LeCroy AP015 service manual / calibration manual

[Warranty]

Hi guys,
got my hands on a defect AP015 current probe and repaired it. Wasn't that hard.
One of the instrument amplifier opamps was broken - changed it and it's now working 
The tolerance of the measurement is currently i bit worse than what is specified, so it needs some calibration.
There are a lot of potentiometers, most of them related to the gain at different amplification stages.
Maybe someone has a service manual or calibration manual, that would help me a lot to get a perfect calibration result.

Thanks in advance!

Regards Warranty

[lukier]

I'm trying to repair one right now. Nothing whatsoever on the scope whatsoever, which is a bit worrying.
If the hall sensor was busted then there should be at least AC and some fixed offset.
That might mean the transformer is busted as one end of this transformer goes "almost" straight into the output. In this design however it goes via these LM7171A in the ProBus connector, so I'll have to check them first.

Which one was broken for you?

Regarding the calibration the AP015 the user's manual has some performance & adjustment procedures, but very basic, touching only the LeCroy part of the probe:
http://cdn.teledynelecroy.com/files/manuals/ap015_current_probe_manual.pdf

I guess the rest of the probe circuitry (in the handle, and most pots there) is Hioki design probably and not documented anywhere

[lukier]

I've found what looks like the transformer outputs on the probe head connector and tested by generating 20V from the function gen, shorted so via 50 Ohm - 200mApp. That gave an output of ~250mVpp (@ 10 kHz) so it seems the transformer is OK.

Need to figure Hall sensor pins and possibly test that out of circuit, but now I think my problem might be in the driving-feedback/amplifier circuitry. Maybe even something as simple as broken relay. Need to investigate more, as long as the magic probe head is OK then the probe should be repairable.

It is quite tricky as some parts there are long gone from the mainstream market, like:
- EL2008CT - power opamp for DC current cancellation,
- MAT04 - probably something related to the Hall,
- RP1-12V - RF relay,
- MAX4113ESA - opamp.

Some modern replacements have worse parameters than the old ones (e.g. MAT14), go figure.

[Warranty]

I've marked the broken one in the picture with the cursor. But I've changed both.
It was easy for me to see that the probe head was working, as the voltage in the coaxial cable was changing with the current through the clamp.


Regards
Warranty

[lukier]

Thanks Warranty!

I did some more googling, some sources indicate that it might not be Hioki design (as normally all non-Tek probes are), but LEM PR50, also sold by Fluke as i50s model.

Teardown of the latter is here:
https://www.eevblog.com/forum/testgear/fluke-i50s-current-probe-rj45-power-supply-layout/

[lukier]

Some markings on the PCB might suggest Preamble Instruments, acquired by LeCroy long time ago. The number on the PCB also points to LeCroy: 71AP0151E

This is not uncommon, some active probes, both single ended and differential were made by Preamble and rebranded by Agilent, probably even after they got acquired by LeCroy.

E.g.:
Agilent 1152A = LeCroy AP022
Agilent 1159A = LeCroy AP034

I just didn't know that Preamble had the facilities to make these magic AC-DC transformers, so I suspected LEM first. Nowadays only Hioki and Tek make this stuff.

[ferdinando]

I contribute with the outcomes of the repair of my AP015, which I damaged after sensing a short circuit current of several Amps.
Symptoms were: probe recognized, clamp open/close recognized, calibration always yielding -25A.
Investigations with the scope and the probe sensing a current, revealed that the second LM7171AIM (the one in between the 2 trimmers, configured as a buffer with 3900 ohm as feedback) received a signal on the pin 3 (+ve input) but produced no output.
Its substitution with a new LM7171AIM from TI fixed the problem.
The trimmer in the middle calibrates the gain, while the other on the edge regulates the bias.