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Re: 5B3 Deluxe compared to 5E3

8/19/2004 9:01 PM
Dr. Photon	Re: 5B3 Deluxe compared to 5E3 by output, he means the end of the cap that goes to a tube grid. The idea is that the "input" end is getting signal from a tube grid, which is at several hundred volts, and the other end is typically brought down to ground with a grid leak resistor. if you measure any voltage on the grids (save fixed bias and grid-leak biased input stages in ancient amps), the caps are shot. You can also test this with the cap's "output" lifted with a multi-meter. Note that you will see a voltage spike as the cap charges through the meter resistance, but it should setle to 0 volts eventually. Note that many of those small capacitor testers do not test capacitors under high voltage conditions. I have not researched this much, but I know heathkit made some vacuum tube based cap testers that are capable of testing a variety of cap parameters under a wide range of voltages (these are the ones with the eye tube - be sure to get the fancier one and not the short/open-only testing version; and fix them up before use)

8/19/2004 9:01 PM

Dr. Photon

Re: 5B3 Deluxe compared to 5E3

by output, he means the end of the cap that goes to a tube grid. The idea is that the "input" end is getting signal from a tube grid, which is at several hundred volts, and the other end is typically brought down to ground with a grid leak resistor. if you measure any voltage on the grids (save fixed bias and grid-leak biased input stages in ancient amps), the caps are shot. You can also test this with the cap's "output" lifted with a multi-meter. Note that you will see a voltage spike as the cap charges through the meter resistance, but it should setle to 0 volts eventually. Note that many of those small capacitor testers do not test capacitors under high voltage conditions. I have not researched this much, but I know heathkit made some vacuum tube based cap testers that are capable of testing a variety of cap parameters under a wide range of voltages (these are the ones with the eye tube - be sure to get the fancier one and not the short/open-only testing version; and fix them up before use)