testing a capacitor

MitchK · 08-28-2007, 06:55 PM

is there any way I can test a capacitor while its still in the amp?

soundmasterg · 08-28-2007, 07:52 PM

Not while it is completely connected. Disconnect the grid end of a coupling cap, hook your meter to the disconnected end of the cap, and to ground, measuring on DC volts, then flip the amp on. The voltage will spike, and then stabilize at some level. A perfect cap would have 0 v, but there is always some leakage. Usually anything more than .25v should get tossed.

You can also use something like a Sprague Tel-ohmike to test a cap outisde of the amp. These units are from the 60's, and they test up to 600v and will test for leakage, ESR, and value. You can find them on ebay for $50 or less and you may have to replace some resistors and caps in them with precision stuff, but they are very useful.

Greg

08-28-2007, 06:55 PM	#1
MitchK Senior Member Join Date: Jul 2006 Posts: 136	testing a capacitor is there any way I can test a capacitor while its still in the amp?

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08-28-2007, 07:52 PM	#2
soundmasterg Senior Member Join Date: May 2006 Location: Cornelius, Oregon Posts: 669	Not while it is completely connected. Disconnect the grid end of a coupling cap, hook your meter to the disconnected end of the cap, and to ground, measuring on DC volts, then flip the amp on. The voltage will spike, and then stabilize at some level. A perfect cap would have 0 v, but there is always some leakage. Usually anything more than .25v should get tossed. You can also use something like a Sprague Tel-ohmike to test a cap outisde of the amp. These units are from the 60's, and they test up to 600v and will test for leakage, ESR, and value. You can find them on ebay for $50 or less and you may have to replace some resistors and caps in them with precision stuff, but they are very useful. Greg

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