The Aavid 92FG is all I found which isn't readily available and not cheap. Does anyone know of any cheap and readily available ones or a good DIY substitute? I guess you could give it an aluminum foil crown. There are better methods but this is inside a closed up tight linear RF amplifier with a finned aluminum heatsink for a case without any internal airflow cooling. Planing on adding some exterior muffin fans.

 

For the odd heat sink needed for a TO-92, diode etc. I have some thin copper sheets that I cut shape and adhere with thermal adhesive such as arctic silver.

 

Years ago I used these but never paid $1.57 ea for them. I see them on Amazon for 50 ea for $39.10. Then of course there is the roll your own varieties.

Ron

 

I was thinking about buying some copper foil and did buy some thermal adhesive. That may be the way to go. Ron I did find those @ 50 cents plus S&H and minimum order $s but they are half the thermal conductivity of the 92FG model. Of course the obvious answer is to find out why they are overheating and frying but haven't dug that deep into it yet. Gotta do some serious desoldering just to get the board out to unsolder the 2 transistors and a domed cap that needs replacing. In no hurry just a todo item.

 

inside a closed up tight linear RF amplifier with a finned aluminum heatsink for a case without any internal airflow cooling. Planing on adding some exterior muffin fans.

Isn't it time to look for a higher powered device when a H.S.. is needed for TO92?
Also it is often wise to vent/cool with positive pressure e.g. A filtered fan output INTO the enclosure, particularly if dusty environment.
Max.

 

Hello,

Here are some pages with alternative ideas for TO92 heatsinks:
http://tech.mattmillman.com/an-easy-way-to-mount-ds18b20-temperature-sensors/
https://digitalnigel.com/wordpress/?p=2413
http://www.theradioboard.com/rb/viewtopic.php?t=7652

Bertus

 

I keep these 2N3404 in my junk box to use for heatsinks in some DIY audio power amps where the VAS runs hot. I've also bent a small strip cut from sheet aluminium. You don't need thermal grease.

You might ask why the transistors are running hot?
Usually it's less hassle to just put in a TO-220 or TO-126 but the oversized transistor junction would be slower for RF.

 

I thought this was enterprising

 

Hello,

@peterdeco , That picture you show is from the first link I gave.

Bertus

 

Ooops. Sorry @bertus.

 

Yeah I like the yellow crimp connector idea and the first thing that came to mind with the ring was "gee you could bolt that thing to a real heatsink". I think that may be the winner here. And of course, once I get them out and ID them (can't find a schematic for this antique) I may be able to "upgrade" them. Anyway it's on a back burner for now but thinking on it.

 

A little tightening up and thermal paste and voila'.

 

Isn't time to look for a higher powered device when a H.S.. is needed for TO92?

I think the problem was the input was too high and it was being overdriven. From what info I could find without a schematic the dead key W input for the linear amp is pretty low. This would be a good amp for a QRP rig.