Re: 1502 TDR RECORD functions


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.

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