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REPAIR HP 8082A
PULSE GENERATOR
June 2018

The HP 8082A Pulse Generator requires a complete strip down to assembly level to clean-up and inspect.
Front view showing damage and staining
Rear view in good condition
The 8082A looks complete, even with feet and rear corners.  Obvious damage to the front panel though, including: 2 control knobs broken; power switch jammed; 2 slide switches broken; 3 other switches jammed; BNC dented.
Front and Rear Panel Assemblies
Lots of staining and corrosion inside.  5 PCB's removed along with inter-connecting ribbon and coax cables.  Front Panel assembly removed by unsoldering variable resistors, as most of these have their control knobs seized on.  The front extrusion was badly corroded and discarded for a spare unit.
 
Damaged Front Panel
After trying various methods, all but 3 of the control knobs refused to budge. Resorted to cutting them off just behind the allen screws and it needed an electric saw to do the job.  The Front Panel cleaned up quite well considering the state it was in.  A testament to HP paint quality!
Refurbished Front Panel
Most of the slider switches were dirty.  These rely on specific PCB tracks together with contact sliders that are held by the rivited on plastic runners and retaining springs.  I had some spares from other units, but these were all different with contacts arranged left facing or edge facing instead of right facing.  Amazing that so many different types exist.
Correct contact sliders on the left hand side of the photo
The slider switches were all carefully cleaned up and reassembled.  The switch circuits were all buzzed out.  There may be some intermittancy to watch out for and the External Input slide switch is slightly damaged.

The other 2 or 3 position slide switches were also cleaned up and buzzed out ok, as was the Power switch.  Surprised that they still work!

A replacement Manual switch is required.
Partly reassembled for testing
3 of the variable resistors were ok and refitted.  4 more are damaged and need replacing, although tempoarily refitted for testing.  1 more disintergrated and needs replacing, 2 fixed resistors temporarily fitted for testing.

The Rear Panel and PCB's were all cleaned up ok.  Rear Panel Voltage Selector and Fuse checked ok.  Powered-up on a Variac with just the Power Supply PCB fitted (08082-66502) and all rails ok, adjusted for +10V, -5V, -10V & -25V.

Front Panel Power Lamp had blown and was replaced with a spare, -5V at 58mA.

Remaining PCB's refitted one by one and power rails and consumption checked.

Started Performance Tests.  Trig Output with repetition rates from 1kHz to 250MHz ok, although a negative going 0.6V square wave terminated output.

No pulse outputs though.  There are 4 outputs from the A3 Repetition Rate Generator (08082-66503) and only 2 are working.
A3 Repetition Rate Generator
The fault was traced to A3 U2, this is a special HP integrated circuit part number 5081-3010 and probably unobtainium!  It is a quad output 50Ω line driver.  A3 U1 is also a HP special 5081-3011.
  
A3 U2 Special IC HP 5081-3010
Need to find one of these ICs if possible.


July 2018

Bought a replacement IC from The Netherlands (thanks Raymond).
Testing produced the same result though!  I had assumed that all 4 outputs were the same. Reading the Manual more carefully showed 2 square wave outputs and 2 narrow 2µs pulse outputs.  So A3 was working after all.
A4 with piggy back A8 PCB
A4 with 2µs delay line on left and heatsink for U5 & U6 on right
Testing A4 PCB is difficult with poor access, modifications and 4 special HP IC's.  No output from U2 Delay Generator and only an output from U4 Word Generator when in square wave mode. U5 Slope Generator and U6 Vernier Output are underneath A8.  No output at all from the front panel BNC's.

Not HP's best design for ease of maintenance.  Considering all the factors, I decided to scrap this Unit for spare parts.  See HP 8082A Parts for details. 
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