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8563E +28V shutdown/oscillates

 

Got an 8563E that the +28V supply shutsdown on.
Looking for CLIP for A6 power supply. Anybody got one?
I think the supply is 8563-60064 so clip 8563-90100.
+28V supply oscillates slowly - its shutting down to 2-3V, and then comes up to +14-16V, and does this every few seconds. No load about 28.5V.

I tried unplugging components to take load off.
If I unplug the A10 YTF/M from A14, voltage comes up to about +23V. Over time, voltage drops somewhat.
If I pull A15 board and YTF/M, I get 26.5V and its fairly stable.

Not sure root cause. Suspect its load/heat related. Not sure what's in the +28V supply circuit. Suggestions welcome. Trying to figure out if its either a "weak" supply or a bad load from the other boards and YTF.

Thanks
Colin VE3MSC
 

Found clip in an old agilent forum posting. Seems that I'm not getting +34V to the LM317T when under load. Diodes check out, so I guess its either bad cap(s) or too much load. Any idea what the load is supposed to be on the +28V supply?

At 09:48 AM 2013-01-12, you wrote:
Got an 8563E that the +28V supply shutsdown on.
Looking for CLIP for A6 power supply. Anybody got one?
I think the supply is 8563-60064 so clip 8563-90100.
+28V supply oscillates slowly - its shutting down to 2-3V, and then
comes up to +14-16V, and does this every few seconds. No load about 28.5V.

I tried unplugging components to take load off.
If I unplug the A10 YTF/M from A14, voltage comes up to about
+23V. Over time, voltage drops somewhat.
If I pull A15 board and YTF/M, I get 26.5V and its fairly stable.

Not sure root cause. Suspect its load/heat related. Not sure what's
in the +28V supply circuit. Suggestions welcome. Trying to figure out
if its either a "weak" supply or a bad load from the other boards and YTF.

Thanks
Colin VE3MSC





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IF it takes seconds to cycle on and off, suspect that it's overheating and
protecting itself. The junction temp would be in the 150-160C range, so the
IC would be really, really hot.

From your last post it sounds like the input voltage is what's dropping out?
That'll do it, too!

Good luck -

Dan
 

I was suspecting overheat as well, but wasn't the case. Turns out it WAS low input voltage - there were 2 x 180uF 40V caps going bad in the low voltage side feeding the LM317 regulator.
There are 4 of these caps in total, and 3 of them were degraded, so I replaced all 4 with 220uF 50V caps.
Things are running properly now. Odd thing is these caps have a useless lead coming out of the top of the can, axial style, and the working leads are radial style. So 3 leads to unsolder. Weird. Thought it might be for shielding.
Thanks everybody.
Colin VE3MSC

At 03:35 PM 2013-01-12, Dan Meeks wrote:
IF it takes seconds to cycle on and off, suspect that it's overheating and
protecting itself. The junction temp would be in the 150-160C range, so the
IC would be really, really hot.

From your last post it sounds like the input voltage is what's dropping out?
That'll do it, too!

Good luck -

Dan

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