LC102 Lead zeroing!!. was zeroing perfect the other day now

[Chad Entringer]

Hi, I recently picked up an lc102 and the lead zeroing only seems to
work after the unit is powered on for some time! About an hour... I
think I noticed the inductance level readings on coils dropping using
shorted leads before it actually zeros. I will do more testing to
verify it drops as its warming up. Noticed many pots on main boards
for adjustment! I am thinking one of these would zero out the
inductance if that is my problem? Any suggestions or thoughts? I do
not have new probes lying around... I don’t think it’s the probes
though since it zeros after long warm up time. Thank you.
Chad.

 

[Wild_Bill]

You will only make any existing problems worse (or create new ones) by
changing the internal service/calibration adjustments.

You will need to attain the proper service literature from Sencore.

There are other reasons that the Lead Zero produces inconsistent results.
The BNC connector on the test lead, or the front panel may be oxidized or
worn out (the front panel BNC is a threaded part, it needs to be tightened
snuggly). The fuse in the input/test connector needs to be gripped securely
by the adapter.
There could be a broken/frayed conductor, or other loose connection in the
test lead.
If you're not using the genuine Sencore test lead, you shouldn't expect good
results. The original part is a length of RG-62 B/U IIRC, and not common
coaxial cable.
The center conductor in the Sencore test lead isn't surrounded by dielectric
material the way most coax is.

Having the Calibrator accessory isn't entirely error-proof if the value
drift hasn't been measured by a traceably accurate reference recently
(within about 1 year).
The values listed on the Calibrator are probably close, but if the accessory
is old, the values have drifted.
Attempting to use the Calibrator without the Sencore test lead isn't going
to result in accurate or consistent readings.

The Sencore equipment that I've used and serviced have all been very well
constructed, and reliable instruments. Tampering with internal settings
should be avoided. Removing the instrument from it's case can result in
calibrated settings being changed if handled carelessly.
Without some other reliable test equipment, and the Sencore service
information, you aren't likely to be able to troubleshoot any problems or
faults this unit might have.

--
Cheers,
WB
..............


"Chad Entringer" <chad@arcadecup.com> wrote in message
news:86d8d42a-1282-4cff-89d9-ff73bdc740d5@r34g2000vba.googlegroups.com...
Hi, I recently picked up an lc102 and the lead zeroing only seems to
work after the unit is powered on for some time! About an hour... I
think I noticed the inductance level readings on coils dropping using
shorted leads before it actually zeros. I will do more testing to
verify it drops as its warming up. Noticed many pots on main boards
for adjustment! I am thinking one of these would zero out the
inductance if that is my problem? Any suggestions or thoughts? I do
not have new probes lying around... I don’t think it’s the probes
though since it zeros after long warm up time. Thank you.
Chad.

 

[Fanboy]

Hi, thank you for the detailed and informative response...
I cleaned the bnc plug, took about a centimeter off of the black lead
where the cable meets the solder point.
Now all works perfect on morning starts. Zeros out and great reads!
Thank you. Must have been a frayed lead.

 

[Chad Entringer]

Boy someone how my profile name changed.. testing to see if back to my
name.. thanks again!

 

[Wild_Bill]

That's great. You may have noticed that the short leads that attach to the
mini-clips can rotate in use, causing more broken strands.
I've put small amounts of hot glue at the entry point of the small leads to
prevent them from rotating in use. This can prevent future surprises, like
not being able to perform the Lead Zero again.

The small lead for the red clip is a section of RG-174 IIRC, and fairly
fragile. Putting a small amount of hot glue at the clip ends of the short
leads will also extend their useful life.

You'll no doubt find out that attempting to attach the mini-clips to the
solder side of a board for in-circuit teast will generally be an exercise in
frustration.

I had a couple of extra probes that are type recommended to be used with the
Cricket transistor testers, so I got some of that RG-62 B/U (I think) coax
and made up a test cable with the probe on the end, instead of the test
clips.
Only two of the sharp pointed pins are needed, of course, and the pins need
to be marked negative and positive.

I'm fairly certain that all of the Sencore LC/Zmeters back to the LC-77 will
give incorrect measurements if the original type, low capacitance coax is
not connected to the input connector, but a probe-type test cable made up
with the correct coax type works very well.
Generally, this leaves the other hand free to select the test functions of
the instrument (the temporary in-circuit connection of the probe is not
suitable for capacitor leakage tests, as leakage testing isn't done
in-circuit).

--
Cheers,
WB
..............


"Fanboy" <chad@arcadecup.com> wrote in message
news:8ade639a-8368-4226-8f98-1a8418be0e48@k8g2000yqn.googlegroups.com...

Hi, thank you for the detailed and informative response...
I cleaned the bnc plug, took about a centimeter off of the black lead
where the cable meets the solder point.
Now all works perfect on morning starts. Zeros out and great reads!
Thank you. Must have been a frayed lead.