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Old 12th Dec 2018, 11:05 am   #21
Superscope
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Default Re: Avo 36 range restoration

Regarding the Plastic Knobs on the 36 Range,

I think I am quite confident now in saying Yes there are indeed two versions of the 36 Range.

The Z control, (Movement Zero adjust) I believe this was always a Slot Screw Head
on all versions.
The earlier Meters up to around 1934 all the Controls are Slot Screw Head.

Later Models from around 1936 have Plastic Knobs on the R and P controls.

This is based on looking at my earlier 36, where I can see no evidence a Plastic
Knob was ever fitted, and I can't see how it would even be possible based on the
way the Screw Head is recessed into the Panel.
Also, why would it have a Screwdriver Slot if it were covered in Plastic?

I also looked up some AVO Advertising in a 1930's copy of Wireless World, and the 36 Range clearly has no Plastic Knobs in the Picture.

This would explain why the Model 6 seems to always have them, and early Models 5's downwards don't.

Unless of course, somebody knows something to the contrary.


Ian
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Old 12th Dec 2018, 12:06 pm   #22
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Default Re: Avo 36 range restoration

I am agree with you. Two versions of Avo 36 range
 
Old 14th Dec 2018, 1:50 pm   #23
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Default Re: Avo 36 range restoration

Finally got the Case off the 36.
Serial number found in Pencil on the back of the Scaleplate! Wicked!

Difficult to read, but in the right Light it turns out to be 5749.
Based on that, it's a 1936 Model and I estimate October-ish.

Bottom Resistance Board, disconnected and has broken Winding's.
Looks like the Board was removed and half halfheartedly put back, no doubt because
whoever couldn't fix it. The Board Mounting Spacers are also missing.

Small Resistance Board, one Winding is clearly Broken.
Resistance Board next to the Meter movement has one Toasted Winding, but might be Ok.

Will test the Meter Movement fully before moving on, but for the moment, I think it
should be possible to get this one back from the Dead.

I noticed the Fuse has been replaced with Fuse Wire (Hence 0 Ohms), and I wonder
how many of these Meters have been Scraped because the repairer didn't know the
Fuse needed to be 4 Ohms.


The other interesting thing I noticed, is that the Horseshoe Magnet is Front/Back, not
Up/Down as on my other 36 Range.

There doesn't seem to be a Schematic available for the 36 Range, so will have to try and
make one myself.

Ian
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Old 14th Dec 2018, 2:52 pm   #24
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Default Re: Avo 36 range restoration

Good notices. It will be a hard job, but possible.

Thanks for the information and photos!
 
Old 14th Dec 2018, 7:09 pm   #25
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Default Re: Avo 36 range restoration

Superscope,

This may help.

Redrawn from the ACWEECO circuit diagram (which is terrible) by me.

May be used non-commercially by forum members, but please acknowledge the source.

Please report any errors detected.

PMM
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Old 14th Dec 2018, 8:39 pm   #26
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Default Re: Avo 36 range restoration

Many thanks for the Schematic PMM,

That is very helpful indeed.
Very nicely drawn as well.


Ian
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Old 20th Dec 2018, 3:45 pm   #27
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Default Re: Avo 36 range restoration

Hello, I have not receive yet my 36 range AVO.

What about yours, Superscope?
 
Old 26th Dec 2018, 8:28 pm   #28
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Default Re: Avo 36 range restoration

The 36 Range Restoration took an interesting turn this week.

Took the Meter Movement out in order to straighten the Pointer,
and test the sensitivity.

I found the Full Serial Number including Date written in Pencil on one
end of the Horseshoe Magnet.

The Number turns out to be 576617, not 5749 as previously thought.

So it's always worth checking the end of a Horseshoe Magnet if you are missing a Date!

Meter Movement turns out to be excellent, no detectable stickiness, and
exactly 3mA FSD without any adjustment.

All four Resistance Boards had OC faults, although I have fixed two Boards already.
Managed to find both ends of the breaks and solder them back together.
Although the Manganin Wire is very difficult to Solder.

The Upper and Lower Resistance Boards however will require some rewinding due to
serious Winding damage.
I have decided to rewind the Damaged Winding's in keeping with the original construction
rather than use Modern Resistors.

The Transformer unfortunately is OC, so it's unlikely I will get the
AC Ranges working. I can't see that this Transformer is repairable.




Ian
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Old 26th Dec 2018, 9:31 pm   #29
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Default Re: Avo 36 range restoration

Good news then, are you going to rewind the resistor by yourself? It is difficult to get the exact wire and a machine is needed. I will want to repair one of my bobines as well due to it has been changed for a pair of resistors. Here is imposible to get the wire.
 
Old 26th Dec 2018, 11:57 pm   #30
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Default Re: Avo 36 range restoration

Ian,

Congratulations on the restoration work. I think the serial number you found puts the date of manufacture at May 1937.

I haven't had the misfortune to need a transformer for such an early Avometer yet, but I don't think it would be the most difficult type to rewind as I don't think it is varnish impregnated. We know the turns ratios so that is a good start. It would be a pity not to get the AC ranges operational so it might be worth asking Ed Dinning what he thinks the prospects are and if he would be willing to consider rewinding it.

PMM
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Old 27th Dec 2018, 5:29 pm   #31
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Default Re: Avo 36 range restoration

Parcel2go lost my AVO36

Very disappointed
 
Old 27th Dec 2018, 8:20 pm   #32
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Default Re: Avo 36 range restoration

I hope it turns up Aitor, give it time. It's not unknown for certain Customs officials to x-ray something heavy and then decide it's a suspect device, then take their time pronouncing it safe and repackaging it before sending it on.

Ian, might a later transformer from a donor be suitable?

Dave
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Old 27th Dec 2018, 9:19 pm   #33
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Default Re: Avo 36 range restoration

Thanks!! I hope so.
 
Old 27th Dec 2018, 10:40 pm   #34
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Default Re: Avo 36 range restoration

Aitor,

Give your Parcel a while longer.
Considering the distance it has had to travel and the Christmas Holidays, it wouldn't
be surprising for it just to have been delayed.
The Customs Guys probably slowed down weeks ago in preparation for the Holidays.

Ian
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Old 27th Dec 2018, 10:53 pm   #35
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Yes, the problem is that 11 December the parcel went abroad England, but never arrived to Spain, I recived days ago other Avo that I ordered after this one.

The seller opened case in Parcel2go because the said that the parcel should be in my hands by 18 December maximum. They also said that they do not know where it is. I hope the parcel will arrive finally in a few days/weeks

Thanks
 
Old 27th Dec 2018, 11:40 pm   #36
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Default Re: Avo 36 range restoration

I am hoping I may have been a bit hasty in writing off the Transformer!

The OC measurement looks like it might just have been a Dry Joint.
Fingers Crossed!

Since I had all the Resistance Boards and the Transformer out for repair, I decided I
would strip down the P and R controls for a thorough clean as
they were so tight, they were difficult to rotate.

For the Record, if anybody needs to do the same cleaning Job, the Brass Spike which
holds the Wiper to the Plastic Control Knob requires an 8BA spanner to remove.

Incidentally, another difference I found, the earlier 36 Range seemed not to have Brass
Spikes on the Potentiometers for connection to the Battery Box. Earlier Models seemed
to have separate Spikes molded into the Front Panel for this purpose.

I have re-wound the 96 Ohm Winding on the Small resistance Board.
Again, for the Record I measured this Winding's original resistance Wire, to a value
of 18.2 Ohms/m.

I used 22.8 Ohm/m Manganin Wire and got the new Winding to within 0.1 Ohm.
Over wound it by a few Cm and worked back for the exact Value.

So the Restoration is progressing well, but still a long way to go.

Ian
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Old 28th Dec 2018, 12:23 pm   #37
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Default Re: Avo 36 range restoration

I have encountered a dry joint on a 1968 Model 8, i think the higher current windings are more susceptible due to an unexpected amount of heat conducting away from the joint during soldering.

I did notice that P & R on the Model 4 (34 range) looked very solidly made, and superior to those made 10 years later. They certainly operate more consistently. I think with the early facia mouldings distortion was an issue- quite a thick, complex moulding. A tiny bit of 3 in 1 tends to ease a bakelite shaft turning within bakelite, and any excess tends to soak into the material itself (as it would into a bronze sintered bush) so there's little danger of it getting where it's not wanted.

Where Model D donor parts were available i had the opportunity to cherry pick P knobs to suit the diameter of the orifice in the facia- but in one case the distortion of the facia had been caused- or perhaps worsened- by exposure to a div with a dishwasher, complete with salt tablets. The meter survived against the odds.

Dave
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Old 3rd Jan 2019, 12:28 pm   #38
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Hello, today I finally received my 36 range Avo. 1 moth waiting for it...

The AVo is not in very good condition. This afternoon I will open it and will take a look inside.

The P and R button are very hard, I can not move them. The :2 button is pressed and I can’t lift it. The movement seems to be ok. The paint of the scale plate is a little bit pelled off but does not affect the numbers or lines, a scanner is necessary to preserve it.

Serial number 26-5007
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Old 3rd Jan 2019, 1:28 pm   #39
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Default Re: Avo 36 range restoration

Excellent News Aitor.

See my Post above about the P and R Controls.
Do you have the Brass Spikes on the back of the P and R Knobs?
or Spikes fitted to Front Panel moldings and wired to the P and R Potentiometers?

Best not to try and force them round in case they fracture.
Simply pop them out after dismantling the Wiper and clean them with WD40 or similar.

As Dave mentioned, you could lubricate with some Light Machine Oil on reassembly.
Although I didn't do this (Didn't have any Oil at Hand) and the Controls rotate just fine after the clean.


The Customs Men have obviously finished their festivities now?
So your AVO collecting can continue without interruption!

Ian
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Old 3rd Jan 2019, 2:11 pm   #40
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Default Re: Avo 36 range restoration

Yes, my AVO collecting will continue!!

I took the case off. The interior is not well, many resistor, broken shunts, screw missing from the magnet, i think same type of washer are missing to attach the magnet to the front panel.

The brass spikes are on the back of the P and R knobs, screwed directed on the knob.

See photos.
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