HP 6012A (1KW, 60V, 50A power supply) teardown - Page 1
Forum section: electronics / testgear

author: uoficowboy
author_rank: Regular Contributor
timestamp: January 13, 2014, 12:57:00 am
content: This is a beastly power supply I just finished fixing up. Before I sell it, I figured I'd post some photos for you all to see.Note that this device is on Ebay. If you want it please contact me and there will be an EEVBlog discountFirst photo shows it with its cover off.Second shows the flyback transformer in the lower right corner, a couple mega input caps on the left, and a relay up top. The transformer in the upper right is used for generating all the control voltages, and the big red and black wires and metal bars on the right are the output terminals.Third photo shows the input caps and some more magnetics.Fourth photo shows the flyback switches (yes there are two!) as well as the flyback diode cards.Fifth photo shows the component side of one of the switch cards. This flyback is very odd - it switches *both* sides of the primary. I have never seen this. It looks in the schematic like this is used so that extra energy in the primary is dumped back into the input caps.

author: uoficowboy
author_rank: Regular Contributor
timestamp: January 13, 2014, 12:57:38 am
content: First photo shows the power switches used on one of the switch cards as well as the big heatsink.Second photo shows the component side of the diode board.Third photo shows the heatsink side of the diode board.Fourth photo shows where the diode board sits.Fifth and sixth photos show the awesome meters on this device - The voltage meter also indicates how much current is allowed at the current output voltage, and the current meter also indicates how much voltage is allowed at the current current level. Very cool.

author: megajocke
author_rank: Regular Contributor
timestamp: January 14, 2014, 04:13:23 pm
content: Nice pictures! I have another HP power supply, a linear 50V 10A 200W unit called HP6002 IIRC, with the same kind of meters. They seem to use the same type of wire in all their products, and it looks quite neat with those stripes in lots of different colors.That arrangement where both ends of the primary winding are switched is quite common in forward converters at high power levels, and it's just as in this flyback converter beneficial because it lets you recover the energy stored in the leakage inductance of the transformer. It's quite uncommon in flyback converters but I guess that's because usually the flyback topology is the first thing abandoned when going for high power levels.The output capacitors see a huge ripple current in a flyback, but there are also seem to be some benefits to using the flyback topology when a wide input and/or output voltage range is required with full power.

author: nctnico
author_rank: Super Contributor
timestamp: January 15, 2014, 09:09:16 am
content: I'm wondering: did you replace the electrolytic capacitors?And why sell it? A beefy power supply is nice to have.edit: I couldn't resist: I snatched one from EbayThe price was just too tempting after some haggling. I like the fact it is switching so it doesn't kill my back when I need to move it.

author: uoficowboy
author_rank: Regular Contributor
timestamp: January 15, 2014, 02:28:53 pm
content: Quote from: nctnico on January 15, 2014, 09:09:16 amHi - I did not replace the electrolytics. They all measured to be fine. I had to replace the card edge connector for the control board as it was flaky. I also repaired some damaged traces that looked to have overheated. After that, the device was very reliable. Before that, the output voltage wandered all over the place like a lost child.Why sell it? Because I imagine I will not need that kind of power any time soon. I already have a full supply of bench supplys. Nothing else capable of that kind of current though. But I have never once in my life needed that sort of current! Plus I could use the money! The last fully functional ones that sold (no longer listed in Ebay's history, but they were when I purchased it) sold for something like $800+.You bought a 6012A? How much did you get it for? It is not exactly a light unit, but lighter than a linear 1KW supply for sure!!Quote from: megajocke on January 14, 2014, 04:13:23 pmInteresting - I didn't know forward converters did that. I haven't worked with them much though. You're right that flyback output capacitors get hit harder - just like boosts. They also can be a bit nasty too stabilize due to their RHP zero. I wish bucks could be used everywhere- cleaner output, no RHP zero.

author: nctnico
author_rank: Super Contributor
timestamp: January 15, 2014, 05:06:14 pm
content: Quote from: uoficowboy on January 15, 2014, 02:28:53 pmI paid $200 for it including shipping within Europe. But it needs some cleaning and some fixing. I just assume the capacitors need to be replaced. The one I bought probably has the blue/black HP logo so it must be around 25 years old. I think I'll also put 4mm output posts on the front, mount an IEC inlet and make the fan temperature controlled. Maybe even throw in a new fan if the old one doesn't run smoothly. All in all a nice project for the weekend.

author: uoficowboy
author_rank: Regular Contributor
timestamp: January 15, 2014, 05:40:57 pm
content: Quote from: nctnico on January 15, 2014, 05:06:14 pmSounds good! By the way - Artek has a pretty good scan of the manual for $12.50, including a schematic that is not split onto many pages. I'd recommend picking it up if you have trouble figuring out what is wrong with yours!Temperature control on the fan would be very nice - it is not quiet! Not as bad as a Kepco supply I had a little while back, but still loud!

author: nctnico
author_rank: Super Contributor
timestamp: February 05, 2014, 07:34:51 pm
content: I did a bit of work on my HP6012A. I received it like this:Some dimbulb decided to remove the potmeter for some kind of remote control. These power supplies allow controlling current and voltage setting by voltage, current or resistance through the terminals on the back.^10 Just remove the jumpers and attach the wires...The inside was just as dirty as the outside:After some carefull (low pressure) spraying with compressed air the inside cleaned up nicely. I didn't wash it because I didn't want to take it apart any further than necessary. Many wires are soldered into the boards directly and these could break when bend too much.After a bit of testing it turned out the power supply was working OK. The output ripple levels are low and it didn't smell like cat pee so the (expensive) capacitors didn't need replacing. Wooohooo!I mentioned putting an IEC inlet on the power supply earlier. Since the power supply can draw 1500W max the inlet would need to be rated for 7A or even better 8A. Most inlets I had lying around where rated for 6A. This lead me to the conclusion I would be better off with a fixed power cord. But not a ridiculous 4mm^2 cord it came with!The next job is adding some front posts and a output on/off switch. There is enough room on the front so that is easy. At least it looked like that. Unfortunately some of the paint came off with the protective tape I use when drilling in front plates:I used some AWG8 wiring and bus bars from a UPS I salvaged. The black/yellow wires are the sense wires which keep the voltage at the output posts at the desired level. When carrying 50 Amps even a short AWG8 wire will have some loss. I used some Kapton tape for extra insulation between the front and the outputs. The output posts I used are rated for 35A each (Hirschmann PKI110).A bit more room for the replacement potmeter (10 turns ofcourse!):I replaced the fan and I also added temperature control. I stuck the NTC resistor (on a thin PCB) to one of the heatsinks. Note that the heatsinks are live in this PSU. While on that subject: I also don't like the open relay.I used the same temperature fan control circuit I used in my HP6024A power supplies (seehttps://www.eevblog.com/forum/testgear/hp6024a-psu-restoration-project/). The only difference is that in the HP6012A I let the fan run at a low speed.For a bit more testing I tried to see what it would do under some real load (yes that is 29A):Even when parallelled the 16A test leads do get a bit warm. The output voltage stays at it's set voltage so the sense leads are doing their job as well. The end result:Unfortunately I was not able to get some original HP knobs. The 80's aluminium knobs where the best I could find quickly. Getting feet for HP equipment is easy so I did put new feet under it. I didn't put the rack mount handles back though; those would just be in the way on my equipment shelve.

author: uoficowboy
author_rank: Regular Contributor
timestamp: February 05, 2014, 08:47:44 pm
content: That's great that you got all that for just $200 shipped! I think you were wise to not try and take it apart - I had to take mine apart (needed access to the bottom of the main PCB) and that was a massive amount of work. Not fun.If you need old style HP knobs - I'd try the HP/Agilent Yahoo group. People there have been able to hook me up with most of the old HP parts that I have needed.That's a nice upgrade with the banana jacks. If it were me I would have also put in another set of bananas for the sense leads - but to each his own!

author: aw_rw1
author_rank: Contributor
timestamp: March 06, 2017, 06:06:39 pm
content: Does anyone know how I could get a replacement switch for the On/Off switch?