An ugly but working HP6060B Electronic Load

[AMR Labs]

So among my e-pay expeditions came across this HP6060B Electronic load. It was priced at $750 and described as a "Signal Generator" guessing the seller got confused with a similarly numbered model 6060B Fluke generator. At the time a few other listed HP6060Bs where at $900 to $4K+. Anyway after some months of having this on my watch, still no takers and I saw the seller came down to $350. Since the unit looked a bit neglected and dirty, plus some obvious minor aesthetic issues offered $200 and the rest is history.

Unit arrived at least well packed, it ought to be as for the first time I ended up paying a bit more shipping than it was shown on the listing. It went from $76.60 but changed to $99.10 at checkout. Not sure what that was all about and have to slug it out with ebay as seller denies having raised his shipping cost last minute after accepting my offer.

Top cover was grimy and dirty, some dents and scratches here and there, and inside all looked ok but quite dusty. The one surprise was that one of the binding posts in the back is missing its cap, broken off I suppose, one thing that conveniently was not shown in the listing pictures. But at least it is still functional. So I am on the lookout for a replacement post, if anyone has one for sale please contact me. HP part number is 1510-0134 and since I would also like to implement the front panel binding post option, I could use 3-4 of these. Keysight lists them as "ordeable" but out of stock. Nothing else out there but the typical aerospace parts sellers that want you to send them a request for RFQ. Yeah right.

Anyway, cleaned up the insides, also disassembled the front panel, and since some of the keys where not working consistently took out the membrane and cleaned the contacts. Put everything back together and the things works perfectly. Strangely the key on the right top ("Input ^") has completely lost its face as if it was shaved off. But at least it still works.

Ordered a rack ear/handle kit to fit, as this unit will go into a 12U rack enclosure cart with casters, above a huge and heavy HP6268B power supply that I just restored.
See thread here: https://www.eevblog.com/forum/testgear/hp6268b-restoration/
Also thinking to install in the same rack my HP3457A DMM that does not get used much, but I figure it will look nice mounted there.

So if anyone has one or more of the heavy duty binding posts used on this load, and willing to sell, please let me know. Don't even need new ones, I'd be happy with used ones as well. Or as an alternative if someone might know the original manufacturer of these, or even an OEM part number, that would also be very helpful. On mine there  are absolutely no markings or numbers. And the service manual being from the 90s no longer includes the detailed parts supplier list, just so now Keysight can sell you an ordeable but out of stock part.

[AMR Labs]

I would like to add the front panel binding post option to my 6060B, and have secured an additional pair of these humongous posts. But it seems that beyond drilling out the two holes in the front panel to secure the posts there is also a plate that looks to be made out of plastic and that goes on the outside of the panel in order to provide additional mounting rigidity. I was wondering if someone that has a 6060B with the original front panel post option could confirm what material this plate made of, is it plastic or perhaps aluminum? Also the dimensions would be nice to have, including if possible the thickness of the material.

I am aware there is a Gidhub page of someone that did 3D print this front plate, but it does not seem like a workable solution to me. First of all it does not really look too well aesthetically speaking, and secondly I have no way or interest of 3D printing something like that anyway. In any event would rather find a piece of the appropriate material, and cut it down to the proper size.

And it goes without  saying that if someone happens to have a 6060B parts unit and would like to sell that panel, I'd be of course very interested. I would even consider buying a second pair of binding posts if also available.

Thanks for any leads.

[Bud]

Unless you intend to mount the unit in a rack, to avoid drilling the front, you could make an L-shaped bracket and fasten it to the mounting holes on the side panel, with binding posts wired to the back of the device.

[AMR Labs]

Yes unit going into a rack. I was actually thinking of using a 1U plate to mount the posts and wire them into the rear posts as an alternative, but giving it a try to get them on the front panel before deciding how to ultimately proceed.

Thanks.

[jwrodgers]

I have just bought one of these and would also be interested in posts for the front panel. Please post back if anyone finds a supplier of posts

[jwrodgers]

Just checked the Keysight parts website and they have 'Quantity on Hand' now, but they are over £43 each! yelp. May be good to replace the broken one you have.

[jwrodgers]

KeySight have these back in stock, in the UK at least, I just checked.

https://www.keysight.com/gb/en/ecom/parts/part-detail.html/1510-0134

[AMR Labs]

Be aware that with Keysight "Ordeable" does not always mean the same as In-Stock. Sometimes its order and wait, besides they had been showing as ordeable for some time (months ago) since I started looking for sources, but I was hoping for other options. In any case £43 each is expensive, but I guess still ok if no other alternative, as there is nothing even close to these super beefy (60Amp PLUS) rated posts out there. Would be nice to have more information on them, like original manufacturer, or a manufacturer part number, which are not in the service manual. The posts itself have nothing written on then, at least not these ones. Would be nice if someone else can also look for any markings, just in case.

Fortunately I managed to get two used and in good shape original posts from someone in France that took apart one of these electronic loads and savaged what was usable. But have not yet decided on adding them to the front panel, as I mentioned in one of my earlier posts above there seems to be a need to reinforce the area where they are mounted to avoid it flexing as the panel itself is very thin and unstable in that area for a pair of posts that most times will have to be tightened down quite a bit with firm turning force. This reinforcing panel which is present on units fitted with the front panel post option from the factory is made out of an insulating material like plastic and is mounted on the outside of the front panel. Someone published the specs to 3D print something similar on Github but its far from looking like the original and I think it does not look too nice either, and since I am in no hurry for now I will wait until a better looking solution comes along.

[jwrodgers]

Instead of 3d printing, I wonder if a piece of 3mm or 5mm acrylic cut in a laser cutter would do the job?
It is available in many colours, I am sure something to match the 6060B is easily possible to get. It's easy to draw up some cad in the likes of fusion360 and laser it out. The laser can also mark the + and -.

I have a k40 that could do this ok, but I need to source some posts first

Check out the colours you can get from perspex.co.uk

I also found some posts from RS rated for 60A as well for about £10 each! RS 175-0163
Only 8 available so I am going now to order 2 before they vanish!

[jwrodgers]

Managed to get 2 Black from RS, but they have discontinued the Red ones. A further search led to the same parts, and other 60A binding posts from Cliff Electronics:

https://www.cliffuk.co.uk/products/terminals/touchproof.htm

Seems like an audio-foolery site, but nice terminals Hope they don't have audio-fool prices.

[amc184]

I was lucky enough to get a Agilent 6060B for a great price a few years back, and one of the first things I did after fixing* it was to relocate the binding posts to the front panel.  Here's a few images for my unit:


Front panel with binding posts and custom panel I had made.


Inside front panel with posts installed, showing the pre-existing holes for the posts.


Where front panel cables are connected, former location of binding posts at the rear panel.


Overall view of the modification.

Some tips and information I recall from when I did this:

• The front panel has three layers.  On the inside is the aluminium sheet chassis, which has holes ready for front panel binding posts.  Then there is the main front panel plastic moulding, this also has holes moulded into it it, easy.  Then there's an outer aluminium sheet with the button legend label.  This outer sheet is the only bit that needed modifying.
• To make the holes in the front panel I drilled a hole through the rough center with the largest drill bit I has to hand (12mm) for each, then grabbed a round file.  I then used the file to enlarge the holes to match the size of the holes moulded into the front panel plastic moulding.
• I designed and got made a custom plastic sheet to go between the posts and front panel.  This is made of a two layer acrylic - there's a thin outer white sheet with a thicker black layer underneath.  Any laser etched lines or areas cut right through the black layer, with can be used for markings.  I tried to match the style of the original button legend.
• I'm actually in the middle of redoing this panel along with making some others in aluminium.  Aluminium backed PCBs with with white soldermask and black silkscreen achieve a very similar look, but are more rigid.  Now that cheap prototype aluminium backed PCBs are available I've been using these for tonnes of stuff like this (and I'm ashamed to say I haven't made one that has electrical functions yet, just mechanical).
• The 6060B doesn't really need this panel to be mechanically robust.  It's just sandwiched between the bind post and a tightly fitting hole in the front panel.  This is not the case for a 6644A and many other models, where there's a thin label then a plastic moulding with open holes for multiple post styles.
• For this unit and others I've relocated the posts on I try and reproduce hop HP / Agilent did the front panel binding post option.  I think the way I did it is the same, where the original current carrying brackets bolted to the PCB remain and heavy gauge cables are added.  I used a 16mm² cable to minimise the voltage drop, with soldered on heavy lugs at both ends.  I would have liked to crimp these - I don't have a heavy crimper at home, but I do have a soldering iron capable of soldering to 16mm² cable (Metcal MX500).
• I also made a blanking plate to close off the original rear panel holes.

Once I've received the new aluminium backed PCB panels I've ordered I'll check they work, and if so I'll post the gerbers up here for anyone to use.

* I bought this in the US and brought it back to New Zealand, and the first thing I always do it set the voltage selector to 240V.  I was reading the silkscreen and realised that it was in the 240V position already .... no way.  Yeah, that was the whole fault, it had been set like that while they had tried it with a 120V supply.  It was USD210 for a tidy example built in 2007, one of my best test equipment buys ever.

[AMR Labs]

Very nice work you did there, and look forward to the Gerber files if your prototype plates work out. Its a good idea, and perhaps even a piece of regular FR4 blank fiberglass PCB might also be strong enough even without the aluminum backing.

One thing I noticed in your pictures is that you set the holes of both posts vertically (where the wire goes into), which would make it a bit difficult to insert the wire into the lower post unless you come from bellow, except for example if the unit is sitting flat on a bench as shown in the picture. In the original 6060B with front panel posts these holes are set to be on the horizontal plane so both wires can easily be inserted from either side of each post.

[AMR Labs]

Managed to get 2 Black from RS, but they have discontinued the Red ones. A further search led to the same parts, and other 60A binding posts from Cliff Electronics:

https://www.cliffuk.co.uk/products/terminals/touchproof.htm

Seems like an audio-foolery site, but nice terminals Hope they don't have audio-fool prices.

I saw those generic 60A Cliff posts a while ago on ebay, but I wondered if that 60Amp rating is for real and how good the manufacturing quality really is. Just compare the threaded shaft diameter to the original HP posts and there is a huge difference. I am assuming the original posts must be rated well in excess of the maximum 60Amp that the load can actually handle. But I guess they might still be a better choice than any of the regular run of the mill binding posts out there, as long as they are well build electrically speaking, and are not just bulked up for appearances.

I was close to ordering these to give them a try but then I found the pair of original posts. I just checked and these generic posts are still available on ebay, look at items 401469598445 (red) and 372181908331 (black). At the time I also did find them I think it was at Newark but not sure if they might still have stock left.

[jwrodgers]

Thanks, I've ordered a few from RS, and I've been thinking about how some folks here have moved the original posts from the back to the front. I am considering doing that, as it will look pretty original. Then I have to decide if I want to put the new cliff posts onto the rear of the case.

I suppose there is no real need for any posts at the rear if the unit is only being used on the bench and not in a production/rack setup. Also, need to check, but I am sure some mods need done to the sensing circuitry when putting the posts on the front to make sure the sense is picked up close to where the posts are installed, I will have a look in the service manual and report back later.

If I decide to move them, I will think about options for sealing the holes at the back of the case to make it look good. Probably acrylic in grey shade to match case with 'connect input to front terminals' or something similar in the right font

[AMR Labs]

BTW does anybody else also find it a bit annoying that the 6060B starts the fan at low speed immediately after power on and runs it continuously even without a load even attached? Mine does, and although it is at the lowest speed, I find it still a bit noisy and unnecessary. Is this normal?

So as a test I did put one of those KSD-01F TO-220 N.O. thermostat in series with the fan supply wire and mounted it on one corner of the heatsink under one of the existing screws. The one I used triggers at 55-C but I think I need to lower the triggering temperature as when the fan comes on after some use it is already running at high speed and the air coming out is already quite a bit warm, although not yet too hot. I ordered and already got a replacement thermostat of 45-C and had been waiting to find time to replace it.

To me ideally the fan should just come on after the temperature of the heatsink rises enough to justify it. That would also prevent some premature dust build up, and in my case I live at at an almost constant 70% humidity and about a mile from the sea coast. So constantly pumping air into an electronic equipment without really needing it seems like something I would like to lessen as much as possible. Any thoughts on this?

[AMR Labs]

Also, need to check, but I am sure some mods need done to the sensing circuitry when putting the posts on the front to make sure the sense is picked up close to where the posts are installed, I will have a look in the service manual and report back later.

HP used to offer a Front Panel upgrade kit for the 6060B, and all it included was the two additional binding posts, and appropriate lengths of red/black #8 wire with fitted terminals on each, plus I assume the front panel reinforcement plate. Personally I would go for #6 fine strand (marine spec) wire which is much more supple and easier to bend although this might still make it a bit more difficult to fit and handle for the installation. Then again for such a short length good quality #8 wire might be more than appropriate to handle 60amps without any appreciable and measurable loss that might influence the accuracy given the readout resolution. And btw I understand that #8 is exactly the same wire size that the factory fitted front posts also used.

[AVGresponding]

Managed to get 2 Black from RS, but they have discontinued the Red ones. A further search led to the same parts, and other 60A binding posts from Cliff Electronics:

https://www.cliffuk.co.uk/products/terminals/touchproof.htm

Seems like an audio-foolery site, but nice terminals Hope they don't have audio-fool prices.

Cliff Electronics are a well known and long established manufacturer in the UK. The quality will be good, if not superb. There's no audiophoolery.

These have been an industry standard for decades:  https://www.cliffuk.co.uk/products/tools/quicktest.htm

[AMR Labs]

Cliff Electronics are a well known and long established manufacturer in the UK. The quality will be good, if not superb. There's no audiophoolery.

These have been an industry standard for decades:  https://www.cliffuk.co.uk/products/tools/quicktest.htm

I think the correct link you meant to publish regarding the quality of the posts is this one instead:
https://www.cliffuk.co.uk/products/terminals/touchproof.htm

The one you posted is unrelated.

[AVGresponding]

No, the link I posted was the one I intended to. Perhaps I should have added some context; the Quicktest is an industry standard, and anyone that works testing and repairing things that can be powered from 1-ph mains is likely to have one for bench testing purposes.

[amc184]

Very nice work you did there, and look forward to the Gerber files if your prototype plates work out. Its a good idea, and perhaps even a piece of regular FR4 blank fiberglass PCB might also be strong enough even without the aluminum backing.

One thing I noticed in your pictures is that you set the holes of both posts vertically (where the wire goes into), which would make it a bit difficult to insert the wire into the lower post unless you come from bellow, except for example if the unit is sitting flat on a bench as shown in the picture. In the original 6060B with front panel posts these holes are set to be on the horizontal plane so both wires can easily be inserted from either side of each post.

Thanks.  I would think that normal FR4 would work fine, but aluminium backed is almost as inexpensive.  The acrylic I'm using now is okay for a 6060B, but in something like a 6644A a better material is really required, and the existing ones I'm about to replace are quite concave once installed (but functional).

It's a good point about the post orientation, I must have thought something different at the time, but what you say makes sense.  The panels I drew up have the orientation notch in all four directions, so they don't restrict how it's used.  I might even rotate them when I put in the new panel.

HP used to offer a Front Panel upgrade kit for the 6060B, and all it included was the two additional binding posts, and appropriate lengths of red/black #8 wire with fitted terminals on each, plus I assume the front panel reinforcement plate. Personally I would go for #6 fine strand (marine spec) wire which is much more supple and easier to bend although this might still make it a bit more difficult to fit and handle for the installation. Then again for such a short length good quality #8 wire might be more than appropriate to handle 60amps without any appreciable and measurable loss that might influence the accuracy given the readout resolution. And btw I understand that #8 is exactly the same wire size that the factory fitted front posts also used.

As far as I've seen the additional plastic moulding in the official option is only decorative, I don't think it would provide more structure (or that any is needed).  You could install the binding posts without adding anything but the hole, I mainly added my panel for the legend and to match other units I've done the same thing to.

The wire I used is about 5AWG, and it's a high flexibility rubber insulated welding cable.  Here's the datasheet:
https://products.lappgroup.com/online-catalogue/power-and-control-cables/harsh-conditions/rubber-cables/h01n2-d.html

It probably drops about 30mV at 60A, round trip.  I'm okay with that, it's probably below what's dropped at the various connections, including the binding posts.

[AMR Labs]

Out of curiosity, where are you getting the aluminum backed PCBs done? I usually deal with PCBWay although have not used them for a while. They do a large range of PCB types with many options, and very reasonable pricing even in small quantities. So far they have always been up to the letter of their claims of quality and delivery times.

One can even choose the color of the solder mask which in this case would allow a bit of better matching the front panel of the instrument. And silk screening a PCB is definitively the easiest way to achieve nice looking labeling results that will never peel or fall off. Very good idea.

I usually use marine grade ANCOR cables which have very fine fully thinned copper strands with very tough but still soft insulation, so its very flexible and easy to handle for its size/diameter in comparison to most regular welding cables.

[amc184]

I use JLCPCB, which are pretty good, but not perfect.  I've never had an issue that would have prevented me using a board, but I've had some with minor cosmetic issues.  In this case, cosmetics are more important than usual.  I get them in batches of 5, so avoiding a one with minor visual issues isn't a problem.

The cable I used was what I could get at the time on a short lead time at reasonable cost in small lengths.  There might be better options, but it was easy to work with for this job.

[AMR Labs]

I've used PCBWay twice for 50 board production runs and every board has so far always been cosmetically perfect. Perhaps keep them in mind for a try on future needs.

BTW wanted to ask, in your 6060B does the fan start running as soon as the unit is powered up? Mine does that and I wonder if it is normal. The manual only speaks about the fan having one (or two?) higher speeds that kick in after the unit starts to heat up due to use, but does not mention anything about the fan always running. I've seen mine going into higher speed on heavy usage after it gets hot, so I assume that the fan must be on low speed when the unit is cold started but to me this makes no sense having it run continuously even when the unit is just sitting idle.

[amc184]

Yes, my one also runs the fan at all times when powered, so it's probably normal behaviour.  I think these were mainly intended for use in an automated test rack, so minimising noise was probably not a priority.

I'm actually looking at trying out PCB Way soon, but maybe not for PCBs.  I'm thinking I might try their CNC machining service for some enclosure parts I need want.  I'm real curious to see the cost - I haven't been able to find any indication from anyone online, so I'll just have to finish my design and submit it to see.

[AMR Labs]

Yes, my one also runs the fan at all times when powered, so it's probably normal behavior.  I think these were mainly intended for use in an automated test rack, so minimizing noise was probably not a priority.

Thanks for confirming that the fan runs all the time as I suspected. I mounted my 6060B in an open frame rack with casters along with a HP3457A DMM, HP6268B Power Supply, and since I still had a bit of room to spare also a Tektronix 2213A scope basically just to get it out of a closet where it has been sitting unused for several years. The 6060B fan noise is still very much noticeable and perhaps even a bit distracting in a quiet environment, although nothing compared to the two fans inside the HP6268B that also run continuously, so I did also put thermostats on those two as well. Forced ventilation in the power supply is only really needed on heavy usage, so now they only run when actually needed.

In my experience the prices at least for PCB production with PCBWay where more than reasonable given the good service overall, and they where always eager to help you with anything else. I think nowadays with so much competition, every player is trying to be better than the rest which seems to be driving down pricing and expanding other services while maintaining quality.