Topics

P6042 Repairing the Probe Cable (WAS: P6042 -- bad line cord)

 

Hi Dwayne,

Your solution to use an HDMI cable as a substitute for the P6042 cable
sounds like a great idea. Before I do any more damage to my P6042s
(explanation follows) I would like to hear from anyone else that
successfully fixed the cable from the head first.

A year ago I mentioned to a friend, who has P6042s, that my P6042s were
becoming intermittent where the cable from the probe entered the P6042. He
said it was very easy to fix this by cutting off the cable at the chassis,
removing the piece inside the chassis, and soldering the remaining cable in
its place. That sounded really simple. What could possibly go wrong?

After trying this myself on the two P6042s I am absolutely certain he never
tried this himself. From personal experience I would advise anyone to avoid
doing this until you have no choice because your cable is so broken that the
P6042 will not work no matter how much you wiggle or push on the cable.

The cable has many conductors in it. To be flexible Tek chose to make six of
the conductors extremely fine. They are the critical AC and DC signal
carrying wires from the head. These wires are by far the finest wire I have
ever seen. Until now I have never found a wire that is impossible to work
on. I have many insulation stripping tools including wire wrap wire
strippers for #28 and #30 gauge wire, Thermal Strippers (required by manned
space missions I once worked on), Telephone linesman strippers, etc. The
insulation on these wires was so delicate that any heat from a thermal wire
stripper or tugging on the insulation with a mechanical wire stripper broke
the entire wire right off.

After a few hours of experimenting I discovered that the heat from a
soldering iron a few inches away from the wires would soften the insulation.
At last I thought I could proceed to tin these wires. The lowest heat that
melted the solder (eutectic 63/37) I use DISSOLVED the copper wire because
it was so thin. Another hour of failed experiments passed before I gave up
trying to tin the wires.

The last thing I could think of that might work was to apply a little solder
in the hole the old wire was soldered to. To do this I used the absolute
minimum temperature necessary to melt the eutectic solder I use. Once the
solder in the hole was melted I pushed an unstripped wire into it. The
insulation puddled on top of the solder so that automatically stripped the
insulation from the wire. After a few attempts I managed to get the copper
wire imbedded in the molten solder. Whether it was in good electrical
contact or just trapped in a blob of cold solder was unknown. This is not my
idea of how to connect a wire to a PC board but it was the best I could do.

After I finished replacing all of the cable wires I confirmed there was
continuity on each wire from inside the chassis to the probe head. My two
P6042s are now sitting under my desk. They never worked after I replaced the
cable. I despair every time I look at them that I ruined an incredibly
valuable instrument.

Dennis Tillman W7PF

-----Original Message-----
From: Dwayne Reid
Sent: Sunday, September 22, 2019 12:39 PM
Subject: Re: [TekScopes] P6042 -- bad line cord

Hi there, Sean.
When you said "bad line cord", I assumed that you meant the AC power cord.
However, upon reading subsequent messages, I'm now guessing that you are
talking about the cord between the current probe and the chassis.

I have a P6042 where the probe cable has died many times. I just kept
cutting it shorter and shorter. However, it finally got to the point where
I had to replace the cable.

I used a HDMI cable and cut the HDMI plugs off. Lots of
individually-shielded pairs.

Working fine so far but I suspect that the particular HDMI cable that I
chose is also not suited for continuous flexing.

Just a suggestion.

dwayne




--
Dennis Tillman W7PF
TekScopes Moderator

johncharlesgord
 

Dennis,

Soldering very fine copper wires can be easier with something like Savbit solder. It is pre-loaded with copper so it won't dissolve (much?) more copper from the wires. It was originally made to prolong the life of copper soldering bits.

--John Gord

On Sun, Sep 22, 2019 at 06:59 PM, Dennis Tillman W7PF wrote:


Hi Dwayne,

Your solution to use an HDMI cable as a substitute for the P6042 cable
sounds like a great idea. Before I do any more damage to my P6042s
(explanation follows) I would like to hear from anyone else that
successfully fixed the cable from the head first.

A year ago I mentioned to a friend, who has P6042s, that my P6042s were
becoming intermittent where the cable from the probe entered the P6042. He
said it was very easy to fix this by cutting off the cable at the chassis,
removing the piece inside the chassis, and soldering the remaining cable in
its place. That sounded really simple. What could possibly go wrong?

After trying this myself on the two P6042s I am absolutely certain he never
tried this himself. From personal experience I would advise anyone to avoid
doing this until you have no choice because your cable is so broken that the
P6042 will not work no matter how much you wiggle or push on the cable.

The cable has many conductors in it. To be flexible Tek chose to make six of
the conductors extremely fine. They are the critical AC and DC signal
carrying wires from the head. These wires are by far the finest wire I have
ever seen. Until now I have never found a wire that is impossible to work
on. I have many insulation stripping tools including wire wrap wire
strippers for #28 and #30 gauge wire, Thermal Strippers (required by manned
space missions I once worked on), Telephone linesman strippers, etc. The
insulation on these wires was so delicate that any heat from a thermal wire
stripper or tugging on the insulation with a mechanical wire stripper broke
the entire wire right off.

After a few hours of experimenting I discovered that the heat from a
soldering iron a few inches away from the wires would soften the insulation.
At last I thought I could proceed to tin these wires. The lowest heat that
melted the solder (eutectic 63/37) I use DISSOLVED the copper wire because
it was so thin. Another hour of failed experiments passed before I gave up
trying to tin the wires.

The last thing I could think of that might work was to apply a little solder
in the hole the old wire was soldered to. To do this I used the absolute
minimum temperature necessary to melt the eutectic solder I use. Once the
solder in the hole was melted I pushed an unstripped wire into it. The
insulation puddled on top of the solder so that automatically stripped the
insulation from the wire. After a few attempts I managed to get the copper
wire imbedded in the molten solder. Whether it was in good electrical
contact or just trapped in a blob of cold solder was unknown. This is not my
idea of how to connect a wire to a PC board but it was the best I could do.

After I finished replacing all of the cable wires I confirmed there was
continuity on each wire from inside the chassis to the probe head. My two
P6042s are now sitting under my desk. They never worked after I replaced the
cable. I despair every time I look at them that I ruined an incredibly
valuable instrument.

Dennis Tillman W7PF

-----Original Message-----
From: Dwayne Reid
Sent: Sunday, September 22, 2019 12:39 PM
Subject: Re: [TekScopes] P6042 -- bad line cord

Hi there, Sean.
When you said "bad line cord", I assumed that you meant the AC power cord.
However, upon reading subsequent messages, I'm now guessing that you are
talking about the cord between the current probe and the chassis.

I have a P6042 where the probe cable has died many times. I just kept
cutting it shorter and shorter. However, it finally got to the point where
I had to replace the cable.

I used a HDMI cable and cut the HDMI plugs off. Lots of
individually-shielded pairs.

Working fine so far but I suspect that the particular HDMI cable that I
chose is also not suited for continuous flexing.

Just a suggestion.

dwayne




--
Dennis Tillman W7PF
TekScopes Moderator

Dwayne Reid
 

Hi there, Dennis.

I have indeed successfully repaired my P6042 by cutting the original cable shorter. No question: this is a painful process but I **WAS** successful. I've actually had to do both ends of the cable (separate occasions) at both the probe as well as the chassis.

The sucky thing about re-terminating the original cable in the chassis is that you lose about eight inches from the cable. Doing the probe end costs about four inches or so.

I've had to do this either three or four times. It finally got to the point where the probe cable was simply too short to be useful.

I use Metcal soldering equipment with 700F tips (sttc-126) - this may be the reason that I didn't have any problems with the conductors dissolving like you mentioned. Although I also have thermal strippers here (Teledyne Strip-All), I don't recall that I needed to use them for the repairs. My recollection is that I used Miller 101S mechanical strippers - I replace these often when the stripping notches get dull.

If you do want to try using the thermal strippers, use it to just melt the insulation. Then use something like the Miller 101 strippers to actually remove the insulation.

The most painful part of the process is dealing with the tight spaces inside the main unit. Repairing the probe was easy - just be careful not to lose the tiny ball-bearing that wants to go wandering off when you disassemble the probe.

Do give it a try again. Make sure that you actually have a couple of hours where you won't be interrupted and when you aren't tired.

dwayne

At 07:59 PM 9/22/2019, Dennis Tillman W7PF wrote:
Hi Dwayne,

Your solution to use an HDMI cable as a substitute for the P6042 cable
sounds like a great idea. Before I do any more damage to my P6042s
(explanation follows) I would like to hear from anyone else that
successfully fixed the cable from the head first.

A year ago I mentioned to a friend, who has P6042s, that my P6042s were
becoming intermittent where the cable from the probe entered the P6042. He
said it was very easy to fix this by cutting off the cable at the chassis,
removing the piece inside the chassis, and soldering the remaining cable in
its place. That sounded really simple. What could possibly go wrong?

After trying this myself on the two P6042s I am absolutely certain he never
tried this himself. From personal experience I would advise anyone to avoid
doing this until you have no choice because your cable is so broken that the
P6042 will not work no matter how much you wiggle or push on the cable.

The cable has many conductors in it. To be flexible Tek chose to make six of
the conductors extremely fine. They are the critical AC and DC signal
carrying wires from the head. These wires are by far the finest wire I have
ever seen. Until now I have never found a wire that is impossible to work
on. I have many insulation stripping tools including wire wrap wire
strippers for #28 and #30 gauge wire, Thermal Strippers (required by manned
space missions I once worked on), Telephone linesman strippers, etc. The
insulation on these wires was so delicate that any heat from a thermal wire
stripper or tugging on the insulation with a mechanical wire stripper broke
the entire wire right off.

After a few hours of experimenting I discovered that the heat from a
soldering iron a few inches away from the wires would soften the insulation.
At last I thought I could proceed to tin these wires. The lowest heat that
melted the solder (eutectic 63/37) I use DISSOLVED the copper wire because
it was so thin. Another hour of failed experiments passed before I gave up
trying to tin the wires.

The last thing I could think of that might work was to apply a little solder
in the hole the old wire was soldered to. To do this I used the absolute
minimum temperature necessary to melt the eutectic solder I use. Once the
solder in the hole was melted I pushed an unstripped wire into it. The
insulation puddled on top of the solder so that automatically stripped the
insulation from the wire. After a few attempts I managed to get the copper
wire imbedded in the molten solder. Whether it was in good electrical
contact or just trapped in a blob of cold solder was unknown. This is not my
idea of how to connect a wire to a PC board but it was the best I could do.

After I finished replacing all of the cable wires I confirmed there was
continuity on each wire from inside the chassis to the probe head. My two
P6042s are now sitting under my desk. They never worked after I replaced the
cable. I despair every time I look at them that I ruined an incredibly
valuable instrument.

Dennis Tillman W7PF

-----Original Message-----
From: Dwayne Reid
Sent: Sunday, September 22, 2019 12:39 PM
Subject: Re: [TekScopes] P6042 -- bad line cord

Hi there, Sean.
When you said "bad line cord", I assumed that you meant the AC power cord.
However, upon reading subsequent messages, I'm now guessing that you are
talking about the cord between the current probe and the chassis.

I have a P6042 where the probe cable has died many times. I just kept
cutting it shorter and shorter. However, it finally got to the point where
I had to replace the cable.

I used a HDMI cable and cut the HDMI plugs off. Lots of
individually-shielded pairs.

Working fine so far but I suspect that the particular HDMI cable that I
chose is also not suited for continuous flexing.

Just a suggestion.

dwayne




--
Dennis Tillman W7PF
TekScopes Moderator

--
Dwayne Reid <dwayner@...>
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
780-489-3199 voice 780-487-6397 fax 888-489-3199 Toll Free
www.trinity-electronics.com
Custom Electronics Design and Manufacturing

fiftythreebuick
 

Hi Dennis-

I've done the "cut off the bad part and reconnect" repair and it worked fine. You're right, there is some touchy stuff there but it did work for me. I don't remember having those problems with melting/disintegrating wire.... Must have been lucky! As I recall, I was using very small diameter Low Melting Point solder by Edsyn and a Metcal fine point regulated iron.

Sorry it's giving you so much trouble. Hope you can find a solution!

Tom AE5I

On Sun, Sep 22, 2019 at 06:59 PM, Dennis Tillman W7PF wrote:


Hi Dwayne,

Your solution to use an HDMI cable as a substitute for the P6042 cable
sounds like a great idea. Before I do any more damage to my P6042s
(explanation follows) I would like to hear from anyone else that
successfully fixed the cable from the head first.

A year ago I mentioned to a friend, who has P6042s, that my P6042s were
becoming intermittent where the cable from the probe entered the P6042. He
said it was very easy to fix this by cutting off the cable at the chassis,
removing the piece inside the chassis, and soldering the remaining cable in
its place. That sounded really simple. What could possibly go wrong?

After trying this myself on the two P6042s I am absolutely certain he never
tried this himself. From personal experience I would advise anyone to avoid
doing this until you have no choice because your cable is so broken that the
P6042 will not work no matter how much you wiggle or push on the cable.

The cable has many conductors in it. To be flexible Tek chose to make six of
the conductors extremely fine. They are the critical AC and DC signal
carrying wires from the head. These wires are by far the finest wire I have
ever seen. Until now I have never found a wire that is impossible to work
on. I have many insulation stripping tools including wire wrap wire
strippers for #28 and #30 gauge wire, Thermal Strippers (required by manned
space missions I once worked on), Telephone linesman strippers, etc. The
insulation on these wires was so delicate that any heat from a thermal wire
stripper or tugging on the insulation with a mechanical wire stripper broke
the entire wire right off.

After a few hours of experimenting I discovered that the heat from a
soldering iron a few inches away from the wires would soften the insulation.
At last I thought I could proceed to tin these wires. The lowest heat that
melted the solder (eutectic 63/37) I use DISSOLVED the copper wire because
it was so thin. Another hour of failed experiments passed before I gave up
trying to tin the wires.

The last thing I could think of that might work was to apply a little solder
in the hole the old wire was soldered to. To do this I used the absolute
minimum temperature necessary to melt the eutectic solder I use. Once the
solder in the hole was melted I pushed an unstripped wire into it. The
insulation puddled on top of the solder so that automatically stripped the
insulation from the wire. After a few attempts I managed to get the copper
wire imbedded in the molten solder. Whether it was in good electrical
contact or just trapped in a blob of cold solder was unknown. This is not my
idea of how to connect a wire to a PC board but it was the best I could do.

After I finished replacing all of the cable wires I confirmed there was
continuity on each wire from inside the chassis to the probe head. My two
P6042s are now sitting under my desk. They never worked after I replaced the
cable. I despair every time I look at them that I ruined an incredibly
valuable instrument.

Dennis Tillman W7PF

-----Original Message-----
From: Dwayne Reid
Sent: Sunday, September 22, 2019 12:39 PM
Subject: Re: [TekScopes] P6042 -- bad line cord

Hi there, Sean.
When you said "bad line cord", I assumed that you meant the AC power cord.
However, upon reading subsequent messages, I'm now guessing that you are
talking about the cord between the current probe and the chassis.

I have a P6042 where the probe cable has died many times. I just kept
cutting it shorter and shorter. However, it finally got to the point where
I had to replace the cable.

I used a HDMI cable and cut the HDMI plugs off. Lots of
individually-shielded pairs.

Working fine so far but I suspect that the particular HDMI cable that I
chose is also not suited for continuous flexing.

Just a suggestion.

dwayne




--
Dennis Tillman W7PF
TekScopes Moderator