root wrote:

When I have encountered power supply problems in the past
I have just replaced all the caps. I have wanted to get
an in-circuit ESR meter but they either came as kits or
were more than I wanted to pay. A while ago someone posted
here that one could get a functional ESR meter from China
for under $30. I hastily did a web search and found this:
http://www.dx.com/p/lcr-t4-meter-tes...ticolor-364576

I ordered one and after several weeks it came today.
I hadn't paid attention to the picture. The device came
without any instructions. There is an EZ-insertion socket
which as far as I can tell utilizes only three pins, say
1,2,3. The unit works fine for testing resistors connected
either from 1-3 or 2-3 or 1-2. I wanted to test some
capacitors in circuit so I cut a clip lead in half and
connected the wire ends to pins 1-3. The device seems
to read electrolytic capacitors as diodes but gives
two uF readings which bear no relationship to the values
written on the capacitors. For example, an 800uF cap
might read 1.3v, 2.1uF.

I am hoping that someone in this group can shed some
light on the device, specifically how it can be used
to tell me which caps have to be replaced in some
device.


** You need to test some known good electros from your parts stock to get a feel for how the meter is working. Do not expect to test capacitance with the cap still in circuit.

Using an ESR meter is much like using a DC voltmeter, the reading gives useful no information unless YOU know what it SHOULD be.

Comparison with a known good electros of the same uF and voltage rating is the best way to know what is normal. Ones that read a few times higher are suspect and any that read 10 times higher are fit only for the bin.



.... Phil