Hewlett Packard 5300B Measuring System


Hewlett Packard 5300B and 5305B Front panel in Check mode
Hewlett Packard 5300B and 5305B Front pan­el in Check mode

Repairing and clean-up of a Hewlett Packard (HP)5300B Measuring System with a 5305B 1,300 MHz Counter module.

This was sup­posed to be just a clean-up project, but this one turned into a bit more work that I had expected.

Hewlett Packard 5300B and 5305B with top cover off
Hewlett Packard 5300B and 5305B with top cov­er off

This HP 5300B sys­tem was pur­chased on Ebay as “pow­ers on, the num­bers dis­play on the screen”. When it arrived I plugged it into my Watts Up? pow­er mon­i­tor and turned it on. Nothing hap­pened, there was no dis­play and the pow­er mon­i­tor showed .000 amps.
The sell­er did make it right by refund­ing part of the pur­chase, so now it was a chal­lenge to see if I could get this unit work­ing again.

Hewlett Packard HP 5300B Top view with cover removed
Hewlett Packard HP 5300B Top view with cov­er removed

To start with the fuse­hold­er cap was not the orig­i­nal and was inter­mit­tent­ly mak­ing con­nec­tion. After replac­ing the cap, I had AC line volt­age to the trans­former and low volt­age AC to the board. I noticed on fur­ther inspec­tion that the trans­former alu­minum sup­port was severe­ly deformed, which was also caus­ing bend­ing of the cir­cuit board and an attached pow­er tran­sis­tor using the alu­minum frame as a heatsink.

HP 5300B Top view of circuit board and transformer
HP 5300B Top view of cir­cuit board and transformer

After a hour of dis­as­sem­bly, straight­en­ing, and reassem­bly it was time to try pow­er­ing up the unit again.
Still no dis­play or DC sys­tem voltages.
After a bit more trou­bleshoot­ing the prob­lem end­ed up being a dam­aged con­tact on the 50 pin Centronics style con­nec­tor that mates to the dif­fer­ent plug-on mod­ules for the sys­tem. Pin 25 DC +22 volt pow­er is con­nect­ed via the plug-on mod­ule to pin 50 (DC-IN) which then is switched by the front pan­el pow­er switch, and then is con­vert­ed to sys­tem volt­ages. This allows the sys­tem to uti­lize a bat­tery pack between the plug-on mod­ules for portable operation.
Most like­ly the dam­age hap­pened at the same time the alu­minum frame was deformed by a severe drop caus­ing the trans­former to move things around inside the case. This was not caused by the most recent ship­ping to my loca­tion, as I also found three of the four plas­tic board mount­ing latch­es dam­aged with miss­ing latch­es, but no remains of the latch­es inside the case when opened.

HP 5305B Board bottom and connector
HP 5305B Board bot­tom and connector
HP5300B Back view and power board
HP5300B Back view and pow­er board

Now that the unit was work­ing, it was time to per­form a through clean­ing and take some pho­tos of the 5305B 1,300 MHz Counter plug-on module.

HP 5305B View of front panel
HP 5305B View of front panel
HP 5305B Board top view
HP 5305B Board top view
HP 5305B board top side view
HP 5305B board top side view
HP 5305B Board top view to front
HP 5305B Board top view to front
HP 5305B Board top view to back
HP 5305B Board top view to back
HP 5305B 1300MHz Board top
HP 5305B 1300MHz A2 Amplifier / Divider board top
HP 5305B Board top B input zoom
HP 5305B Board top B input to A2 board zoom
HP 5305B Board top A input zoom
HP 5305B Board top A input zoom
HP 5305B Board top B output divider zoom
HP 5305B Board top A2 board out­put divider U26 hp 1820–0557 zoom

The Hewlett Packard 5305B is a beau­ti­ful exam­ple of qual­i­ty engi­neer­ing from the mid 70’s by the design team at HP. This unit was built in late 1981.

I still need to check the cal­i­bra­tion of the 10.000 MHz oscil­la­tor, but cur­rent­ly do not have any­thing accu­rate enough to do the job.

Hmmm, sounds like anoth­er future project!

4 Replies to “Hewlett Packard 5300B Measuring System”

  1. Beautiful pic­tures of the instru­ment. I am pleased to use such an instru­ment with option­al TCXO. Regards Ferenc, YU7BX

  2. Hi,
    I have a 5305B with sim­i­lar prob­lem of no or gar­bled dis­play on 7segment leds. The unit used to make a sharp buzzing noise when work­ing, but eversince the noise has gone the dis­play is gone too. 

    Pls sug­gest pos­si­ble repair tips.

    Thanks !


    1. Hi Salman,
      Most like­ly there was a prob­lem with bad capac­i­tors in the pow­er con­vert­er section.
      The +22 volt sup­ply is con­vert­ed to AC and is then rec­ti­fied and fil­tered to make the sys­tem volt­ages +5, ‑5, +17, ‑17, and +3.5V.
      The short­ed or faulty capac­i­tor caus­es exces­sive cur­rent draw in the con­vert­er and can make hum­ming or buzzing noises.
      I would sus­pect that the noise stop­ping is relat­ed to a diode, pow­er tran­sis­tor, or trans­former (-3011, ‑3012) fail­ing due to the exces­sive current.
      Usually there will be visu­al signs of over­heat­ing of the failed component.

      Greg (Barbouri)

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