Well, since I was told that replacing all the tubular wax caps in a receiver was a good idea, I decided to use this pre-war Silvertone Tombstone I am restoring with distorted audio as a test case.

Of the three wax capacitors I have replaced so far two of them are well out of tolerance. I noticed that the measured value of the capacitance of the wax capacitors actually changes when changing scales while measuring the wax units on my capacitance tester. This does not occur with the modern replacement polyester film units I am using as replacements. I assume this is due to the ESR of the old caps being a significant value relative to the impedance of the tester??

This has been interesting. I will be measuring more cap units as I replace them ( 9 in total ) - a slow restoration but a very interesting one.

Comments Welcome
Thanks
Lou

:Well, since I was told that replacing all the tubular wax caps in a receiver was a good idea, I decided to use this pre-war Silvertone Tombstone I am restoring with distorted audio as a test case.
:
:Of the three wax capacitors I have replaced so far two of them are well out of tolerance. I noticed that the measured value of the capacitance of the wax capacitors actually changes when changing scales while measuring the wax units on my capacitance tester. This does not occur with the modern replacement polyester film units I am using as replacements. I assume this is due to the ESR of the old caps being a significant value relative to the impedance of the tester??
:
:This has been interesting. I will be measuring more cap units as I replace them ( 9 in total ) - a slow restoration but a very interesting one.
:
:Comments Welcome
:Thanks
:Lou
:
:
:

:Thanks for the insight Ed

I am almost finished with replacing Caps in this Silvertone set and I am going to compare the performance of it before and after re-capping.

Lou

:Well, since I was told that replacing all the tubular wax caps in a receiver was a good idea, I decided to use this pre-war Silvertone Tombstone I am restoring with distorted audio as a test case.
::
::Of the three wax capacitors I have replaced so far two of them are well out of tolerance. I noticed that the measured value of the capacitance of the wax capacitors actually changes when changing scales while measuring the wax units on my capacitance tester. This does not occur with the modern replacement polyester film units I am using as replacements. I assume this is due to the ESR of the old caps being a significant value relative to the impedance of the tester??
::
::This has been interesting. I will be measuring more cap units as I replace them ( 9 in total ) - a slow restoration but a very interesting one.
::
::Comments Welcome
::Thanks
::Lou
::
::
::
:
:Check for LEAKAGE CURRENT. This is typically a problem with old wax paper caps. With the radio completely disconnected from the power source, disconect one end of the cap. Charge the cap to its rated voltage from an external power supply. (If you do not have a power supply, charge from line voltage for ten seconds through a 33K or so resistor in series with a 1006 diode {Radio Shack}) (Use isolation transformer if available, and be very careful). Come back several minutes later; the cap should still have voltage on it. Leaky paper caps, besides impairing operation, can damage tubes and transformers. Checking capacitance values does not detect leakage, but could account for different readings on different scales. As a quick and dirty check for leakage, measure the resistance of the disconnected cap on the highest resistance scale. You should get a reading that then goes to an open. Disconnect one end of the meter; wait ten seconds; then reconnect the meter; a good cap will still show open; a leaky cap MAY show resistance, which then goes to open. NOTE: this may not pick up on caps that show leakage at their working voltage. Ed M
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