Restoration AVO 40

Avo 40 to be restored, need help.

The movement i think was changed in 1977.

As i found it:

One more photo

Firstly i was thinking in taken it for parts, specially the movement to my AVO 7, but after testing it, i think it is worth to be restored.

That movement as i said i think is a replacement, and does not have the overload protection system, so, i do not want to put in my AVO 7.
Also i think that if i finally decide to restore it, i will need the correct movement.

Moderator: Could you change the title of the thread to: Restoration AVO 40?

[The Philpott]

The scale-plate is Model 8 Mk II or III type, so if the movement is also Model 8 it is not compatible with any Model 7 or 40 anyway (but worth keeping as a spare)

Did you manage to get the spare Model 7 movement off ebay?

Dave

Yes, I bought it, but the seller did not send it to Canary Islands, do not know why, so I tell him to send it to my mother in law house, in the mainland.

After Christmas I will receive it. With that and my original plate, I can finish model 7

Now I need help with this AVO 40 it seems to be a coil missing on the left hand, there are couple of wires there and a few new wires bad soldered in the variable resistance that I eliminate.

So I need electrical diagram of this Avo 40 and a original movement.

At Richards page I found a similar Avo 40, but not the same circuit.

Thanks

After removing the incorrect movement and remove a couple of non original and very bad soldered wires, the aspect is this. (See photos)

I drawn 2 circles on the wires that i think goes into a missing coil (i do not have the electrical diagram)

[Superscope]

Hi Aitor,

Schematic for a Model 40 Mk II attached.

I assume it's a Mk II looking at the construction.

It looks like the Coil you are looking for actually resides on the Meter Movement Frame itself.
There are Two Coils (Bobins), one either side of the movement. See Photo.

One is the Swamp Resistance for the Meter and the other is the Divide by Two Shunt Resistance.
Off hand, I don't know which one is on the Left or Right side.

I think this is what you are looking for.


Ian

Thanks very much, the photos of the inside that you have loaded correspond to my model, but in Richard´s page, i understand that the AVO 40 with the arrows in the Knobs are MK1, and also he says that the same panel is used for both models (mk1 and mk2) without MK marks, but with the differences of the arrows.

So, mine has the arrows and is marked in the front panel "model 40" so it should be MK1, but inside it looks very is as the photos you posted, so i do not know exactly which model is it.

I attached photos of the front panel.

Also, in Superscope´s first photo i can see the original shunt, that has been substitute for 2 resistances in mine (first photo is mine, second photo is the one Superscope load before)

Thanks very much for the schematic, just waiting to confirm which MK is this AVO 40

[Superscope]

The Front Panel is definitely a Mk I

So I think your Meter is simply a later Mk I.
Very unlikely anybody rebuilt a Mk II interior on a Mk I Front Panel due to the amount of work involved.

So if AVO called it a Mk I, then it's a Mk I, just has the later style Movement and Interior.
I have no idea when the change in Movement happened on the Model 40's, but earlier Mk I's have a very different interior to the one in your Meter.
I'm guessing that your Meter Dates from sometime before 1956


Ian

Thanks!!

Could you load a photo of more detail of the bobin at the left hand side?, i am in a doubt about the connection of those wires involved.

Aitor

I see that the plastic "P" button is broken, do not know how difficult could be to get a new one, i did not see anyone on the internet

Today i repaint a little bit the knobs, they are very worn out nut the result is acceptable!

Also I am waiting to receive this AVO 40mkII to be restored as well, it has a bakelite case, i think that is correct.


No inside photos yet

As i said in the survey thread, this AVO was made in 1952, so the label on the right hand side and probably the case and instructions plate are from another Avo as i was told.

I think that my Avo 40 mk2 from 1957 should have metal case. Doesn’t it?

Hello. Can anybody confirm if the Avo 40 mk2 used a metal battery cover or the Bakelite one with the 2 sticks probes and the “mysterious” probe or even used both?

[The Philpott]

Mine has the aluminium cover, i believe it is original. This Model 40 lacks a serial number on the scale plate but SR22568 is hand engraved into the front on the meter.

(Sometimes a bakelite battery cover leaves slight marks on the inside of the leather strap where the edges have chafed.)

Dave

I have seen the AVO40 mk2 with aluminion case and both battery cover so I am not sure if both were available in the 50’s

Here is the AVO40 mk2 fully working. I cleaned the front panel, repair the smallest shunt board with on other one from an avo 40 for spare parts. Also solder many cold joints an clean the blades of the knobs.

Paint the case with Martele and put one leather slide knob that I recover from an old and broken Bakelite case

Just waiting for the red and black cap and the 3 feets.

Finally I put a Bakelite cover with stick probes

[Techman]

I just got my 'inherited' 40 MK2 out of the cupboard. It needs a good clean and the last time I used it to monitor something I seem to remember it was all over the place, so needs to be taken apart some time and looking at. I note that the end of the number on the bottom right of the scale is 961.F. which would indicate a date of September 1961. Pictures below:-