Restoration: how far should it go??

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Sun Jun 15 14:56:19 2003

> My Jupiter Ace, BTW, is almost repaired. I've got the 16K RAM Pack, manual
> and demo tape for it. The only thing missing is the power supply. If I can't
> locate an original PSU, I'll build a one-amp linear regulated 9V PSU with a
> "crowbar" overvoltage protection circuit. Yes, I'm paranoid enough to add a
> crowbar...

Fairly pointless. The only thing that 9V supply feeds is a 7085
regulator. If that fails, then the 9V will cook the chips anyway.

The original PSU is unregulated (just transformer, bridge rectifier,
smoothing cap). There's little point in regulating it -- the 7805 will
stand up to 35V on the input IIRC (it may well go into thermal shutdown
if you give it excessive voltage, but it shouldn't short). No sensible
fault in a simple unregulated linear PSU will make the output go up by a
factor of 4 or so.

If you want to add a crowbar, put one set to trip at a little over 5V
across the 5V line on the Ace's PCB...

> I try and replace as little as possible. If a chip has failed and I've got
> both a replacement chip and a replacement board, I'll fit a socket and use
> the chip. If I need to, I will repair damaged tracks on the board.

Me too. And I also regard sockets as a sensible modification. But I only
ever used turned-pin (machined pin) sockets now. Yes, they're expensive,
but so is my time in tracing bad connections.

> with a solder-sucker. NEVER use desolder wick on through-hole boards - it
> eats pads and tracks for breakfast.

The only use I've found to solderwick is to clean up the pads on an
SMD-based board when replacing a component there. I never use it on
through-hole boards.

-tony
Received on Sun Jun 15 2003 - 14:56:19 BST