Author Topic: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown (img links updated)  (Read 12146 times)

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Offline SharpEars

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There are many pictures of the outside of this beast, but I just got one of these and had to take a peek inside with all of the shielding removed. Let me share the view (pre-cleaning):



A bit dusty in here, but man no less than four transformers (maybe a fifth one stashed under the board at the bottom left) and holy cow if that's not the biggest heat sink I've ever seen in a PS (running horizontally along the center of the image). Quite a bit of empty space in the top right corner around the transformers, which was somewhat unexpected. Btw, what's going on at the top left with those funky coils? That's a wacky arrangement, I have to say.

This thing is a beast weighing in at 62 lbs (28.2 kg) and took quite a bit of strength to get into the basement.

Tell me what you think...

12/15/14 - Update: Added pics of the unit in operation in the following msg: Unit in operation
« Last Edit: December 17, 2014, 02:56:45 am by SharpEars »
 

Offline radhaz

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #1 on: December 09, 2014, 04:46:23 am »
Wow.
Does it work?
 

Offline SharpEars

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #2 on: December 09, 2014, 04:50:34 am »
Wow.
Does it work?

Heh, don't know I'm waiting for a 3000 Watt 110V to 220V converter to come in the mail, before I can even test it with US line voltage. These supplies (and larger ones) are built to be 200-240V input only, there is no 110/120 volt option.
 

Online IanB

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #3 on: December 09, 2014, 05:03:46 am »
Heh, don't know I'm waiting for a 3000 Watt 110V to 220V converter to come in the mail, before I can even test it with US line voltage. These supplies (and larger ones) are built to be 200-240V input only, there is no 110/120 volt option.

That's a strange and expensive option. Are you not aware that nearly all US homes are supplied with 240 V?
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Offline johansen

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #4 on: December 09, 2014, 05:15:45 am »
you can't wire in a 240v outlet?

 

Offline radhaz

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #5 on: December 09, 2014, 05:24:20 am »
I'm guessing a dim bulb tester is out of the question here. Good luck on first power up!

Heh, don't know I'm waiting for a 3000 Watt 110V to 220V converter to come in the mail, before I can even test it with US line voltage. These supplies (and larger ones) are built to be 200-240V input only, there is no 110/120 volt option.

That's a strange and expensive option. Are you not aware that nearly all US homes are supplied with 240 V?
 

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #6 on: December 09, 2014, 12:32:34 pm »
Thanks for the peek inside! Looks really nice!

Compared to the 6010A I looked inside some time ago ( http://www.daqq.eu/?p=838 ) it seems to use newer stuff, but there are similarities...
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Offline SharpEars

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #7 on: December 09, 2014, 01:00:57 pm »
Heh, don't know I'm waiting for a 3000 Watt 110V to 220V converter to come in the mail, before I can even test it with US line voltage. These supplies (and larger ones) are built to be 200-240V input only, there is no 110/120 volt option.

That's a strange and expensive option. Are you not aware that nearly all US homes are supplied with 240 V?

I am aware of this fact, but the question isn't one of being wired, but one of being wired in a conveniently usable location. I am sure I have 240 V going to some appliance somewhere in the house, but am not willing to move said major appliance out of the way to use the outlet. I need 220/240 V to be available in the basement by my work table, without running conduit with with 240 V from the mains, a major undertaking.

On the expensive option side of the equation, it's nothing compared to the 6675A itself...
 

Offline macboy

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #8 on: December 09, 2014, 01:29:00 pm »
Heh, don't know I'm waiting for a 3000 Watt 110V to 220V converter to come in the mail, before I can even test it with US line voltage. These supplies (and larger ones) are built to be 200-240V input only, there is no 110/120 volt option.

That's a strange and expensive option. Are you not aware that nearly all US homes are supplied with 240 V?

I am aware of this fact, but the question isn't one of being wired, but one of being wired in a conveniently usable location. I am sure I have 240 V going to some appliance somewhere in the house, but am not willing to move said major appliance out of the way to use the outlet. I need 220/240 V to be available in the basement by my work table, without running conduit with with 240 V from the mains, a major undertaking.

On the expensive option side of the equation, it's nothing compared to the 6675A itself...
Do you already have a 25 A or 30 A 120V circuit in that location?
 

Offline SharpEars

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #9 on: December 09, 2014, 02:14:55 pm »
Do you already have a 25 A or 30 A 120V circuit in that location?

Nope, stuck with a common NEMA 5-20R at the moment, so that's my limit for now. On the other hand, at 20 A, that's still a good 2400 Watts which is close to the limit of its max input (assuming 100% efficiency in the 120 -> 240 V conversion, which is of course is unrealistic - 85% is what I am hoping for).

Realistically, I'm not going to need max load (120 V/18 Amps) capability every day either, though, but it's good to know that it has the capacity, when presented with a proper high amp circuit. I have multiple other high power supplies at the location (e.g., two 60V/9A 6654A and a 35V/15A 6653A, among other lower end HP supplies) and I can't run them full load all at once in any case, nor do I need to.

I will always have the option to wire 240 V to the location if I see a big need, but for now assuming the PS works well, I will be quite happy with what it offers given the circuit and voltage capabilities I presently have.
« Last Edit: December 09, 2014, 02:21:23 pm by SharpEars »
 

Online nctnico

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #10 on: December 09, 2014, 09:11:40 pm »
That is an interesting power supply. I just can't understand why they used modular jacks as board-to-board connectors :palm: Sooner or later these will cause problems.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline SharpEars

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #11 on: December 09, 2014, 09:15:09 pm »
That is an interesting power supply. I just can't understand why they used modular jacks as board-to-board connectors :palm: Sooner or later these will cause problems.

Well one can theorize all one wants, but HP power supplies with their multiple modular jacks have withstood the test of time and been very reliable, some going for over 20 years of daily use and RJ-12 tipped cables were/are relatively cheap, so...
« Last Edit: December 09, 2014, 09:28:44 pm by SharpEars »
 

Offline SharpEars

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #12 on: December 10, 2014, 04:41:25 am »
I just wired a temporary 240 V circuit by using two 180 degree out of phase hot connectors and a ground, because I couldn't wait any longer for the step up transformer to arrive. Talk about creating a temporary fire hazard  >:D and breaking multiple codes and ordinances, but hey when there's a need to test, there's a need to test...

The power supply is working perfectly  :-+ ! It just needed a slight voltage calibration, which took me all of two minutes to perform using a calibrated HP 6 1/2 digit voltmeter.

Now all I have to do is clean out the dust, close it back up, wire in a proper power connector worthy of its power rating and then I'll post some pics of it in operation...
« Last Edit: December 10, 2014, 04:44:20 am by SharpEars »
 

Offline T3sl4co1l

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #13 on: December 10, 2014, 09:07:05 am »
Those cores on the top left look like they might be hall effect current transformers?

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Offline HighVoltage

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #14 on: December 10, 2014, 09:36:41 am »
These older HP Power Supplies are just amazing.
I just bought an older analog version, the HP6266B in a broken state and all it needed was a new "Crowbar" resistor.
https://www.eevblog.com/forum/repair/hp-6266b-%2840v5a%29-crowbar-repair-and-tear-down-pictures/

They take a lot of space away in the lab and they are heavy, but they last almost forever
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Offline SharpEars

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #15 on: December 10, 2014, 01:00:05 pm »
These older HP Power Supplies are just amazing.
I just bought an older analog version, the HP6266B in a broken state and all it needed was a new "Crowbar" resistor.
https://www.eevblog.com/forum/repair/hp-6266b-%2840v5a%29-crowbar-repair-and-tear-down-pictures/

They take a lot of space away in the lab and they are heavy, but they last almost forever

That is exactly why I love these HP/Agilent/Keysight power supplies, 10-15 years old and it's working like new and will easily last another 10-15 or more years. About the only maintenance item is to vacuum dust out of it every fifteen years of heavy usage and even that is optional.
 

Offline TunerSandwich

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #16 on: December 10, 2014, 01:16:43 pm »
mmmmm.....that thing is pure pornography.....I would hate to have to pay the power bill on running that thing all day, and then the cost of sucking the heat out of the room....still want it  :-+
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Offline SharpEars

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #17 on: December 10, 2014, 06:19:42 pm »
mmmmm.....that thing is pure pornography.....I would hate to have to pay the power bill on running that thing all day, and then the cost of sucking the heat out of the room....still want it  :-+

When you've running a power supply that consumes in excess of 2,000 watts, you don't need a room heater for that room. In the summer time especially when it gets really hot, I prefer to build/test lower power circuits  :-/O .
 

Offline pomonabill221

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #18 on: December 11, 2014, 07:16:55 pm »
If I'm not mistaken, these monster HP supplies have a pre regulator that is an scr chopped supply that feeds the linear portion.
The chopper is pretty efficient as it is on or off, no linear operation and very low heat generated, and course-regulates the raw DC to the linear regulator.

The chopped supply tracks the desired output so the linear section has very low power dissipation and heat as the input/output delta to the linear section is small.

This is also why you don't see a HUGE transformer... keeps the weight down too  YEAH, RIGHT!   :-DD :-DD :-DD

I am basing this on the HP 6428b that I used at Hughes back in the 80's though....  that was 20v@45amps.

You have a GREAT power supply!
Let's see some front panel pictures too!
« Last Edit: December 11, 2014, 07:26:28 pm by pomonabill221 »
 

Offline johansen

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #19 on: December 12, 2014, 01:00:01 am »
If I'm not mistaken, these monster HP supplies have a pre regulator that is an scr chopped supply that feeds the linear portion.
The chopper is pretty efficient as it is on or off, no linear operation and very low heat generated, and course-regulates the raw DC to the linear regulator.

that explains the 3800VA input requirement as well.
 

Offline SharpEars

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #20 on: December 12, 2014, 03:25:47 pm »
Let's see some front panel pictures too!

I will definitely post more large operation pics, including the front panel, once I get the power cord and more permanent 240V supply voltage sorted out...
 

Offline bktemp

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #21 on: December 12, 2014, 03:40:20 pm »
If I'm not mistaken, these monster HP supplies have a pre regulator that is an scr chopped supply that feeds the linear portion.
The chopper is pretty efficient as it is on or off, no linear operation and very low heat generated, and course-regulates the raw DC to the linear regulator.

The chopped supply tracks the desired output so the linear section has very low power dissipation and heat as the input/output delta to the linear section is small.

This is also why you don't see a HUGE transformer... keeps the weight down too  YEAH, RIGHT!   :-DD :-DD :-DD
This does not make sense to me:
Why does a scr bases preregulator reduce the transfomer size?
The transformers in these preregulator based power supplies are huge compared to normal ones that use multiple taps at the secondary winding (the preregulator scr is on the red heatsink):
https://www.eevblog.com/forum/repair/hp-6266b-%2840v5a%29-crowbar-repair-and-tear-down-pictures/

This monster power supply seems to be a SMPS.
 

Offline T3sl4co1l

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #22 on: December 12, 2014, 09:40:58 pm »
SCR pre-regulator also requires a massive iron cored choke.

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Offline SharpEars

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Re: HP/Agilent 6675A, 0-120 V / 18 A 2160W Power Supply teardown
« Reply #23 on: December 16, 2014, 03:45:43 am »
I finally finished assembling and installing the 12/3 power cable terminated with a NEMA 6-15P plug (250 V / 15 A) and got the voltage converter (120 V -> 240 V / 3,000 W) working.

So, here's the full frontal pornography as promised. In case it isn't blatantly obvious, the power supply is at the bottom with two 6 1/2 digit voltmeters on top of it. The HP in the middle is the more accurate of the two and well within calibration. Those are hand made 8 AWG copper leads you see coming out of it. The Fluke on top needs a little fine tuning  :-/O in the calibration department, but it's not too far off (Elenco leads coming out of that one).

Sadly, there's a narrow scratch on the protective plastic panel which is over the display. It is visible in some of the pics, but is purely cosmetic and doesn't affect operation in any way. It is far more prominent in pics at certain angles than during actual usage, but if anybody knows where I can get a replacement piece of clear plastic, I would be very appreciative.

Sorry, but all pics for now are at no load. It is amazing how accurate the voltages are compared to the typed in settings.

Small note for any photography snobs: All pics were taken at ISO 10,000 hand held on a Canon 6d with basement lighting, so no complaints about ISO noise in the pics, please. Also, I had issues with postimg and switched to imgur through my phone, so the quality has been made much worse. I will fix this when I get home...

You can click on any image to make it larger and click again to reduce it back to "postcard" size:

===================================================================================

Please keep in mind that the unit has 35 mV programming resolution, so it rounds the entered voltages to the nearest discrete step. Treat the HP in the middle's reading as gospel:

120 volt test (no load):



5 volt test (no load):



Now you probably would not use a supply like this for a 1.2 volt DUT, would you? That's more of a job for a 6632A, as long as your needs stay under 5 amps. If you do wind up putting this supply to the task though, rest assured that it does a dandy job within its 35 mV programming resolution restrictions, of course:



The beautiful rear ends, pun intended  :) , showing old-school programming interfaces galore:



Some load tests coming in the near future (no sexual puns necessary for that statement). But don't expect to see 120 V at 18 Amps, unless I choose to burn my house down :palm: .
« Last Edit: December 17, 2014, 02:57:44 am by SharpEars »
 

Offline Vgkid

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The pictures aren't showing :( .
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