Hi all,
I was going to use again (after many years) my A6302 current probe with the AM503 probe amp. Problem I have is that I cannot zero the DC offset of the combo at lower than 20mA/div sensitivity.
Going through the manuals I came across a procedure to adjust the PROBE DC offset, which could help.
However, my A6302 probe has NO adjust trimmer as shown in the attached page! I even disassembled the probe but there's no option to adjust.
Does that mean there are TWO versions of this probe in existing? Anybody can offer me a way out here? I know there existst an A6302XL but that only means a longer cable (and consequently lower BW).
thanks,
Jan
I was going to use again (after many years) my A6302 current probe with the AM503 probe amp. Problem I have is that I cannot zero the DC offset of the combo at lower than 20mA/div sensitivity.
Going through the manuals I came across a procedure to adjust the PROBE DC offset, which could help.
However, my A6302 probe has NO adjust trimmer as shown in the attached page! I even disassembled the probe but there's no option to adjust.
Does that mean there are TWO versions of this probe in existing? Anybody can offer me a way out here? I know there existst an A6302XL but that only means a longer cable (and consequently lower BW).
thanks,
Jan
Hello Jan,
(This is Alan Martin. We met at RMAF 2014 with Mr. Curcio)
I checked all six of my working A6302 current probes and none have the DC offset adjustment on the head.
Usually residual DC offset is caused by residual magnetizm in the head. The AM503 degausser is often too weak to properly degauss the head. Use a tape head degaussers to go around the probe head and into the jaw opening if possible.
Next overhaul the AM503. remove the knob and apply a drop of Teflon or light machine oil to the shaft and sleeve.; wiping off excess. Reinstall the knob. Rotate that knob and shaft to get the lube worked in. There may be a bearing at the rear of the switch deck that could also use a drop, and the leaf indexing springs perhaps as well.
With the aluminum sides off of the amp you should also clean the fragile leaf contacts that are riveted to the PCB and actuated by the large grey cam. I use Ever Clear brand alcohol from the liquor store as this is fairly pure ethanol without denaturing agents. Vodka might also work.
Be sure to terminate the coax output from the amplifier with a 50 ohm BNC feed through ot the readings will be 2X high.
Best of luck. AM
(This is Alan Martin. We met at RMAF 2014 with Mr. Curcio)
I checked all six of my working A6302 current probes and none have the DC offset adjustment on the head.
Usually residual DC offset is caused by residual magnetizm in the head. The AM503 degausser is often too weak to properly degauss the head. Use a tape head degaussers to go around the probe head and into the jaw opening if possible.
Next overhaul the AM503. remove the knob and apply a drop of Teflon or light machine oil to the shaft and sleeve.; wiping off excess. Reinstall the knob. Rotate that knob and shaft to get the lube worked in. There may be a bearing at the rear of the switch deck that could also use a drop, and the leaf indexing springs perhaps as well.
With the aluminum sides off of the amp you should also clean the fragile leaf contacts that are riveted to the PCB and actuated by the large grey cam. I use Ever Clear brand alcohol from the liquor store as this is fairly pure ethanol without denaturing agents. Vodka might also work.
Be sure to terminate the coax output from the amplifier with a 50 ohm BNC feed through ot the readings will be 2X high.
Best of luck. AM
Hi Alan, thanks for the tips!
I just bought a 2nd probe, see how that works (you can never have enough probes, current or otherwise!
But I am still puzzled by that page from the service manual I showed above that clearly shows an adjustment possibility.
Opening up the probe there's no adjustment on the little PCB either. A Puzzle.
Jan
I just bought a 2nd probe, see how that works (you can never have enough probes, current or otherwise!
But I am still puzzled by that page from the service manual I showed above that clearly shows an adjustment possibility.
Opening up the probe there's no adjustment on the little PCB either. A Puzzle.
Jan
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