Let me start by saying I haven't used one of the small ESR meters,
although from the vast number of positive comments I've read about the
Bob Parker model, I don't believe that there is a more effective unit
in that price range.

I've used several models of the Sencore LC analyzers, and the most
difficult aspect of in-circuit testing is dealing with the original
equipment Lo Capacity (actually low capacitance) test cable with the
mini-grabber hooks.
Sencore suggests that their 3-spike probe accessory 39G85 Touch Test
Probe can be used with the LC cable mini-grabber hooks, for probing
circuit boards on the solder side.

The Sencore tweezer accessory (looks like a divider) probe is
adjustable and has sharp points for probing boards, although the $99
price might be ojectionable to many occasional users, like myself.

I found out by experimenting, that the LC76 model can be used with a
common pair of test probes (and a BNC-bananna adapter), for in-circuit
capacitor Value and ESR checks. The LC76 has a zeroing pot on the front
panel which is used to set the display to 0.00 ohms with the lead tips
shorted, prior to doing in-circuit ESR checks.
This method may also work well with the earlier models.
Holding 2 probes in one hand, the ESR button can be reached with the
free hand, still not especially comfortable, but not so difficult with
a little practice.

Of course, one would not attempt to check in-circuit components for
Leakage.. bad idea.

The LC77 and newer models are more sophisticated, and don't accept the
characteristics of probe leads (errors are displayed when the test lead
Open/Short setup is performed). The LC input cable type is 93 ohm
impedence RG-62B/U which has a low capacitance of about 13pF per foot.
The original LC cable is a section of RG-62B/U with a short length of
RG-174U going to the + hook.

I didn't particularly like the idea of using the grabber hooks attached
to the TT probe, with the loose connections of the hooks when checking
for low ohms, so I made a probe with a section of RG-62B/U cable and a
modified 39G85 probe. A hole was drilled in the probe top end for the
coax to enter, then discarded one spike and soldered lengths of
finely-stranded flexible wire to the remaining 2 spikes. Short lengths
of black and red shrink tubing were placed on the outside/visible ends
of the spikes to identify them as +/coax center conductor, and
-/shield.
The spike tips don't flex far enough to pinch them together to perform
the lead Short setup, but lightly jabbing them into a piece of clean
metal (a coin, for example), will set the input circuit properly. To
check that the input is zero, press ESR and Coils - Inductor Value to
confirm readings of 0.00 (while the tips are still shorted).
Not having to hold 2 probes with one hand (chopsticks position) is
convenient. A similar probe body could be fabricated from plastic
tubing or similar material.

The complete analyzer features of the Sencore LC units makes them very
versatile instruments. The additional features can often be used for
many types of testing.

Additionally, the ESR ohms measurement is reliable for checking low
value resistors (out-of circuit), for those users that might not have a
milliohm meter.

Inconsistent readings on LC meters can be caused by a poor connection
at the front panel cable BNC connector. This is a key element in the
test circuit. High quality panel and cable connectors are best, and
routine inspection and cleaning will eliminate problems. I usually
clean the center conductor contacts with DeoxIt (on a toothpick for the
female contact) to remove any oxidation, especially if the analyzer
hasn't been used for a considerable time.
The test connector internal wiring is switched thru relays, and worn or
oxidized contacts can also contribute to inconsistent readings.

Cheers
WB
.................

Ray L. Volts wrote:
Out of curiosity, who among you own and/or use both a Sencore Z-meter
(pre-LC103) and one of the portable, dedicated ESR testers? How does the
latter stack up against your Z-meter in terms of measurement speed, accuracy
and ruggedness? Which do you use more often on your bench?

What's your take on Sencore's assertions below. That it's marketing hypeis
a given, but do the following also happen to be true and troublesome in your
experience with the portable testers?

"Normal ESR limits vary between aluminum and tantalum types and their
values. Small value electrolytic capacitors; 0.1, 0.22, 0.33, and 0.47 µFd
are now common among electronic circuits. ESR on electrolytic capacitors
above 1000 µFd is less than 0.5 ohms requiring 0.01 ohms of resolution for
good/bad testing. Testers that only test ESR do not accurately test
capacitors below 1 µFd and do not provide the resolution to good/bad test
ESR on capacitors over 1000 µFd."

and

"In circuit capacitor and inductor testing accuracy is plagued with many
parallel components and circuit paths. In-circuit ESR only testers often
miss bad capacitors in-circuit when they are reduced in value, shorted or
leaky. This can add hours to a repair job."

Would one of the ESR-only meters be a recommended investment, given that I
already own an LC-75 and don't currently do field work? Or should I bite
the bullet and just use that cash toward an eventual purchase of the LC103
(which does the in-circuit tests)?

Thanks,
Ray