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From: Jeff Layman <Jeff@invalid.invalid>
Newsgroups: sci.electronics.design
Subject: Re: Simpson 260 repair
Date: Sat, 5 Apr 2025 08:12:06 +0100
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On 04/04/2025 18:01, Cursitor Doom wrote:
> On Fri, 4 Apr 2025 11:43:22 -0400, bitrex <user@example.net> wrote:
> 
>> On 4/4/2025 11:36 AM, bitrex wrote:
>>> Picked up a Simpson 260 6M at the local thrift store, I was initially
>>> disappointed to find it had a sticking meter but some gentle rocking
>>> freed it.
>>>
>>> Unfortunately the movement resistance is a little high, about 1880 ohms
>>> vs the 1800 in the service manual. This causes the movement to not fully
>>> deflect when 50 uA (sourced from an HP 6177B, and monitored by a
>>> recently lab-calibrated 3478A) is run through it, it goes to more like
>>> 48.5 out of 50.
>>>
>>> Is it correct that recharging the meter movement is the only thing that
>>> can help in this situation? It seems a relative error of 3% is actually
>>> still barely within factory spec so probably best to just let it go and
>>> enjoy a meter that's nice enough for the 10 bucks I paid for it, lol
>>
>> Oops, I meant to post this in sci.electronics.repair but here we are.
> 
> I did wonder! Simpsons are nice meters. Really nice and broadly the
> equivalent of the UK AVO brand (still in business AFAIK). I really
> like these old analogue meters. People say stuff like 'well, the
> trouble with them is they load a circuit too much compared to modern
> DVMS' but that *can* be desirable in many cases. Repairing vintage
> radios you find that oftentimes the servicing instructions have
> voltages printed on them which were read by meters with 20k ohms/volt
> or less, so at high impedance parts of the circuit a modern DVM will
> give completely wrong readings. Also I find it's much easier to peak
> signals with a moving coil meter than a DVM. And another thing - you
> want to monitor a voltage constantly over days and weeks (or a
> current) you can do this with an analogue meter without having to
> worry about the battery draining. And when reading high currents,
> there's no time limit like you find with modern DVMs. You can leave it
> hooked up to 10 or 12 amps for as long as you like.
> I could go on, but there's just a few of the reasons I like these old
> beasts.

There's something very satisfying watching a perfectly-damped needle 
move across the face of a meter and come to a steady halt. I was given 
an Avo Multiminor almost 50 years ago and occasionally still use it.

Rather OT for this group I also have a couple of Post Office and British 
Telecom meters (ex my F-i-L. He started working for them in the early 
50s and retired in the early 90s):

<https://www.radiomuseum.org/r/gec_multimeter_4_gpo_g_469.html>
Unfortunately the shunts are missing. It's built like a tank (the case 
is steel); the leather case is a bit battered but ok.

<https://www.ebay.co.uk/itm/166536768299>
The one I have is almost unused. Seems that an updated version is still 
available:
<https://www.telenco.uk/tester-sa-9083>
I wonder how long it will be before it becomes fully redundant when the 
change to FTTP is complete.

-- 
Jeff