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
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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
