UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - TO-5 chassis mount heatsink?

G6Tanuki · 18th Jun 2015, 3:21 pm

I have a need to mount four TO-5 type transistors in good thermal-contact with a big flat-faced and large heatsink, but electrically insulated from it.

(The transistors being the thermal-sense elements of a low-source-impedance bias supply - being for a sort-of double-AN758 type linear amplifiier).

In the past it was possible to buy a cast alloy block with a very-accurately-bored hole for the TO-5 to be pressed into, which then had two smaller holes for bolts to attach the block to the bigger heatsink (with mica washer and red 'top hat' nylon insulators providing electrical insulation).

I could have sworn the ones I used 25 years ago were by Thermalloy, but looking at their website now the nearest I can find is this:

http://www.aavid.com/products/standard/1130bg

but I don't think it would necessarily have good-enough thermal conductivity to accurately (and rapidly) track the temperature of the main heatsink-block.

Any ideas? Or do I have to do a rework and use a BD135?

18th Jun 2015, 3:21 pm	#1
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	TO-5 chassis mount heatsink? I have a need to mount four TO-5 type transistors in good thermal-contact with a big flat-faced and large heatsink, but electrically insulated from it. (The transistors being the thermal-sense elements of a low-source-impedance bias supply - being for a sort-of double-AN758 type linear amplifiier). In the past it was possible to buy a cast alloy block with a very-accurately-bored hole for the TO-5 to be pressed into, which then had two smaller holes for bolts to attach the block to the bigger heatsink (with mica washer and red 'top hat' nylon insulators providing electrical insulation). I could have sworn the ones I used 25 years ago were by Thermalloy, but looking at their website now the nearest I can find is this: http://www.aavid.com/products/standard/1130bg but I don't think it would necessarily have good-enough thermal conductivity to accurately (and rapidly) track the temperature of the main heatsink-block. Any ideas? Or do I have to do a rework and use a BD135? Last edited by G6Tanuki; 18th Jun 2015 at 3:29 pm.