1502 TDR RECORD functions


Reginald Beardsley
 

My 1502 arrived today.

Unfortunately, I either have a fault in the RECORD function or completely misunderstand the manual.

The paper feeds if I push the switch up. However, I do not get an accurate trace and the CRT sweep stops until I power cycle it. If I push the switch down and hold it for a photo the sweep also stops. When I release the switch the paper feeds.

I did get a couple of sweeps in the form of a vertical line about 1 division high which tracked the shorted BNC connector waveform but nothing I would interpret as a "flood" of the CRT at the end of the sweep to make the graticule visible..

I fed the BNC signal to a 200 MHz DSO which revealed that the 1502 is producing alternating 4.8 and 11.1 microsecond pulses at ~25.5 kHz.

I'd planned to measure the rise time of the 1502 pulse on an 11801 but I can't see how I can do that if the pulse periods alternate.

Happily, it does appear to be able to resolve discontinuities in cable adapters and connectors in a manner comparable to and 11801 &SD-24.

Can anyone explain what is going on? I'm about to start reading the service manual.

Reg


Tom Gardner
 

Do you have a good supply of paper for the chart recorder? If not, whether the chart recorder works is moot! Personally I think the X-Y output module is more useful: at least that can be fed to a digitising scope.

The service manual is worth reading. There are minor differences between the civilian and the military (Patriot battery) manuals, but nothing that I have found significant.

On 29/11/21 22:14, Reginald Beardsley via groups.io wrote:
My 1502 arrived today.

Unfortunately, I either have a fault in the RECORD function or completely misunderstand the manual.

The paper feeds if I push the switch up. However, I do not get an accurate trace and the CRT sweep stops until I power cycle it. If I push the switch down and hold it for a photo the sweep also stops. When I release the switch the paper feeds.

I did get a couple of sweeps in the form of a vertical line about 1 division high which tracked the shorted BNC connector waveform but nothing I would interpret as a "flood" of the CRT at the end of the sweep to make the graticule visible..

I fed the BNC signal to a 200 MHz DSO which revealed that the 1502 is producing alternating 4.8 and 11.1 microsecond pulses at ~25.5 kHz.

I'd planned to measure the rise time of the 1502 pulse on an 11801 but I can't see how I can do that if the pulse periods alternate.

Happily, it does appear to be able to resolve discontinuities in cable adapters and connectors in a manner comparable to and 11801 &SD-24.

Can anyone explain what is going on? I'm about to start reading the service manual.


Reginald Beardsley
 

All I have is the roll of paper that came with it. Since my post I've read the service manual and now understand the BNC output waveform. The narrow pulse is the sampling arm signal.

I just made a test with the chart recorder removed and I get a proper sweep. So it appears that the fault is in the Y-T chart recorder. The X-Y module attached to an Ardinuo/MSP430/STM32 to dump digits to a USB flash drive or SD card should be far more useful. I suspect a bspoke module for that would not be difficult to make.

I'm getting TDR responses with the 1502 from RF adapters and connectors which look to my eye to be quite comparable to the 11801/SD-24.

A working 11801 & SD-24 are difficult to find, 10x+ as much money and have *no* component schematics available.

The 1502 has schematics and appears to be easily hacked to be a very useful RF connector TDR system.

First up is LED graticule illumination.

Have Fun!
Reg


John Parkins G8KVP
 

Hello Reg,

The 1502 is the first time 2 of my hobbies have come together, electronics and woodwork.

I can get rolls of paper that fit our credit card machine and with a fine blade they can be cut down to the right size on the bandsaw. Not that I use a lot of paper.

You mention the the illumination....... Something I've looked at and it all seemed a bit tight, so it never got done. Keep us informed on how you go about it, then I might have a go. I have to say it's the only downside to my machine.

Good luck.


Monday, November 29, 2021, 11:43:40 PM, you wrote:

RBvgi> All I have is the roll of paper that came with it. Since my post I've read the service manual and now understand the BNC output waveform. The narrow pulse is the sampling arm signal.

RBvgi> I just made a test with the chart recorder removed and I get a proper sweep. So it appears that the fault is in the Y-T chart recorder. The X-Y module attached to an Ardinuo/MSP430/STM32 to dump digits to a USB flash drive or SD card should be far more useful. I suspect a bspoke module for that would not be difficult to make.

RBvgi> I'm getting TDR responses with the 1502 from RF adapters and connectors which look to my eye to be quite comparable to the 11801/SD-24.

RBvgi> A working 11801 & SD-24 are difficult to find, 10x+ as much money and have *no* component schematics available.

RBvgi> The 1502 has schematics and appears to be easily hacked to be a very useful RF connector TDR system.

RBvgi> First up is LED graticule illumination.

RBvgi> Have Fun!
RBvgi> Reg


RBvgi>





--
Best regards,
John mailto:john@...


Tom Gardner
 

On 29/11/21 23:43, Reginald Beardsley via groups.io wrote:
All I have is the roll of paper that came with it. Since my post I've read the service manual and now understand the BNC output waveform. The narrow pulse is the sampling arm signal.

I just made a test with the chart recorder removed and I get a proper sweep. So it appears that the fault is in the Y-T chart recorder. The X-Y module attached to an Ardinuo/MSP430/STM32 to dump digits to a USB flash drive or SD card should be far more useful. I suspect a bspoke module for that would not be difficult to make.
The XY module is trivial to make; the mechanics are more difficult than the electrics. The schematics are in the manual.

Do have a look at the PSU caps. On mine C6246 and C6341 had spewed acid across the track. Fortunately the simple PCB was easily repaired.


I'm getting TDR responses with the 1502 from RF adapters and connectors which look to my eye to be quite comparable to the 11801/SD-24.
The 1502 is a fun instrument to use; I've a bit of a fetish for them.

Fortunately mine is calibrated in metres, so I don't have to mentally work out what 0.1ft is :)


A working 11801 & SD-24 are difficult to find, 10x+ as much money and have *no* component schematics available.
I suspect that schematics would have to include a symbol for "black arts employed here". Even the 485 schematics include capacitors that aren't on the board, because they are in the board or are other parasitics :)

The 1502 has schematics and appears to be easily hacked to be a very useful RF connector TDR system.
And take it to hamfests to measure cable impedance and  length :) People like looking at the hypnotic twinkling trace.


Tom Gardner
 

On 30/11/21 07:10, John Parkins G8KVP wrote:
Hello Reg,

The 1502 is the first time 2 of my hobbies have come together, electronics and woodwork.

I can get rolls of paper that fit our credit card machine and with a fine blade they can be cut down to the right size on the bandsaw. Not that I use a lot of paper.

You mention the the illumination....... Something I've looked at and it all seemed a bit tight, so it never got done. Keep us informed on how you go about it, then I might have a go. I have to say it's the only downside to my machine.
ISTR that the paper has holes down one side, and that a photodetector detects the holes.
ISTR that someone has synthesised the signal from the photodetector so that the chart recorder works without the holes.

I don't know since I've never bothered with a recorder; I simply bought a cheap XY output plugin.


fiftythreebuick
 

Tom, the 1502 is one of the most useful instruments around!

I just finished finding the fault in a long string of Christmas lights with mine! :-) Definitely something essential to have around...

Tom


Tom Gardner
 

On 01/12/21 21:51, fiftythreebuick wrote:
Tom, the 1502 is one of the most useful instruments around!

I just finished finding the fault in a long string of Christmas lights with mine! :-) Definitely something essential to have around...
Now that hadn't occurred to me!

That's a really excellent example of using whatever is available to solve the problem at hand :)

Thanks!


Paul Amaranth
 

Was that incandescant or LED lights?

I have an entire bin full of LED strings that are dead and that might
be worth a try.

Paul

On Wed, Dec 01, 2021 at 01:51:54PM -0800, fiftythreebuick wrote:
Tom, the 1502 is one of the most useful instruments around!

I just finished finding the fault in a long string of Christmas lights with mine! :-) Definitely something essential to have around...

Tom
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows


Glydeck
 

Good question. I don’t think it matters. An interruption in the transmission line does not care if it’s a LED or a bulb. I’m so trying this on some recalcitrant light strings.

Glydeck KD6NEW

On Dec 1, 2021, at 6:32 PM, Paul Amaranth <paul@...> wrote:

Was that incandescant or LED lights?

I have an entire bin full of LED strings that are dead and that might
be worth a try.

Paul

On Wed, Dec 01, 2021 at 01:51:54PM -0800, fiftythreebuick wrote:
Tom, the 1502 is one of the most useful instruments around!

I just finished finding the fault in a long string of Christmas lights with mine! :-) Definitely something essential to have around...

Tom
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows





ChrisBeee
 

Tom,
you definitely made my day with this very convincing excuse for having one of those instruments!! =D
Chris

On Wed, Dec 1, 2021 at 10:51 PM, fiftythreebuick wrote:


Tom, the 1502 is one of the most useful instruments around!

I just finished finding the fault in a long string of Christmas lights with
mine! :-) Definitely something essential to have around...

Tom


Jim Ford
 

Hmmmm.... I  wonder if the wife will let me buy an 11800 series scope and an SD-24 for finding bum bulbs?  I suppose it would only work for strings and not net lights.    Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: "ChrisBeee via groups.io" <chrisbeee@...> Date: 12/1/21 9:24 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] 1502 TDR RECORD functions Tom, you definitely made my day with this very convincing excuse for having one of those instruments!! =DChrisOn Wed, Dec  1, 2021 at 10:51 PM, fiftythreebuick wrote:>> Tom, the 1502 is one of the most useful instruments around!> > I just finished finding the fault in a long string of Christmas lights with> mine!  :-)  Definitely something essential to have around...  > > Tom>


 

I have to ask how you handle the transition from coax to the Xmas lights? And how you interpret the results.

A picture of two may be worth a 1000 words.
D.

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Glydeck via groups.io
Sent: 02 December 2021 05:23
To: TekScopes@groups.io
Subject: Re: [TekScopes] 1502 TDR RECORD functions

Good question. I don’t think it matters. An interruption in the transmission line does not care if it’s a LED or a bulb. I’m so trying this on some recalcitrant light strings.

Glydeck KD6NEW
On Dec 1, 2021, at 6:32 PM, Paul Amaranth <paul@...> wrote:

Was that incandescant or LED lights?

I have an entire bin full of LED strings that are dead and that might
be worth a try.

Paul

On Wed, Dec 01, 2021 at 01:51:54PM -0800, fiftythreebuick wrote:
Tom, the 1502 is one of the most useful instruments around!

I just finished finding the fault in a long string of Christmas lights with mine! :-) Definitely something essential to have around...

Tom
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows





fiftythreebuick
 

I've also use a TDR to find where the yard men cut the romex going to our front lamp post as well. Such a useful tool! :-)

Tom


fiftythreebuick
 

Hi Paul-

These are incandescent but LEDs should work fine too. One nice thing is that the display reacts so quickly, so that when you move the string around you can spot intermittents, even if they're quite brief.

Tom


fiftythreebuick
 

Chris, you NEED one! :-)

The first time I tried this was many years ago and out of a string of 100 bulbs, it found each of 13 open bulbs! Oh, that that time I was actually using a 1S2 in a 556 mainframe. Had to bring the lights to the scope that time... <laughing>

Tom


Jim Ford
 

You didn't have it in a conduit?  That cut could be spectacular if the line were energized!       Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: fiftythreebuick <spitfiremarkiv@...> Date: 12/2/21 10:00 AM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] 1502 TDR RECORD functions I've also use a TDR to find where the yard men cut the romex going to our front lamp post as well.  Such a useful tool!  :-)Tom


fiftythreebuick
 

Hi Jim-

No, it was a very old run of romex that was installed long before we bought the house. And you're right, if they had cut it with the switch on, we'd'a known it at the time! <laughing>

Tom


Tom Gardner
 

To a first approximation the transition wouldn't matter. I'd just use any old BNC-to-croc clips cable, and then ignore any reflections at the beginning of the trace.

I wonder if intact bulbs would appear as inductive blips on the trace, which would make counting along to the failed/short bulb easier.

If I have time, I might have a play, but I'm busy plus An Event occurred today :(

On 02/12/21 09:28, David C. Partridge wrote:
I have to ask how you handle the transition from coax to the Xmas lights? And how you interpret the results.

A picture of two may be worth a 1000 words.
D.

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Glydeck via groups.io
Sent: 02 December 2021 05:23
To: TekScopes@groups.io
Subject: Re: [TekScopes] 1502 TDR RECORD functions

Good question. I don’t think it matters. An interruption in the transmission line does not care if it’s a LED or a bulb. I’m so trying this on some recalcitrant light strings.

Glydeck KD6NEW
On Dec 1, 2021, at 6:32 PM, Paul Amaranth <paul@...> wrote:

Was that incandescant or LED lights?

I have an entire bin full of LED strings that are dead and that might
be worth a try.

Paul

On Wed, Dec 01, 2021 at 01:51:54PM -0800, fiftythreebuick wrote:
Tom, the 1502 is one of the most useful instruments around!

I just finished finding the fault in a long string of Christmas lights with mine! :-) Definitely something essential to have around...

Tom
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows











Paul Amaranth
 

I had a few moments and tried this with a dead string of LED lights.

I can see the end of the string when I short the socket for the
next string, but I can't see any difference when pulling LEDs out.

If I pull out the first LED and short the socket with a screwdriver,
I can see that on the screen, but not for the second LED.

I would think the pulse magnitude is insufficient to cross the LED
semiconductor junction. Obviously not an issue with incandescant
lamps.

Pity, I have a ton of dead strings.

Paul

On Thu, Dec 02, 2021 at 10:17:24PM +0000, Tom Gardner wrote:
To a first approximation the transition wouldn't matter. I'd just use any
old BNC-to-croc clips cable, and then ignore any reflections at the
beginning of the trace.

I wonder if intact bulbs would appear as inductive blips on the trace, which
would make counting along to the failed/short bulb easier.

If I have time, I might have a play, but I'm busy plus An Event occurred today :(


On 02/12/21 09:28, David C. Partridge wrote:
I have to ask how you handle the transition from coax to the Xmas lights? And how you interpret the results.

A picture of two may be worth a 1000 words.
D.

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Glydeck via groups.io
Sent: 02 December 2021 05:23
To: TekScopes@groups.io
Subject: Re: [TekScopes] 1502 TDR RECORD functions

Good question. I don’t think it matters. An interruption in the transmission line does not care if it’s a LED or a bulb. I’m so trying this on some recalcitrant light strings.

Glydeck KD6NEW
On Dec 1, 2021, at 6:32 PM, Paul Amaranth <paul@...> wrote:

Was that incandescant or LED lights?

I have an entire bin full of LED strings that are dead and that might
be worth a try.

Paul

On Wed, Dec 01, 2021 at 01:51:54PM -0800, fiftythreebuick wrote:
Tom, the 1502 is one of the most useful instruments around!

I just finished finding the fault in a long string of Christmas lights with mine! :-) Definitely something essential to have around...

Tom
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows

















!DSPAM:61a945ff152291116790165!
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@... | Unix/Linux - We don't do windows