1 Aug
2015
1 Aug
'15
1:36 p.m.
On 2015-Aug-01, at 1:26 PM, Eric Smith wrote:
On Sat, Aug 1, 2015 at 2:14 PM, tony duell <ard at
p850ug1.demon.co.uk> wrote:
The circuit used in the PS only ties the reference output (pin 6 of
the DIP) to the non-inverting input of the amplifier (pin 5), so I
don't think there's any other likely explanation, though since I
haven't actually been able to pull the board out yet to inspect it
more closely, I suppose there might be a very small chance of
something else being shorted to those pins.
Just a suggestion: you're sure there no ground reference problem on pin 7 (V-) of the
723? (hence raising the Vref).
I've seen small 723-based supplies with sense leads where the 723 V- is on the neg.
sense lead rather than neg. output lead.
The root
cause of the failure appears to be that the internal voltage
reference of the uA723, which is specified as 7.15V ?0.35V, is now
9.4V. The uA723 needs to be replaced. The uA723 is still readily
That's an unsual failure. I've had 723s go internally short-circuit and
then the output voltage is essentially the input voltage, but never
seen the reference drift.