Calibrate an E3611A and E3614A HP power supplies

[drakke]

There are functional as far as I know but I would like to calibrate it. The service manual specifies that I need an electronic load and a load resistor to perform the calibration.

Has anyone done this without the electronic load (I am just a beginner)?
Where can I get a load resistor?

Thanks.

[sync]

Use a multimeter in amps mode directly connected to the power supply (instead of the load resistor). The accuracy of the multimeter in the amps range should considerably better than the 0.5% of the power supply meter.

btw: open the power supplies and look for leaking electrolytic capacitors (dark discoloration of the PCB tracks). I just repaired an E3611A which had them.

edit: no electronic load is needed for calibration.

[rdl]

If you haven't already, check for any "Service Notes" you may need to take care of.

http://servicenotes.literature.keysight.com/litapp/SearchSN.do?method=openExternalSNSearch&prodNum=E3611A

http://servicenotes.literature.keysight.com/litapp/SearchSN.do?method=openExternalSNSearch&prodNum=E3614A

[drakke]

Thanks everyone for all the help.

The voltage readings of the E3611A are out of spec. I tested with a multimeter directly attached to the posts.

20v range: 0-33v, 1-1.60A (should be 0-20v, 0-1.5A)
35v range: 0-40.8v, 0-0.90A  (should be 0-35v, 0-0.85A)

It looks like something is broken. Is this a miscalibration or a malfunction?

It is a little dirty outside and in. And the current knob has a bent post but still seems to work. Replacement Bournes pots are relatively cheap on ebay.

I also looked at the 'service notes'. How do I know that a modification has not already been done? Do I check for the error/symptom?

[sync]

20v range: 0-33v, 1-1.60A (should be 0-20v, 0-1.5A)
35v range: 0-40.8v, 0-0.90A  (should be 0-35v, 0-0.85A)

It looks like something is broken. Is this a miscalibration or a malfunction?

That is normal. From the manual:
Operation Beyond Rated Output
The output controls can adjust the voltage or current to values
above (up to 5%) the rated output as indicated on the front
panel display. Although the supply can be operated in the 5%
overrange region without being damaged, it can not be guar-
anteed to meet all of its performance specifications in this
region.

The 20V range is usable up to 24V at full load (depends on mains voltage). Above there will be ripple on the output.

I also looked at the 'service notes'. How do I know that a modification has not already been done? Do I check for the error/symptom?

The service notes specify the serial numbers which are affected. Then check the power supply (components) if the modifications are already done.

I would make following modification:
E3611A-02

E3611A-04
I found 6.8uF too much. It makes the voltage adjustment too slow. 1uF is ok. A 35V rated cap is not good. There are the 40V output voltage across it. 50V or higher is ok. It doesn't have to be a tantalium. A film or ceramic is ok.

E3611A-06A
Use a 3W or more rated resistor. It will get very hot (at 40V output voltage). My goes over 120°C. Keep space between the PCB and the caps (see picture). I think a 1.5kohm resistor will work too and won't get so hot.

Then I would make the following modifications only if it oscillates.
E3611A-03
E3611A-05

[rdl]

I don't know, both those readings are way more than 5%.

33 volts from a 20 volt supply? That is more than an order of magnitude more than the 5% the manual says should be possible. My 16 volt E3610A only adjusts up to about 16.8 volts. I'd be very suspicious that something odd was going on.

20v range: 0-33v, 1-1.60A (should be 0-20v, 0-1.5A)
35v range: 0-40.8v, 0-0.90A  (should be 0-35v, 0-0.85A)

It looks like something is broken. Is this a miscalibration or a malfunction?

That is normal. From the manual:
Operation Beyond Rated Output
The output controls can adjust the voltage or current to values
above (up to 5%) the rated output as indicated on the front
panel display. Although the supply can be operated in the 5%
overrange region without being damaged, it can not be guar-
anteed to meet all of its performance specifications in this
region.

The 20V range is usable up to 24V at full load (depends on mains voltage). Above there will be ripple on the output.

[sync]

I don't know, both those readings are way more than 5%.

33 volts from a 20 volt supply? That is more than an order of magnitude more than the 5% the manual says should be possible. My 16 volt E3610A only adjusts up to about 16.8 volts. I'd be very suspicious that something odd was going on.

Put your E3610A into the 8V range and try again.

The E3610A .. E3612A only switch the transformer tap and the current range. But not the range of the voltage control. So in the lower voltage mode it is possible to set a voltage which is higher than the power supply can deliver. It's limited by the rectified transformer voltage and the regulator dropout. It's depends on the mains voltage and the load. 33V with no load on the 20V range is not a fault. My E3611A goes to 31V.

[rdl]

Ah, I see. My 3610 basically goes to 17 volts in either range. There is less than 1 volt difference maximum output voltage between the two ranges. Because the 3611 had a much larger difference between maximum voltage in the two ranges (33 vs. 40) I thought it must work differently.