OMG, What a Monstrosity!

It looks like either a voltage regulator or load bank. Just think of the quasi-complimentry audio amp you could make with that! With 80 transistors in parallel for each half the output impedance would be under .1 ohm.

With no real heat-sinking it's more like a couple of watts each.

Nah, the amount of heat sink area per transistor is way too low for such an application.

I think it's more likely that it's a medium-current (maybe 10-20A) power selector/multiplexer for turning individual loads on and off.

There does seem to be some heavy bus wire snaking around all the transistors. If it didn't snake around all the transistors, I'd guess it to be some point of power cross-point switch.

Tim.

The OP mentioned the liquid-cooling pipes visible in the second photo...

I thought that was a bussbar paralleled with a PC trace, although now that you point it out to me it looks more like plumbing. (How the transistors are heatsinked to the plumbing I cannot quite fathom).

Tim.

I may be wrong but it looks quite like a transistor memory circuit from a computer with water cooling, there are capacitors on each transistor and two banks of 12 connections possibly for addressing the memory cells and a further 8 connections down one side maybe for a data bus?

Chris

The pipe zigzags between the transistor rows, probably brazed onto the metal plate holding all the transistors. The pipe in the middle is the cool water inlet feeding two zigzags with outlets on each side.

When you consider how long it takes 3kW to heat up a pint of water in a kettle this heatsink would be good for several kW.

I used to work on IBM mainframes which took around 150kW of power (the previous generation took nearer 400kW). They used a 400hz 3ph supply to reduce transformer size. The transformer assemblies included a rectifier pack and had similar pipe work for water cooling. The logic boards were forced air cooled with water filled radiators between the card frames. Each frame had a local regulator for the ECL logic supplies which was a water cooled block with a bunch of TO3 transistors mounted on it. All the cooling was chilled to a few degrees C.

When you commissioned one of these machines you used to get a jar full of white powder to put in the water system, they said it was a corrosion inhibitor but we always reckoned it was the ashes of deceased IBM employees.

Some numbskull deleted the part of my post where I said that upon closer inspection, I saw the water cooling tubes.

Totally WAG.

If you look closely you'll see the cooling tubing apparently brazed to the heatsink. That's all that's needed.

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That strikes me as odd. Is it supposed to be a jab at IBM. or is it supposed to be an extreme example of their employees' devotion?

If you had worked for IBM in the days when mainframes took 300kW you would understand (in the UK anyway, I expect it was the same elsewhere). Most regarded it as a job for life, we were just speculating it continued beyond the grave.