Derek ^ wrote:

[Sinclair X10]
Did it work? I was at uni at the time studying electronics. The
lecturers poured scorn on it because the output transistors and diodes
did not have good enough characteristics to switch off the current
pulse through the inductive voice coil of the speaker without a lot of
power loss. Sure enough the only one I ever saw had burnt out output
transistors.

Work? Not in any meaningful way, no. The output devices didn't blow up,
but did run "rather warm" and any audio output I managed to achieve was
grossly distorted. Also the output was completely unfiltered with the
result that reception of the Light Programme on 200 kHz was completely
wiped out. I went back to EF86s and EL84s after that experience...

Legend has it they had been used as hard core under a new drive.
Sinclair bought them and paid to have them dug up.

I've never heard that one before. I thought the "transistors as
hardcore" story related to Mullard Research Labs (later PRL) at Redhill?

Thinking back it must have been just before the UK semiconductor
industry went over to silicon. They could have been the tail end of
Ge. transistor production ??

I suspect that came later. The Mullard/Philips alloy junction devices
(AF115/6/7) had a long run in portable radios and also TV IF strips.
Then the early transistorised UHF TV tuners had Ge devices (AF186, IIRC).

--
Andy