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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 9th Jul 2019, 6:57 pm   #2201
The Philpott
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Default Re: AVO Multimeter survey

Yes 17754-74 would be July 1934; on examples from the 1930's the decade is assumed, thus my early smooth side DC Avominor 1034-93 originates from Sept. 1933.

The figures for production between Sept. 1933 and Sept. 1936 are surprising- around 40,000 units. This was a popular device! From Sept. 1936 to June 1941 another 22,000 were produced.

In the 1930's (certainly on full size avometers anyway) sometimes the serial number and date codes are reversed, which can cause confusion.

Dave
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Old 12th Jul 2019, 11:26 am   #2202
micheal
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Default Re: AVO Multimeter survey

DC Avominor serial number 95965-1058 this must have been one of the last to be produced, i'm surprised Avo were still making these as late as 1958.
Had to rewind the 60volt and one of the 300volt bobbins.
The later ones had the strengthening skirt removed so making the case the same as the very early one.

Mike
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Old 12th Jul 2019, 1:16 pm   #2203
The Philpott
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Default Re: AVO Multimeter survey

I'm also very surprised they were making the DC version in '58, i would have thought the Universal AC version would have pushed it out sooner, primarily by better accuracy with the larger scale (the glass is also of a sensible thickness..)

The use of smooth-side mouldings for the cases suggests to me there could have been a stockpile of the early mouldings which were dusted off and used when the meter was nearing the end of it's production..? I assume that the later moulding was introduced due to breakages of the early one.

Dave
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Old 13th Jul 2019, 11:46 am   #2204
micheal
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Default Re: AVO Multimeter survey

I think the strengthening skirt was added because the cell was prised out with a screw driver and the thin case could not stand the strain and broke.

Early case's had 6v,120v and 300v markings where the later versions had 6v,60v and 300v. and a thicker overall case, so probably a new moulding.

Mike.
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Old Today, 8:01 am   #2205
AndyGilham
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Default Re: AVO Multimeter survey

Quote:
Originally Posted by AndyGilham View Post
A new ebay purchase
Avometer Model D (10S/10610) - Serial Number 19110-345 (March 1945)

Looks to have a missing Terminal Knob, so i will 3D print a replacement. Other than that, it looks in good condition. I will upload some photographs once its delivered.

Regards
Andy

As promised, please find attached some photos of the Moel D.
The instrument front panel is missing a terminal, but generally its in good shape.
The first thing i noticed internally was the resistors. It seems at some point one of the current shunts on the shunt board had burnt out (low current, 0.015A??), and so replaced by 2 series resistors.

Additionally, one of the shunts on the resistance board has been wrapped in a solder resist tape. I assume this was due to the windings becoming loose.

Andy
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Old Today, 11:17 am   #2206
The Philpott
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Default Re: AVO Multimeter survey

Hi Andy, the translucent tape is often in evidence on the 150v winding pictured- not sure why.

I think that the scorched lower left winding replaced by resistors is probably the 7.5vAC winding. That's a typical place for the lowest ACV range to be.

Dave
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Old Today, 11:24 am   #2207
The Philpott
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Default Re: AVO Multimeter survey

Ouch- just noticed the safety cut-out's contact leg has been arc damaged in photo 4- the big carbon contacts are aligned to open after the inboard gold-silver contacts, which (you hope) protects the latter.

Dave
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Old Today, 5:50 pm   #2208
The Philpott
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Default Re: AVO Multimeter survey

Model D- I can confirm that the burned out winding in pic 4 should be around 283 ohms..So the repairer did their sums right, even if they did rush it.

Dave
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Old Today, 10:50 pm   #2209
AndyGilham
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Default Re: AVO Multimeter survey

Thanks for the observation and the update on the resistors. It’s a nice assembly, but does not look as robust as the model 7... which is strange, being a ministry variant
Andy
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