Electronics > Repair
Quick Repair: Standford Research PS350 5KV 5mA(Fixed but working on calibration)
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smgvbest:
I thought this would be a longer repair log but it's going to be really quick.
I got a PS350 off eBay for a decent price (made an offer and was accepted)
Listing stated for parts/not working.   transformer loose inside unable to test.

This is the only image I had before the repairs


I I got it and indeed something was loose inside.   I opened it open and barely hanging on was the large 2amp 750uH Inductor 
I did not do any kind of power test at this point for safety reasons.



This was the bad boy



I removed it completely and tested it on the LCR meter and it measure at 775uH and everything else was in spec so it was good but the legs were busted.   I found and ordered a replacement (Part # is  HL-20154/AB from hurricaneelectronics.com.) then thought since it was measuring high anyways I could try un-winding the legs 1/2 turn to lengthen them. which I did.  trimmed to length and cleaned the ends and measured it at 749.3uH (can't beat that) put it back in and gave it the power on test.

It came to life.



so now it was powering up.   I did some quick tests and thing looked ok but there where several switch issues.
on the rear the Set/Mon switch was busted so I replaced it

this is the switch I replaced


and this is new one in place



next I found the front panel Off/On/Trip switch was not functioning correctly in the off position.  ie. once the HV output was enabled it could not be disabled via the switch.  only a power off or a condition which tripped a limit would disable the output

in this image it is the black switch on the left


I removed the switch to properly test is and indeed the off position was always open.  the momentary switch part worked fine so you could enable the output.

this is the switch from the back side.   removing it was easy but the front panel had to be removed to make it easier to work with.


this switch is a Marquardt 1808.0202 6A IP40 Momentary Rocker Switch SPDT On-Off(On).   finding this one was a pain and only found it in the UK.   so again I ordered the part then figured I would try repairing the switch (something I've not done successfully before)

so I opened it up and the contacts where crusted. I pulled the center rocker bar (don't know correct name for it) out and sprayed the whole thing in contact cleaner.  let it set for a bit the used a q-tip to get in there and get that crusty stuff out.   after not to long a time I got the contacts looking pretty good and after reassembling the switch was surprised it worked (meaning it moved to each position correctly, which is usually where I've gone wrong.   I put it on the meter and tested each position and they all worked now.  So I put the switch back in.

While i had it opened I noticed 3 chips where not populated.


these are the GPIB interface chips including the
TMS9914A
75160A
75161A

on the back you see that Opt 01 is installed but these chips and the GPIB connector are not there



I located the IC's on ebay and ordered them.   and I found a GBIP connector with break/out board that will allow me to wire up the 24 pin ribbon correctly I hope and restore the GPIB interface

so now that all that was done I gave it a power on and Low and HV test
this is at 50V


Now shown is my meter reading 50V also so it was working find at a low voltage.

next I hooked up a 1000:1 HV Probe to my meter and connected to the output of the PS350 and programmed in 5000V
after hearing the static sound of it charging up I read 4.996V on the meter so I was getting 4996V out of this supply. :-+



The front switch now worked and I could now turn off the HV output.

I checked more voltage settings and all where within tolerances.

A few final clean up items.  the main board needs a good cleaning off which I have yet to do.
I repaired the case and cleaned it up also

which you may have noticed in the front pictures
here's a side photo as well



all the screws were rusted so I took some fine sand paper to them and cleaned it off the a ultra black paint marker and restored the color to them.  I had to repair the front face as it was bent badly and the rear of the case was bent also which I repaired.

I think I can call this fixed, it was a easy repair really

I also did find the schematics for it so have them as a reference.
Standford wants $100 for the hard copy of the manual with schematics for those wanting original.  you can order on their site www.thinksrs.com

hope you enjoyed this even though I forgot the before photos.

Sandra
alm:
That unit must have been abused. Mechanical damage on the inside, back and front. Maybe shipped loose in a box and knocked around? Dropped multiple times? Seems very smart to me to treat a HV power supply that way :P.
smgvbest:
good question and very probable. I will say it arrived to me packed very well with a hard foam all around and it was centered in the shipping box which was oversized.

but i agree,  who ever owned it or worked on it (though I see no signs of anyone working on it) was very rough on it.
BFX:
 :-+ nice repair and nice photos  8)
enjoy new gear  :-DMM
eb4eqa:
Nice writing and pictures. Thanks for sharing.

Roberto
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