HP 6632B power supply / electronic load in UK

[AndyC_772]

Heads up for those of us in the UK:

http://www.ebay.co.uk/itm/AGILENT-HP-6632B-Bench-DC-Power-Supply-0-20VOLT-5-AMP-Programmable-/350709211031?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item51a7e5df97

Provided you don't mind that the output is on a set of screw terminals at the back, the 6632B is a superb lab power supply, and this seller has 8 left at the best price I've seen anywhere.

They're accurate, very low noise, the start-up and shut down characteristics are exemplary, and they have an excellent meter built in which saves needing a separate multimeter to measure the output voltage and current. Also, the output stage can sink just as much current as it can source (5A @ 20V), so it can be used as an electronic load as well as a power supply.

Downsides? Big, surprisingly heavy even for their size, you'll probably want to fit some binding posts for easy connection, and you have to set voltage and current by entering numbers on a keypad or by programming it remotely - but for quality and versatility I've yet to use a better PSU.

[Rick]

Heads up for those of us in the UK:

http://www.ebay.co.uk/itm/AGILENT-HP-6632B-Bench-DC-Power-Supply-0-20VOLT-5-AMP-Programmable-/350709211031?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item51a7e5df97

Provided you don't mind that the output is on a set of screw terminals at the back, the 6632B is a superb lab power supply, and this seller has 8 left at the best price I've seen anywhere.

They're accurate, very low noise, the start-up and shut down characteristics are exemplary, and they have an excellent meter built in which saves needing a separate multimeter to measure the output voltage and current. Also, the output stage can sink just as much current as it can source (5A @ 20V), so it can be used as an electronic load as well as a power supply.

Downsides? Big, surprisingly heavy even for their size, you'll probably want to fit some binding posts for easy connection, and you have to set voltage and current by entering numbers on a keypad or by programming it remotely - but for quality and versatility I've yet to use a better PSU.

You can place the binding posts on the front panel. The holes are there I think I can feel them but did not check to see inside (from the front panel you will not have the sense possibility on the DUT). I got mine from Finland and it is very nice. Had never used such a nice piece of equipment.

[AndyC_772]

I didn't fancy modifying the unit itself, so I just ran a bundle of cables from the rear connectors to a little box attached to the rack mount ears. The box provides both the main power terminals and the remote sense connection, and there's a 10 ohm resisor between power & sense so I can use just the power terminals on their own for convenience.

[Rick]

I didn't fancy modifying the unit itself, so I just ran a bundle of cables from the rear connectors to a little box attached to the rack mount ears. The box provides both the main power terminals and the remote sense connection, and there's a 10 ohm resisor between power & sense so I can use just the power terminals on their own for convenience.

What is the 5th binding post ?

[lewis]

looks like mains earth

[AndyC_772]

Correct - the outputs are usually floating, but can be earthed. There's a fifth screw terminal on the back for this purpose.

[mikeselectricstuff]

<nips out to workshop with  tape measure to check available gear-shelf space>
Now only 7 available 

[cyr]

Thanks for the heads up, I'm not in the UK but international shipping wasn't unreasonable so I nabbed one as well.

I have one of these already, from probably the same guy in Finland already mentioned. Always regretted I didn't get both units he had left, very useful bit of kit.

They are usually listed for 500$ or more on ebay, even non-working ones...

[bingo600]

That's a nice offer.

I have  2 from finland , and absolutely love them.
But they are "noisy" , and i had to buy a fanless E3610A to do long term OCXO tests.
I have my lab besides the bedroom , so it was the wifes order - To get the "silent"one

/Bingo

[noodlebear]

Just bought one of these. Thinking I may replace the fan when it gets here. Does anyone know what size the fans are?

Thanks

[mikeselectricstuff]

User manual : http://cp.literature.agilent.com/litweb/pdf/5962-8196.pdf
Service manual : http://cp.literature.agilent.com/litweb/pdf/5962-8119.pdf

[senso]

Same here, just bought one, great opportunity to buy a real power supply for my small lab at home.
Thanks for sharing, and thanks Mike for the manuals.

[nctnico]

Still 8 available... It looks like a nice PSU but 20V is a bit low-ish and it is very large.

[AndyC_772]

Just bought one of these. Thinking I may replace the fan when it gets here. Does anyone know what size the fans are?

I have three of these, and although they're all quite old, the fans seem to be OK. I've not felt any need to change them.

The only problem I've had is that the case itself vibrated and made a lot of noise on one unit. The mains transformer leaks quite a strong magnetic field, and the case has to be tightly supported in order to keep it quiet. There's a pad stuck to the top of the transformer which is supposed to support the lid, but it can compress over time and allows the lid to move slightly. The fix is a small self-adhesive rubber foot stuck to the top of the transformer, 5 mins work at most.

[Narmaraktuk]

There is a service note for fixing an output glitch: http://cp.literature.agilent.com/litweb/pdf/6632B-09.pdf.

[noodlebear]

I have three of these, and although they're all quite old, the fans seem to be OK. I've not felt any need to change them.

I've just heard that the fans can be quite noisy. Given the availability of near silent pc fans, I was thinking of quieting it down a bit.

[bingo600]

There is a service note for fixing an output glitch: http://cp.literature.agilent.com/litweb/pdf/6632B-09.pdf.

Implemented here with a 1n4148

/Bingo

[alm]

Near silent PC fans will usually move much less air and are able to overcome less static pressure than the old noisy types.

[bingo600]

I have three of these, and although they're all quite old, the fans seem to be OK. I've not felt any need to change them.

I've just heard that the fans can be quite noisy. Given the availability of near silent pc fans, I was thinking of quieting it down a bit.

Please let us know if you find a suitable replacement fan.
It needs to deliver a lot of air to the heat tunnel , original is afaik a Pabst 612

I have found a replacement , the 632 NU (33dB) , it has same specs as the old 612 (40dB) , but i can't seem to get my hands on it.
http://www.ebmpapst.com/en/products/compact-fans/axial-compact-fans/axial_compact_fans_detail.php?pID=160978

HP 66332A, 6632B, 33B, 34B, Service.pdf - Pg.77 fandriver circuit

/Bingo

[nctnico]

I have three of these, and although they're all quite old, the fans seem to be OK. I've not felt any need to change them.

I've just heard that the fans can be quite noisy. Given the availability of near silent pc fans, I was thinking of quieting it down a bit.

Those silent fans are usually crap. What you need is a good fan from Papst which provides at least the same airflow as the original (or your PSU will overheat) and a temperature control circuit. I've build a temperature controlled fan in my HP6002A PSU. When the PSU is not heavily loaded the fan is off. It only comes on when the heatsinks get over approx. 35 C but the speed depends on the temperature of the heatsinks. The fan is only at full power when the heatsinks are approx 50 degrees. The circuit consists of a temperature sensor, an opamp, an emitter follower to provide power to the fan and some passive components.

[AndyC_772]

The fan speed on the 6632B varies with output (or input) current. It's a gentle enough whirr at idle, but does become quite loud at full load.

[bingo600]

The fan speed on the 6632B varies with output (or input) current. It's a gentle enough whirr at idle, but does become quite loud at full load.

My units whirr are a "BIT" more than gentle , even at idle.
But i guess it depends if they're in a silent environment. 

But i still love them , and did some accuracy/profiling with a GPIB and a HP 34401A

I got an Agilent & a HP unit from Finland
It's fun to notice that the newer Agilent uses another regulator loop  than the older HP

/Bingo

[bingo600]

Ohh i did do a voltage calibration on the Agilent.

Here are before & after (unloaded psu)

I think i got it quite nice in the Cal. , just following the quite easy procedure & used my 34401A DMM

/Bingo

[AndyC_772]

My units whirr are a "BIT" more than gentle , even at idle.
But i guess it depends if they're in a silent environment. 

It's all relative. Mine live in a lab with a rather noisy old Tek scope, and a stereo that's on the big side for the room

[noodlebear]

I have found a replacement , the 632 NU (33dB) , it has same specs as the old 612 (40dB) , but i can't seem to get my hands on it.
http://www.ebmpapst.com/en/products/compact-fans/axial-compact-fans/axial_compact_fans_detail.php?pID=160978

As far as I can see this one moves more CFM than the original with only 17.4 dBA. There is no graph available for the fractal with CFM and pressure though.

http://www.fractal-design.com/?view=product&category=4&prod=75