vigorianer · Aug 27, 2022

I fitted my 2 90 with new 6L6 tubes. Latest model.
on the back I have a grid cover. When measuring the temperature, I have left - fan side 25 degrees and right - 50 degrees.
the temperature builds up here.
Do the tubes burn faster here than on the cooler left side?
What do you all mean?

Henz · Aug 27, 2022

With the fan hitting channel A the most, one would think that those tubes would last longer than the tubes on ch.B . But it may not matter. Some boogies don't have any cooling fans.

vigorianer · Aug 27, 2022

however, these 2 90 models do not use rear grilles.
The air can circulate more evenly here. In my model, the difference is very large. Any experiences?
Also use TAD REDBASE tubes with PC 31 = ??

Henz · Aug 27, 2022

Mine has no grill. But my tubes on channel B definitely run hotter to touch. I have no experience with TAD tubes. Did you mod your 2:90 to put the grill on?

Henz · Aug 27, 2022

Hey brother, are you comfortable removing the cover of your 2:90 ? I have had mine powered down for a few weeks or so. I put it on the bench. I took some continuity measurements and I'm getting continuity where I believe I shouldn't be and I don't have anyone locally that owns one to compare. Strange, very strange. For example, if I take a probe from my voltmeter and put it on the feedback lead on either channel and touch the first cap (.1) , I get continuity. That's completely two separate channels. There should be no continuity. Other areas in the amp as well. Based on the schematic, it makes no freaking sense!

vigorianer · Aug 29, 2022

I drilled my grill on the right side - without a fan with 5 x 12 mm holes so that less heat builds up here. During the subsequent measurement, the temperature remained at 50 degrees, but the waste heat was able to dissipate more quickly. Must relieve the grill even more on the right side to achieve even cooling.