Power Trans. Sockets or not

[mashaffer]

What are the pros and cons of using sockets for power transistors. (TO-3 and TO-220)? I like the idea of not having to solder (and desolder for replacement or modification) the leads directly but am concerned about having good contact (and cooling with TO-3).

I have one amp that uses TO-220 for drivers and output transistors and my plan is to bolt directly to the heat sink (using heat sink compound) and then isolate the entire heatsink from the chassis. I would like to use sockets or some other push on connectors for the wiring though. Any advice on this (whether to do it and what to use for connections).

mike

[anatech]

Hi Mike,
I've seen too many amps to count over the years, and most used sockets with TO-3 transistors. The only bad or burned contacts have been with poorly serviced units. Provided you use good sockets I don't see a problem here.
-Chris

[ilimzn]

Originally posted by anatech
Hi Mike,
I've seen too many amps to count over the years, and most used sockets with TO-3 transistors. The only bad or burned contacts have been with poorly serviced units. Provided you use good sockets I don't see a problem here.
-Chris

This is my experience also. One warning though, you should avoid using TO3 parts that were previously soldered, in sockets, and also prevent thermal grease from getting into socket contacts.

[rpapps]

Hi
I'm showing my age here but years ago I used to service mainframe computer systems for Honeywell.
A particular model of multi platter hard disc drive used a voice coil type structure to drive the head positioner.
All the transistors on the driver board were socketed for ease of replacement.
This product had a high failure rate due to transistor burnout on the driver board. Oxidation of socket contacts caused some transistors to not conduct forcing others to take the load resulting in overheating and failure.
My solution, remove the sockets and hard wire the transistors.
The drives had a much better uptime afterwards. (I got an award)
Just my two cents worth.
Cheers
Rob

[Tony]

the leach super amps published in audio magazines used sockets for to-3's. but then the pins for the base and emitter contact pins from the sockets were actually soldered to the pins of the to-3's. this was how dr. leach did it!

[anatech]

So then, what was the use of using sockets in the Leach? On higher current transistors (20A and up) there may be a higher rated socket, but you are better off soldering these. For normal output transistor use the currents should not be that high or you are beyond the SOA curve. And .. use a decent brand of socket. You can't blame all sockets if someone uses cheap ones.

-Chris