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Old 26th Apr 2020, 6:03 pm   #2501
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Default Re: AVO Multimeter survey

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Originally Posted by Phil G4SPZ View Post
Quote:
Originally Posted by Aitor Eneko View Post
Hello, no, it is not my personal collection... I think there are not duplicated entries, they are variant for example in PF conector or not, baquelite or aluminium case...
Sorry. I glanced at the list and I saw several Type D Mod 2 entries that appeared identical, that was all.

No, on model D i forgot to put the differences, you are right.

There are 2 model AVO D, and 3 variations on the second model.

Model 1 have a fuse.

Model 2 (second one on the list) has the front panel of a model 40 and high voltage bobins.

Model 2 (third one on the list) has front panel rom model D and aluminium case.

Model 2 (fourth one on the list) has front panel from model D and baquelite case.
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Old 2nd May 2020, 7:01 pm   #2502
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Default Re: AVO Multimeter survey

Once again, hope everybody is doing well in the Current Climate.

Thanks to everybody who has provided Data on the early models.

Obviously, there are not so many of the early Models about, so there
has not been so much feedback.

But now it's time for the more common Model 7!

Model 7

Ok, it's time to get those Fantastic and unvalued Model 7's out.

The original Serial Numbers for Model 7's took the Format of :
7 "Month,Year" - "Serial Number".
The Serial Number Format seems to have changed in 1947.
The replacement of the Horse-Shoe Magnet Meter Movement is believed to have also occured 1947.

I am trying to ascertain if the Serial Numbers changed at the same time the
the Horse-shoe Magnet Meter Movement was replaced.

To confirm if this was the case, I would be interested to know which Model
7's out there have a Horseshoe Magnet Meter Movement and of course their corrisponding Serial Number.

Also, for younger Model 7's, I would still be interested in an update of the Case Style (Alloy or Bakelite), Colour and if Pf Sockets are present.
And of couse any other interesting features.

Also, I would be interested in any Model 7 Mk II's that have the older Style Domed Terminals (ie, Without 4mm Banana Sockets).

This information was not recorded previously.

I am happy to recieve PM's if the owners would prefer not to broadcast these Details.


Regards


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Old 2nd May 2020, 9:34 pm   #2503
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Default Re: AVO Multimeter survey

Hello, my AVO 7 has the following serial number 7441-5429 with Horse shoe magnet and without PF. with aluminium case.

There are Avo 7 from this era with aluminium case an bakelite and with o without PF and as far as i know perhaps the change of the magnet was on 1942. We must find a 1943 or higher AVO 7 to check my info.
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Old 2nd May 2020, 9:44 pm   #2504
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Default Re: AVO Multimeter survey

Hi Aitor,

The Horse Shoe Magnet Movement was in production until at least 1947.

This co-incides with the Serial Number Format change, hence an attempt to see if
these changes happened together at the same time.

If they did, the Model 7 Serial Number Format will be a very useful indicator of the
Movement Type. (At least as to it being a Horse Shoe type or not).


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Old 2nd May 2020, 11:12 pm   #2505
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Default Re: AVO Multimeter survey

Hello Ian,

I have two Model 7 Mk II instruments with the older black domed terminals. They’re probably my favourite 7s, although both currently need attention. They both have black crackle-finish alloy cases and PF sockets.

The serial numbers are 53379-A-155 and 62451-A-256 and I’m pretty sure they are already in the ‘database’. Thanks for your continuing efforts!
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Old 3rd May 2020, 10:46 am   #2506
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Hi Phil,

Thanks for the update.

Yes, the Model 7 is wonderful Instrument, very underestimated and over looked.
I have found the build quality to be of an exceptional standard.
Still useful for many tasks, and many still 100% within Spec after 60+ Years.

Although I understand very early ones were a bit ropey, and I have found very late ones (1970's) to be less substantially built!



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Old 3rd May 2020, 7:18 pm   #2507
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Default Re: AVO Multimeter survey

What we really need is somewhere we can all upload images of the meters we own, external and internal, a library of visual information.
I don't think this forum is suitable, as its for discussion rather than a gallery.

However, if everyone is interested, I can look into a site that does this and we can set some rules and started uploading image data

Any opinions?

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Old 3rd May 2020, 8:28 pm   #2508
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Hi Andy,

For the purposes of a Visual Gallery of AvoMeters, that Site already exists, it's the
Richards Radios Web Site.

A very well written and informative Website.



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Old 3rd May 2020, 11:13 pm   #2509
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Ian,
I know Richards website very well and it’s fantastic, we can never replace that great site. , i’ve Visited his house and seen his collection first hand.... awesome!

But that not what I meant.... I am talking about each of us uploading of our own meters. We can then see all the little variations we talk about. Imagine a model 7 folder with 50+ sub folders and each folder under a serial number and containing photo of the instrument and it’s internals.

I already take stacks of folders for each of mine and keep them separate so I have quick visual reference of the instruments and their internals.

Andy
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Old 4th May 2020, 12:02 am   #2510
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Default Re: AVO Multimeter survey

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I already take stacks of folders for each of mine and keep them separate so I have quick visual reference of the instruments and their internals.
Sadly, I'm not so well organised! I think the task of opening up and photographing even my small collection would remain in the 'round tuit' pile for ever...
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Old 4th May 2020, 11:22 am   #2511
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Default Re: AVO Multimeter survey

I did start some time ago trying to photograph everything I have. I need to finish it and do something with it, though I won't go to the extent of opening meters. I need to complete an audit of my collection also.
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Old 6th May 2020, 5:52 pm   #2512
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Default Re: AVO Multimeter survey

Andy made an interesting comment in post 2492. In my collection of full sized avometers there are 3 which have additional scale markings which indicate that they may be different from some of their siblings.
My markings:
VT Ltd on HRM 1226-150
G&H on model 8 45836-C-456
GH on model7 6412-A-748
Perhaps others might like to look closely at the lower right hand side of the scale plate as there may be others. Perhaps these meters were specially made for particular clients. Or is it just that the scale plates or the movements were outsourced.
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Old 6th May 2020, 10:31 pm   #2513
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Default Re: AVO Multimeter survey

Post No.2512
-Have noticed G&H on a couple of Avominor scaleplates. Assumed this was outsourcing as it is not in quite a well hidden location.

'The following is hazardous and should not be attempted due to risk of fire and/or explosion:'

Managed to re-stuff a BLR121 battery this evening, courtesy of a small 'sparkling thunder' bottle rocket made by Bright Star Fireworks.
I picked up an expended rocket and noticed the plastic thinwall tube was very close in size and flexibility to the tube i needed. Procured a fresh rocket and emptied it, then washed out the tube as the powder can be quite corrosive. The plastic was cut down to 30mm, which slid quite well into the BLR121 clamshell.
I had a pack of (five) CR1025 lithium cells and a spring of a suitable length and strength. The positive terminal of the end cell sat against the spring, and the neg. against the stainless end terminal of the battery, as per the original arrangement. It's vital to retain the stainless end pieces if a re-stuff is attempted. (One is wider and is designed for the pos. end)

The screamer rocket in question is 15" in length including the stick. It came in an assortment a few years ago.

The pd off-load is 16.4v with these new cells, which is well within the adjustment pot. range- and it probably uses a fresh section of the high resistance adjustment pot. so may result in cleaner operation.

The most critical part i have found is finding a nice shiny spring of a suitable rating. The battery clamshell has been taped up but the spring i used is not quite strong enough to try and force it apart.

Dave
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Old 7th May 2020, 2:45 pm   #2514
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Default Re: AVO Multimeter survey

Para 1 should read 'in quite a well hidden location'
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Old 8th May 2020, 1:06 pm   #2515
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Dave,

What is the diameter of those CR1025's ?

I've restuffed with x10 Alkaline 1.5v Watch Battery's up till now.
(Ok, I know their Cells, but nobody calls them Watch Cells!

But it's a lot to pack in and the Life expectancy of those cheap "Pound Shop"
ones leaves a lot to be desired.

Lithium I think will be much longer Life.
Do Lithium Cells exhibit the same type of Corrosion when they run flat like those Watch Battery's (Cells) do?


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Old 8th May 2020, 2:18 pm   #2516
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Default Re: AVO Multimeter survey

I think the code is CR1032 = 10mm diameter, 3.2mm thick. The common CR2025 is 20mm diameter, 2.5mm thick.

Pound shop cells tend to leak whilst still in the packaging! Whilst many of them are OK, they don’t have the shelf life that lithium cells do.
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Old 8th May 2020, 8:11 pm   #2517
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Default Re: AVO Multimeter survey

The CR1025 Lithiums i bought are 10mm diam, 2.5mm thick. The gap remaining to be filled (as there are only five cells) is around 17.5mm (so a 20mm spring was ok, diameter around 8mm which i got away with.)

I don't think i have encountered an oozing lithium button cell yet, but believe them to be less corrosive than alkalines. When they do vent they have a very distinctive sweet smell.
These ones had an expiry date Dec 2023.

Both of the BLR121's i had previously restuffed with alkaline AG10's had just started to weep (expiry date Dec 2018 as i recall) but pd was still up at 15.2v. You just can't trust 'em....but the quick clean up job was really my fault for leaving them 1.5 years overdue.

Fortunately I found enough springs and rockets to re-pack all 3 of my batteries, and they're all making good contact..for once!

Dave
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Old 8th May 2020, 9:29 pm   #2518
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Default Re: AVO Multimeter survey

I believe the capacity in mAh of the CR1025's is a little lower than the alkalines. I will update in future if they cause any trouble. They were cheap- too cheap really, at £2.50 for ten. But we'll see.

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Old 8th May 2020, 9:46 pm   #2519
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Default Re: AVO Multimeter survey

Capacity is less of an issue than leakage-free long life! I doubt whether even one-hundredth of the mAh capacity is ever used up in taking actual resistance readings.
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Old 8th May 2020, 10:36 pm   #2520
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Agreed Phil- i think the VC1 voltage converter unit is only rated for 80 or 90uA output, for most tests i imagine the demand is a fraction of this.
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