[Test-Equipment] Repair HP410B (triax cable request)

Mon Sep 29 21:35:51 EDT 2014

I have some fairly small 3 conductor shielded Teflon here, it is a little
stiff but it might work, I would be glad to send you a hunk if you want to
try it ... tom, N3LLL

-----Original Message-----
From: Test-Equipment [mailto:test-equipment-bounces at mailman.qth.net] On
Behalf Of Robert Myers
Sent: Monday, September 29, 2014 6:40 PM
To: 'Discussion of Electronic Test Equipment'
Subject: Re: [Test-Equipment] Repair HP410B (triax cable request)

Yes, Barry  

You may want to replace he 'Common' and 'Ohms' leads with neoprene covered
wire as it is nice and flexible.

The DC line is actually a shielded cable, but it would be nice to get some
extra flexible cable for that, too.

The original Triax is very stiff which makes that molded square strain
relief pretty much a requirement.  I was thinking you could replace that
cable and make your own square piece out of Lexan or phenolic.  You have to
get the dimensions just right so that when the thing is bolted back together
it (that square piece) is held not too hard, but just right.  So measure it
carefully before you destroy it or throw it out!

Also, you may have to add some heat shrink (or layers) to the new Triax
(just say 1 inch in length) if its diameter is less the original.  This
would be to ensure that it is pinched tightly enough by the partially open
hole in the metal bottom piece it exits through.  Without that 'hold' the
cable could move in and out (even without any rotational torque).  After a
while, this would cause the soldered portions of that cable within that
bottom enclosure to probably fatigue and break.

Cheers,
--- Rob

-----Original Message-----
From: Test-Equipment [mailto:test-equipment-bounces at mailman.qth.net] On
Behalf Of Barry
Sent: September-29-14 9:51 AM
To: Discussion of Electronic Test Equipment
Subject: Re: [Test-Equipment] Repair HP410B (triax cable request)

Hi Rob,

Yes, the molded plastic strain relief is nice to have as long as the triax
is good.  When it fails, though, you have to do the best you can with what
you've got.

In the case of this meter, the triax is is in pretty good shape so am
considering leaving it alone.  It could use new wire on the Common and Ohms
leads but those are pretty easy.  Not sure about the DC lead.  It may also
be good as well.

Thanks for the reply!
Barry - N4BUQ

----- Original Message -----
> From: "Robert Myers" <rsmyers at rogers.com>
> To: "Discussion of Electronic Test Equipment" 
> <test-equipment at mailman.qth.net>
> Sent: Friday, September 26, 2014 9:53:06 PM
> Subject: Re: [Test-Equipment] Repair HP410B (triax cable request)
> 
> You say you 'may' need to refurbish the cable.  But you might want to 
> see if you can salvage the original cable.
> 
> It has a rectangular molded polystyrene piece -- molded right on to it 
> at the end that is housed within that bottom metal plate -- that gray 
> bottom plate that covers the place where all the cables are soldered 
> to the female receptacles that are mounted on, and go through to the 
> top
of the upper
> phenolic piece.   It is to provide a countering torque that will be
required
> during (the necessary) external portion of the cable's manoeuvring.  
> It is to ensure no rotation beyond the entry point plug-in/out module.
> 
> Now, that same metal cover plate has sort of semi-circular holes in it 
> that 'grip' the various exiting cables good and tight at that exit 
> point -- tighter as the metal plate is tightened down against the 
> phenolic top portion of the small cable junction enclosure (the cable 
> 'plug-in/out module,' of the main HP-410B unit).  This also, is to 
> prevent the user's manoeuvring of the cables (during measurements) 
> from causing a turning of the cables within the plate/ phenolic 
> enclosure that makes up that removable 'plug in unit' at the bottom of 
> the HP-410B.  Turning inside would quickly break the solder 
> connections - as you can imagine).  But it alone, is not enough to 
> prevent turning of the triaxial AC/RF probe's cable - it needs more.
> 
> The already mentioned rectangular molded piece is the additional 
> measure used to stop the triaxial cable from rotating (under the metal 
> cover, that
> is) and thus loosening, and eventually breaking the solder connection.  
> That is the only cable with that molded piece.  It is required on that 
> cable in particular (and not the others) because that cable is 
> stiff-'ish' and turning it to measure something can easily translate 
> into a high torque at the solder point.  I the case of the cable, the 
> tight exiting hole on the metal cover are not sufficient.
> 
> If you open it up you will see what I mean.
> 
> Regards,
> --- Rob
> VE3JQL
> 
> 
> -----Original Message-----
> From: Test-Equipment [mailto:test-equipment-bounces at mailman.qth.net]
> On Behalf Of David DiGiacomo
> Sent: September-25-14 1:02 PM
> Cc: Test Equipment
> Subject: Re: [Test-Equipment] Repair HP410B (triax cable request)
> 
> On Thu, Sep 25, 2014 at 9:39 AM, Barry <n4buq at knology.net> wrote:
> > I have an HP410B I'm going to refurbish.  As part of that process, I 
> > may
> need to replace the triax cable that feeds the AC probe.
> >
> > I think Belden 9222 is a possibility; however, I don't find that 
> > online in
> anything less than 100 ft. spools and at more than $1 per foot, that 
> ends up a bit cost-prohibitive.  Anyone happen to have any of that for 
> sale (by the foot)?  I think the original cable is about 4 feet long.
> 
> 
> Would this work?
> 
> http://www.ebay.com/itm/36-Trompeter-P1A3T10PDB-36-Cable-Assembly-Tria
> x-TRC-
> 50-1-BNC-M-TRC-M-NOS-/311087878350
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