On Thu, 16 Aug 2012 10:24:56 -0700 (PDT), whit3rd
wrote:


On Tuesday, August 14, 2012 11:01:12 AM UTC-7, Tom Gardner wrote:

Imagine if it only needs 5v, I have plenty of old computer PS's, any

reason I couldn't cob something external using one of those?

Yes, several reasons.
Firstly, a computer PS gives an order of magnitude more power than you
need or want (think: replacing fuse with a penny).

You obviously do not understand electricity - the device will only
take the current it requires - regardless how "stiff" the supply is.
Second, it has a fan. Airflow will pull gunk into the power supply.
Third, it's not likely to fit inside (and will be a mechanical problem to
mount nearby, and regulation suffers if it isn't close by its load).

Not hard to prevent dirt from getting in and damaging the PS, and the
regulation is not affected by distance AT ALL if the wire is heavy
enough.

Best would be to disassemble the unit and inspect the power supply it
has. Repair cracks, replace scorched and damaged components, check
fuses. It's likely the PS was ordered special, with some spares. The
DRO manufacturer didn't repair dead ones, just swapped in a spare.
And when the spares were gone, suggested 'buy a whole unit' because
that's profitable for them. No one ever TRIED to fix a power supply.

Any good electronics tech can troubleshoot and repair what you have, or
any careful technician can determine the exact power requirement for the
unit (reverse-engineer the power unit) and find an off-the-shelf replacement.

Or just do as suggested and use an external supply - oversize is NOT a
problem - undersize is.