Re: HP-8753E Power Cycles at Start Up
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Not so easy to recap. Do you have a list of suitable replacements from DigiKey or Mouser? How do you get the boards out? Do I have to unsolder anything? Is the power switch mounted?to the PCB? I have the PreReg supply split open. I also do not think this is the problem because the manual troubleshooting points to the +5v supply which is where my troubleshooting pointed?from a different?direction. If the?caps are easy to get at with the boards out I can check them for value and resistance. I prefer to identify a?definite fault rather than randomly replace components.? I put the?8753B on a?variac and dropped?the?voltage to 100VAC but could?not?trigger the fault. This probably eliminates the rear half of the PreReg with the two big capacitors,?but not the front board with the six big?caps.? It worked fine for?a?few hours but the next time I turned it on the?fault returned. I took?the?Pr-Regulator out and split the?module and turned it on and it?is back to working perfectly. I wiggled all?connectors?and cannot?get?it to quit again. I don't think it is a bad connection. I checked the current in all wires to the display when the fault was happening and there was nothing obvious (disconnecting the display cured the fault repeatedly but it was only because it dropped the drain on the +5v. It is an LCD display). It seems more like a marginal?trip point setting which is why I have the supply open.?
On Sun, Aug 28, 2022 at 4:42 PM tony sayer < tony@...> wrote: In message <[email protected]>, Burt K6OQK
<biwa@...> writes
>? ? Rich,
>
>? ? I have cured a lot of weird problems by fixing the obvious things
>? ? first.? I suspect that if you were to re-cap the power supply
>? ? module you would be pleased.? That's been my experience in 90% of
>? ? the symptoms you describe.
FWIW - Mine too!...
>
>? ? Burt, K6OQK
>? ?
--
Tony Sayer
Bancom Communications? ?U.K.
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