[time-nuts] HP Z3801A Internal Power Supply issues

Alex Pummer alex at pcscons.com
Sun Jan 31 05:04:33 UTC 2016

power supply runs for a while, output current increases, but voltage 
stays correct -> problem is in the load circuit, load circuit working 
for a while load current increases, but it recovers after pause -> look 
for some tantalum capacitor in the load circuit, they recover often  a 
few times before they finally die,

On 1/30/2016 6:21 PM, Artek Manuals wrote:
> My Z3801A began to die over the last few days. It would work for an 
> hour or two then produce a receiver error and communications problems. 
> Turn it off, let it sit awhile, back on and it would start the survey 
> and then begin to recover. Tonight it finally went dead with high 
> current on the main input . The feed supply has a 2amp current limit 
> so I have not blown the two 3amp fuses
> I have a schematic of the supply reverse engineered by Stefan 
> Hegnauere a few years ago (thank you very much) and a limited theory 
> of operation description so I am not totally dead from a 
> troubleshooting point of view although if one of the DC-DC converters 
> is dead then I will likely have to scrap the supply
> Questions
> 1) Any prior experience as where to look first I checked the 
> electrolytics and at first glance they seem fine, no loss of magic 
> smoke or any parts obviously hot or bulging. ESR 's look good on those
> 2) Will this supply function unloaded while I troubleshoot it on the 
> bench out of the unit?
> 3) Anyone tried independent powering the Z3801? looks like two 5V 
> supplies and +/- 15V..not hard to to do
> 4) Anyone with a good supply from a parts unit want to part with same?
> Dave
> ArtekManuals.com

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