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Old 17th Sep 2018, 7:28 pm   #1
Vintage_RC
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Default GEC Selectest Super 50 Mk2 fifty year MOT

I've known this instrument almost since it was new. I joined a company as an R&D engineer in its newly formed electronics division in 1969. As it turned out I was the only R&D engineer and a few pieces of test equipment had been purchased and this Selectest Super 50 was one of them. I worked on a couple of projects with them but they closed the division down after about 3 years and I acquired the meter when much of the lab equipment was disposed of. It then became my main test meter at home but steadily fell into disuse with the advent of decent digital multi meters at affordable prices. That said, every now and again it would get put into use when an analogue meter was the better choice. The only maintenance it has ever had was when I had to refit the loose glass, it has never been calibrated. With the meter around 50 years old I decided to see how its accuracy had stood up to the test of time. I have (hopefully) attached the results of my checks, the main reference was an AD584L (0.05%). It is not a complete check but covers all the ranges I am likely to use. As you will see, other than a few readings at low deflections, the accuracy is still better than 1%. This surely says a lot for the design and quality of this meter which was always in the shadow of the much more popular AVO 8.
Alan
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Old 17th Sep 2018, 8:44 pm   #2
The Philpott
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Default Re: GEC Selectest Super 50 Mk2 fifty year MOT

No need to recalibrate for loss of flux then- quite surprising.
I still haven't got round to putting my AD584L reference into a proper enclosure. It's certainly a handy thing to have around.

Dave
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Old 17th Sep 2018, 8:53 pm   #3
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Default Re: GEC Selectest Super 50 Mk2 fifty year MOT

I bought my Selectest Super 50 just under 40 years ago. It appeared to be new, but had been rejected or just put aside because the glass had "fallen in". I fixed that, and it has never missed a beat since. If I need to measure in the EHT section of a scope, the 2,500v range is useful, backed up by a genuine HV probe.
I have never had an AVO7,8 or 9, though I did have one of the baby ones about 60 years ago.
The Selectest always gets my vote.
Les.
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Old 17th Sep 2018, 9:25 pm   #4
mark_in_manc
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Default Re: GEC Selectest Super 50 Mk2 fifty year MOT

Hi Vintage RC. Where was SEL? I think GEC had a place on Silk / Adephi St in central Salford - I've lived there and I still work around there, so I'm interested to know.
cheers
Mark

(Edit - the Selectest meters I have seen were branded SEL (Salford Electrical Instruments), which I think was a GEC brand - but perhaps they were made elsewhere in the GEC empire too).
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Old 17th Sep 2018, 9:59 pm   #5
chriswood1900
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Default Re: GEC Selectest Super 50 Mk2 fifty year MOT

Mark
From a local history site I think.

Salford Instruments which started in 1910 as a member company of GEC Electrical Components Ltd. had its factory at Peel Works, Barton Lane, Eccles, Manchester M30 0HL. The firm though still active ceased trading in 2003.
Hope that snip-it helps
Chris
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Old 17th Sep 2018, 10:10 pm   #6
Andrewausfa
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Default Re: GEC Selectest Super 50 Mk2 fifty year MOT

I'd be interested to know if people with a Selectest and an AVO prefer one over the other and if the Selectest has any quirks.

I've wanted a Selectest DIII for some time, the ones with the red Art Deco-ish fixture on the front for the set zero. Always thought they look rather handsome.

Andrew
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Old 17th Sep 2018, 10:14 pm   #7
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Default Re: GEC Selectest Super 50 Mk2 fifty year MOT

Quote:
Originally Posted by mark_in_manc View Post
Hi Vintage RC. Where was SEL? I think GEC had a place on Silk / Adephi St in central Salford - I've lived there and I still work around there, so I'm interested to know.
cheers
Mark

(Edit - the Selectest meters I have seen were branded SEL (Salford Electrical Instruments), which I think was a GEC brand - but perhaps they were made elsewhere in the GEC empire too).
Hi Mark, on the back it has the following:-
MADE IN ENGLAND BY SALFORD ELECTRICAL INSTRUMENTS LTD, SALFORD
A SUBSIDIARY OF THE GENERAL ELECTRIC CO LTD OF ENGLAND

Alan
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Old 18th Sep 2018, 12:07 am   #8
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Default Re: GEC Selectest Super 50 Mk2 fifty year MOT

Selectest 50 fan here, too- I like the lightness, big clear glass and scale numbering over the Bakelite AVO 8s, though the plastic body, PCB- equipped AVO 8s of MkV on are probably lighter than the Selectest. Surprised really that the GEC product wasn't more popular. Yes, the glass on mine came unstuck too, but not too much of an ordeal to re-stick. The Melamine (?) case on my Mk2 has faded to a fetching pale pink- much nicer than the sober lab grey of the Mk3!

Slightly OCD question- the Selectest 50s generally seen have, like early AVO 8s, 1-2.5-10 voltage range incrementing, I have a vague feeling that the very late Mk3s (or the PO issue thereof?) may have used a 1-3-10 scheme like the later AVO 8s. Or am I maybe just imagining things?

Generally, I like a clear analogue meter for current measuring (it rarely needs to be hyper-accurate) and DMM for voltages but it's not hard and fast. I think the apparent resolution of DMMs can distract many folk from making a sensible value judgement on necessary accuracy, a good analogue meter gives a useful grounding here (so to speak!),

Colin
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Old 18th Sep 2018, 2:48 pm   #9
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Default Re: GEC Selectest Super 50 Mk2 fifty year MOT

I have one of each (both Mk3s). Both have had loose glasses at one time or another. The GEC is easier to read I find, so it lives on the bench, along with a digital. Horses for courses, as Colin says.
PS. It was made in Eccles
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Old 18th Sep 2018, 3:00 pm   #10
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Default Re: GEC Selectest Super 50 Mk2 fifty year MOT

Re. Andrew's query, having seen photos of the internals of a period Selectest, the design approach is rather different to an Avo of the same vintage. As regards the former the shunts look to be set out in a more orderly and more accessible fashion, but i got the impression the movement was not particularly accessible by comparison with Avo.

I believe the air ministry would have had contracts with both companies, since one version of the Selectest has identical ranges and facilities (and scale increments) to a Model D Avo.

The glass, then,seems to be prone to coming loose in both designs. With what seems to be improved glue in the '60's, some Avometer Model 8 MkIII's left the factory without the metal clips retaining the glass....which can and should be retro-fitted as a safeguard.

I have nothing against the Selectest, have been tempted occasionally. Silly prices get asked for smart older examples.

Dave
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Old 18th Sep 2018, 4:33 pm   #11
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Default Re: GEC Selectest Super 50 Mk2 fifty year MOT

I have attached a photo of my Selectest which was the subject of the accuracy tests above. The case is sound with no cracks but at sometime it developed the small blotches you can see. I can't recall when they appeared but it was a long time ago. They don't come off with safe cleaning agents. By the way, has anyone got a pdf copy of the manual they could send me?
Alan
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Old 18th Sep 2018, 8:13 pm   #12
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Default Re: GEC Selectest Super 50 Mk2 fifty year MOT

Quote:
Originally Posted by Andrewausfa View Post
I'd be interested to know if people with a Selectest and an AVO prefer one over the other and if the Selectest has any quirks.
The Selectest 50 has encouragingly big and business-like terminal posts, but the 4mm hole in the top is actually quite shallow and leaves quite a bit of typical 4mm plugs exposed. Conversely, the AVO 8's 4mm terminal posts (those that have them) are quite compact and low-profiles but the 4mm drilling is somewhat deeper. I think the latching "reverse polarity" on the AVO 8 V and later is preferable to the non-latching one on the Selectest 50 and earlier Bakelite AVO 8s, it's more convenient when transferring attention from one polarity wrt to a point to the other, but others may differ. I think that the modern advice generally is to avoid handling a meter if possible when measuring high voltage in particular, which seems wise.

The GEC meter does seem to be more production orientated, both "traditional" and "modern" versions of the AVO meter look to be trickier and more labour intensive to make. I actually quite like the AVO 8 V, but inside it looks to be a missed opportunity, something of a bitsa with PCBs and flexible ribbon connections mixed with point-to-point componentry looking unrefined and pre-production in nature. The sort of thing that would have made a contemporary Japanese production engineer think "nothing to fear here".... Both Japan and the US were producing multimeters of 50k and even 100k/V at the time.
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Old 18th Sep 2018, 8:22 pm   #13
MotorBikeLes
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Default Re: GEC Selectest Super 50 Mk2 fifty year MOT

Mine is a Super 50 Mk 111. Voltage scaled 0-20 and 0-100.
Various ranges differ between current and voltage, not just a simple 1-2.5-10. Definitely not a 1-3-10.
I used to have a "p[ink" one, but must have sold it years ago. I had a few (ex-CTV rental company) "mini" Selectests. Forget the actual designation, but save 50k ohms per volt, limited ranges, and smaller movement of course. All well past their best as you can imagine. I think I still have a couple. Plenty good enough for outside service I imagine.
Les.
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Old 19th Sep 2018, 9:24 am   #14
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Default Re: GEC Selectest Super 50 Mk2 fifty year MOT

I have both the Mkii (pink) and the Mkiii (grey). They obviously realised their mistake and the later model has full depth 4mm sockets.

My Mkii probably hadn't been calibrated for years and the magnetic shunt needed a tweak as all ranges were reading low.
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Old 19th Sep 2018, 9:31 am   #15
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Default Re: GEC Selectest Super 50 Mk2 fifty year MOT

I used a pink one at a place I worked at circa 1970 - I thought it was rubbish, the meter ballistics seemed all wrong - but then I had been brought up from an early age on an AVO 8 MkII.
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Old 19th Sep 2018, 11:03 am   #16
FIXITNOW
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Default Re: GEC Selectest Super 50 Mk2 fifty year MOT

I have a post office version 14C
I picked up at a local radio rallies bring and buy stall some years ago.
its a very useful meter but I do not use it often
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