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

[Kenneth G. Gordon]

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