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 HP3562A Dynamic Signal Analyzer
=================================

:Author: David Douard
:Category: Electronics
:Tags: HP3562A, repair, test equipment, DSA
:series: HP 3562A
:series_index: 1

One of my old test gears waiting for my attention in the cellar was a
HP 3562A Dynamic Signal Analyzer. Back then I bought this device
mainly for doing audio analysis (I was building my HiFi system, mostly
based on Nelson Pass' schematics), mainly to display spectrum
responses and compute THD and so.

I did not reall know what this test equipment is capable of. But `Dave
Jones's video #528`_ (and several wonderful videos on `w2aew's
channel`_) gave me the desire of playing a bit more with this old but
very impressive HP3562A.

.. _`Dave Jones's video #528`: https://www.youtube.com/watch?v=Y0jkPLuFdnM&t=1876s
.. _`w2aew's channel`: https://www.youtube.com/user/w2aew


Quick tour
==========

Here is the beast:

.. image:: {static}/images/hp3562a/front.jpg
   :alt: Front view of the HP3562A DSA

I said the beast, because despite being an amazing piece of test
equipment, it's also very big (576mm x 426mm x 222mm), very heavy
(26kg) and... unfortunately quite loud.

My version of the instrument is rather "recent", and manuals available
on Keysight web site concern only the earliest models
(ref. 03563-90210) and are of poor quality, with missing pages etc. So
I bought the correct Service Manual (HP ref. 03562-90213) on ebay from
`Artek Media`_.

.. _`Artek Media`: http://www.artekmedia.com/

Since it was on my "bench", I decided to see a bit inside, using the
occasion to investigate and fix the only real problem I have (as far
as I know) with my device: the dimm display.

.. image:: {static}/images/hp3562a/front_open.jpg
   :alt: Inside the HP3562A DSA

The unit consist in mostly 4 parts:

- a big switching power supply (with huge capacitors) on the left side
  of the enclosure, under the display,

- the display unit: a very nice HP1435A Digital Display; we'll discuss
  it a bit more later,

- the digital section consisting in 8 boards (rear right),

- the analog section consisting in 6 boards (front right).


The general block diagram:

.. image:: {static}/images/hp3562a/hp3562a_block_diagram_new.png
   :alt: General block diagram of the HP3562A

The instrument is built around 2 buses:

- the control bus which allows the main CPU to control all the
  assemblies, and

- the global bus which is used to transfer measurement data between
  assemblies.

In the HP3562A, the process control is distributed away from the
system CPU: each assembly has its own processor or state machine which
controls its local operations. The main CPU tells each assembly which
process to execute and monitors the overall functionning and data
processing of the instrument.

For the record, the block diagram from Service Manual 03562-90219
looks like:

.. image:: {static}/images/hp3562a/block_diagram.png
   :alt: General block diagram of the HP3562A from earliest Service Manual


Power Supply
============

.. image:: {static}/images/hp3562a/hp3562a_a18_psu_block_diagram.png
   :alt: Block diagram of the switching power supply unit


.. image:: {static}/images/hp3562a/a18_psu.jpg
   :alt: Picture of the HP3562A A18 PSU PCB board

The primary capacitors are huge Sprague caps (1400µF 250V):

.. image:: {static}/images/hp3562a/caps.jpg
   :alt: Picture of the HP3562A main filter capacitors

The power line filter is also pretty impressive:

.. image:: {static}/images/hp3562a/filter.jpg
   :alt: Picture of the HP3562A line filter module

The PSU generates:

- 5V @30A (!)

- +/- 30V

- +/- 15V

- +8V

- +2.6V

The switching chopper runs at 128kHz and is regulted on the 5V output
rail by PWM of the primary transformer. All secondary voltages but the
5V are generated by linear regulators.


Next
====

In the `next part <{filename}/hp3562a_2.rst>`_, we will describe the
Digital Section of the instrument.