Topics

P6137 scope probe repair


Tom Lee
 

Hi Jared,

It's great that you confirmed the diagnosis given by the capacitance measurements. It's also great that you have the option of returning it (I missed that part; I would've advised doing just that -- oh well!). If you didn't have that option, I'd have proceeded to torture you with more suggestions to fix it, but that's not necessary now.

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 1/17/2021 15:41, Jared Cabot via groups.io wrote:
Well inamongst all the shouting, I found the problem.
It seems the cable was pulled and the center conductor has retracted into the inner insulation, pulling away from the end-cap at the scope end.

Unfortunately I have no way to satisfactorily uncrimp and them recrimp the end connector to enable me to cut half an inch off the end of the cable to reterminate it, so I'll be returning it to the seller as faulty for a refund.

Thanks all for the info and help! :)




John Gord
 

Tom,
Few of the probe instruction manuals I can still find have schematics. I opened up an early P6106 compensation box, and it has two unshielded inductors (ferrite rod cores?) placed close enough together that they might couple a little. Intentional?
--John Gord

On Sun, Jan 17, 2021 at 03:08 PM, Tom Lee wrote:


Thank you for that information, John! I deeply appreciate it. Are you aware of
any other examples?

—Cheers,
Tom

Sent from my iThing, so please forgive typos and brevity.

On Jan 17, 2021, at 3:03 PM, John Gord via groups.io
<johngord=verizon.net@groups.io> wrote:

Tom,
The p6131 2m and 1.3m probes used a T-coil in the compensation box.
(Schematic in manual 070-4210-01)
--John Gord

On Sun, Jan 17, 2021 at 01:11 PM, Tom Lee wrote:
Next, your trivia about T-coils makes it sound like many probes use
them. As far as I am aware, the total number is two: P6047 and the
oddball 1kilohm P6048. If you are aware of any others, I would very much
like to know their model numbers so that I can update my spreadsheet.
T-coils are very much the /exception/, rather than the rule, in probes.




John Gord
 

Tom,
How about I mail it to you? I assume the address after your signature will work.
--John

On Sun, Jan 17, 2021 at 03:19 PM, Tom Lee wrote:


Hi John,

I see that the 070-4210-01 manual isn't on tekwiki, and after an
exhaustive 5 second google search, I can't seem to find one on the web.
Do you know of an online source for it? (I'll keep googling, but being
the lazy SOB that I am, I thought I'd ask you first.)

And if it isn't online, could I perhaps prevail upon you to scan it
(even crudely) and upload it to tekwiki? My database is limited largely
to what I've been able to get from online sources, plus whatever reverse
engineering I've done, which means that my database is pretty complete
until I get to the era when Tek began to reconsider their documentation
philosophy. The P6131 is right at the 3dB corner...

Thanks again!

--Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 1/17/2021 15:08, Tom Lee wrote:
Thank you for that information, John! I deeply appreciate it. Are you aware
of any other examples?

—Cheers,
Tom

Sent from my iThing, so please forgive typos and brevity.

On Jan 17, 2021, at 3:03 PM, John Gord via groups.io
<johngord=verizon.net@groups.io> wrote:

Tom,
The p6131 2m and 1.3m probes used a T-coil in the compensation box.
(Schematic in manual 070-4210-01)
--John Gord

On Sun, Jan 17, 2021 at 01:11 PM, Tom Lee wrote:
Next, your trivia about T-coils makes it sound like many probes use
them. As far as I am aware, the total number is two: P6047 and the
oddball 1kilohm P6048. If you are aware of any others, I would very much
like to know their model numbers so that I can update my spreadsheet.
T-coils are very much the /exception/, rather than the rule, in probes.





Jared Cabot
 

Yeah, I could have a go at somehow uncrimping it (I have many crimpers, I'm sure one would fit well enough to crimp it back down again), but weighing up between potentially butchering it and just returning it to have another go at a cheap probe in the future, the decision fell in favour of living to see another day and another probe. :D

Well, unless there is some surefire way to uncrimp the connection? The actual termination of the cable looks very straightforward.

Jared.

On Mon, Jan 18, 2021 at 08:56 AM, Tom Lee wrote:


Hi Jared,

It's great that you confirmed the diagnosis given by the capacitance
measurements. It's also great that you have the option of returning it
(I missed that part; I would've advised doing just that -- oh well!). If
you didn't have that option, I'd have proceeded to torture you with more
suggestions to fix it, but that's not necessary now.

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu


Roy Thistle
 

On Sun, Jan 17, 2021 at 03:41 PM, Jared Cabot wrote:


It seems the cable was pulled and the center conductor has retracted into the
inner insulation, pulling away from the end-cap at the scope end.
Others reading this might be interested. I have, and have had HF probes... and many times the trouble is with the cable. HF probes are in my experience... somewhat delicate... and don't like to be rough handled... relative to the some of older, and lower frequency probes that came with some of the 400, and 7000 series scopes. Those probes seem to be able to take reasonable abuse.
If you don't need the bandwidth... or are buying one just as a hedge... I opine it is better, and usually a lot cheaper, to get the older ones, as above. They seem to last a lot better.
I reckon that problems with HF probes are both because of necessity of the way the cable is constructed, and the reduction in quality that has occurred.


Tom Lee
 

Hi Jared,

Given a choice between trying to fix it, and returning it to the seller, I'd vote "return to seller" overwhelmingly. If the choice were between trying to fix it and junking it, I'd try to fix it. Here, get your money back.

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 1/17/2021 16:47, Jared Cabot via groups.io wrote:
Yeah, I could have a go at somehow uncrimping it (I have many crimpers, I'm sure one would fit well enough to crimp it back down again), but weighing up between potentially butchering it and just returning it to have another go at a cheap probe in the future, the decision fell in favour of living to see another day and another probe. :D

Well, unless there is some surefire way to uncrimp the connection? The actual termination of the cable looks very straightforward.

Jared.


Jared Cabot
 

Yeah, it pains me to see how these probes are so tightly coiled in the photos on various auction websites... I wonder how many have been inadvertently damaged just by the sellers ignorance as to proper handling of these things..
I'm slowly searching for good deals on these probes for my 2467B, it's a 4 channel but I only really need two probes, and I can wait for a good deal to pop up. My trusty TDS210 gets me by with most stuff for now. :D

Jared

On Mon, Jan 18, 2021 at 10:10 AM, Roy Thistle wrote:


Others reading this might be interested. I have, and have had HF probes... and
many times the trouble is with the cable. HF probes are in my experience...
somewhat delicate... and don't like to be rough handled... relative to the
some of older, and lower frequency probes that came with some of the 400, and
7000 series scopes. Those probes seem to be able to take reasonable abuse.
If you don't need the bandwidth... or are buying one just as a hedge... I
opine it is better, and usually a lot cheaper, to get the older ones, as
above. They seem to last a lot better.
I reckon that problems with HF probes are both because of necessity of the way
the cable is constructed, and the reduction in quality that has occurred.


I think I'll do exactly this. I'm not so desperate to get this probe fixed that I can't wait for another one to come along. :)

On Mon, Jan 18, 2021 at 10:15 AM, Tom Lee wrote:


Hi Jared,

Given a choice between trying to fix it, and returning it to the seller,
I'd vote "return to seller" overwhelmingly. If the choice were between
trying to fix it and junking it, I'd try to fix it. Here, get your money
back.

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu


Leon Robinson
 

Jared
What about a short piece of brass tubing slipped over the crimp
area and crimp the center conductor in it.

Leon Robinson    K5JLR

Political Correctness is a Political Disease.

Politicians and Diapers should be changed
often and for the same reasons.

On Sunday, January 17, 2021, 5:41:55 PM CST, Jared Cabot via groups.io <jaredcabot=protonmail.com@groups.io> wrote:

Well inamongst all the shouting, I found the problem.
It seems the cable was pulled and the center conductor has retracted into the inner insulation, pulling away from the end-cap at the scope end.

Unfortunately I have no way to satisfactorily uncrimp and them recrimp the end connector to enable me to cut half an inch off the end of the cable to reterminate it, so I'll be returning it to the seller as faulty for a refund.

Thanks all for the info and help! :)


Jared Cabot
 

Ok, so repair is back on the table.

The seller gave me a full refund and told me to keep the probe. :)

I was thinking about how to uncrimp the connection, I think if I cut the cable flush, then dig out the remaining cable inside the crimp, I might be able to carefully form the crimped portion back to enough of a round shape to re-use.
Then I can reinsert the cable and recrimp.
I think I should only lose half an inch to an inch of cable so performance should remain in the 'good enough' region.

Now I have the probe for free, I have nothing to lose so lets see how badly I mess it up.
At least I'll have the spare parts from each end of the probe if the cable proves to be unrepairable....


Tom Lee
 

Cool, Jared! Document with pics as you go. I'm sure that you'll learn a great deal and will have good advice for the next person to attempt a probe repair.

And if you ever get a chance, I personally would like to see what the internals of the compensation box looks like, to compare with the innards of the 6131. I'm guessing that they would be quite similar, but it would be nice to know the real answer.

--Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 1/18/2021 00:45, Jared Cabot via groups.io wrote:
Ok, so repair is back on the table.

The seller gave me a full refund and told me to keep the probe. :)

I was thinking about how to uncrimp the connection, I think if I cut the cable flush, then dig out the remaining cable inside the crimp, I might be able to carefully form the crimped portion back to enough of a round shape to re-use.
Then I can reinsert the cable and recrimp.
I think I should only lose half an inch to an inch of cable so performance should remain in the 'good enough' region.

Now I have the probe for free, I have nothing to lose so lets see how badly I mess it up.
At least I'll have the spare parts from each end of the probe if the cable proves to be unrepairable....




Jared Cabot
 

WINNER, WINNER, CHICKEN DINNER!
It's ALIVE! :D

So I managed to dig out the cable from the connector after I cut it off the cable flush with the connector.
The end cap and second ring (and insulator) just gently pull away with the careful use of some sharp side cutters to act as if you were pulling them off with your fingernails.
Then I used a 2mm drill bit to drill the core out and then pulled the outer insulation out too.
After that, some small pointy pliers were used to round out the crimped portion and gently knocked in a 4mm drill bit backwards to act as a drift to round it out to as much as possible.
Using the piece of outer insulation pulled out from the connector, you can estimate how much to push back in, it's about 17mm or so.
Then it was pretty much just a matter of cutting back the cable by about an inch and then terminating the cable in a similar manner to any other coax. (I trimmed some of the shield braid off to make insertion easier).

Now, I got me a working scope probe! All I need to do now is find a crimper that will crimp a hex shape about 4.2 - 4.4mm across flats and it's pretty much finished. I am one happy boy. :D
So, now I'm off to ebay to try my luck with some other cheap probes I think. D

Here are some photos I took, a video will be up on Youtube soon too so I'll link it here when it's online, or you can keep an eye on my channel, NearFarMedia.


Innards of the Circuit Board Assembly:
https://i.imgur.com/wxCDifj.jpg

The cable connector disassembled:
https://i.imgur.com/xeiT8e0.jpg

The working probe!:
https://i.imgur.com/kROO6jp.jpg


Milan Trcka
 

Jared,
I share your pain. I had an almost the same problem with a similar (if not identical) probe. Went through a fair amount of discovery. The center conductor appears to be non-solderable using standard fluxes (rosin and acid). I suspect it may be inconel or similar alloy.

To uncrimp: Dremel tool and fine abrasive wheel and very careful cutting will liberate the cable and the center conductor. Alternately just chop off the cable end past the break, usually within a couple of inches of the exit from the strain relief on either end (as proven).

To crimp (much more difficult): Thin-wall brass tubing for the outer jacket (alternately it appears that an insert for 1/4" plastic tubing used for compression fitting might work); crimp with a hex die in a coax cable crimper - some tools have up to three different diameters. For the inner conductor I used a stainless steel tube from a hypodermic needle (brass tubing would be better - did not find any). Crimp on the wire and solder to the SS tube (needs special flux). Crimp can be made with an adjustable 4-jaw pin crimper such as Cannon or Bendix - type.

In any case this is a laborious process needing not-quite-common materials and special tools. If available, great. If not, it may not be worth the effort to locate/obtain them.

Sincerely hope this may provoke a more constructive discussion.

Milan


Tom Lee
 

Fantastic, Jared -- well done! I'm happy that the capacitance method pinpointed the location of the break to that level of precision, and that you devised a repair method that doesn't totally maul the cable.

A virtual merit badge inducting you into the /Order of the Witches' Hat/ to you!

-- Cheers
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 1/18/2021 07:12, Jared Cabot via groups.io wrote:
WINNER, WINNER, CHICKEN DINNER!
It's ALIVE! :D

So I managed to dig out the cable from the connector after I cut it off the cable flush with the connector.
The end cap and second ring (and insulator) just gently pull away with the careful use of some sharp side cutters to act as if you were pulling them off with your fingernails.
Then I used a 2mm drill bit to drill the core out and then pulled the outer insulation out too.
After that, some small pointy pliers were used to round out the crimped portion and gently knocked in a 4mm drill bit backwards to act as a drift to round it out to as much as possible.
Using the piece of outer insulation pulled out from the connector, you can estimate how much to push back in, it's about 17mm or so.
Then it was pretty much just a matter of cutting back the cable by about an inch and then terminating the cable in a similar manner to any other coax. (I trimmed some of the shield braid off to make insertion easier).

Now, I got me a working scope probe! All I need to do now is find a crimper that will crimp a hex shape about 4.2 - 4.4mm across flats and it's pretty much finished. I am one happy boy. :D
So, now I'm off to ebay to try my luck with some other cheap probes I think. D

Here are some photos I took, a video will be up on Youtube soon too so I'll link it here when it's online, or you can keep an eye on my channel, NearFarMedia.


Innards of the Circuit Board Assembly:
https://i.imgur.com/wxCDifj.jpg

The cable connector disassembled:
https://i.imgur.com/xeiT8e0.jpg

The working probe!:
https://i.imgur.com/kROO6jp.jpg




Lawrance A. Schneider
 

On Sun, Jan 17, 2021 at 08:33 PM, Jared Cabot wrote:


I wonder how many have been inadvertently damaged just by the sellers
ignorance as to proper handling of these things..
Hello Mr. Cabot,

I left teaching to work in the Postal Service; reason being I took a huge pay raise by doing so. I made more than the Chairmen of the Mathematics Dept. . Go figure!

In any event, the Postal service has their own school in Norman OK. I hated it there; every time they sent me there, I would great people with "Home, ET go home." and point towards the north-east sky. The instructors there had a huge problem with ET's wrapping the test leads around the meters we use there and - well you outlined 'what' in your missive; it "pains" me too. I never 'wrapped' my leads preferring to let them 'dangle' whenever I needed to do some trouble shooting on a faulty machine. Were I to have a bad test lead, I would naturally just fix it. However, many 'bosses' of the maintenance department knew nothing about how we worked. So, my fellow ETs form other areas would request a new set of leads rather than fix what they broke by tightly wrapping. The instructors there got tired of fixing broken meter cables.

If you can indeed send it back, do so. Otherwise, it might be a fun project to 'try' to do the repairs.

Thanks, larry


Lawrance A. Schneider
 

Great fix. I hope you put your pictures in the group photo area.

larry


Jeff Woolsey
 

On 1/18/21 10:20 AM, Milan Trcka wrote:
Jared,
I share your pain. I had an almost the same problem with a similar (if not identical) probe. Went through a fair amount of discovery. The center conductor appears to be non-solderable using standard fluxes (rosin and acid). I suspect it may be inconel or similar alloy.

I, too, have a problem with P6137 probes.   I have three of them: one is
fine, one has a broken/lost probe tip, and the third also has a broken
tip but it's stuck in the witches' hat.  This means that the probe works
fine with the hat, but is unusable without it...   Someday when I've
saved up enough pennies, two new probe tips for me.

--
Jeff Woolsey {{woolsey,jlw}@jlw,first.last@{gmail,jlw}}.com
Nature abhors straight antennas, clean lenses, and empty storage.
"Delete! Delete! OK!" -Dr. Bronner on disk space management
Card-sorting, Joel. -Crow on solitaire


Jared Cabot
 

I just uploaded a video showing the repair process, link below:
https://youtu.be/xSJzuXy4pgA

I've also put the images from my previous post into the photos section here too:
https://groups.io/g/TekScopes/album?id=259576


Jacques DULONGPONT
 

Very intersting video. Most probably the solution for one of my defective
probe.

Thanks

Jacques

Le mar. 19 janv. 2021 à 16:05, Jared Cabot via groups.io <jaredcabot=
protonmail.com@groups.io> a écrit :

I just uploaded a video showing the repair process, link below:
https://youtu.be/xSJzuXy4pgA

I've also put the images from my previous post into the photos section
here too:
https://groups.io/g/TekScopes/album?id=259576






 

On Tue, Jan 19, 2021 at 04:04 PM, Jared Cabot wrote:


I just uploaded a video showing the repair process, link below:
https://youtu.be/xSJzuXy4pgA

I've also put the images from my previous post into the photos section here
too:
https://groups.io/g/TekScopes/album?id=259576
Nice Job, Jared!

Raymond


Dave Daniel
 

BTW, that spring-loaded pin on the BNC connector end is not a ground pin. It indicates to the scope that the probe is a 10x probe so that the scope can display the proper voltage values. Remove the pin and the scope will treat the input as a 1x probe, even though the displayed waveform will be correct for a 10x probe.

DaveD

On Jan 19, 2021, at 10:39, Jacques DULONGPONT <ankorjd@gmail.com> wrote:

Very intersting video. Most probably the solution for one of my defective
probe.

Thanks

Jacques

Le mar. 19 janv. 2021 à 16:05, Jared Cabot via groups.io <jaredcabot=
protonmail.com@groups.io> a écrit :

I just uploaded a video showing the repair process, link below:
https://youtu.be/xSJzuXy4pgA

I've also put the images from my previous post into the photos section
here too:
https://groups.io/g/TekScopes/album?id=259576