[Heath] Yet more on my IP-27...

[Mo]

I built this one and it has saved me lots of frustration and work.  It seems
to be a very good design and parts are available from several sources.  You
can even use it to measure the impedance of speakers, etc. (low values)

http://www.ludens.cl/Electron/esr/esr.html


73 de
Mo, AK4RM


> -----Original Message-----
> From: heath-bounces at puck.nether.net 
> [mailto:heath-bounces at puck.nether.net] On Behalf Of Kenneth G. Gordon
> Sent: Saturday, June 23, 2012 11:38 PM
> To: Heath at puck.nether.net
> Subject: Re: [Heath] Yet more on my IP-27...
> 
> 
> On 23 Jun 2012 at 18:00, Mo wrote:
> 
> > One of the best parts is that the ESR meter will measure in-place 
> > capacitors.  No unsoldering unless it measures defective.
> > 
> > 73 de
> > Mo, AK4RM
> 
> Thanks, Mo. I have a nice ESR meter, which seems to work 
> extremely well. 
> Since I only finished building it a while back, I have not 
> used it much. It is a 
> "Dick Smith" job, and is very nice.
> 
> 
> > >     There has been considerable discussion of old
> > > electrolytic caps and how to determine if they need replacing 
> > > on another couple of lists I am on.  One of the best ways to 
> > > determine a bad electrolytic cap is NOT by measuring the 
> > > value of capacitance but rather measuring the ESR.  The ESR 
> > > should be only be an ohm or two at most.  Many times an older 
> > > electrolytic will measure correct capacitance but have an ESR 
> > > of 10-20 ohms which is bad.  The higher ESR will cause 
> > > heating and in some cases, an explosion as the electrolyte 
> > > heats up to the point of causing pressure buildup or physical 
> > > leakage!  If you don't have an ESR meter, you might consider 
> > > building or buying one for future repairs.  I know some 
> > > people who measure the ESR on all the electrolytic caps 
> > > before they actually start the repair. Jerry W5JH
> 
> That last sounds like a most excellent idea. As I said, I 
> have a nice Dick 
> Smith ESR meter which seems to work very well indeed. All I 
> have to do is 
> get familiar with it.
> 
> It showed this 3000 MFD 75 VDC cap as being a dead 
> short....after the fact, 
> dang it.
> 
> Also, I have at least two different digital multimeters which measure 
> capacitance: both of those showed this cap as 0 MFD, which is a dead 
> short...but again, after the fact.
> 
> I had thought about testing all the caps BEFORE I started 
> refurbishing this 
> IP-27, but since the number of parts soldered to each end of 
> the cap were 
> rather substantial, I decided against it.
> 
> Obviously, I shouldn't have. If I had been more familiar with 
> the Dick Smith 
> meter, I would never have worried about unsoldering parts.
> 
> Oh, well. Live and learn...some more...again... :-)
> 
> Ken W7EKB
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