Seeing as we're on Sinclair and I'm bored, some trivia for people.
Sinclair Radionics was the main company in the late 1970's of Clive Sinclair, the slightly less competent Madman Muntz of the UK. He produced all the consumer crap you're all probably aware of but also developed some test gear.
No coincidence it looked like and shared a lot of parts with this equals button encrusted scum imposter calculator:
Eventually they evolved into something usable-ish:
About then they started developing something a few of us own today!
Perhaps unsurprisingly being Clive, he buggered the company thoroughly, it got bought out by NEB (Labour's scheme to try and get large businesses under state control), who buggered it further, also unsurprising. Clive Sinclair and Chris Curry (guy who founded Acorn and ARM) bailed out. Sinclair went in the direction of computing with Sinclair Research as did Chris Curry who had enough of his shit pretty damn quickly and started Acorn
The company was renamed by NEB to Thandar Instruments. Familiar name.
Looking a bit more familiar now. In fact Thandar made a lot of test gear which stacked neatly:
They even reused the CRT from Sinclair's failed NEB portable television effort to make a scope, the one pictured below I repaired a few years back:
Now onto an interesting thing. I have only ever seen one in existence in the rotten test gear stores of Cossor, but yes there was an actual Sinclair branded power supply called the PL310 back in the day. I think it had a VERY short run before the company was rebranded to Thurlby. But it did indeed exist and had Sinclair at the top left instead of Thurlby. That might explain why the first run of them was "problematic"
I have considered creating a web site archiving information and manuals for British test gear manufacturers recently as a lot of this history is missing or fragmented.
Edit: also a point to make. One of Sinclair's most amazing products was a digital watch which exploded regularly. Current drain was pretty high so it'd finish off the sealed button cell batteries very quickly which would over-discharge and explode. My daughter has an illuminated llama toy which has them in it which suffers from the same thing. It occasionally goes BANG! rather loudly in the middle of the night. You wouldn't want it on your wrist