Introduction
In early 2009, I bought an AvoMeter Model 9 SX for about £10.
It needed a bit of a clean, but otherwise it works fine. The
lower terminals have at some point been replaced by the newer
safety types, and some of the bronze paint has come off. This
didn't matter to me as I wasn't looking for a pristine example,
but rather a model that wasn't too expensive and works, as I
intend to make good use of it. All the AC, DC and Ohms ranges
work, and the batteries that were included with it also seem to
work fine.
The serial number indicates that this model would have been
made in 1963. As far as I'm aware, the only difference between
this Model 9 SX and the earlier Model 8s, is that it has a metal
case and that some of the internal components are potted. This
model is also known as Test Set Multi Range No. 1. The
only other examples of Test Sets/Model 9s that I have seen have
been a few photographs on the internet, and a couple in college,
however, all these have been newer (late 1960s/early 1970s) and
have had different scales (similar to the newer models such as
MkIV).
Switches and Cut-Out
The AvoMeter has a interesting (and useful) cutout mechanism,
which will disconnect the meter from the inputs in the event of
an overload. When the pointer bashes the end of the scale, it
triggers the mechanism which pops out the switch on the front.
You then remove the overload, and press the switch back in.
Unfortunately, the cut out doesn't work on this particular
meter.
I'd have to say that these old Avos have the best range
switches of any multimeters. Many people debate which multimeter
has the best range switches, and my vote goes to the old Avo.
They are wonderfully solid and clicky :).
At the time of updating this page (2014), the AvoMeter is in
pieces. I had taken it apart to clean the switches and
investigate how the cut out mechanism works. I was unable to
repair the cut out, but so far haven't got round to putting the
meter back together. That will have to be a job for a rainy day.
Information and Photographs
Have a look at http://www.richardsradios.co.uk/testsetno1.html
for more information on AVO Meters, and a comparison of the
newer and older scales.
Below are several pictures of my AVO Meter. Click on the images
to see them at their full resolution.
The AVO Meter on my desk. The Metal case is probably the most
heavy part of this model. Some of the bronze paint from the top
and the white paint from the front has come off, and the lower
terminals have been replaced by the safety type which are often
found on newer multimeters.
The instructions on the back explain how to operate the
instrument. These ones aren't in very good condition but are
readable. I don't know who owned this meter previously, but it
could have been a school. There's a sticker on the bottom of the
meter which says it was originally with the Royal Electrical and
Mechanical Engineers.
The AvoMeter correctly measures the 5 Volt output from the
fixed power supply. The inexpensive digital meter is also
connected to the same power supply.
Centre of the scale
Start of the scale
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