[time-nuts] HP-58503A

EB4APL eb4apl at gmail.com
Fri Jan 2 11:15:02 EST 2015


The past week I had to replace more than 30 capacitors in various of my 
home electronics, some were bulged and others not so.
There were 7 in a computer motherboard, 10 in other, 8 in a TV set power 
supply, 2 in an external USB disk power supply and the rest in other 
things, I know the grand total because I kept it together to test a 
cheap EMS meter against a LCR bridge.
In my experience, all bulged capacitors are very ill, high ESR and very 
low capacitance, causing a lot of symptoms to appear (many of them 
intermittent).  And when a capacitor bulges normally some or all of its 
neighbors are bad also, even without any external sign. I check them 
with a bridge and this is confirmed most of the times, so I suggest to 
replace the bulged capacitor and when you are there check or replace the 
others, they will bulge or burst in short time, high ripple currents and 
heat makes electrolytics the less reliable electronic components today.

Best regards,
Ignacio EB4APL

On 02/01/2015 a las 14:34, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
> On 1 January 2015 at 17:03, Andy Bardagjy <andybardagjy at gmail.com> wrote:
>> Sounds like the GPS receiver is hosed. I think there are two different receivers used in the 58503a, unfortunately I'm away from my lab, otherwise I could check mine. It is a standard part, and may be available on the surplus market.
>> Before replacing, I'd check the usual suspects, power supply health (look for failed electrolytics) and re-seat the gps board to board connector.
>> Happy to measure things on my 58503a.
> The fact it originally failed with errors indicting the GPS receiver
> was not ok (nt Power- OK, OCXO- OK, EFC-OK GPS RCV-err. I, but later
> he can't communicate with the 58503A over RS-232, to me indicates the
> problem is not likely to be the just (if at all) the GPS receiver.
> As you say, power supply is a possible problem.
> I have a 58503A here that has a problem. Sometimes when power is first
> applied, the "Alarm" light stays on, and the log show power supply
> voltage errors. Yesterday I must have switched the thing on/off about
> 30 times before I managed to get the "Alarm" light to stay on. At the
> time I had a handheld DVM connected to the +15 V rail with the "peak
> hold" mode enabled. At least according to the handheld DVM, the +15 V
> rail was normal, so either the transient is too short for my handheld
> DVM to see, or the 85050A is reporting data voltage data incorrectly.
> Both are fairly like I suspect.
> I noticed a *very* slight bulge at the top of on a 100 uF, 400 V
> capacitor on the switch mode power supply.  For various reasons, I am
> not going to change that cap now, but obviously a failed cap could
> cause this sort of problem.
> Dave

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