Would you pay $100 for a HP6115A psu ?

[BravoV]

Edit :
The title is no longer relevant anymore since I scored it for $85, shot few photos at post #26 -> HERE, and this thread grows into discussions about this HP 6114/5A power supply.


Title should be self explanatory and would like to hear your opinion or suggestions if any, got an offer locally from a tech surplus shop.

I will have the luxury to inspect it physically and they allow me to bring my own DMM and load to verify it, but no internal inspection though. 

[Bored@Work]

In Europe yes, good deal.

[eevblogfan]

look ... no doubt ... very low noise high performance power supply , if you have the money , yea I would have , if that's needed of course ...

[sorin]

no
too old

[c4757p]

no
too old

Yes, it can't supply those new electrons we invented last year...
 

[robrenz]

The 6114A AND 6115A specs are extremely good.  try finding a modern supply this quiet or stable for less than several thousand dollars.  No current power supply by Agilent comes close until you spend over $5000.00 from what I have been able to find. The Power Designs Precision supplies are also in this category.
 $100.00 guaranteed working I think is a good deal.

[Jay_Diddy_B]

Hi,

You can read about the HP6114A which is very similar to the HP6115A in the HP Journal.

http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1972-11.pdf


The only downside to these supplies is the way the output voltage is controlled:



The use a constant current source into a decade resistor. If the switches are dirty the output voltage will jump.

There is an overvoltage crowbar (SCR) that can be used to protect your load.

The decade resistor contains some close tolerance resistors.



Jay_Diddy_B

[PedroDaGr8]

You also don't mention if it has the 10-turn Current Pot

[ivan747]

no
too old

Yes, it can't supply those new electrons we invented last year...
 

You always manage to brighten my day. But 30 year old electrons aren't the same as the newer ones, they are kinda slow. They get slower with time, I dunno.

I still like this supply. I would buy it if shipping wasn't a problem. Robrenz is right on the money. The specs are great, the resolution is good, the price... it always seems to be great. Please don't advertise this model around guys! And for god's sake don't let Dave make a video! Look what happened to the rubidium standards, they doubled the price since the video!

[BravoV]

Thanks for nay or yay sayers, your opinions are much appreciated. 

no
too old

I guess thats too brief. 

The 6114A AND 6115A specs are extremely good.  try finding a modern supply this quiet or stable for less than several thousand dollars.  No current power supply by Agilent comes close until you spend over $5000.00 from what I have been able to find. The Power Designs Precision supplies are also in this category.
 $100.00 guaranteed working I think is a good deal.

Yep, "mainly" this is your fault, especially after seeing your adventure with that fine 6114A of yours. 

I'm aware that it's accuracy might be drifted, but this can be calibrated. My main interest is the voltage range 0-100 Volt and the "stability factor", totally agree with your assessment, this beast definitely not an average adjustable lab psu performance at the price of $100.

Hi,

You can read about the HP6114A which is very similar to the HP6115A in the HP Journal.

The only downside to these supplies is the way the output voltage is controlled:

The use a constant current source into a decade resistor. If the switches are dirty the output voltage will jump.

There is an overvoltage crowbar (SCR) that can be used to protect your load.

The decade resistor contains some close tolerance resistors.

Jay_Diddy_B

Thanks for the link, yes, I'm aware of the mechanical switch weakness, but after reading Robrenz's work on his 6114A, I'm convinced, although I doubt my self to have the same level of skill in restoring old instruments as he did. 

How do you expect people to answer if you don't say what country you are in?  In the US you can get a better deal.

Nope, don't have the luxury of ebay-ing used T&M instruments from US, the cheapest shipping cost it self from US might be > $300. 

You also don't mention if it has the 10-turn Current Pot

The problem I have is the seller still can not find it in their warehouse. 

Will this 10 turns pot matter much ? Any chance of modding it my self ? What value of this current pot ?

I still like this supply. I would buy it if shipping wasn't a problem. Robrenz is right on the money. The specs are great, the resolution is good, the price... it always seems to be great. Please don't advertise this model around guys! And for god's sake don't let Dave make a video! Look what happened to the rubidium standards, they doubled the price since the video!

Nope, I will personally pick it up at the seller's warehouse.



Again, just to repeat, I will have the chance to inspect and test it physically, isn't this factor it self worth some pennies compared to online purchase ?


Quoted some of it's spec :

Constant voltage spec :
Load regulation : 0.0005% + 50uV
Line regulation : 0.0005% + 100uV
Ripple & noise : 40 uVrms/100uV p-p
Temp Co : 0.001% + 15uV
Drift (over 8 hours under load) : 0.0015% + 15uV
Transient recovery time : < 50uSec with 10mV of nominal output
Output impedance : 0.05 mOhm in series 3 uH inductor
Output voltage accuracy : 0.025% + 1mV

Constant current spec :
Load regulation : 0.01% + 500uA
Line regulation : 0.005% + 20uA
Ripple & noise : 200uA rms/1mA p-p
Temp Co : 0.02% + 25uA
Drift (over 8 hours under load) : 0.25% + 4mA

[PedroDaGr8]

Yeah you can add it manually later. It's a simple ten turn pot with a vernier dial. I'll see if I can give you the exact model number this weekend.

Personally I think it is worth $100. I have a 6114a and love it. The thing just exudes quality. The only thing comparable in this price range are the PD Precision supplies. They command a similar price range, though this one beats then on the spec sheet anyways.

Sent from my EVO using Tapatalk 4

[BravoV]

PedroDaGr8, thanks for the trouble.

Btw, do you have a particular photo shot at that pot where it installed ? Cause I don't see it at your HP 6114A teardown thread.

Looking at the schematic, is the current adjust pot has the value of 10 Ohm ? 

[PedroDaGr8]

PedroDaGr8, thanks for the trouble.

Btw, do you have a particular photo shot at that pot where it installed ? Cause I don't see it at your HP 6114A teardown thread.

Looking at the schematic, is the current adjust pot has the value of 10 Ohm ? 

it's mounted to the front where the current knob is on the regular version. It replaces the regular pot, with the regular knob replaced by a ten turn vernier dial.   As for the resistance value and model number I'll let you know this weekend

Sent from my EVO using Tapatalk 4

[robrenz]

Cheapest 10 turn 10 ohm pot I could find was $57.00 plus about $19.00 for a turns counting dial.  More than I paid for the power supply that had them. That does not mean this is a bad deal but if you have to spend $76.00 additional to get 10 turns it might influence your decision.  Many people don't realize how expensive the low ohms 10 turns can be.

[sync]

This is the current adjust pot. It has 1k. No problem finding a 10 turn one.

[robrenz]

You are correct, I assumed the previous posts were the correct pot. $10.00 now

[edavid]

Personally, I don't like the 10 turn current limit pot, because it takes forever to set it.  This is not a precision current source, after all.

[sync]

Use a 3 turn one.

But 0.01% load regulation for constant current mode is not bad at all for a power supply.

[robrenz]

6114A or 6115A is better or equal to the rigol dp832 Dave just looked at on current regulation and ripple.

6114A or 6115A at 0.8A  line and load reg. is max 0.08% same on the new Keithley 2450 SMU ($5400.00) line and load reg. is max 0.025%  Only 3 times better for 54X the money

This is a place where the Power Designs power supplies cannot compete. They were not designed for high accuracy current regulation, only general current limiting. They do not spec current regulation at all and testing I have done on the Power designs thread show they are very temperature sensitive on the current regulation.  A better TCR shunt may fix this problem but I have not had a chance to try it.  (PD fanboys relax, I have several of them )

[robrenz]

I just bought a 6115A today to keep my 6114A company.  It will need more TLC than the the 6114 did

[BravoV]

This is the current adjust pot. It has 1k. No problem finding a 10 turn one.

Thanks for spotting that !  Low resistance multiturns pot is really expensive as Robrenz mentioned.

I just bought a 6115A today to keep my 6114A company.  It will need more TLC than the the 6114 did

LOL ... when will this end Robrenz ? 

How is the new 6115A condition compared to the 6114A ? On the TLC, make another new restoration thread on this newly acquired beast please.

Btw, just an update, apparently this deal is on hold, cause the seller did a major warehouse restructuring and their merchandises were moved around, and this psu is still missing, probably buried somewhere. 

[robrenz]

I just bought a 6115A today to keep my 6114A company.  It will need more TLC than the the 6114 did

LOL ... when will this end Robrenz ? 

Someone has to keep your power supply thread going. I have spent less than the cost of 1 Rigol  DP832A and I have 8 independent floating power supplies that are more accurate, higher resolution, better stability, lower ripple. But I think I am done on power supplies. 8 (not counting the 2 BOSS bipolars) is plenty. 

How is the new 6115A condition compared to the 6114A ? On the TLC, make another new restoration thread on this newly acquired beast please.

Looks similar but with busted ground jack, power switch, and some of the panel markings look messed up. But for what I paid I can afford lots of TLC and a 10 turn 1k pot with turns counter.  I may do a video on the restoration.

[BravoV]

Someone has to keep your power supply thread going. I have spent less than the cost of 1 Rigol  DP832A and I have 8 independent floating power supplies that are more accurate, higher resolution, better stability, lower ripple. But I think I am done on power supplies. 8 (not counting the 2 BOSS bipolars) is plenty. 

Talking about digital age, actually I'm thinking to make a digital control module that provides adjustable reference voltage and also equipped with a dial or usb connectivity to be connected to these great old analog psus on their remote programming connectors in the back. Its like turning it into modern gadget  like current digital control PSUs while still have the proven performance and stability.


So the 6115A came without the 10 turns pot ? When you do the teardown, please take a shot especially at the 10t pot size and it's mounting location, cause there are many difference sizes for this kind of pot.

[robrenz]

Talking about digital age, actually I'm thinking to make a digital control module that provides adjustable reference voltage and also equipped with a dial or usb connectivity to be connected to these great old analog psus on their remote programming connectors in the back. Its like turning it into modern gadget  like current digital control PSUs while still have the proven performance and stability.

Great minds think alike

[robrenz]

6115A just arrived today.  Power switch was broken as listed but jumpering that it works fine. A standard 7/8" diameter 2W 10 turn will fit in the current limit pot location. (makes sense since it was an option anyway)

[BravoV]

Great minds think alike

Nice to hear that !  Whats your plan regarding the digital module ? I guess I will just follow your step on this one.

6115A just arrived today.  Power switch was broken as listed but jumpering that it works fine. A standard 7/8" diameter 2W 10 turn will fit in the current limit pot location. (makes sense since it was an option anyway)

Congratulation, sorry to hear about the switch, but is it working fine ?

Geezz... don't know if all planets in the solar system are lining up or just pure coincidence, guess what, my 6115A is also arrived safely at home too !  Weird huh ?

Unbelievable, this beast when I tested at the shop with my dmm for almost 1 hour with loads, the voltage and the current are still so accurate after > 30 years and both regulations are solid like a rock ! 

It has the 10 turns pot installed, and also it has a label stated "Option 910" (check below photo), not sure what it is, and I can't find it in the manual for the standard optional features.  The back plate for securing the remote terminals, and also the 4 rubber feets are missing  , but no big deal I think, especially I got an extra discount and ended up with the price at $85, not bad eh ?

Now, frankly speaking, I feel a bit demotivated to do the restoration after seeing your job on your 6114A, really, my kungfu is not good enough as yours. 

Few shots of my dusty 6115A.

[robrenz]

Great minds think alike

Nice to hear that !  Whats your plan regarding the digital module ? I guess I will just follow your step on this one.

That would be a huge mistake, I am sure my current electronic prowess is not even close to yours, really.

The unit seems to work fine I but have not loaded it down yet.

Congratulations, I am glad you got one in great shape.

I think the 910 is the regular separate pot for the millivolt setting instead of the dekadial pot like on mine.

Those square holes on the bottom are for a molded removable plastic foot bar, one at the front and one at the back. My PS happens to have them this time.

We paid almost the same amount. Mine was $41.00 plus $40.00 shipping. but I have to buy a switch, 1k 10 turn, and a turns counter so you got a better deal.

Yours does not need much restoration but I am sure you can do an excellent job.

[BravoV]

I guess I will have to improvise for those 4 rubber feets, its not easy to find the right size for those tiny square holes.

Btw, because of your 6114A restoration thread, I bought this top tier quality Japanese made melamine sponge. 

[robrenz]

AFIK there is no variation in quality of these sponges. The cheap ones are exactly that, the same sponge for less money. The ones I use are no name bought in bulk packs.

[BravoV]

AFIK there is no variation in quality of these sponges. The cheap ones are exactly that, the same sponge for less money. The ones I use are no name bought in bulk packs.

LOL .. Just teasing you ..  , actually bought that because of it's big size.

Btw, does yours have the metal plate at the back for protecting those terminals ? I assume its "C" or "7" shape ?

Now question regarding those heavily scratched heatsink fins at the back, I know its purely cosmetical, any idea or suggestion to fix that "easily" ? As a pro machinist, I strongly believe that you still have tons of tricks behind your sleeve on such matter. 

[robrenz]

Here is a picture from the listing of the back cover.

I will probably remove the heat sink completely, (it is actually 2 pieces) and glass bead all the paint off. Then straighten the bent fins and deburr all the edges then repaint.  I may change my mind when I see all that that entails.  Second best will be to blend sand the existing paint to the aluminum to remove all the chipped paint edges. The edges of the paint chips will show thru the new paint.  The problem with that will be masking off everything to be able to spray it.  If you don't spray the entire exposed surface, the paint will need to match pretty closely and that won't be easy.  I know most are saying right now who cares about the stinking paint chips on the heatsink?  But to me that is what a restoration is all about, sorry.... I can't help myself.

[BravoV]

Here is a picture from the listing of the back cover.

Question, are that two screws the only screws that are holding that cover plate ?

Btw, what is that back plate shaped like ? "C" ? "L" or "7" ?

I will probably remove the heat sink completely, (it is actually 2 pieces) and glass bead all the paint off. Then straighten the bent fins and deburr all the edges then repaint.  I may change my mind when I see all that that entails.  Second best will be to blend sand the existing paint to the aluminum to remove all the chipped paint edges. The edges of the paint chips will show thru the new paint.  The problem with that will be masking off everything to be able to spray it.  If you don't spray the entire exposed surface, the paint will need to match pretty closely and that won't be easy.  I know most are saying right now who cares about the stinking paint chips on the heatsink?  But to me that is what a restoration is all about, sorry.... I can't help myself.

Sigh ... this is what I'm afraid of, avg Joe like me don't have any cool sand blasting equipment to strip off those paint like you do. I guess sand paper is the only option or through nasty paint stripper chemical. 

Any other options ?

Btw, about the paint, apart from grey colored, are you planning to use just ordinary paint or a specialized one that suitable for "heat"-sink ? 

[SeanB]

If you remove all the other metal then simply dunk it into a concentrated caustic soda solution for a few seconds and get it in all the crevices using a plastic brush while wearing long rubber gloves, and then rinse it a few times in fresh water. The NaOH will make short work of stripping the anodising and dirt from it. Then use some lemon concentrate in water to build up a new film ( I used ascorbic acid as I had a lot around, but citric acid works as well) on the now bare aluminium. You can then paint it with some matt black or satin black spray paint, 2 thin coats works well to cover without affecting thermal resistance much. After paint is dry bake in an oven at 130C max for about 3 hours to cure the paint well.

[PedroDaGr8]

OK, sorry for the delay. Lots of things came up here. Here is the pic I promised:



It's just a simple Bourns 1k +/- 5%, Lin 0.5% pot Model: 3540S-501-102

[SeanB]

Do not forget the 100n 100v ceramic cap across the pot as well, though often I see the cap connected between the lower terminal and the wiper. These pots do suffer from zipper noise as you rotate them from the discrete jumps in resistance as the wiper moved from the one turn of resistance wire to the next along the track.

[PedroDaGr8]

Do not forget the 100n 100v ceramic cap across the pot as well, though often I see the cap connected between the lower terminal and the wiper. These pots do suffer from zipper noise as you rotate them from the discrete jumps in resistance as the wiper moved from the one turn of resistance wire to the next along the track.

Are you sure on that. I don't think these pots are high enough in wattage to have that. I took apart a 20K pot the other day (spectrol I think) and it had a single coil of resistance wire that the wiper moved up and down. Monday I'll try to dig it out and take some pics.

[SeanB]

Look carefully at the track and you will see it is made from insulated resistance wire wound on an enamelled copper wire mandrel, the inner side having the enamel stripped so as to touch the wiper track. They do make a lot of wiper noise, just take one, apply 1V across the track and use an amplifier to listen to the noise from the wiper as you rotate it.

[BravoV]

If you remove all the other metal then simply dunk it into a concentrated caustic soda solution for a few seconds and get it in all the crevices using a plastic brush while wearing long rubber gloves, and then rinse it a few times in fresh water. The NaOH will make short work of stripping the anodising and dirt from it. Then use some lemon concentrate in water to build up a new film ( I used ascorbic acid as I had a lot around, but citric acid works as well) on the now bare aluminium. You can then paint it with some matt black or satin black spray paint, 2 thin coats works well to cover without affecting thermal resistance much. After paint is dry bake in an oven at 130C max for about 3 hours to cure the paint well.

SeanB, is that for stripping the heatsink's paint ? or just cleaning the aluminium surface that already has it's paint stripped ?

If its for stripping the paint, should I protect those exposed aluminium from the chipped/scratched paint ?

Sorry, I'm not understand your post clearly.

OK, sorry for the delay. Lots of things came up here. Here is the pic I promised:

It's just a simple Bourns 1k +/- 5%, Lin 0.5% pot Model: 3540S-501-102

Hey PedroDaGr8, thanks a lot for the effort ! 

Even though my 6115A has 10 pots (the photo at 1st post was randomly grabbed from the net), this photo at least will be a reference for me to compare if I managed to tear it down. Yeah, don't have time for internal inspection yet since I travel a lot  , actually my deal was made during my traveling last week.

Do not forget the 100n 100v ceramic cap across the pot as well, though often I see the cap connected between the lower terminal and the wiper. These pots do suffer from zipper noise as you rotate them from the discrete jumps in resistance as the wiper moved from the one turn of resistance wire to the next along the track.

Do you mean to add an extra cap apart from the one that already soldered at the pot as shown by PedroDaGr8 's photo above ?

[SeanB]

If you have a black anodised and not a painted part this strips the anodising very fast. If it is painted it needs most of the paint gone first then this will remove any small bits left. I use this to strip faded or worn anodising so that the part is now smooth and has a consistent finish for recoating or just anodising again. It does remove metal though, so thin parts may etch through. Gloves, eye protection and a firm bristle plastic brush are needed.

If it is a 10 turn pot replacing a single turn one add the cap, otherwise leave it alone. It is only something you will need if you are powering a speaker from the output of the pot and the noise is objectionable, with a DVM it just makes it move up in single digits on the LSB with little dithering between each position.

[robrenz]

Question, are that two screws the only screws that are holding that cover plate ?

Yes

Btw, what is that back plate shaped like ? "C" ? "L" or "7" ?

I will make a drawing and post it

Btw, about the paint, apart from grey colored, are you planning to use just ordinary paint or a specialized one that suitable for "heat"-sink ? 

regular paint, it should not get hot enough to need high temp paint.

[robrenz]

drawing of the rear connection cap. material is the same vinyl covered aluminum as the side plates.

[BravoV]

If you have a black anodised and not a painted part this strips the anodising very fast. If it is painted it needs most of the paint gone first then this will remove any small bits left. I use this to strip faded or worn anodising so that the part is now smooth and has a consistent finish for recoating or just anodising again. It does remove metal though, so thin parts may etch through. Gloves, eye protection and a firm bristle plastic brush are needed.

Its not anodized, its painted and scratched badly at the back. You should check the photos I posted at previous page, thats mine.

Repost here on how it looks like.

If it is a 10 turn pot replacing a single turn one add the cap, otherwise leave it alone. It is only something you will need if you are powering a speaker from the output of the pot and the noise is objectionable, with a DVM it just makes it move up in single digits on the LSB with little dithering between each position.

Yep, my PS came with the factory's installed 10t pot, it should have the cap like Pedro has.

[BravoV]

drawing of the rear connection cap. material is the same vinyl covered aluminum as the side plates.

Robrenz, wow .. I didn't expect you made that nice drawing using cad and with all the details, thank you Sir ! 

Rather than using metal, maybe I will use a transparent/clear acrylic for that plate.

Although I don't have time yet to tear it down and do internal inspection, played and tested it for few hours at this weekend, damn, this thing is my new favorite bench PSU for now. Also after seeing your chart, the more I appreciate it's performance, ok, I'm in love. 

Re-posting your chart here, hope you don't mind.

[robrenz]

Although I don't have time yet to tear it down and do internal inspection, played and tested it for few hours at this weekend, damn, this thing is my new favorite bench PSU for now. Also after seeing your chart, the more I appreciate it's performance, ok, I'm in love. 

Re-posting your chart here, hope you don't mind.

No problem showing the chart, that is the only thing that can convey the effective specifications when you have a percentage plus counts.  Those last 2 agilents that beat the 6114/5 are >$4000.00 and >$5000.00 and only the PD2020 is better below 0.7V for <$100.00  We didn't even talk about ripple or stability specs they are only better on the >$5000.00 B29XXA SMU with the low ripple filter.

[BravoV]

We didn't even talk about ripple or stability specs they are only better on the >$5000.00 B29XXA SMU with the low ripple filter.

Ok, I think its enough, please .. stop ! 

Just don't want too many people to know what this gem capable of, otherwise it will be harder to get them cheaply in the future. 

[robrenz]

Or voltage/resistance remote programming or 1:1/variable ratio tracking or auto parallel/series operation.

BTW I am going to make some 10 turn 20R pots to replace the one turn. With a turns counter that will give 10µV/div setability.

[BravoV]

BTW I am going to make some 10 turn 20R pots to replace the one turn. With a turns counter that will give 10µV/div setability.

Good idea, how are you going to hook up this extra fine adjustment pot with the existing 1K current pot ? I'm assuming by series right ?

Talking about low resistance precision 10 turn pot, few of my spare 5 watter pots starting from 1.15 Ohm, 20 Ohm and 250 Ohm. 

[robrenz]

BTW I am going to make some 10 turn 20R pots to replace the one turn. With a turns counter that will give 10µV/div setability.

Good idea, how are you going to hook up this extra fine adjustment pot with the existing 1K current pot ? I'm assuming by series right ?

This is for the voltage control, replaces the one turn millivolt dial.  No relation to the current pot.

Talking about low resistance precision 10 turn pot, few of my spare 5 watter pots starting from 1.15 Ohm, 20 Ohm and 250 Ohm. 

Very nice, its a shame that 20R pot won't fit into the 6115A

[Fsck]

you could always use it as an external "upgrade"

[BravoV]

This is for the voltage control, replaces the one turn millivolt dial.  No relation to the current pot.

Doh, I misread it, sorry.

Very nice, its a shame that 20R pot won't fit into the 6115A

Really ? I haven't open up mine yet, damn. 

you could always use it as an external "upgrade"

Lol .. yeah, but that will need some serious case modding which I want to avoid, I guess I will have to wait until Robrenz posted the restoration and modding on his 6115A .

[BravoV]

Reading non-contiguous separated pages of scanned schematic is PITA  , decided to stitch them up into a big single page.

Sharing the HP 6114A and 6115A schematic diagram in single big sheet, stitched and applied minor post processing to sharpen and reduce the grayish background into white.

WARNING ! Huge picture !

[BravoV]

Added different colors on each boards for better clarity when trouble shooting ! 

[robrenz]

Nice job, thanks.  I did that manually with printed pages but yours is nicer

[robrenz]

Just picked up another 6115A with the 10 turn current adjust.  Very nice condition and It has the last cal tag from HP labs dated 1/25/1992 Just hooked it up to the 8846A untouched to see how far off it is. Spec is .025%+1mV.

1V +144µV = .014%
5V  -390µV = .0078%
10V -.00235V = .0235%
20V -.0025V = .0125%
50V -.008V =.016%
100V -.0179V =.0179%

Almost 22 years since its last cal and it is well within spec. 12 hour drift test after letting the reading settle for 4 hours was 9µV total span. The 4 hour initial settle drift was 400µV. Combined that is still within the 8 hour drift spec.

THESE THINGS ARE AMAZING!

[alm]

Reading non-contiguous separated pages of scanned schematic is PITA  , decided to stitch them up into a big single page.

Note that you can also get high quality scans for about $10 from ArtekManuals and Qservice. Most of the Artek ones have stitched schematics, and otherwise it only takes one email to get a fixed one. Contrast, resolution and noise is usually much better than freely available scans.

But I think I am done on power supplies. 8 (not counting the 2 BOSS bipolars) is plenty. 

Just picked up another 6115A with the 10 turn current adjust.

I think you might be the exception to the adage "you can never have too many power supplies" .

Just hooked it up to the 8846A untouched to see how far off it is. Spec is .025%+1mV.
[...]

Impressive performance, especially the low offset at the lower ranges. It desperately calls for comparison with other bench DMMs. I know some old meters from HP et al. that go for less than one eighth of the 8846A retail price .

[BravoV]

THESE THINGS ARE AMAZING!

Congratulations ! 

Can't agree more, and since I have only 5.5 digits DMM, basically when I set the meter with 3 digits mantissa, its basically won't bulge. One of the best and most stable adjustable PSU that I have ever used. 

How is the condition ?

Reading non-contiguous separated pages of scanned schematic is PITA  , decided to stitch them up into a big single page.

Note that you can also get high quality scans for about $10 from ArtekManuals and Qservice. Most of the Artek ones have stitched schematics, and otherwise it only takes one email to get a fixed one. Contrast, resolution and noise is usually much better than freely available scans.

I'm aware of that, and bought two manuals from Artek while ago, but for this HP 6114/5A full schematic, just download my stitched photo, its more than enough to see all circuit's details.

[BravoV]

Almost 22 years since its last cal and it is well within spec. 12 hour drift test after letting the reading settle for 4 hours was 9µV total span. The 4 hour initial settle drift was 400µV. Combined that is still within the 8 hour drift spec.

Looking at above numbers, just curious if this is what people called that an "aged & cooked" voltage reference and/or other precision components are much better than new one ?

[robrenz]

I think you might be the exception to the adage "you can never have too many power supplies" .

There will be a Power Designs sale in the near future.  The better HP spec especially on current and the extremely flexible remote control and series, parallel, and tracking flexibility means I am jumping ship The Power Designs are extremely good but they were not designed for accurate current sourcing.

Impressive performance, especially the low offset at the lower ranges. It desperately calls for comparison with other bench DMMs. I know some old meters from HP et al. that go for less than one eighth of the 8846A retail price .

Please don't feed or encourage the wild animals

[robrenz]

How is the condition ?

Excellent external condition, but as expected the pots need a serious clean and lube.

[GreyWoolfe]

I just started reading this thread and what a tease .  I guess I missed the boat on your August comment BravoV, the cheapest on ePay right now is $199, "used but works good.  Satisfaction guaranteed."  BUT, there is no return/exchanges.  High price is $650.  I guess the cat is already out of the bag.

Tom (with PSU envy)

[BravoV]

There will be a Power Designs sale in the near future.  The better HP spec especially on current and the extremely flexible remote control and series, parallel, and tracking flexibility means I am jumping ship The Power Designs are extremely good but they were not designed for accurate current sourcing.

Doh ... all HP 611X series lovers will be doomed, this man is jumping ship from his truck loads of PD psus, hurry !!!    ... j/k

Excellent external condition, but as expected the pots need a serious clean and lube.

Great to hear that ! 

Btw, photo shots of the process details while you clean & lube that pot please, really eager to learn & watch how you do that, must be very interesting, pretty please.

I just started reading this thread and what a tease .  I guess I missed the boat on your August comment BravoV, the cheapest on ePay right now is $199, "used but works good.  Satisfaction guaranteed."  BUT, there is no return/exchanges.  High price is $650.  I guess the cat is already out of the bag.

Tom (with PSU envy)

Tom, blame it on PedroDaGr8 and Robrenz especially after watching his restoration thread at his 6114A, I did ruin my keyboard after watching that because of excessive drooling. Both are guilty of making this infectious HP611XA addiction started here in this forum, at least to me. 

[SeanB]

Pity the PD ones will be too heavy to send to ZA unless you send then slow mail.

[saturation]

.. with this confirmation of its capabilities, I think we won't see the 6114 or 5a in the $100 range for sometime  .  Its performance is impressive  ! 

I think you might be the exception to the adage "you can never have too many power supplies" .

There will be a Power Designs sale in the near future.  The better HP spec especially on current and the extremely flexible remote control and series, parallel, and tracking flexibility means I am jumping ship The Power Designs are extremely good but they were not designed for accurate current sourcing.

Impressive performance, especially the low offset at the lower ranges. It desperately calls for comparison with other bench DMMs. I know some old meters from HP et al. that go for less than one eighth of the 8846A retail price .

Please don't feed or encourage the wild animals

[BravoV]

I think its just the matter of time that some experienced fellows here in this forum that have this gem will come up with the digital front end for it's remote terminals to tame this beast. I will be sitting nicely at the corner watching & lurking closely for this as I'm not qualified for that. 

[alm]

What would be the point? Do you often build automated test setups? Are rotary encoders and buttons somehow superior to the knobs / thumb wheels they're trying to imitate? The course voltage controls are actually digital on this supply.

Digital controls from the remote programming input will require a voltage source with a better accuracy than the power supply for it not to degrade performance. Stability would mostly be a function of the stability of the programming voltage, so this will require an extremely stable and accurate DAC. HP made a power supply programmer controlled via GPIB, but I'm pretty sure it doesn't have the resolution or accuracy for this.

[robrenz]

Agreed, but I am thinking a relay matrix that can connect the rear connections of three 6114/5As in all of the possible combinations of remote programming, remote sense, normal/auto series, normal/auto parallel, auto tracking, 1, 2, or three units, etc. with necessary connections available at a front panel including connect/disconnect from load relay would be very nice. That would be one very accurate 300VDC supply and they can float at 300V.  A simple mcu interface for all the myriad combinations of relay combinations might be appropriate here. Being able to do a few keystrokes to get any of the features above without dragging all the units out and doing a bunch of wiring on the back would be pretty nice.  Just thinking out loud, I have not thought it through yet.

The output capacitor is even connected by the rear terminals so it can be disconnected when appropriate for sensitive current limit situations.

[robrenz]

Digital controls from the remote programming input will require a voltage source with a better accuracy than the power supply for it not to degrade performance.

My new Keithley 2450 SMU  will be a >= accuracy programming voltage but only when using source read back. It will be a nice way to programmatically control the 611X's

[BravoV]

What would be the point? Do you often build automated test setups? Are rotary encoders and buttons somehow superior to the knobs / thumb wheels they're trying to imitate? The course voltage controls are actually digital on this supply.

Thats it, automated or scripted voltage & current setting from PC or mcu.

Not complaining about the encoder buttons, its just you can't jump / simulate manually with those buttons or by tuning the pot say for example from X to Y volt in short period, or a gradual but stable change like from X -> Y volt in Z sec/min/hour.

Digital controls from the remote programming input will require a voltage source with a better accuracy than the power supply for it not to degrade performance. Stability would mostly be a function of the stability of the programming voltage, so this will require an extremely stable and accurate DAC. HP made a power supply programmer controlled via GPIB, but I'm pretty sure it doesn't have the resolution or accuracy for this.

Any idea roughly on how much stability the external v-ref needed to maintain it's original performance ?

Agreed, but I am thinking a relay matrix that can connect the rear connections of three 6114/5As in all of the possible combinations of remote programming, remote sense, normal/auto series, normal/auto parallel, auto tracking, 1, 2, or three units, etc. with necessary connections available at a front panel including connect/disconnect from load relay would be very nice. That would be one very accurate 300VDC supply and they can float at 300V.  A simple mcu interface for all the myriad combinations of relay combinations might be appropriate here. Being able to do a few keystrokes to get any of the features above without dragging all the units out and doing a bunch of wiring on the back would be pretty nice.  Just thinking out loud, I have not thought it through yet.

The output capacitor is even connected by the rear terminals so it can be disconnected when appropriate for sensitive current limit situations.

+1 This too, thanks Robrenz ! 

[alm]

Not complaining about the encoder buttons, its just you can't jump / simulate manually with those buttons or by tuning the pot say for example from X to Y volt in short period, or a gradual but stable change like from X -> Y volt in Z sec/min/hour.

That's true, but for most applications you don't need the high accuracy of this power supply, however. Doing this with lower accuracy would be much easier. Then you could just hook up an isolated 10-bit DAC or so to an op-amp. Or the HP power supply programmer I already mentioned if you have GPIB. Keep in mind that this power supply may not be designed for fast slewing of its voltage or current (150ms up and 1.5s down with no load). It does not have a downprogramming circuit, for example, so lowering the voltage with a large cap connected and a light load will take forever (and may even blow pass transistors if this was as well designed as some of the Harrison ones ).

Any idea roughly on how much stability the external v-ref needed to maintain it's original performance ?

Look at the specs (0.025% + 1 mV output voltage accuracy and 0.0015% + 15 uV 8h drift). The specs specify voltage programming accuracy as accuracy of the remote source + 0.2 mV, so you would need something like 0.01% + 100 uV accuracy and 0.0005% + 100 uV drift for it not to degrade the accuracy too much.

[johnh]

Back in March I paid $40 US for a HP6114.   

Then there was the shipping back to Australia  $200  (Used a freight forwarder)
For that and some other stuff plus some things my wife bought

Some of the heat sink fins were bent. But, managed to straighten then up.

 

[BravoV]

That's true, but for most applications you don't need the high accuracy of this power supply, however. Doing this with lower accuracy would be much easier. Then you could just hook up an isolated 10-bit DAC or so to an op-amp. Or the HP power supply programmer I already mentioned if you have GPIB. Keep in mind that this power supply may not be designed for fast slewing of its voltage or current (150ms up and 1.5s down with no load). It does not have a downprogramming circuit, for example, so lowering the voltage with a large cap connected and a light load will take forever (and may even blow pass transistors if this was as well designed as some of the Harrison ones ).

Well, realistically I don't aim for the v-ref has fast slew rate more than, say 500 ms (half sec), this should be  "relatively easy" and manageable right ?

Just want to be sure, you're worry about the AC loop stability, right ? CMMIW 

Look at the specs (0.025% + 1 mV output voltage accuracy and 0.0015% + 15 uV 8h drift). The specs specify voltage programming accuracy as accuracy of the remote source + 0.2 mV, so you would need something like 0.01% + 100 uV accuracy and 0.0005% + 100 uV drift for it not to degrade the accuracy too much.

Alm, just asking as a noob, is this enough that the programmer equipped with such devices, not very ambitious though, like < 5 ppm/C voltage reference chip, and with the final driver say like using a chopper op-amp with offset like < 5 uV with drift of < 50nV/C ?

[robrenz]

The voltage programming current is a maximum of 1µA when using the required 32 kOhm resistor do you need a buffer?

[alm]

You're going to need some sort of high resolution voltage divider, most likely a good DAC. I think there's a thread on this forum about a high-end DAC based on an LT appnote. If you want to keep the floating supply, this programmer will need to be isolated from the USB connection if you use USB. I believe the 6115A has a sensitivity of 1V/V on the programming interface, so you'll need to amplify it to the 0-50 V range.

Downprogramming may be even slower than 500 ms. If there's no load, the output cap will need to be discharged through the power supply, which might take up to 1.5s according to the specs. Of course it will be much faster with a large load that quickly discharges the cap.

There's nothing wrong with using a programmer with a much lower accuracy, but it won't be a good replacement for the front panel controls and is kind of a waste of this high end power supply. If you have a GPIB interface, the HP 59501A may not be a bad deal. It's sometimes offered for $30 with few bids, and offers an isolated 10-bit DAC.

[uoficowboy]

Reading non-contiguous separated pages of scanned schematic is PITA  , decided to stitch them up into a big single page.

Note that you can also get high quality scans for about $10 from ArtekManuals and Qservice. Most of the Artek ones have stitched schematics, and otherwise it only takes one email to get a fixed one. Contrast, resolution and noise is usually much better than freely available scans.

Yep - I have the manual for the 6114A from Artek and it indeed has a fully stitched schematic. $12.50 well spent.

[BravoV]

You're going to need some sort of high resolution voltage divider, most likely a good DAC. I think there's a thread on this forum about a high-end DAC based on an LT appnote. If you want to keep the floating supply, this programmer will need to be isolated from the USB connection if you use USB. I believe the 6115A has a sensitivity of 1V/V on the programming interface, so you'll need to amplify it to the 0-50 V range.

Which thread is that ? Mind pointing that out please.

Yeah, I've been thinking about that 1V/V too, and 6115A capable of up to 100V. 

Downprogramming may be even slower than 500 ms. If there's no load, the output cap will need to be discharged through the power supply, which might take up to 1.5s according to the specs. Of course it will be much faster with a large load that quickly discharges the cap.

Looks like its not that easy isn't it ? I guess I'm a bit naive on what to expect. 

There's nothing wrong with using a programmer with a much lower accuracy, but it won't be a good replacement for the front panel controls and is kind of a waste of this high end power supply. If you have a GPIB interface, the HP 59501A may not be a bad deal. It's sometimes offered for $30 with few bids, and offers an isolated 10-bit DAC.

Still that programmer output range at +/- 10V, high voltage like at 50 or even 100V is quite challenging isn't it ?

[alm]

Which thread is that ? Mind pointing that out please.

Sorry, don't have a link handy and don't have time to dig it up. Your Google should work just as well as mine. I think it was based on AN86.

Still that programmer output range at +/- 10V, high voltage like at 50 or even 100V is quite challenging isn't it ?

They use a trick to scale the voltage up to the desired range. Don't remember the details, see the 59501A manual. I guess you could use the same trick with whatever programmer you decide to build. Of course scaling up the output it will make the system more sensitive to noise and offsets, and the scaling resistors will need to be stable.

[saturation]

Bravo, thanks a ton for the stitched schematic.  The amount of time I saved perusing the circuits was so great, I should have done this myself a while back. 

[mmagin]

Thanks so much for the stitched schematic.  I was suffering with the unstitched one for a couple evenings.

I have a 6115A which needed a new C2 for correct +/- 28V reference supplies, but I still don't have the 16V supply properly adjustable, it stays stuck at 19V.  I seem to have a later rev of the A2 board, and the R3 is already populated, though I tried shorting it too and the problem remains.  I need to do some measurements and see if it is inputting what it should to the op-amp or if the op-amp is possibly bad.  Q1 and Q2 at least pass the usual diode-test checks and the surrounding passives test correctly.

That may be all that's wrong with the supply, it currently outputs too high of a voltage, and before I proceed with checks and adjustment the 16V supply is the priority.

(As an aside, I'm so glad I got a DE-5000 LCR meter!)

[BravoV]

mmagin, my pleasure.

What happened to the C2 ?

Also if you don't mind to share the problems you encountered and the fixes if you've done it here.

[mmagin]

mmagin, my pleasure.

What happened to the C2 ?

Also if you don't mind to share the problems you encountered and the fixes if you've done it here.

C2 just suffered the usual high ESR of old capacitors.  Others are nominally okay so I left them for now.  A2U1, which via web searches I cross referenced to a NTE part and then to the LM741 (essentially identical specs) seems to have had a failure of its output stage, it wasn't able to pull down R7 to affect the Q1/Q2 pass transistors (verified before I replaced it by lifting the lead of R7 and measuring its output.)

With the op-amp replaced (Digikey still has the metal-can 741, didn't have to go to shady ebay sellers or make up an adapter board!), I've adjusted the 16 volt supply to within a few millivolts.  I'm going to have to go through all the adjustments once it's fully warmed up to get it back into proper shape, but the output is only off by about 0.13% to 0.23% depending on what part of the output range it is in.

Not sure if perhaps the failed capacitor and insufficient filtering of the +28V rail led to the failure of the opamp, may think about replacing all of the electrolytic capacitors.  hmm.

[mmagin]

Also, C1, the 1 uF film cap across the transformer was making a dreadful amount of buzzing noise.  At first I thought it was the transformer, but I only heard it from one side and I actually could feel the vibration on the capacitor!

Replacing it with a (higher voltage spec, but not too huge) 1uF film capacitor I had on hand has made the supply silent.  Hurray.

[mmagin]

Yep, 1 film cap, 1 electrolytic cap, 1 op-amp and it's back to working correctly and was successful at adjusting it.   I think the millivolts pot may be a bit cruddy, but things seem to basically be correct and the regulation is very solid. 

Still intending to replace the other electrolytics someday, but not right now.  The two large screw-terminal caps seem to use a terminal spacing that is no longer the standard.  Sadly the ones I paid darned good money for are just a little too wide to fit.  I'm thinking about making an adapter PC board to replace each with 2-4 smaller leaded electrolytics each plus a screw, nut, and a brass spacer to give similar standoff distance.  I discovered that there are tin-plated solderable standoffs available with a nice shoulder to fit in a hole in a board, but none commonly available quite as large as I would want to replace screw-terminal caps.

[bitseeker]

If you do go with the adapter board, do post your results here. I recall someone had fit components into some vintage HP gear by soldering to the beautiful gold pads/traces because the original screw contacts didn't fit. So, an adapter would be nice to see.

[mmagin]

If you do go with the adapter board, do post your results here. I recall someone had fit components into some vintage HP gear by soldering to the beautiful gold pads/traces because the original screw contacts didn't fit. So, an adapter would be nice to see.

If I do I will certainly share KiCAD files (and probably an OSHPark shared project too).

[bitseeker]

Fantastic!

When I one day get a 6115A to keep my 6114A company, that adapter may come in handy.

[Peter_O]

Just got an 1986 HP6114A in good condition. Voltage is off <40mV. Stability at 12V is <100µV over 10h, if I can trust my 5.5 digit DMM.

1
The voltage switch seems to have some contact problems. For a lot positions the voltage is floating within the respective digit. When giving a little pressure to move towards the switching point, the voltage stabilizes.

Any advice to get the switch running again and not damaging it?
Maybe contact spray is the wrong approach.

2
There is some chirping noise from the transformator. Something I should do with that?

[coppercone2]

No, the front panel interface with all those switches is a complete pain in the ass if anything goes wrong with it. Quite frankly, those switches suck. If the replacements were cheap maybe, but you are going to get robbed buying replacements for those. Replacing them is extremely annoying also. Taking them apart is even worse, expect crappy brittle plastic, if you want to service them with grease and cleaning, there is a good chance of damage.

[Peter_O]

Not that encouraging. Thx anyway!

I had the idea to spray some non agressive cleaning stuff into these guys without taking them apart.
Eg. Kontakt 61 (not the agressive Kontakt 60) or Teslanol® T6-OSZILLIN.

[coppercone2]

you can do it, just.. you need to be REAL careful

for 60? year old plastic you don't have that much leeway. Dunno if that will get in there, they are not service friendly. I think you need to take them apart and carefully wipe that brass. Mine had like, fossilized shmoo. But my switch was dicky and when I took it apart and put it back together, the front end control circuit broke, so I decided fuck this thing and scrapped it. It would be going back and forth between the control circuit and the front panel. Now you could replace that nice resistor network with a potentiometer set as a rheostat and.. forget about the precision... but the amplifiers in there not that impressive. I really dislike how the stuff in the front is just pressed tight into a wedge like a garage door too. Needs screws.

Its like 4 spring loaded multimeters that shoot plastic out.


GOd, when I look at robrenz restorations, I feel like I bought a fucking giant dilapidated apartment projects complex. I wanna throw all my shit in a swimming pool and stir it with a boat paddle. 

[Peter_O]

It's a later year, 1986. So just 35 years.  :-)
But from the odor it seems to have some smoker's years in it's vita.

I think, I'll give it a try with the non aggressive cleaner. If that does not work, I can always follow that nice restauration report and take the stuff apart. Maybe I'm lucky. ("Well punk, do you think, ..."     )

[bitseeker]

So, did ya get lucky?

[Peter_O]

So, did ya get lucky?

Yes, I did. 

I took the switch block apart and blew some Teslanol® T6-OSZILLIN and compressed air through existing holes of the switches. Same with the meter input switch.
Now it's working perfectly fine, as my other new old companion, a 3455 for 140 Euro incl. shipment, shows. E.g. 5V stay within +/- 20µV over an hour.

[coppercone2]

ah, you did not take the switch bank apart like I did. I should have left it alone but the inside was filled with chunky grease.

I should have put it in a bag of oil, ultrasonic it, and flush it with a generous amount of oil then like spin dried it

is there a safe solvent to totally soak plastics in that will dissolve old grease? I figure alcohol would crack the casing. I dunno if you can just throw it into a cup of warm WD40 or something.

[Peter_O]

ah, you did not take the switch bank apart like I did. I should have left it alone but the inside was filled with chunky grease.

I read your restauration report with great interest and it encouraged me to start desoldering the whole switch assembly.
I took the bank apart but did not open the switches.

is there a safe solvent to totally soak plastics in that will dissolve old grease? I figure alcohol would crack the casing. I dunno if you can just throw it into a cup of warm WD40 or something.

I decided to use Telsanol, as it is described to be not agressive but to clean and lubricate. There were some encouringing posts in german forums. It seems to lubricate the plastics to some extend, at least the black got darker. The cleaning results are excellent. Just a short spray into the switch, some full switching cycles and every position is making perfect contact again. Before cleaning the .1 switch was so bad that I feared, there might be no pcb track left.


Now there is only the chirping noise from the transformator area left. Maybe I take the idea from somewhere above and try a new 1µF film capacitor.

[coppercone2]

what bugs me about not taking it apart is that there were like.. chunks in there. It looked like old fat on a frying pan that got used dirty too many times. I imagine if you don't fully open and flush it, they would just be sitting in the bottom of a switch.

If its totally dormant or benign I don't know, but it sure bothered me. I had to scrub mine with a brush with alcohol to get it all off. If you can handle not knowing whats in there, or not being bothered by a little bit of orange grease, you are fine.

To be honest I did full cleanup of mechanical gearbox before, and its satisfying while its open, but when you re-grease it it ends up looking like shit anyway. The switch gets almost no use compared to a gear box though, so I don't think you have traditional gear box problems of grease loaded with metal, its just some what oxidized. But having the switch fully open lets you put like.. actual grease in there (i.e. like smear). So theoretically it should offer a longer life. What I know with multimeters is you are supposed to take them apart and put actual grease there. If the lubricant you used has a similar staying power its fine.

I recommend just living with it and NOT taking the switch apart because its hardly anything. I just think the solution they did with that switch is pretty bad.

Don't even know if you will live long enough to re service that switch anyway... based on how well they last. OCD hurts here

If you can't help yourself beware there is a little brass plate there that is fitted over some thin plastic pegs. robrenz has a photo of it. If you take the switch apart, you won't know exactly where to put the brass plate (it has multiple alignment holes that all fit over the pegs), so you will have a offset. Its perilous. The spring shoots plastic out, its held in kinda loosely also. And IIRC they don't always snap back together so you might have a plastic welding job there. You need to like tap on the top to make sure the little brass plate is not stuck to the top while you lift the top of so it remains correctly positioned. Don't haphazardly put it back together if you mess up.

I musta put it back together or just deformed something that prevented the front panel from working right, so I tried to replace it with a helipot, but then there was another problem and I lost my cool. Maybe if I took a break for a month and left it on a shelf i coulda had it back together working with a few minor repairs. But I also think some time during this madness I lost a spring.

[Peter_O]

Don't even know if you will live long enough to re service that switch anyway... based on how well they last. OCD hurts here

Meanwhile the solvents should have vaporated and the switches are still fine. I will let it rest for now.

But I managed to cure the chirping sound from the trafo area. It was the 1µF foil capacitor.