TO-3 power transistor orientation

[polsol]

In power amps, from memory, I've only ever seen TO-3 power transistors orientated with the 'top hat' section upwards when horizontally mounted on heat sinks.
I assume there wouldn't be a problem mounting them 'upside down' with the terminals at the top?
The reason for doing so is that I need more clearance between the connecting leads and the amp boards themselves.
So I thought it better that I should ask before trying.

 

[adason]

sure, its all good, as long its thermal transfer is adequate

 

[JonSnell Electronic]

Like a resistor, it makes no difference upside down, on its side etc.

 

[T117]

The resistor dissipates power better in a horizontal position.

 

[AndrewT]

A To3 has the emitter and base pins offset so that it cannot be inserted the wrong way around.
But if you offered up from the reverse side of the board you would be swapping the emitter and base leads.
You would need to redisgn the layout to specially suit upside down mounting.

 

[polsol]

Thanks for the respondents thus far.
Not knowing how these transistors are fabricated (or more so how the chips are bonded to the shell) and would affect the bonding.
I thought this would be the case.
If it wasn't I guess that they wouldn't work in the Southern Hemisphere.

Thought it circumspect to add a for the later comment

 

[rayma]

how the chips are bonded to the shell.

https://upload.wikimedia.org/wikipedia/commons/d/d9/Darlington_transistor_MJ1000.jpg

 

[polsol]

A To3 has the emitter and base pins offset so that it cannot be inserted the wrong way around.
But if you offered up from the reverse side of the board you would be swapping the emitter and base leads.
You would need to redisgn the layout to specially suit upside down mounting.

Thanks Andrew, taken care of.
The leads are 'flying' from the PCB to the power transistors so that's not a problem.

 

[polsol]

https://upload.wikimedia.org/wikipedia/commons/d/d9/Darlington_transistor_MJ1000.jpg

Thermally fused or mechanically inserted rather than with an adhesive?

 

[sreten]

Hi,

There is no problem upside down underneath
a heat sink flange, as opposed to top mounting.

As said the two pins will be reversed though.

rgds, sreten.

 

[polsol]

Thanks everyone for their input.
Highly appreciated.

 

[Welcome]

They're best mounted on a rotating spit, for even heat distribution.

 

[polsol]

They're best mounted on a rotating spit, for even heat distribution.

Can you recommend a noiseless motor though?

 

[rayfutrell]

A To3 has the emitter and base pins offset so that it cannot be inserted the wrong way around.

Actually they can be. I once saw a TO3 transistor inserted in the socket backwards. They had to bend the pins to fasten the transistor to the heat sink. I called all the technicians over and asked what bleeping idiot did this. Naturally no one would admit to doing it. There's an old joke that you can't make anything foolproof because the fools are too ingenious.

 

[Welcome]

If you make something idiot proof, someone will just make a better idiot.

 

[polsol]

"There's an old joke that you can't make anything foolproof because the fools are too ingenious."
"If you make something idiot proof, someone will just make a better idiot."

Thanks for those, actually hadn't come across them before. Provided me with an early morning chuckle.

 

[Enzo]

One of my favorite bits of dialog, and I cannot recall where it is from:

"What kind of fool do you take me for?"

"First class."