UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Test Gear and Workshop Equipment

Notices

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

Closed Thread
 
Thread Tools
Old 24th Apr 2019, 6:48 pm   #1
Chiltern
Heptode
 
Join Date: Dec 2008
Location: Somerset, UK.
Posts: 553
Default 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
Attached Thumbnails
Click image for larger version

Name:	ASIDSCN8730.jpg
Views:	67
Size:	72.2 KB
ID:	181787  
Chiltern is offline  
Old 24th Apr 2019, 6:55 pm   #2
Sinewave
Octode
 
Sinewave's Avatar
 
Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
Default 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.
__________________
Avometer, vintage Fluke and Marconi collector. Also interested in vintage Yaesu and KW.
Sinewave is offline  
Old 24th Apr 2019, 7:28 pm   #3
pmmunro
Octode
 
Join Date: Jul 2004
Location: Dundee, UK.
Posts: 1,797
Default 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
pmmunro is offline  
Old 24th Apr 2019, 7:56 pm   #4
Sinewave
Octode
 
Sinewave's Avatar
 
Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
Default 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.
__________________
Avometer, vintage Fluke and Marconi collector. Also interested in vintage Yaesu and KW.
Sinewave is offline  
Old 24th Apr 2019, 8:34 pm   #5
Sinewave
Octode
 
Sinewave's Avatar
 
Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
Default 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!
__________________
Avometer, vintage Fluke and Marconi collector. Also interested in vintage Yaesu and KW.
Sinewave is offline  
Old 24th Apr 2019, 9:58 pm   #6
The Philpott
Dekatron
 
The Philpott's Avatar
 
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,081
Default 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
The Philpott is offline  
Old 25th Apr 2019, 8:30 am   #7
Chiltern
Heptode
 
Join Date: Dec 2008
Location: Somerset, UK.
Posts: 553
Default Re: AVO 7, MkII

Quote:
Originally Posted by The Philpott View Post
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
Many thanks, a minute or so and the screw revealed and removed, off came the back. Strangely the glue holding the thin fibre panels has dried out so they are loose and also loose screw in the cover. A screw holding a coil to the meter casting had come out, the thread stripped. I have moved the coil in the picture to show it, it was perfectly in place and it took a little time to identify where the screw, washer and sleeve had come from.

A little loctite may hold it, if not it might require tapping out to the next BA size, a small job for today.

Alan
Attached Thumbnails
Click image for larger version

Name:	ASIDSCN8732.jpg
Views:	68
Size:	65.5 KB
ID:	181813   Click image for larger version

Name:	ASIDSCN8733.jpg
Views:	70
Size:	66.6 KB
ID:	181814  
Chiltern is offline  
Old 25th Apr 2019, 1:29 pm   #8
Guest
Guest
 
Posts: n/a
Default Re: AVO 7, MkII

That is a common problem. With loctite 270 you can fix the screw
 
Old 25th Apr 2019, 6:57 pm   #9
The Philpott
Dekatron
 
The Philpott's Avatar
 
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,081
Default 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
The Philpott is offline  
Old 25th Apr 2019, 7:38 pm   #10
Sinewave
Octode
 
Sinewave's Avatar
 
Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
Default 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.
Sinewave is offline  
Old 25th Apr 2019, 8:35 pm   #11
The Philpott
Dekatron
 
The Philpott's Avatar
 
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,081
Default 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
The Philpott is offline  
Old 25th Apr 2019, 8:56 pm   #12
Guest
Guest
 
Posts: n/a
Default Re: AVO 7, MkII

You can use a 9volt cell instead of two 4,5 volts without drilling
 
Closed Thread

Thread Tools



All times are GMT +1. The time now is 7:44 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.