Hi, just had to literally strip down a old Pioneer VSA-E07. While I'm in there I thought best to put new grease on the amp transistors, but, what type of grease do I need?
General purpose heatsink compound is fine.
https://cpc.farnell.com/servisol/20...g-tube/dp/SAHEATSINKCOMP?st=heatsink compound
https://www.farnell.com/datasheets/1792677.pdf
https://cpc.farnell.com/servisol/20...g-tube/dp/SAHEATSINKCOMP?st=heatsink compound
https://www.farnell.com/datasheets/1792677.pdf
PC/CPU thermal grease (ie, Arctic Silver) is usually conductive. You either need to be either extremely lucky or extremely careful to get away with using it to mount TO-3 or flatpack power transistors. The white stuff is less thermally conductive, but you don’t need to take pains to prevent shorts from collector to heat sink.
On amplifiers with grounded collectors (typical hi-fi amps don’t do this), you can go ahead and use AS.
On amplifiers with grounded collectors (typical hi-fi amps don’t do this), you can go ahead and use AS.
The type of thermal compound that you use is less important than the flatness of
the surface of the heatsink and the parts, the idea is to keep the grease as thin as possible.
Mayonnaise is not bad. You just need somthing to fill the voids between two surfaces.
the surface of the heatsink and the parts, the idea is to keep the grease as thin as possible.
Mayonnaise is not bad. You just need somthing to fill the voids between two surfaces.
Last edited:
Mayo may be pretty bad after 10 or 20 years.
You do want it thin. Squeegee it on with a razor blade. When it’s right, the surface tension will hold the two together like a suction cup - they will take some force (or twisting) to get them apart.
You do want it thin. Squeegee it on with a razor blade. When it’s right, the surface tension will hold the two together like a suction cup - they will take some force (or twisting) to get them apart.
It would be best to read the product datasheet. Some thermopastes have dielectric resistance declared (e.g. 15...45kV/mm), some declare that the product is non-conductive, Arctic Silver 5 states:
"Not Electrically Conductive:
Arctic Silver 5 was formulated to conduct heat, not electricity.
(While much safer than electrically conductive silver and copper greases, Arctic Silver 5 should be kept away from electrical traces, pins, and leads. While it is not electrically conductive, the compound is very slightly capacitive and could potentially cause problems if it bridges two close-proximity electrical paths.)"
https://www.arcticsilver.com/as5.htm
I had a bad experience with the Arctic Silver#5 when I built some Rod Coleman regulators. While on the breadboard my voltages would sometimes be fine and then on next start-up they'd be not correct. Rebuilt the whole circuit more than once. Finally seemed to correct after I cleaned off the Arctic Silver 5 stuff and replaced that with the Kera-therm pads. I couldn't measure any conductivity but that is was it seemed to be. I am a novice builder so I hate to point fingers. I believe Rod Coleman prefers one utilizes mica with thermal compound over the pads.
Ah, I seee, I'll take a look at the service manual, if not there I might use pads instead? Seems to be good to use?
Silicone thermal pads allow you to operate without having to use thermal goo, but they are generally not quite as good as mica with goo. Mica is on the whole is a pretty poor heat conductor - It works because the insulator is thin. The combination of mica and thermal compound gets the job done.
Its better to use tomato ketchup than use mayonnaise or better still the best of both worlds: ''SAUCYSAUCE''. But Australia is too far away from me.....
. I personally use out-of-date sun-cream which handles just fine🙂. Now seriously: Kera-therm V.S. combination of mica and thermal compound-for TO-204-2/TO-3/?
. I personally use out-of-date sun-cream which handles just fine🙂. Now seriously: Kera-therm V.S. combination of mica and thermal compound-for TO-204-2/TO-3/?
Last edited:
Mica and grease for TO-3’s. Sil-pads for flatpacks. Why? You have to do TO3’s one at a time (even in large groups). For a bank of flat packs, you use a single strip cut from the 12”x11” squares they sell. That’s hard to do with mica and grease.
AS5 is conductive enough to be a pain in the ***. Other formulations we use at work to mount microwave power devices are very conductive. With lesser formulations you get too much ground inductance (since it only grounds well through the mounting screws) and you get an expensive inefficient high phase noise oscillator instead of a power amp.
AS5 is conductive enough to be a pain in the ***. Other formulations we use at work to mount microwave power devices are very conductive. With lesser formulations you get too much ground inductance (since it only grounds well through the mounting screws) and you get an expensive inefficient high phase noise oscillator instead of a power amp.
