Repairing avo 7 movement help

Hello, as you know i need a meter for my AVO 7 movement. Mine was in very bad condition due to bad manipulation in the past. Both springs very bend, the parts for overload protect had been taken apart, etc.


I decided today to try to repair it in my job, where i have better tools than in my house.

Firstly i took apart the movement, the coil has continuity (i test it with my AVO 9 ) and the coil with the spring. As one of the spring was in very bas condition, desoldered it and with a tweezers i was able to give the spring its original form. The other one recover its form with the tweezers without taken it apart.
After that i weld the spring again.

To finish the job, i must know if there is any part missing in the overload system (see photo) because when i tried to mount that parts, the system does not work, i think that perphaps a washer is missing, because the parts got stuck when i pur the screw. Any help about this system, as photos will be appreciated.


Thanks,

Aitor

Here is the system that i need to know how is mounted.


Thanks

[Sinewave]

Wow.

You are very brave attempting that.

I can't offer any help, though I wish you luck.

[MrElectronicman]

Yes Wow! you are brave doing that.

I tried repairing my first Avo movement, which is why I now have a second one.

The pointer broke on first one, and one of the hair springs was disconnected from the coil, when I attempted to fix it, I messed up the coil, and I know the pointer is very tricky to straighten, even worse when it actually in two pieces.

I gave up as someone had played with the magnet to boot, so it was a exercise in futility.

Good luck

It is quite difficult I must say.

I just mount everything to check and it works fine. Except the springs are not solder yet because firstly y must find the way for te overload system

[Andrewausfa]

I've taken some shots of mine, I took them before you've just answered that it works just now. Anyway, I took them so you get them Obviously I don't want to take it apart as it's fully working.

Andrew

Thanks, but I can not see the overload system that is the parts does I must put altogether.
I will appreciate photos of this system or explanation of the way the pieces should go

[Andrewausfa]

By 'overload' do you mean the Cut-Out? Not sure what you mean.

Andrew

The different parts in the photo of my second post

Thanks

Is this the movement with the semi isolated needle so a gross overload wouldn't bend the needle just trip the cutout? Or are all AVOs like this?

I think that we can find this movement in model 40 and model 7. Sure Philpott, Richard or others members could ask better your question. Avo 8 does not use this over load system

[The Philpott]

Yes i think that's correct, the acceleration trip is on the Mod 7 and Mod 40.
I have never seen it operate! I certainly don't know how to put it back together, but getting this far is impressive as we can see those springs were very badly tangled.

Dave

I found the way.

The problem is the upper spring, i desoldered it and now there is a problem with the exact position to be weld again. I mean the exact position in the axe. First attempt too high and the spring touch the iron plate, second attempt too low and the spring touch the coil.

Third attempt in a few days...

[Phil G4SPZ]

The upper spring isn't supposed to be soldered to the pointer at all.

This is the later version of the acceleration trip. I repaired an identical one of these several years ago, using Araldite to refix the pointer drive lever to the inside of the moving coil. The attached picture shows what the assembled mechanism should look like. The long spring should take the form of a "lazy-S" shape, as its purpose is merely to hold the pointer gently against the closed end of the slot. Excessive acceleration causes the pointer to move along the slot against the wire spring pressure, and the various cams translate this motion into a push on the cut-out rod. Ingenious, but enormously fiddly to repair.

These are really tricky to get right, but you have done admirably so far!

Phil

Thanks. I finally finish this work and the meter is working but not fine. Sometimes when testing low voltages or low ohms, the pointer gets stuck. I took it down twice but did not find any problem. I will fix the long spring as you told me. I solder it to the pointer because i found it like that.


Thanks

Aitor Eneko