Solartron PSU strangeness.

[beam me up schottky]

Recently bought a Solartron AS1412.2 bench PSU. Opened it up for a nose about, as you do with a new toy, and found an aspect of it's construction that I've never seen before.
Red heatsinks on the pass transistors !! The fins are red and the flat centre section where the transistors are mounted is natural aluminium.

Anyone seen red heatsinks before ? Any thoughts on why red ?

[AlanBeckett]

Yes and no.
In the attic I have some TO5 ones which look like motorbike cylinder heads. Some are blue and some are red although I don't know, or at least can't remember, why.
Alan

[Skywave]

Red heatsinks on the pass transistors !! The fins are red and the flat centre section where the transistors are mounted is natural aluminium.

Anyone seen red heatsinks before ? Any thoughts on why red ?

Yes, I have seen them before: they're TO-3 heatsinks, aren't they? I've also seen TO-5 heatsinks in that colour, light/bright blue, green and the common black. I've also seen red aluminium blocks for a pair of OC81 that could thus to be thermally joined as well as providing a heatsink. This colouring is brought about my an aluminium process called anodising (if my memory serves me well). This all started about the mid-'70s. I do believe that certain manufacturers simply used the colours to try to distinguish their particular products from the competition. Perhaps it was 'Redpoint' that went in for red; perhaps it was 'Redpoint' who started the whole colour fad off in the first place.
With passing of the years since, traditional black is now the colour - which makes engineering sense, since that is the colour that will give the most efficient transference of heat to the surrounding air.

Al.

[beam me up schottky]

As you say Al, any other colour than black doesn't make sense from an engineering perspective, as in black body effect. They are TO 3 heatsinks, I wonder if they are Redpoint, I remember that brand. Will have a look later.