Avo model 4 34 ranges

I received the AVO a week ago. it was in not very good state due to the age.

I clean it and i applied horse grease to the leather strap.

When i opened it, i see 2 non original modern resistors and 2 hand made wire resistors but not on the shunt board. There were also a couple of red an green modern wires. I test all the ranges and everything was ok, the movement was a little bit sticky, with a very light oil (moebius) for pocket watches, the movement now is perfect.

I took apart the modern wires and repaired same solderings i decided to take apart the upper shunt board and re-wind the broken wire resistor. i used the same wire that somebody uses but in the correct place. Also there was a missing nut that fix the lower shunt board an the transformer that i replaced with a original brass one with washer from an Avo 40.

I will look for the correct resistor wire in the future to replace the two modern resistors.

Now i am preparing the case for painting with the original crackeled black paint and will reproduce the tag inside the battery cover. Also i am preparing a system to use a modern D cell in my AVOs as you can see in the photos attached.


A question:

On the tag attached at the bottom i can read:

"...if accidentally blown (the fuse) should be replaced by the spare fuse inside the battery box.."

The battery box is a wooden box, i can not see a place where the fuse should be

any idea?

The serial number is 93-2011, it was made in September 1933, there is another older example on the survey list from August 1933, but i have read that this model was made between December 1933 and June 1934, so the model 4 seems that began to be produced before August 1933.

I noticed that in this unit, the horse shoe magnet is in horizontal position and in other unit a have seen photos, (Dave Philpott Avo´s i think) it is in vertical position. Do not know its serial number. I think horizontal position units are later than the vertical ones that are more older.

So, i think:

1) There are 2 variations of AVO 4 34 ranges

-Vertical magnet (the older one)
-Horizontal magnet

2) The 34 range AVO was produced much earlier than we know. Perhaps before August 1933.

[pmmunro]

Aitor,

The date of introduction of December 1933 was based on the oldest trade advertisement which I could find but the serial numbers of these 34-range meters indicate that production began earlier.

I can't explain why it would not have been advertised earlier; the information is based on a careful search which I would have expected to show up any earlier advertisements, but ACWEECO's policy on advertising was not entirely logical at the time. It may be that all production was assigned to a particular customer, such a government ministry, before December.

My only Model 4 is serial number 14-2098 which would suggest that 90 instruments were made in 8 months, roughly 12 per month. That's not a large number for commercial production.

The fuses were available from ACWEECO on an exchange basis.

PMM

[The Philpott]

My Model 4 certainly does have the vertical horseshoe magnet with the 'clamp type' magnetic shunt.

Aitor, I wonder if your 93-2011 was returned to the factory for a replacement movement to be fitted- the writing on the rear of the scale plate and the excellent condition of the front of the scale plate might indicate this. I am interested to see meters which have Fahrenheit on the scale plate- for the American/Canadian market?

I don't know how the spare fuse was held. There was no indication in the battery box.

Dave

I found the same serial number on the baquelite case under the movement.

Also a few numbers in pencil on the rear of the scale plate.

The scale plate is in very good condition, the movement looks very well and I do not find evidences that it was replaced. Who knows....

I had a look to the back of the scale plate. the numbers are 34-2306 and then a date 22-2-49, also a signature and a name? ket?

Perhaps as Dave suggested, that is the original serial number of my Avo 34 ranges, and 22-2-49 was the date it was repaired.

So if it is correct, we have another serial number for the list.

34-2306 March 1934 (The original serial number of my AVO?)
93-2011 September 1933 (my AVO actual scale plate)

I wonder if in 1949 the person who repaired it used a new old stock plate or a existing one from another Avo...

So, the survey list should be like this:


83-1909 August 1933
93-2011 September 1933
14-2098 January 1934
XX-2152 February 1934?
34-2306 does not exist March 1934

The XX-2152 Avo could be very probably 24-2152.

yesterday i made one of the cylindrical piece where the shunt board is attached.

Hello, today I rewind another resistor on the small upper board. The wire i used was originally from an Avo 40 board.

Only rest to rewind the resistor on the large board at the bottom. But I can see that originally there were 2 wire resistor on that board, now is a pair of resistor in parallel. As soon as I find an schematic to see the original values of both resistors i will rewind them too.

Has anybody have the schematic or the value of those missing wire resistor?

Originally Posted by Aitor Eneko

Has anybody have the schematic or the value of those missing wire resistor?

The Avo 36 range i think uses resistors with the same values. The schematic is not the the same because of the divide 2 button.

Can anybody confirm the resistors are the same for both Avos (34 and 36 ranges)?

Thanks,

Aitor Eneko

[pmmunro]

Aitor,

I have a print from the ACWEECO drawing, dated 3-3-46, for the 34-range Avometer but the quality of the print and the original drawing are both very poor. The title of the drawing is just decipherable and reads "34-range Universal Avometer (Improved Type)" but this could either mean that the 34-range meter was an improvement on a previous model, such as the 20-range Avometer or that the drawing records some improvement to the original version of the 34-range instrument.

In any case it does not help a great deal as there are no component values marked on the drawing. Quite why it would have been redrawn in 1946, I don't know but it may have been to replace lost records. In such an event, the component values may not have been available at the time and it was intended to add them later. I can't say I think much of their drawing office quality standards of the time!

The attachment is just the circuit diagram part of the drawing as the whole print is bigger than my scanner.

PMM

Thanks very much for the circuit diagram.

I will have a look.

Do you think that the value of the resistors on the shunt boards are the same (at least the lower longer board)?

In a few days i will finish the case, with the original crackeled paint, is not easy to reproduce it.

Just need a brass screw like in the photo attached. I wonder if somebody have one to sell, i do not find it here.

long 27,75mm
thick 2,55 mm
head 4,75 mm

I noticed that the one that Avo used at the same place on Avo 36 ranges, has a bigger head, otherwise the same.

[Sinewave]

They're usually 6BA threads.

Any idea where to find one??

[stevehertz]

There's a seller here of 6BA brass cheesehead bolts (if that's what's required): https://www.ebay.co.uk/itm/6BA-Brass...2E6IHMjNpzrp8Q

thanks, i will try to contact him, it seems that the longer one that he has is 1", i need 27,75 mm, thats is a little bit more than 1""

Thanks very much, very kind of you!

[Andrewausfa]

That's 1 3/32" in our Imperial measurement system. Might be easier to find 1 1/4?

This chap is where I get my BA nuts and bolts

http://www.ba-bolts.co.uk/brasscheese.html

Andrew

Thanks very much, i will contact with them!!

Aitor Eneko