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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 19th Jun 2018, 10:19 pm   #1
Superscope
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Default Original AVO Test Leads. A problem you may not know you have!

Was just checking out an AVO 8 I bought recently, which
clearly had an intermittent fault.

Problem turned out to be in the Conical Test Clips.
I had assumed, these were a straight piece of Metal from the Terminal
connector to the Test Clip.
But No!
The Test Clip seems to be Stainless Steel, and this is screwed into the Brass
contact which then plugs into the Test lead.
There was corrosion in the Joint which required cleaning. Problem solved.

That prompted me to check all the Conical Test Clips in my collection.

I was surprised how many were OC or High Z.

I also noticed that there is a variation in the inside Diameter of the Test Lead Socket.
This means that conical Clips from different periods don't necessarily make a good electrical contact to the Test lead.

So for the AVO collectors out there, don't forget to check the Leads, they are likely to be intermittent.

Doesn't effect the Croc Clips of Brass Probes.


Ian
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Old 19th Jun 2018, 11:14 pm   #2
Craig Sawyers
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Default Re: Original AVO Test Leads. A problem you may not know you have!

OK - I'll bite - how does the blighter come apart?

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Old 19th Jun 2018, 11:20 pm   #3
Sinewave
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Default Re: Original AVO Test Leads. A problem you may not know you have!

Although I have Avo leads, I do not use them, but I have found a similar issue in the past.
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Old 19th Jun 2018, 11:27 pm   #4
Phil G4SPZ
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Default Re: Original AVO Test Leads. A problem you may not know you have!

That's a good tip. I'm sure I have at least one of these which is intermittent - I may have thrown it out by now though. I presume you unscrew the tip to start the dismantling process?

I confess I don't like these particular test prods and prefer to use the standard straight push-in type.
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Old 20th Jun 2018, 12:38 am   #5
turretslug
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Default Re: Original AVO Test Leads. A problem you may not know you have!

Agreed- the contact problems make them something of a liability and potentially a hazard. I always found them a somewhat clunky design anyway as well as unreliable, there can't be many post-WW2 things that they are useful for probing around! As Phil says, the slim, hard-point probe is much more useful day-to-day anyway. I prefer to use a set of the RS multi-option test leads with the point, spring-hook, croc-clip, lug options on sliding shroud 4mm plugs with the likes of AVO 8 and Selectest 50- I'd rather safety for both DUT and myself over doctrinaire authenticity for this sort of thing,

Colin.
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Old 20th Jun 2018, 7:43 am   #6
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Default Re: Original AVO Test Leads. A problem you may not know you have!

Can't disagree with anything said there!

I too, find the Conical Test Clips and the Leads a bit unwieldy & Clunky
to use, but you can say that about the AVOmeter, but we still Love them!
Much better off using a Modern Test Lead for sure.

I just like them to work properly.

Once cleaned (I used a small Brass Wire Brush on the Stainless Thread),
they work fine. Provided of course, the Clip is matched with the correct
Test Lead so a tight electrical contact is made which is not always the case.

A very brief dismantling description as follows:

Looking down the Connector end, first unscrew the outer Brass retaining Screw.
That's the Top Brass piece in my earlier Photo.
You will need to make a special Tool for this, as if it is tight you will most
likely bend a small Screwdriver if you tried to use it.
Pretty easy to make using a small diameter piece of Aluminum Tube found
at most hobby Shops.

Then with a pair of pliers, unscrew the Brass Connector (the lower Brass
piece in my earlier photo). The Steel Test Clip should not rotate, but if it
did (it's probably Shot!) it would need to be secured via it's flat end.

Once unscrewed, the Steel Test Clip pushes out the Clip end.
Don't try to remove it, or insert on assembly in the connector end.

Chances are, the Thread on the Steel Clip is Black and might even be loose.
Classic case of DMC going on there I think.

Assembly is the reverse of course.

Don't try to unscrew the long Probe from the Conical Body, it doesn't work like that, and you will break it!

Finally, get those Leads and clips out and re-discover the Joys of 1960's
Test Leads.


Ian
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Old 20th Jun 2018, 8:04 am   #7
barrymagrec
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Default Re: Original AVO Test Leads. A problem you may not know you have!

My Dad had a pair of these probes when I was a kid - like most test leads they eventually went iffy and fell out of use.

I noticed the other day that he had screwed part of one onto a piece of stick to hook the window closed as he can no longer reach up to the handle. Good kit always has it`s uses.
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Old 20th Jun 2018, 8:29 am   #8
The Philpott
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Default Re: Original AVO Test Leads. A problem you may not know you have!

That problem with the differing diameters is indeed a pain, and potential hazard. I bag up all compatible sets separately in avoidance of this. If there were a chance of them getting jumbled up i would most likely use those coloured (silicon?) rubber ID sleeves that i used to see on Dad's Marconi kit.
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