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Old 23rd Feb 2010, 9:20 pm   #521
M0XNA Neil
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Default Re: AVO Multimeter survey

SPCh,

Interesting, as I have an AVO 8 Mk6 which is marked as a Test Set No 1 Mk4 with NATO stock Number 6625-99-722-8684. The Rev M.C. is also non-latching in line with the military version. My instrument has an AVO sticker on the side indicating that it was repaired by AVO in October 1996. The AVO is very accurate and looks brand new with no wear marks on the plastic terminal posts.

Neil.
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Old 23rd Feb 2010, 10:16 pm   #522
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Default Re: AVO Multimeter survey

Thanks Neil,

That's a first for me - some pictures would be a bonus.

(This Survey has thrown up several interesting developments)
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Old 23rd Feb 2010, 11:25 pm   #523
M0XNA Neil
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Default Re: AVO Multimeter survey

Here is a picture of the TS1 mk4
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Old 24th Feb 2010, 2:02 pm   #524
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Default Re: AVO Multimeter survey

Early TS1 meters are essentially screened, panclimatic Model 8 variants with a range sequence of 1 - 3 -10 in place of the 1 - 2.5 - 10 sequence of the commercial design.

The nearest commercial types would be the 8SX (S - screened, X - Panclimatic). Both the 8SX and the equivalent TS1 were produced during the Model 8 Mk II and MK III periods.

I do not have to hand any information to correlate TS1 to Model 8 Mk I production but screened panclimatic versions of the previous High Resistance Avometer were made between 1948 and 1951 so it is likely that there were Mark I Model 8SX instruments. (The designation Mk I was of course not used, mark numbers only starting at Mk II).

When Avo were taken over by Thorn, a redesign was demanded to reduce production costs and this resulted in the Model 8 Mark IV. The Mk IV used printed disc switches in place of the leaf spring function switches of all previous Model 8 meters. The disc tracks were silver plated and suffered from silver migration and whiskering. The case of the Mark IV was a thermoplastic case, a technique new to Avo. Possibly through lack of design experience, the thermoplastic case was prone to cracking around the securing screw holes and it is rare to find one intact.

The production life of the Mark IV was very short, c1970 to 1972, possibly due to these defects. It may have been an intentionally interim design. It is unlikely that ministry procurement assessment and specification processes would have been rapid enough for such a short-lived model to have completed the process.

The Model 8 Mark V design was intended to rationalise the entire Model 8/9 range by meeting the specification for all variants, including panclimatic and military requirements. This specification included severe drop-test demands in the NATO specification which is at odds with anecdotal accounts of minor drops and falls causing movement pivot bridges to break. The bridge design was changed from plastic to phosphor bronze during Mark V production, possibly to address this problem.

This explains why there are no specifically panclimatic versions of the Model 8 Mark V; they were all considered to be panclimatic. I don't know why the screening can was no longer specified; it may be because the centre pole movement was inherently screened.

Neil's TS1 Mk 4 would correspond most closely to a commercial Model 8 Mark 6 or possibly Mark 7. The clue is the lack of 3000V terminals which were deleted due to the cost of the multiplier resistors and possibly concerns about safety and certification. (It would be interesting to know how often the high voltage terminals were actually used, except just for the experience).

PMM.
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Old 24th Feb 2010, 6:43 pm   #525
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Default Re: AVO Multimeter survey

PMM,

Thanks for the reply. My TS1 Mk4 is indeed an AVO 8 Mk6 with a non-latching reverse m.c. I have added some clearer pictures showing the front and the MoD markings on the side of the instrument. Having never opened it up, as the calibration sticker is still intact, did the AVO 8 Mk5 have a more robust range switching mechanism than the AVO 8 MK4?

Also, do you know when MoD stopped using the AVO 8 as a TS1 and I assume started using the Fluke 25 as their general purpose meter?

thanks,

Neil.
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Old 24th Feb 2010, 8:14 pm   #526
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Default Re: AVO Multimeter survey

Hello SPCH,

AVO Mod 9 MK II Serial nr on scale plate = 7767-1166
This was bought in the UK on 24/09/1968 for £25.00 brandnew. This was my first piece of test equipment when I started in the radio trade at (15 years old) and it cost me four weeks wages. It still works and is used quite often. (although the Hi-ohms range is no longer used)
I have the original handboek, garuntee card and test leads.

groet,

Waveguide.
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Old 24th Feb 2010, 8:42 pm   #527
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Neil,

I think it is fair to say that the function selector switches in the Model 8 Mark V are much more substantial than those in the Mark IV. For the Mark V, a completely new design of function selector switch was adopted. This uses sprung sliding switches which run over printed circuit segments. The same arrangement is used in the Mark 6 & Mark 7.

The Mark V has flexible printed wiring between the main board and the top board around the movement. This is easily damaged when flexed as it must be to gain access to the movement and the components around the movement. The Mark 6 and Mark 7 do not have flexible printed wiring and use quite a simple arrangement of two stacked printed circuit boards. The layout of these PCBs dictates the revised switch layout in which the current and voltage segments of the AC and DC switches are partial mirror images. (This can be very confusing if you try to use a Mark 6 or 7 alongside a Mark V).

The 0688 label suggests that your meter was made in 1988. By this time the digital Avometers DA 116 and DA117 (Autoranging) were available and the DA 116 was used by the Royal Navy, and probably other services as "Digital Multimeter SET 6625-99-539-4008". As far as I have been able to tell by comparison, this is identical to the commercial DA 116. One sample of the DA116 which I have has a Faslane calibration label dated February '01 and another claiming it for HMS Upholder, commissioned in June 1990 and sold to Canada to become HMCS Chicoutimi in 1998. (http://en.wikipedia.org/wiki/HMCS_Ch..._%28SSK_879%29). This meter was made in April 1988.

I do not know when the Fluke 25 came into NATO service but there are also NATO stock numbers for the Fluke 27 and the 8025.

PMM
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Old 24th Feb 2010, 11:23 pm   #528
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Default Re: AVO Multimeter survey

PMM,

I guess that my TS1 Mk4 AVO 8 Mk6 is one of the last to be used due to the introduction of the DA116. Thanks for the info on the digital AVOs, I had forgotten about them. I also have a Fluke 8060A (manufactured March 1995) which came from the Royal Navy (SSCP) which has the NATO number 6625-01157-2246. This number series is similar to the Digital Multimeter number series you quoted above. The Fluke 8060A is a 4 1/2 digit true RMS hand-held meter, so probably went into a higher classification of instrument.

thanks,

Neil.
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Old 1st Mar 2010, 12:17 pm   #529
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Default Re: AVO Multimeter survey

Hi,

Just aquired high resistance AVOmeter type HRM serial No. 2000-450

See my post (Unusual AVOmeter) in test equipment forum for more details

Thanks
Trevor
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Old 5th Mar 2010, 7:12 pm   #530
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Default Re: AVO Multimeter survey

Hi,
I Have just aquired a Model 7 but I cannot find a serial number. I have looked at the RHS of the dial and although I can see No. the space is empty.

Any thoughts?

Rob
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Old 5th Mar 2010, 8:11 pm   #531
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Rob,

If your Model 7 is one of the newest, there will not be a serial number on the scale plate. There would originally have been a self-adhesive label half way along the right-hand side of the case just below the seam line between the front panel and the case. In some meters there was a second serial number label in the battery box.

If your meter is one of these, the instruction plate on the back of the case will give the Dover address.

PMM.
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Old 6th Mar 2010, 12:22 am   #532
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Default Re: AVO Multimeter survey

Hi PMM,
The address on the back is Avocet House, Vauxhall Bridge Road, SW1

Regards

Rob
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Old 6th Mar 2010, 10:35 am   #533
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Default Re: AVO Multimeter survey

Quote:
Originally Posted by pmmunro View Post
Rob,

'If your Model 7 is one of the newest, there will not be a serial number on the scale plate.'
Did this apply to the later models of the AVO 40 as well?

Perhaps Rob's AVO has been fitted with a replacement movement?
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Old 6th Mar 2010, 12:56 pm   #534
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Default Re: AVO Multimeter survey

Is there any internal identifing features that indicate what mk/age my Avo meter is at all?

Rob
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Old 8th Mar 2010, 1:53 pm   #535
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Rob,

Assuming you have been unable to find a serial number on the scale plate - at the extreme lower right-hand edge (or left-hand on some military versions) - there are many other ways to date an Avometer.

First we need to know the model, and there is a choice of over 20 model types, many of which were made in different 'Marks' with production from 1923 to 2009.

The designs developed to suit component and material availability over the years and that gives a clue to time of manufacture.

A good start would be an external photograph - that alone might be enough to give a range of five years or less.

PMM
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Old 8th Mar 2010, 5:50 pm   #536
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Default Re: AVO Multimeter survey

Hi PMM
I have attached some photos as suggested

http://i934.photobucket.com/albums/a...8/DSCF2070.jpg
http://i934.photobucket.com/albums/a...8/DSCF2069.jpg
http://i934.photobucket.com/albums/a...8/DSCF2068.jpg
http://i934.photobucket.com/albums/a...8/DSCF2065.jpg
http://i934.photobucket.com/albums/a...8/DSCF2064.jpg
http://i934.photobucket.com/albums/a...8/DSCF2062.jpg
http://i934.photobucket.com/albums/a...8/DSCF2061.jpg

It does appear to have been worked on at some point in time which may explain the lack of serial no (new meter). It also appears to have a burnt out wirewound but this is not clear in the photo.

Regards

Rob
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Old 8th Mar 2010, 8:35 pm   #537
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Default Re: AVO Multimeter survey

Russell,

Late Model 40s, made in Dover also had self-adhesive serial number labels on the right-hand edge.

Rob,

Your model 7 was made after 1956, as indicated by the type of main terminals and the red crackle paint on the magnet blocks. Officially it is a Model 7 Mark II.

If the back case is original, the address shows that your meter was not made later than mid 1964 when production moved to Dover. Production of Model 7 meters continued in Dover for at least another ten years after the move. Later, Dover made Model 7s had unpainted magnet blocks.

The carrying case is a military and will have a NATO number on the front. As far as I know these dark olive green cases were never sold new on the commercial market. As your meter does not have a NATO number along the top edge of the front panel, it is very likely that the meter and carrying case met after the case left the army.

The lack of a serial number could, as you suggest, be because the movement has been replaced at some time. However, check the extreme lower left edge of the scale plate as well as the right; this would disprove my view that it is a civilian meter if the serial number is on the left. Official repairers were meant to transfer the serial number to the new movement.

PMM.
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Old 8th Mar 2010, 8:58 pm   #538
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Default Re: AVO Multimeter survey

Hi PMM
The case is olive green and carries a number across the front and the same number inside.
Alas, I can find no serial no.
The case has the most awful smell to it - is it some form of waxed canvas??

Rob
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Old 8th Mar 2010, 9:34 pm   #539
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Default Re: AVO Multimeter survey

Hi SPCh, My avo meter is MODEL 8 MK V OXXXX 8V/1/79
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Old 10th Mar 2010, 9:21 pm   #540
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Default Re: AVO Multimeter survey

My main Avo is:-
AVO 8 Mk V
on side - 0028643 MA
8V
on scale Pt No5270-455CH 8 mK5

Another with cracked glass,
AVO8 Mk V
on side - 1278M90219 1 - 86
on scale Pt No 5270 - 455 CH7 8 Mk

Another,
model 7
No 73487 - A- 1057

All in good working order.

AVO model 8
6790C 1263D
I've had this one from new in 1964 in its original leather case but it reads inaccurately now. Must get around to fixing it.

I also have another MK5 which is almost empty but has a good glass if only I can remove it.

Jim
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