Am 14.11.18 um 18:41 schrieb Dr. David Kirkby:
On Thu, 8 Nov 2018 at 21:43, Dr. David Kirkby <
drkir...@kirkbymicrowave.co.uk> wrote:
On Thu, 8 Nov 2018, 14:53 George Atkinson via time-nuts <
time-nuts@lists.febo.com wrote:
Last month I was at the UK “National” hamfest and in the flea market area
a seller had a HP 58503B for sale. It was missing the cover and power
supply (AC mains version)including mounting. However it was only £3 (<5$)
so it was a no-brainer to buy it. Research shows that PSU failure is fairly
common on these units.
I had the PSU fail in my 58503A. It keeps trying to start, then stops. I
have checked capacitors with an ESR meter, but could not fix it.
Three is a good chance your unit takes the same PSU. If so
https://www.ebay.co.uk/itm/BEL-POWER-MAP55-4003-55W-Quad-Output-Embedded-Switch-Mode-Power-Supply-SMPS/132833037734
may be of interest. I had an offer of £45 accepted yesterday.
Dave.
Well, the bad news is the PSU I received was faulty (no output whatsoever),
and the seller has checked another, and that too is dead, so it looks like
he has rejects. He has refunded me and does not want the one he sent back.
So now I have two non-working supplies. The new one does not power up at
all. The old one does, but cycles on/off.
If more than one replacement unit does not work, then it is not
improbable that the switcher needs a minimum load to start.
Also, a shorted capacitor can show excellent ESR.
I once had a cycling power supply in a W&G TSA-2 spectrum analyzer.
It delivered power for some seconds, and that was enough to trace
a voltage to a faulty feedthrough capacitor. A DVM with enough digits
helps a lot. Towards the short, the voltage sinks mV by mV.
regards, Gerhard
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