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Azur Electronics

I bought 2 'faulty' HP 3762A Data Generators for spares or repair on eBay for £10. Their original cost was $9,125 each in 1980. These versions were made for British Telecom to test 68 & 140Mbit/s transmission systems. Options included are: 801 Front Cover (missing); H76 BT Special. The BT reference is "Tester No 273A/HPU/1". Together with the HP 3763A Error Detector, this forms a dedicated error rate measurement system for evaluating high speed digital transmission systems.

Front view
Rear view
Top view with cover removed
Bottom view with cover removed
July/August 2007

These units are very well constructed and the only damage was one bent front panel and various broken switches. Easily swapped over to make one good unit. No actual faults were found. The original intention was to re-use the switches for a different project as this was much cheaper than buying just the switches!

Once I had figured out what the equipment did, I decided to keep it as a useful signal/pulse generator. The external clock input means that it can generate a wide range of pulse frequencies and configurations. I haven't yet decided what to do with the second unit. Lots of useful spares in it, but finding the Manual would be good start.

The 3762A Data Generator produces PRBS and WORD sequences in the frequency range 1 kHz to 150 MHz. Internal crystal oscillators provide clock and data outputs at two frequencies f1 and f2, where f1 and f2 depend on instrument option. An external clock signal is required to provide clock and data outputs over the complete frequency range. Burst mode control of the Data Generator is possible via a burst gate input.

Clock and data inputs, generated from internal frequencies, can be offset by up to +- 60ppm from f1 or f2. Data output format is: Coded Mark Inversion (CMI) at frequencies of 139.264Mb/s and 141.040 Mb/s; or Binary (RZ or NRZ) over the complete frequency range. Option H76 provides frequencies of 139.264MHz (f1) and 68.736MHz (f2) for BT 140Mbit/s and 68Mbit/s.

October 2010

Have now acquired the companion HP 3763A Error Detector. Testing of both units is held up by needing the Operating & Service Manuals.

January 2011

Download Operating Manual for 3762A and 3763A.

August 2015

Fails Operator's Checks so more work required. 

March 2017

Have finally obtained the Service Manual, big thanks to Dave at Artek Manuals who managed to buy the Manual and specially scanned it for me, all 362 pages!

April 2017

Converted the front panel connections: Clock Input; Clock Output; Output A; Output B from 75Ω to 50Ω.  The Trigger Output was already 50Ω.

Tested the 3726A by carrying out Adjustments and Performance Tests from the Manual.  Some minor issues but considered to be tested ok.

Testing 3762A

Clock Input: 1kHz to 150MHz, 50Ω (Modified), 300mVpp to 3Vpp max.
                  Green LED indicates correct input level.

Clock Output: as selected, 50Ω (Modified), 1Vpp to 2Vpp, Offset 0V to ±2V,
                   Normal or Inverted, or ECL.

Trigger Output: one pulse every sequence or word, 50Ω, 1Vpp min.
                   Every 16-bits in 10101 pattern and every 8 bits in ALT mode.
                   Position is determined by Word A switches and is 2-bits wide.

Output A: CMI/RZ/NRZ, 50Ω (Modified), 1Vpp to 2Vpp, Offset 0V to ±2V,
                   Normal or Inverted, or ECL.

Output B: As Output A, except CMI mode not available.

Rear Panel Connections

Monitor 1: as Output A, ECL, binary NRZ before coding.

Monitor 2: as Output B, ECL, binary NRZ before coding, except CMI mode not available.

Clock: as Clock Output, ECL.

Burst Gate: Input, 50Ω, disables internal and external clocks
                 for burst mode operation, ECL.

Alt Word Control: Input, Hi-Z, dc to 100kHz, frequency controls changeover rate  of 8-bit words in alternating word mode.


PRBS: Pseudo Random Binary Sequence, positions 210-1, 215-1, 223-1,
         maximum length sequences are prduced with lengths of 1023, 32767
         & 8388607 bits. Zeros can be substituted for parts of each sequence
         up to 999 bits.

16-bit & 10 bit: two independant 16-bit or 10-bit words are generated with
         content determined by Word A & Word B switches.

10101: two 101010.... 16-bit repetitive patterns are generated.

ALT: an input at the rear panel Alt Word Control connector changes the Word A
       pattern between continuously recycling the first 8-bits of Word A and
       second 8-bits of Word A. Similarly for Word B.

The 3762A is a complex and adaptable Data Generator with a lot of useful functions. Reference to the Operating and Service Manual is required to operate it correctly.  Thanks again to Artek for supplying the Service Manual.

May 2017

Dismantled the second unit to assembly level. All the parts are available, see HP 3762A Parts

March 2021

Functional testing of all power rails, front panel controls, inputs and outputs; in preparation for more work on the HP 3763A Error Detector.