From:
           
           kg 
    Date:
           3/5/2001 7:04 PM
 Subject:
           some cap information



DUT is paper-housed multi-section electrolytic capacitor. green and blue
sections rated to 350wvdc. red section rated to 400wvdc. power supply was
adjusted to rated working voltage, and connected to DUT through 1k 10w wire
wound resistor. voltage across said resistor was monitored wrt time. 
 

section         freq    cap     df      esr             
green   before  120Hz   45.80   0.071   1.10            
                1KHz    38.42   0.363                   
        after   120Hz   46.70   0.036   0.28            
                1KHz    44.46   0.127                   
red     before  120Hz   46.98   0.115   0.80            
                1KHz    37.90   0.322                   
        after   120Hz   48.43   0.083   0.22            
                1KHz    42.90   0.163                   
blue    before  120Hz   107.20  0.079   0.63            
                1KHz    85.92   0.442                   
        after   120Hz   110.00  0.041   0.17            
                1KHz    104.00  0.165                   
 
Changes                                                 
section freq    cap     % cap   df      % df    esr     % esr
green   120Hz   0.90    1.97%   -0.035  -49.30% -0.82   -74.55%
        1KHz    6.04    15.72%  -0.236  -65.01%         
red     120Hz   1.45    3.09%   -0.032  -27.83% -0.58   -72.50%
        1KHz    5.00    13.19%  -0.159  -49.38%         
blue    120Hz   2.80    2.61%   -0.038  -48.10% -0.46   -73.02%
        1KHz    18.08   21.04%  -0.277  -62.67%


in all cases, current into DUT was down to 1mA in less than 3 minutes of
elapsed time (green section). blue section was down to 1mA in less than 1.5
mins., whereas red section took 2.5 minutes. leakage was thus acceptably low
in ALL cases. power supply was unregulated but of VERY low impedance
(2ndary ~1R dcr), well filtered (500uF), and was adjusted via variac on
primary.
 
in all cases, value of capacitance was increased, particularly at 1KHz. in all
cases, the dissipation factor was improved, showing an improvement in
dielectric properties. in all cases, ESR was improved as well, as should be
expected, since ESR is proportional to df.
 
of particular note is the fact that effective power supply impedance was 1k,
generally the value of impedance found between main B+ node and g2/preamp
supply nodes.
 
DUT was approximately 35 years old and had not been used in at least 15
years. pictures of DUT and test setup may be provided on request. readers are
reminded that this is one individual case, and that results may vary.
 
personally, i must say that i was absolutely shocked at how well this old cap
held up... especially when all sections were stressed to 50v overvoltage and
leakage increased only 3-5mA.
 
kg