Would you pay $100 for a HP6115A psu ?

[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 .