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

[Guy G. Giacopuzzi]

What ESR meter do you use, and why do you like it?
Guy,
WA6OQQ

On 6/23/2012 2:26 PM, Jerry Haigwood wrote:
> Ken,
>      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
>
> -----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 12:55 PM
> To: Ron; Robert Groh
> Cc: Heath at puck.nether.net
> Subject: Re: [Heath] Yet more on my IP-27...
>
> On 23 Jun 2012 at 8:56, Ron wrote:
>
>>   >  don't leave those old electrolytics in there!
>>
>> I am not sure I agree. I've restored many, many Heathkit instruments
>> and in just about all, electrolytics that measured OK stayed that way
>> for a long time. Of course, all electrolytics will go bad *eventually*
>> -- including brand new ones -- but this may happen 20 years later, or
>> 50 years, or tomorrow...
>>
>> -- Ron
> Well, I suspect from what I have seen in this instrument while restoring it
> that it had been abused over a long period of time by students at a
> University teaching lab.
>
> I am not too surprised at finding bad electroltyics in it.
>
> However, although I don't routinely replace electrolytics in the equipment I
> restore, I have found too many bad or leaky or leaking or weak ones to put
> much faith in them...even when new.
>
> When I finally replaced all the electrolytics in one of my SB-200s after one
> failed (rather spectacularly too), all the remaining caps tested at less
> than 1/2 of their original capacitance: many were down to 1/3 of their
> original value.
>
> Ken W7EKB
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