[time-nuts] HP 5370B Leds pulsing slowly, buttons selecting normally, PB LEDS scannning and appears to be reading o/k

[Mark C. Stephens]

Correct, C3 (17000uf @ 10v) is measuring 39uf :)
I have a 29000 at 10V, same dimensions, do you think the rectifiers can hack that big fella?
10000uf is quite a bit more.
Out of interest, this cap was replaced before, it is not a blue Sprague or Mallory but a grey Phillips Cap.


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Adrian
Sent: Saturday, 6 July 2013 9:19 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] HP 5370B Leds pulsing slowly, buttons selecting normally, PB LEDS scannning and appears to be reading o/k

sounds quite typical for a dried out electrolytic cap.
Look for the unregulated -10V that goes into the regulator circuit.
Most likely C3 on the power supply motherboard is dead.

Adrian

Mark C. Stephens schrieb:
> Checked the PSU voltages on the PSU card next to the 10811.
> The -5.2 is reading -4.2.
> Took a look with the scope and instead of a nice flat DC I see a 4V Peak to Peak spike @ 100Hz.
> Trying to track down a service manual.
> Any ideas on this one guys, if the Pass tranny was shorted, it would be a lot more than 4.2V unless the overvoltage Zener is able to sink all that current...
>
>
> -marki
>
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] 
> On Behalf Of Mark C. Stephens
> Sent: Saturday, 6 July 2013 8:18 PM
> To: time-nuts at febo.com
> Subject: [time-nuts] HP 5370B Leds pulsing slowly, buttons selecting 
> normally, PB LEDS scannning and appears to be reading o/k
>
> I went to use my 5370B todayt and noticed the LEDS on the display are slowly sort of pulsing bright one after another.
> Also all the push button LEDS are going on and off one by one.
> The strangest thing is that it appears to be working o/k via HPIB.
>
> I don't have extender boards but I do have a signature analyser.
>
> Could it be something silly like one of the PSU regulator has gone kaput?
> Has anyone seen this issue before?
>
>
> -marki
>
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