Hewlett Packard 522B counter - Page 1
Forum section: electronics / testgear

author: MaxFrister
author_rank: Regular Contributor
timestamp: July 15, 2022, 06:57:51 am
content: I recently picked up an new project, a Hewlett Packard 522B counter.So far I've given it a good cleaning and tested the 49 vacuum tubes. Waiting on new caps and NOS tubes.

author: bd139
author_rank: Super Contributor
timestamp: July 15, 2022, 07:11:31 am
content: Very cool. Interested to see how your refurb goes

author: AVGresponding
author_rank: Super Contributor
timestamp: July 15, 2022, 01:49:03 pm
content: Up to 200V pk-pk trigger!

author: edpalmer42
author_rank: Super Contributor
timestamp: July 15, 2022, 04:13:49 pm
content: This is one of the very few cases where HP rebadged another company's product. This is an EPUT (Event per Unit Time) meter from Beckman/Berkeley. I had one long ago. I think mine had 6 digits.Ed

author: MaxFrister
author_rank: Regular Contributor
timestamp: July 15, 2022, 05:02:29 pm
content: Basic specs:Measures: Frequency, period, time interval measurement, ratio, total eventsIntroduced: 1953Original price, $900 — approx. $10k in today’s dollarsFrequency measurement: 10cps to 150kcps (cycles per second, hertz has not been invented yet).Time interval: 10uS to 27.8 hoursIncludes self check49 Vacuum tubesBased upon AC-4A/B counter modulesPower required 260WattsWeight 45lbs in the “portable” caseOvenized crystal oscillator.Stability: 10ppm per week, can be standardized to WWV (if only it still existed).Accuracy: +/-1 count + stabilityInput required +/-0.2V to 100V, positive or negative triggering.Input: direct coupled, 1M ohm impedance shunted by 50uuF (the picofarad had not been invented).Can provide an overflow count to allow more than 5 digits of countingCan provide 90V to power a photo tubeWith an optional circuit, can provide output for a plotter or printerThis particular unit was manufactured circa 1956 and the last cal was in 1971.Manual:http://ftb.ko4bb.com/manuals/24.113.155.190/HP_522B_Frequency_Counter_Service_Manual.pdfManual for AC-4A/B counter modules:http://www.hparchive.com/Manuals/HP-AC-4A-4B-Manual.pdfHP Journal Article: Sept/Oct 1953:http://www.hparchive.com/Manuals/HP-523B-Manual.pdf1954 catalog entry:http://www.hparchive.com/Catalogs/HP-Catalog-1956-10-Revised.pdfRelated machine: 523B:http://www.hparchive.com/Manuals/HP-523B-Manual.pdfRelated machine, HP 524B (Circa 1952):http://www.hparchive.com/Manuals/HP-523B-Manual.pdfHP Journal Article HP 524B, March/April 1954:http://www.hparchive.com/Manuals/HP-523B-Manual.pdf

author: Wrenches of Death
author_rank: Regular Contributor
timestamp: July 16, 2022, 03:02:58 am
content: Quote from: MaxFrister on July 15, 2022, 05:02:29 pmPretty sure that WWV is still kicking. The last time I checked, they were up on 2.5, 5, 10, 15, and 20 megacycles. I haven't heard them on 25 megacycles in a very, VERY long time.WoD

author: MaxFrister
author_rank: Regular Contributor
timestamp: July 16, 2022, 01:31:20 pm
content: I’m glad to hear that WWV is still kicking. I recalled reading that they were planning to shut it off.Here is a pic of the 522B internals before cleaning and disassembly

author: MaxFrister
author_rank: Regular Contributor
timestamp: July 16, 2022, 01:48:56 pm
content: Of the 4 dozen tubes around 5 tested bad or weak.

author: MaxFrister
author_rank: Regular Contributor
timestamp: July 16, 2022, 01:50:25 pm
content: Most of the replacements have arrived. Of course the one I needed first for the PS arrived from that awful auction site not as NOS but old and bad.

author: MaxFrister
author_rank: Regular Contributor
timestamp: July 16, 2022, 01:51:45 pm
content: I’ve started the cap replacement. Here I’m using a period appropriate Cornell-Dubilier BF-70 analyzer to reform a NOS can cap.

author: TimFox
author_rank: Super Contributor
timestamp: July 16, 2022, 04:22:37 pm
content: Amusing detail about the CDE test unit: the "common" post is red, while the "R" and "C" are black.

author: MaxFrister
author_rank: Regular Contributor
timestamp: July 16, 2022, 04:42:21 pm
content: Quote from: TimFox on July 16, 2022, 04:22:37 pmAnd indeed common is positive. That seems to have been "common" for magic eye bridges. My Heathkit C-3 Condenser checker is the same except that the common terminal is also black. I have to remember that little quirk every time I get it out.

author: edpalmer42
author_rank: Super Contributor
timestamp: July 16, 2022, 07:56:43 pm
content: I see you're looking for a hard copy of the manual. I'm not sure what you've found online, but I spent a few minutes and came up with the following:Manuals:https://www.ebaman.com/remository/ELECTRONICS/Test-Equipment/HPAgilent/Counters/HP-521/http://www.ko4bb.com/getsimple/index.php?id=download&file=HP_Agilent/HP_522B_Frequency_Counter_Service_Manual.pdfhttp://bama.edebris.com/manuals/hp/521a/http://www.hparchive.com/Manuals/HP-523B-Manual.pdfIt looks like the 521, 522, and 523 counters are all nearly the sameOther Info:https://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1953-09.pdfhttps://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1952-11.pdf

author: MaxFrister
author_rank: Regular Contributor
timestamp: July 16, 2022, 08:43:24 pm
content: Someone has sent me a clean copy of the schematics. They should be available in a couple of days athttp://www.ko4bb.com/getsimple/index.php?id=manuals.

author: Cubdriver
author_rank: Unknown
timestamp: July 17, 2022, 07:20:57 am
content: Cool old beast, and definitely a room heater! Nice score!-Pat

author: MaxFrister
author_rank: Regular Contributor
timestamp: July 18, 2022, 03:57:34 am
content: Here is a picture of the bottom of the instrument. The object on the right is a delay line.

author: MaxFrister
author_rank: Regular Contributor
timestamp: July 18, 2022, 04:02:49 am
content: It was a bit of a challenge to find room for the replacement caps:

author: MaxFrister
author_rank: Regular Contributor
timestamp: July 18, 2022, 04:04:38 am
content: Here's a pic of the high-tech selenium rectifier:

author: Cubdriver
author_rank: Unknown
timestamp: July 18, 2022, 05:00:55 am
content: What's that towards the rear on the right side of the chassis underside picture - a stack of doorknob caps, or a tapped coil? Despite having one for several years now I have never opened and looked at the underside.Great pictures, too!-Pat

author: MaxFrister
author_rank: Regular Contributor
timestamp: July 18, 2022, 05:34:02 am
content: That's the delay line, DL101. Ten sections of 60mH and 68pF each.It's part of the reset circuit. According to the manual:"The pulse to the Signal Gate is delayed twenty microseconds by Delay Line DL101 to give the counter circuits time to reset and stabilize before they receive the new signals."

author: MaxFrister
author_rank: Regular Contributor
timestamp: July 19, 2022, 04:00:40 am
content: It can count!After completing the recap I installed just 2 of vacuum tubes and brought up the machine on a variac and dim-bulb. After verifying that the -105V rail was present, I added 2 more tubes and tried the +200V rail. Also present.At that point I removed the dim bulb and reassembled the machine. Again I bought it up on the variac and confirmed that current draw was okay. Somewhat to my surprise it almost worked. The count was off but consistent.After 50+ years since the last calibration, the machine was due for adjustment. After I adjusted the power supply and the “phantastron” dividers it passed self-test. After tweaking the OCXO, it was accurate.Summary:Replaced AC cord.Replaced 8 vacuum tubesReplaced the selenium rectifierReplaced paper and electrolytic caps (I left the original precision paper/oil caps as they tested okay).Adjusted the machine.Beware: It turns out that 2 of the caps are marked in reverse polarity in the original schematic and the machine was wired that way. I’m not sure how they got away with that but maybe old caps are not as touchy about reversed polarity as new ones. Anyway, C130 and C131 should have the polarity reversed on the negative rails.

author: Cubdriver
author_rank: Unknown
timestamp: July 19, 2022, 04:41:31 am
content: Looks great! Nicely done!-Pat