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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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24th Apr 2019, 6:48 pm | #1 |
Heptode
Join Date: Dec 2008
Location: Somerset, UK.
Posts: 555
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AVO 7, MkII
Recently bought an AVO 7, MkII, dated 362.
Intention to adapt the battery compartment to take a PP3, but first I've got to get the back off. Removed all the screws but mystified with the fitting pictured. Does the chrome ring come off with the cover, is something broken off here? It is a nice meter, came with the leather case, instructions, leads and even the original box so I'd like to take care not to force anything. Alan |
24th Apr 2019, 6:55 pm | #2 |
Octode
Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
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Re: AVO 7, MkII
A pp3 is 9 volt, how would you use that in the Avo?
That ring is usually filled with wax (or something wax like) as a tamper seal. Behind the wax is another screw. The chrome ring is threaded also.
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Avometer, vintage Fluke and Marconi collector. Also interested in vintage Yaesu and KW. |
24th Apr 2019, 7:28 pm | #3 |
Octode
Join Date: Jul 2004
Location: Dundee, UK.
Posts: 1,813
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Re: AVO 7, MkII
The batteries which are normally used in an Avometer Model 7 are two 1289/3LR12 plus a 1.5 Volt 'D' cell.
The Model 7 uses the D cell to bias the rectifier on AC ranges and is the only conventional Avometer which needs a battery other than for the resistance ranges. PMM |
24th Apr 2019, 7:56 pm | #4 |
Octode
Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
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Re: AVO 7, MkII
Oops silly me, I just realised there are two 4.5v batteries for the resistance range, I kept thinking about the 15v for the model 8. Those 4.5v batteries are still available though.
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Avometer, vintage Fluke and Marconi collector. Also interested in vintage Yaesu and KW. |
24th Apr 2019, 8:34 pm | #5 |
Octode
Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
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Re: AVO 7, MkII
This reminds me I've got a 7 Mk2 here which I fitted with two new 4.5v batteries last year. I'd better take them out whilst it's not in use, just in case!
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Avometer, vintage Fluke and Marconi collector. Also interested in vintage Yaesu and KW. |
24th Apr 2019, 9:58 pm | #6 |
Dekatron
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,108
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Re: AVO 7, MkII
Yep, dig the gritty black composition out as carefully as you can, revealing a brass grub screw. As this screw comes out, it releases the (top hat shaped) nickel plated washer which can be levered out.
The presence of the black stuff indicates the inside of the meter was last seen by the manufacturer! Dave |
25th Apr 2019, 8:30 am | #7 | |
Heptode
Join Date: Dec 2008
Location: Somerset, UK.
Posts: 555
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Re: AVO 7, MkII
Quote:
A little loctite may hold it, if not it might require tapping out to the next BA size, a small job for today. Alan |
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25th Apr 2019, 1:29 pm | #8 |
Guest
Posts: n/a
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Re: AVO 7, MkII
That is a common problem. With loctite 270 you can fix the screw
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25th Apr 2019, 6:57 pm | #9 |
Dekatron
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,108
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Re: AVO 7, MkII
I have always found that the glue used to hold the thin insulation sheets to the inside of the case is no longer doing it's job very well. If it's the black glue it's soluble in WD40 (one of the few places in an AVO where WD40 can be used!)
It seems that PP3 alkalines are well up to the job of powering the high resistance range, it's a mod i have done a few times. Dave |
25th Apr 2019, 7:38 pm | #10 |
Octode
Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
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Re: AVO 7, MkII
Pardon my ignorance but I don't see the gain in the mod when the 4.5v batteries are readily available.
__________________
Avometer, vintage Fluke and Marconi collector. Also interested in vintage Yaesu and KW. |
25th Apr 2019, 8:35 pm | #11 |
Dekatron
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,108
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Re: AVO 7, MkII
In my case it's a combination of future-proofing against non-availability, and grabbing what's easily to hand. There are adaptors, so i am told, that can use AA cells to make up a 3-pack, but they are a little oversize and need dremelling to fit in the AVO (apparently)
I can't answer for Alan of course! Dave |
25th Apr 2019, 8:56 pm | #12 |
Guest
Posts: n/a
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Re: AVO 7, MkII
You can use a 9volt cell instead of two 4,5 volts without drilling
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