Now, the problem presented itself when I tested the unit. Because all of these analog pots are older than dirt, tiny crap inevitably got inside of them. The result of this is a very VERY serious problem. To make matters worse, the main voltage control pot is not wirewound. It has a solid circular (ring) resistive metallic (or more likely ceramic because it's a Cermet pot) element inside and offered (notice the past tense here) seemingly true contiguous adjustment.
So, the solution to the dilemma was to take a single 10 kOhm Chinese Bourns imitation 10-turn pot and replace the two (coarse and fine) with the single multi-turn pot.
My only concern is not knowing how many watts of power are being placed through the pot itself to make sure that this is within the 0.6 W or so that it is rated for. In a conventional voltage regulator circuit, the current flowing between the Adj and Out pins is tiny. In this particular supply's circuit, who knows...
Does it deal with the range switchover on the transformer?
ELECTRIC CORPORATION
VOLT AMPERE TESTER
SUN VAT -40
AMMETER ELECTRICAL
ZERO ADJUSTMENT
This adjustment knob is used to periodically set
the ammeter pointer to the zero (0) line
electronically. When adjusting zero, the TEST
SELECTOR must be set to #2 CHARGING position
with the Load Leads connected to the battery
(Figure 1).
QuoteMy only concern is not knowing how many watts of power are being placed through the pot itself to make sure that this is within the 0.6 W or so that it is rated for. In a conventional voltage regulator circuit, the current flowing between the Adj and Out pins is tiny. In this particular supply's circuit, who knows...
Yeah, I'd be surprised if there was much going through it. Of course, if you really want to know, "take it apart"...again.
What it definitely does not do is control positive, zero or negative current into the load, which is what I thought it would do.
A beginner's question: do PD models that do not have dedicated CC/CV signalling bulb have any means to notify the user when control is switched to CC? Or one should recognize the decreasing voltage level on the meter?
I plan to buy a nice vintage PD supply but I have never used any yet.
First: thanks for the offer. In fact I am sitting in Europe but I do have a US address for shipping. But: I am a newbie to PD supplies only. I am an electrical engineer myself, so maybe you would like to preserve your supply for a real beginner who needs a starter kit.
But still, I am looking for a DC supply for daily use (I am not satisfied with my current one) and I believe keeping these vintage stuff alive is a good thing (and they also look nice). Your offer is thus interesting to me and I am also willing to pay a reasonable price for it (I am currently searching on ebay).
What modifications have you made on your model? I will have to modify my one anyway because of the different input voltage levels here.
First: thanks for the offer. In fact I am sitting in Europe but I do have a US address for shipping. But: I am a newbie to PD supplies only. I am an electrical engineer myself, so maybe you would like to preserve your supply for a real beginner who needs a starter kit.
But still, I am looking for a DC supply for daily use (I am not satisfied with my current one) and I believe keeping these vintage stuff alive is a good thing (and they also look nice). Your offer is thus interesting to me and I am also willing to pay a reasonable price for it (I am currently searching on ebay).
What modifications have you made on your model? I will have to modify my one anyway because of the different input voltage levels here.
Yes, I was thinking about giving it away as a prize if I ever get around to delivering that presentation on op-amps that I promised last year but have yet to deliver on.
As far as the mods/repairs, the heater coil and thermostat were gone when I got the unit. There were some other minor issues, but nothing major. The heater being out just means that the voltage reference wasn't inside a nice temperature controlled chamber. I rewound the heater with some resistance wire. I didn't want to mess with the mains voltage that was powering the heater, so I have rewired it to the unused phase of the secondary that supplies unregulated DC to the series regulator. The thermostat is just a simple comparator with hysteresis and a MOSFET. It seems to maintain the oven temps with a little better variation than how (I've read) the originals perform, and I am not able to measure any disruption in the output from the heater switching on/off. Of course, my circuit is just a hand-soldered protoboard mounted to the main PCB via some screws, standoffs, and holes I drilled in the PCB. Not pretty, but functional.
If you're OK with voltage adjustment via a potentiometer, there are lots of the older HP supplies like the 6237B on eBay for very cheap. IMHO the nicest "vintage" supplies are the HP 6114A and 6115A. I've repaired and completely refurbished several of these, and I love them and will never part with them They are really scarce now, but if you're not in a hurry, put a watch on eBay. Unfortunately, there are a few sellers up there with completely ridiculous asking prices and what amount to permanent auctions on these. This tends to mislead the usual eBay surplus scavengers into thinking that's what they can get for the partially functional or physically damaged units that they bought for next to nothing. But if you watch, you can still occasionally find one at a reasonable price, or maybe even talk a seller down by showing him what they actual sell for. The last one I bought I paid $75 (shipped). This is all eBay US, so maybe the situation is different where you are.
There are other good, but inexpensive, supplies out there, I am sure. This might be a good topic for a separate thread on the forum. Another option, if you want a project, is to get one of these old supplies and scrap everything except the chassis, KV divider, and transformer. Building a very good quality series regulator is not very complicated with all the wonderful ICs out there now.
First: thanks for the offer. In fact I am sitting in Europe but I do have a US address for shipping. But: I am a newbie to PD supplies only. I am an electrical engineer myself, so maybe you would like to preserve your supply for a real beginner who needs a starter kit.
But still, I am looking for a DC supply for daily use (I am not satisfied with my current one) and I believe keeping these vintage stuff alive is a good thing (and they also look nice). Your offer is thus interesting to me and I am also willing to pay a reasonable price for it (I am currently searching on ebay).
What modifications have you made on your model? I will have to modify my one anyway because of the different input voltage levels here.
Yes, I was thinking about giving it away as a prize if I ever get around to delivering that presentation on op-amps that I promised last year but have yet to deliver on.
As far as the mods/repairs, the heater coil and thermostat were gone when I got the unit. There were some other minor issues, but nothing major. The heater being out just means that the voltage reference wasn't inside a nice temperature controlled chamber. I rewound the heater with some resistance wire. I didn't want to mess with the mains voltage that was powering the heater, so I have rewired it to the unused phase of the secondary that supplies unregulated DC to the series regulator. The thermostat is just a simple comparator with hysteresis and a MOSFET. It seems to maintain the oven temps with a little better variation than how (I've read) the originals perform, and I am not able to measure any disruption in the output from the heater switching on/off. Of course, my circuit is just a hand-soldered protoboard mounted to the main PCB via some screws, standoffs, and holes I drilled in the PCB. Not pretty, but functional.
If you're OK with voltage adjustment via a potentiometer, there are lots of the older HP supplies like the 6237B on eBay for very cheap. IMHO the nicest "vintage" supplies are the HP 6114A and 6115A. I've repaired and completely refurbished several of these, and I love them and will never part with them They are really scarce now, but if you're not in a hurry, put a watch on eBay. Unfortunately, there are a few sellers up there with completely ridiculous asking prices and what amount to permanent auctions on these. This tends to mislead the usual eBay surplus scavengers into thinking that's what they can get for the partially functional or physically damaged units that they bought for next to nothing. But if you watch, you can still occasionally find one at a reasonable price, or maybe even talk a seller down by showing him what they actual sell for. The last one I bought I paid $75 (shipped). This is all eBay US, so maybe the situation is different where you are.
There are other good, but inexpensive, supplies out there, I am sure. This might be a good topic for a separate thread on the forum. Another option, if you want a project, is to get one of these old supplies and scrap everything except the chassis, KV divider, and transformer. Building a very good quality series regulator is not very complicated with all the wonderful ICs out there now.
If you ever decide to give that supply away I will sign up. I have been wanting to get a Power Designs supply for awhile, and my current bench supply is really starting to act up. Oh and Im also a relative beginner. I just like high quality gear that you can actually repair (My background is in technician work).
Those HP supplies look beautiful. Remind me of this one...
http://www.ebay.com/itm/272157564667?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
What are some general usages of a supply with so much precision? Maybe setting bias currents on transistor pairs? Most of the opamp circuitry I have worked with hasnt been too fussy (yet atleast )
A beginner's question: do PD models that do not have dedicated CC/CV signalling bulb have any means to notify the user when control is switched to CC?
If you're OK with voltage adjustment via a potentiometer, there are lots of the older HP supplies like the 6237B on eBay for very cheap.
IMHO the nicest "vintage" supplies are the HP 6114A and 6115A. I've repaired and completely refurbished several of these, and I love them and will never part with them They are really scarce now...
To add a digital readout to a vintage analog power supply, connect a free cheapie multimeter from Harbor Freight.
Yeah, I've been looking for a 6114A with 10-turn pot at a reasonable price for, I don't know, a year now? Like you said, the flippers on eBay want way too much for them. $300+
What do you find to be the primary pros/cons of the HP 6114A/6115A vs the PD 2005/2010/2020/4010/5020 precision supplies?
Ah, yes. Those little DVM modules are cool. They get up to 5 digits for a few bucks more.
Thanks for the links. I'll probably end up going the DIY upgrade route, depending on how my patience lasts.
Nice comparison. #1 HP push wheels worry me a bit, too. The PD knobs look cool and unusual. #2 is the reason I waited to buy a 2010, no custom oven. #3 & 4 are the primary reasons I'd like to get one of the HP's. #5 I suppose could be a DIY upgrade to the PD. #6 for the PD is especially nice with panels that have engraved labels.
There's rarely a need for that much precision in a voltage supply. I do also have a precision current source, and I've used that to characterize transistors and LEDs. It's just more controllable to set current directly rather than trying to hit a target current with a voltage source. A hundredth of a volt on a PN junction actually makes a significant difference in current.
What I like about the supplies is that they are very low noise, pure linear supplies - not even a switching pre-regulator to introduce switching noise. They do not have a fan, so silent operation. The schematic is available, and there is a "Theory of Operation" section in the manual that is a good way to learn more about the design of series voltage regulators. And they seem to last forever if you take care of them. Plus, there's just something about restoring one of these things to near original condition that is satisfying. So much of what is manufactured these days has a shelf life of at most a few years. It's just wonderful to see a piece of solid engineering like this, even if the tech is a little dated, and to bring it back to life and think about it maybe making some future engineer happy long after I am gone.
Ah, yes. Those little DVM modules are cool. They get up to 5 digits for a few bucks more.
Thanks for the links. I'll probably end up going the DIY upgrade route, depending on how my patience lasts.
Nice comparison. #1 HP push wheels worry me a bit, too. The PD knobs look cool and unusual. #2 is the reason I waited to buy a 2010, no custom oven. #3 & 4 are the primary reasons I'd like to get one of the HP's. #5 I suppose could be a DIY upgrade to the PD. #6 for the PD is especially nice with panels that have engraved labels.
On the pushwheels: I have disassembled and cleaned two sets of them. It's not bad if you are careful. robrenz has some good tips on this in the topic he posted about his 611xA rebuild.
Can you use any of the PD supplies in a constant current mode?
So, what I did instead was used my digital cutting machine to cut new numbers out of white adhesive vinyl. Kind of a pain in the ass to get them all aligned right, but it looks nice. Next time, I think I might try cutting all the numbers into a strip of static cling vinyl instead and then wrapping it around to wheel and applying white spray pain. Let it dry, remove the cling stencil and voilĂ !
Anyway. Very nice power supplies. Also, I made up some custom adapter boards to replace those 4-Terminal Sprague caps with standard 10mm Snap Caps. They're up on OSHPark if anyone wants them.
Anyway. Very nice power supplies. Also, I made up some custom adapter boards to replace those 4-Terminal Sprague caps with standard 10mm Snap Caps. They're up on OSHPark if anyone wants them.
BTW - can you give a link to the OSHPark project? I searched for it, but wasn't able to find it.
Anyway. Very nice power supplies. Also, I made up some custom adapter boards to replace those 4-Terminal Sprague caps with standard 10mm Snap Caps. They're up on OSHPark if anyone wants them.
BTW - can you give a link to the OSHPark project? I searched for it, but wasn't able to find it.
Yes, I actually need to upload new Gerbers first. One of the pads was off by 0.5mm (they still worked fine, but I might as well fix it). I'll do that tonight and pop the link here).
I also bought a physical copy of the 6114A service manual and scanned it plus the schematics in at 600DPI. I spent 12 hours stitching the schematics together, cleaning it up, and adding stuff from the Eratta sheet. I'll upload that, too.