23 Aug
2014
23 Aug
'14
11:30 p.m.
On 8/23/2014 7:12 PM, Chuck Guzis wrote:
Josh,
I'd first try lifting one side of CR22 and see if your +5 returns.
If not, you can remove IC 63 (probably what, a 7805?) and see you can
read anything at the high side of C67. You should be able to--unless
you've got a bad diode.
If the CR22 maneuver doesn't result in any improvement, then you've
probably got a fault somewhere else on the board. Make a quick
resistance check while you have IC 63 out with the power off, checking
the resistance between the +5 lead and ground.
That should get you started on where to look.
--Chuck
Thanks! Lifting CR22 (which took awhile to find, it's actually clear on
the other side of the PCB from the rest of the supply) made no
difference in behavior.
Removing IC 63 (which is a 7805, nice guess) and reading voltages on the
positive lead of C67 yields about 15VDC. The resistance between the +5V
lead of the IC63 socket and ground is about 3.5K ohms, so it doesn't
look like there's a dead short here. Would the 7805 be a likely suspect
here? Any easy way to test it?
Thanks,
Josh