Hewlett Packard 522B counter

[MaxFrister]

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.

[bd139]

Very cool. Interested to see how your refurb goes 

[AVGresponding]

Up to 200V pk-pk trigger!   

[edpalmer42]

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

[MaxFrister]

Basic specs:

Measures: Frequency, period, time interval measurement, ratio, total events
Introduced: 1953
Original price, $900 — approx. $10k in today’s dollars


Frequency measurement: 10cps to 150kcps (cycles per second, hertz has not been invented yet).
Time interval: 10uS to 27.8 hours
Includes self check

49 Vacuum tubes
Based upon AC-4A/B counter modules
Power required 260Watts
Weight 45lbs in the “portable” case

Ovenized crystal oscillator.
Stability: 10ppm per week, can be standardized to WWV (if only it still existed).
Accuracy: +/-1 count + stability

Input 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 counting
Can provide 90V to power a photo tube
With an optional circuit, can provide output for a plotter or printer


This 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.pdf

Manual for AC-4A/B counter modules:
http://www.hparchive.com/Manuals/HP-AC-4A-4B-Manual.pdf

HP Journal Article: Sept/Oct 1953:
http://www.hparchive.com/Manuals/HP-523B-Manual.pdf

1954 catalog entry: 
http://www.hparchive.com/Catalogs/HP-Catalog-1956-10-Revised.pdf


Related machine: 523B:
http://www.hparchive.com/Manuals/HP-523B-Manual.pdf

Related machine, HP 524B (Circa 1952):
http://www.hparchive.com/Manuals/HP-523B-Manual.pdf


HP Journal Article HP 524B, March/April 1954:
http://www.hparchive.com/Manuals/HP-523B-Manual.pdf

[Wrenches of Death]

Ovenized crystal oscillator.
Stability: 10ppm per week, can be standardized to WWV (if only it still existed).

Pretty 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

[MaxFrister]

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

[MaxFrister]

Of the 4 dozen tubes around 5 tested bad or weak.

[MaxFrister]

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.

[MaxFrister]

I’ve started the cap replacement.  Here I’m using a period appropriate Cornell-Dubilier BF-70 analyzer to reform a NOS can cap.

[TimFox]

Amusing detail about the CDE test unit:  the "common" post is red, while the "R" and "C" are black.

[MaxFrister]

Amusing detail about the CDE test unit:  the "common" post is red, while the "R" and "C" are black.

And 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.

[edpalmer42]

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.pdf
http://bama.edebris.com/manuals/hp/521a/
http://www.hparchive.com/Manuals/HP-523B-Manual.pdf

It looks like the 521, 522, and 523 counters are all nearly the same

Other Info:
https://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1953-09.pdf
https://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1952-11.pdf

[MaxFrister]

Someone has sent me a clean copy of the schematics.  They should be available in a couple of days at http://www.ko4bb.com/getsimple/index.php?id=manuals.

[Cubdriver]

Cool old beast, and definitely a room heater!  Nice score!   

-Pat

[MaxFrister]

Here is a picture of the bottom of the instrument. The object on the right is a delay line.

[MaxFrister]

It was a bit of a challenge to find room for the replacement caps:

[MaxFrister]

Here's a pic of the high-tech selenium rectifier:

[Cubdriver]

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

[MaxFrister]

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."

[MaxFrister]

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 tubes
Replaced the selenium rectifier
Replaced 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.

[Cubdriver]

Looks great!  Nicely done!

-Pat