Precision Designs 2005p Power Supply Manual - Page 1
Forum section: electronics / testgear

author: msobreira27
author_rank: Contributor
timestamp: November 01, 2017, 07:58:47 pm
content: Does Any body have the pdf or scan of the manual for the Power Supply Precision Designs 2005p? I just bought one from ebay and I know it will need some fixing.My idea is to transform the power supply in a digital programmable power supply - Digital potentiometer to control the adjustment (AD5272 eval board, 20kOhms 1024 position potentiometer), Arduino to handle the keyboard and send the I2C messages to the eval board to control potentiometer and timing and possibly a ICL7135 4 1/2 voltmeter - all pretty much "of the shelf" stuff.I looked all over the internet and could not find the manual - I found a page:www.rako.comthat has the 2005A manual scanned, and some description, but I figured that the 2005p has an specific complete manual as described below.I found on copy on ebay, but it does not ship overseas:https://www.ebay.com/itm/POWER-DESIGNS-2005P-PRECISION-DC-POWER-SUPPLY-MANUAL-SCHEMATICS-PARTS-LIST/391469202554?hash=item5b2561fc7a:g:SsoAAOSwn8FXSz9pThanks,Mauro.

author: timb
author_rank: Super Contributor
timestamp: November 01, 2017, 09:24:00 pm
content: FYI, I have one of these I scrapped for parts due to a blown reference module. So if you need replacement transistors, transformers, pots or whatever, let me know. I’ve also got a professionally sanded and repainted case available, along with a scratch free front panel.I was never able to find the manual for this specific unit, but found it to be similar to the 2005 (non-A) construction wise. In fact, the main board was identical to the 2005 if I recall.Keep in mind the 2005 and 2005A also feature the same remote programming capability. The only difference is the 2005P’s limited front panel.

author: msobreira27
author_rank: Contributor
timestamp: November 03, 2017, 06:50:12 pm
content: Thanks for the offer, waiting on mine to arrive. Indeed it is probably a better deal to get the 2005A but I got mine for 50 dollars on ebay and the seller said it was in good working condition except for the power lamp...so for the specs I took the bait!

author: timb
author_rank: Super Contributor
timestamp: November 03, 2017, 10:15:40 pm
content: As for remote control, I considered this awhile back and thought of using a multiplying current DAC instead of a digital potentiometer for control. A 14 to 16 bit unit would be ideal. You want a unit without a built in reference. I actually drew up a circuit using an LT part and successfully simulated it, but never got around to trying it out. I can dig up the circuit if you want.The problem with using a digital pot is accuracy and linearity. Ultimately, you could use a digital pot, but you’d need to add an ADC to read back the voltage and implement closed loop control in software. With the DAC method, you could do without the ADC by implementing a lookup table of DAC codes vs power supply output voltage, since you’d have more bits to work with and better linearity.The other problem with a digital pot is compliance voltage. Most have a 5V limit, which is well outside the 20V you’ll need with the power supply. Higher end current DACs can do 30V or more.HP actually used to make a “Power Supply Programming” box for their older power supplies that were remote programmed with resistance, just like the Power Designs supplies. It was essentially two multiplying DACs with a GPIB interface. So the idea is sound. Remember, a DAC is nothing but a network of resistors.

author: msobreira27
author_rank: Contributor
timestamp: November 05, 2017, 10:28:23 pm
content: Timb,Many thanks for the input. Very good info!I figured out that the two programming boxes HP made were the Agilent 59501A and 59501B (12bit DAC converters, 1000 positions in two decades). The manual for the 59501B is in the following link:https://www.excaliburengineering.com/media/datasheets/Agilent_59501B_usm.pdfthey sell pretty cheap on ebay - some less than 30USD. for the price I bought one.The best source of info I found regarding the 2005 PD power supplies are in this site:http://www.rako.com/Articles/29.htmlIt says, on the programming part:• Select a programming resistance by multiplying the desired output voltage by 1000 (the programming constant is 1000 ohms per volt). A constant current of 1 milliampere will flow through this resistance, and its wattage rating should be chosen to minimize drift due to heating.After reading the manual for the programming box, it seems that the resistors required are set by the coarse and fine adjustments in the front panel, then voltage input from the DAC corrects the drop of voltage which a resistor would provide to programming terminals of the power supply.Posting the files for your programming DAC box will be nice if you can find it, as your solution should present much better resolution.I would not went into this without your post. Thanks again!