Dear Forum members

I have a radio gram which has the set B6CA38A made by Philips India. Recently it developed a hum problem. On investigation I found one of the 50ufd capacitor faulty. I measured the capacitance of both. The healthy one showed a value 47ufd whereas the faulty one showed a value 0.008ufd. So practically the value of the faulty part had nearly become zero. This resulted in increase of the AC reactance to a very high value causing the hum.I had a spare filter capacitor, though old one, but on measuring the capacitance I found the values as 67ufd/75ufd. If I use this capacitor what problem would it cause? I understand that if a higher value of the filter capacitor is used then the valve EZ80/EZ81 is more stressed. But a filter capacitor which is old and due to aging whose capacitance value has increased will also cause the same problem which a new capacitor of higher value would have caused? Is it possible to detect by performance vise whether the filter capacitor value has increased or not?

Regards

P.Rajan

A little rewiring solves your problem.
Connect te good half (47uF) direct to the rectifier tube as first capacitor (C25) and the new cap as second, the second is connected via a filtercoil (output transformer).
If the bad cap is already the second (C26), no rewiring is necessary.
Soundman2

Do keep in mind
That an electrolytic capacitor usually degrades when it has not been in use for a long time.
Which means that the vèrry thin layer of aluminium oxide that serves as diëlectricum needs to be "reformatted"
This degrading of the diëlectricum makes the insulation value of the capacitor poor;
measuring the microfarads value gives the (wrong) impression that this increased
But anyway, from 50 uF to 70 uF is not critical; rectifier tube may have problems when you increase to more than 100 uF
Nico

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