[NJARC] Mega 328 Tester

Thu Dec 31 18:04:20 EST 2015

AaronFor reforming electrolytic capacitors, I prefer the high voltage power supply with a series resistance.  The enemy of all electronics components is heat.  With the method described earlier, heat is not an issue because current is limited to 10 mA, worse case, and the capacitor under test never gets above room temperature.  I personally wouldn't (again) risk damaging a cap checker or any other piece of test equipment when a simple power supply will do the trick.  I now speak from experience about this!
Yes, I have noticed what you describe, when the whole reforming process has to be repeated.  But I was careful to mention that I only bother to reform higher quality filter capacitors like those found in high end commercial and military radios.  The consumer and low end "commercial" radios like hallicrafters and the like; I just replace them outright.  
HP, the military and others spend the extra money to buy a better grade of filter capacitor.  Once reformed, I have had no issues with any of them drawing excessive charging current days or weeks later.  But, as is often said, your mileage may vary.  
As an aside, it's funny to think that when a lot of our favorite radios were designed and built, no one was then thinking "I hope this thing lasts for 70 years!"  But with a little TLC and modern components, it certainly has a better chance.
Have a great new year!Jim

      From: Aaron Hunter <ahunter01 at comcast.net>
 To: NJARC <njarc at mailman.qth.net> 
 Sent: Thursday, December 31, 2015 11:56 AM
 Subject: Re: [NJARC] Mega 328 Tester

I read with interest the comments from our learned radio collectorexperts.  So I decided to run a test of the multi tester against my 40+year old Heathkit capacitor testor.

First let me preface this with my electronic training.  I graduatedfrom Philadelphia Wireless Technical Institute 50+ years ago.  Mygrades were not stellar, so I won't go into them.  What I did manage tounderstand and learn, I've forgotten years ago.  I now drive a schoolbus, so you can see how my electronics background has paid off.  LOL

I fired up my Heathkit IT-11 and tested some electrolytics and comparedthe results with the multi tester.  The first thing I noticed this timewas I had the Heathkit switched to non-electrolytic for the leakagetest the other day.  This is why two of the dented electrolytics testedbad then but good when forced up to a working voltage of 450 with 500Volts applied for a minute or two.  The other two dented capacitorswere also forced to the working voltage, again using 500 Volts.  Theytook several minutes to reach the working voltage, one getting warm andthe other showed signs of leakage, didn't take notice if it was warm ornot.

The first three tests were with the Heathkit and bringing thecapacitors up to the working voltage, then testing with the multimeter.  (Make sure to short the capacitor before inserting in the multimeter.)  I reversed the next two tests, using the multi meter first tosee if there was a difference in readings after bringing the capacitorup to working voltage with the Heathkit.

Notice on the 5th capacitor, I took multiple readings with the multitester and got varying results for value.  I couldn't find the specs.but it appears the 4th digit is meaningless and the 3rd questionable. To me, it seems to have an accuracy (regarding reproducibility) ofabout +- 10%.

The last two tests were with capacitors of the same value but differentmanufacturers.  They had even higher ESR values, which I don't know ifthat's good or not.

I still question reforming capacitors.  Did you recheck the capacitorafter it sat for several days with no voltage?

Years ago, when my Sansui 5000 was about 8 years old, one of thechannel fuses popped.  When I inserted another fuse, it worked fineuntil the next day when it would pop the fuse or take out the outputtransistor.  I found if I inserted a resistor into the fuse socketfirst, I could then replace the fuse and use it off and on for the day,but the next day would have to do the resistor trick again.  This madefor difficult normal trouble shooting techniques, so I pulled the minielectrolytics on the problem board.  Using the technique mentioned inan earlier email, I watched the current draw when voltage was appliedand found the culprit.  Once it got up to operating voltage, voltagecould be applied off and on all day and the capacitor would chargequickly each time.  But let it sit for a day and you'd start all overagain.  So again I ask, were those reformed capacitors rechecked aftera few days to see if they needed reforming again?

I hope my chart comes across, otherwise this email was all in vain.

Aaron Hunter

PS  I threw out the dented electrolytics!

 On Wed, Dec 30, 2015 at 11:31 AM, AaronHunter <ahunter01 at comcast.net>wrote:

_________________________________________________________
I hope everyone realizes when checking capacitors, only the value ischecked, not the leakage current. 
I had some fairly new electrolytic capacitors that had dents in thecans.  I checked them with the checker and a good capacitance value wasshown.  When I check them with my HeathKit capacitor checker, alldented capacitors had high leakage current.  The only one of the groupto escape a dent tested good.

Aaron Hunter

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