How much clearance does a PT need?

[PharmRock]

As mentioned in other posts, I am building a hybrid 50w plexi/jcm800.  The new build will be housed in a head cab that I had for an 18w TMB , which is a little shorter than your typical head cab.  The PT I am using for this amp is a standup transformer, and when test mounted on the chassis I end up having about 3/4" from the top of the transformer to bottom of the top board of the head cab.  The cab has a top and rear vent. 

Is there anything I need to worry about with the limited clearance between the PT and head cab? I know that PTs can get a little warm, but I'm figuring that with the vents I should be ok. 

Thanks for the advice!

[Latole]

3/4 inches clearance; it is not very much and with heat from Power Tubes.....

With a top and rear vents, Yes it is ok. IMO.

Picture of the top vents will help ; how much square inches ?

[tubenit]

I use stand up PT's in my amps also.  And add vents above the power tubes.

With respect, 10thtx

[scstill]

That is a great question. First pic is my nice and tight vintage car radio with PT and 6v6 glass PushPull 10w.
I'm repurposing to a 5c3 style guitar amp (second pic). Hope heat doesn't come back to burn me :-)

[jordan86]

As other have stated, Id be more concerned about Power tube heat. Less so about power transformer. I’ve never had one get THAT hot. I’d prioritize venting to the tubes if it were me. In the end, will probably cause more pain to your head cab more than your tubes and tranny.

[PharmRock]

3/4 inches clearance; it is not very much and with heat from Power Tubes.....

With a top and rear vents, Yes it is ok. IMO.

Picture of the top vents will help ; how much square inches ?

Both vents are pretty decent sized.  The top vent is 16.5x1.25 (~20 in²) and the rear vent is 14x2.25 (~30 in²).  Pics attached. 

The interior volume of the cab is about 1600 cubic inches, with my 17x8x2.5 chassis taking up about 340 of that. 

That is a great question. First pic is my nice and tight vintage car radio with PT and 6v6 glass PushPull 10w.
I'm repurposing to a 5c3 style guitar amp (second pic). Hope heat doesn't come back to burn me :-)

That looks like a much tighter fit than what I'm fretting over!  Hope you have some good ventilation for it.

I use stand up PT's in my amps also.  And add vents above the power tubes.

With respect, 10thtx

That's a great looking cabinet tubenit.  I really like the circular ventilation holes.  Looks "organic".

[Bieworm]

I use stand up PT's in my amps also.  And add vents above the power tubes.

With respect, 10thtx

Wow!!! That's almost a very exclusive piece of furniture.  Perfect for storing expensive bottles

[HotBluePlates]

I use stand up PT's in my amps also.  And add vents above the power tubes.

Wow!!! That's almost a very exclusive piece of furniture.  Perfect for storing expensive bottles

Tubenit does some outstanding & very beautiful woodworking!  Don't forget to check out his guitars.