EDC 501J - Page 1
Forum section: electronics / testgear

author: gilbenl
author_rank: Regular Contributor
timestamp: April 01, 2015, 04:04:55 am
content: Picked up an EDC 501J DC standard for $200+SH. It has 10V and front panel switch (2n Binary) options. Advertised as fully functional with 30 day warranty.Arrived today and its got me nervous. On the 10V range, its nonresponsive to switch input, overload remains illuminated and output is 15.9V. 100mv range seems to work fine and produce a very stable output, albeit out of cal. The front panel switches are dicky and its generally dirty. No visible abuse or tampering inside or out. The seller agreed to send me an RMA and refund purchase and shipping.Before I box it up, is this somethingworthfixing? It'd be nice to have, but not in the form of a money/time pit.Does anybody have a full service manual for it?

author: TiN
author_rank: Super Contributor
timestamp: April 01, 2015, 04:18:27 am
content: Check if sense connection is alright. Usually there are shorting plugs between output and sense.

author: gilbenl
author_rank: Regular Contributor
timestamp: April 01, 2015, 02:34:10 pm
content: They're bridged. I'm fairly confident that I can track down the problem if I have a service manual and possibly without. I'm really asking if I overpaid and should take the opportunity to get out from under it or if, when fixed, its worth something more than $200.

author: TiN
author_rank: Super Contributor
timestamp: April 01, 2015, 03:03:30 pm
content: I have similarMV106box. If you don't have bunch of precision LTZ1000 or LMx99 references and don't need to calibrate 6.5+ digit DMMs, then this EDC unit could serve you well as DC standard. It could be something as simple as loose wire or connector, due to shipping stress, or could be completely dead inside with parts fried.Is it worth a risk, is up to you, but I would try to fix it if it's just 200$. But if u can get RMA unit, then probably not worth risks.

author: gfiber
author_rank: Contributor
timestamp: April 01, 2015, 04:38:45 pm
content: http://www.krohn-hite.com/htm/ServiceSupport/PDF/Manuals/501-J%20Manual.pdfThe above link should help if the event the unit did not come with a manual. No schematics however.

author: gilbenl
author_rank: Regular Contributor
timestamp: April 01, 2015, 05:35:37 pm
content: Thanks-Was able to get block diagrams from Krohn Hite, but no schematics and its missing the page where it actually shows the test points. Waiting for a call back from another person at Krohn Hite who is more familiar with these. I've gone through and reseated the IC's, edge connectors etc. We'll see...Update: D'OhKrohn Hite engineer solved my problem in a sentence: "Put jumpers between B-F and C-E on the amphenol connector" The 100mV range uses a different output config, which is why it didn't overload. Works like a charm-Just needs a little IPA and Deoxit. Jumper diagram below for the next guy...FWIW-Guys at Krohn Hite were awesome even though this was an inherited model that they don't see often. If I were in the market for something new, I'd definitely buy from them for the quality of support alone.

author: SilverSolder
author_rank: Super Contributor
timestamp: March 15, 2017, 06:57:28 pm
content: Apologies for re-awakening a soundly sleeping thread... Did you ever get a diagram for your unit?I called Krohn-Hite and agree they are a super bunch of people to deal with, but they did not have a diagram for this unit...

author: fenugrec
author_rank: Frequent Contributor
timestamp: March 15, 2017, 07:59:10 pm
content: Funny thing, I was considering buying a used EDC 501 a few days ago, and found service manuals with at least partial schematics, but I don't remember what website it was from...

author: fenugrec
author_rank: Frequent Contributor
timestamp: March 15, 2017, 08:05:59 pm
content: Aha !http://www.ianjohnston.com/index.php/videos/21-video-blog-018-building-a-front-panel-for-an-edc-501j-voltage-standard

author: SilverSolder
author_rank: Super Contributor
timestamp: March 16, 2017, 10:34:06 pm
content: Funny, I stumbled on the same site yesterday! - very thorough man, Mr. Johnston (thank you, if you are reading this!)

author: cellularmitosis
author_rank: Unknown
timestamp: July 12, 2017, 04:15:30 am
content: Just got one of these off of ebay. I was also seeing very strange output until I stumbled upon this thread, put jumpers in as described above, and it worked!

author: cellularmitosis
author_rank: Unknown
timestamp: July 12, 2017, 04:28:08 am
content: Looks like that amphenol connector served as a remote breakout for binding posts allowing for remote sense / force leads (see attached diagram, from the manual).

author: cellularmitosis
author_rank: Unknown
timestamp: September 11, 2017, 04:36:02 am
content: These units have a handful of 0.1uF 100V MKC 1860 polycarbonate film capacitors. Unfortunately, most of them look a little leaky, and they are no longer made.http://www.vishay.com/docs/26028/26028.pdfThere is also a 0.22uF 400V MKT 1813 polyester cap in this device, and it looks like those are still available at Mouser:http://www.mouser.com/Vishay/Passive-Components/Capacitors/Film-Capacitors/MKT1813-Series/_/N-9x371?P=1z0sea2Z1z0zls5http://www.mouser.com/ds/2/427/mkt1813-239775.pdfI'm wondering if I can just go with polyesters to replace the polycarbonate caps?

author: powersupply
author_rank: Contributor
timestamp: November 03, 2017, 07:14:51 am
content: I just got my hands on a EDC 501J it has the 6 BCD sets of switches. It was around 160 US dollars delivered. It did not work till I read this blog and made the jumpers for it, it now works. My calibrated HP 34401A meter displays 100.008 millivolts when I flip the switches to 100 millivolts. This puts it at 8 microvolts off. (Warm up time has only been 30 minutes).The Resolution according to the manual: (It has options *B and *D installed)Basic Model 10 V range =10 ppm or 100 µV* Option D 100 mV range =10 ppm or 1 µV* Option B 10 V range =1 ppm or 10 µV* Options B & D 100 mV range =1 ppm or 0.1 µVAccuracy:±0.002% of programmed value + 0.0005% or range +3µV.So in terms of accuracy, assuming the 100.008 millivolts stays true and the meter is spot on, this 501J is +8 microvolts off and should be no more than 3 microvolts off (range + 3 microvolts). However for my purposes it will be fine if it stays at this level of accuracy.All in all I think I got a bargain from EBAY.Thanks to whomever did the research on those jumpers.

author: bitseeker
author_rank: Super Contributor
timestamp: November 09, 2017, 03:50:00 am
content: powersupply, on the BCD front panel version like you have, you can go beyond 9 for each digit (they're hexadecimal). Although such values are "illegal," they're supported. For example, in your photo, to get 100mV set the switches to 81 81 81 81 81 82 (i.e., 99.9999 + 0.0001 = 100.0000).You could also compare that with setting the MSD to 82 and the rest to zero.Note that the maximum output is 11 volts. So, the use of illegal values is limited.

author: powersupply
author_rank: Contributor
timestamp: November 09, 2017, 01:24:34 pm
content: Thank you bitseeker, very good information,ps

author: BertSP
author_rank: Contributor
timestamp: November 30, 2017, 12:27:21 am
content: I also just picked up a 501-J on eBay and thanks for the info on shorting the Amphenol, without it this would have been a dud. Instead its seems to work.Now on to calibrating it if possible. Any pointers would be helpful, I have the BCD type.Are the option codes evident?Thanks