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Capacitor substitution values?
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Fozzy The Bear:
All of this really depends on the circuit it's in. If it's a timing critical circuit (as in some parts of a monitor), then you must use the exact value or you'll get some odd results.

If you can't get an exact value like 500mfd  you can make up the value by putting 2 X 250mfd caps in parallel. Or putting a 470mfd and a 30mfd in parallel to make 500mfd. Exact value is always best! but watch the tolerances as well they can be anything from 5% to 30% try to match the original tolerance range or be inside of it.

Best Regards,
Julian (Fozzy The Bear)
ChadTower:

Cool.  FWIW, I spent half the weekend emailing back and forth with Bob Roberts coming up with a replacement for an OOP multican capacitor... his advice was that going up a bit is acceptable but never go down.

I need to get an ESR meter... the least expensive new one I've seen so far is $200.   :P
Fozzy The Bear:

--- Quote from: ChadTower on January 27, 2008, 10:21:26 pm ---I need to get an ESR meter... the least expensive new one I've seen so far is $200.   :P

--- End quote ---

Here's a trick that works if you don't have an ESR Meter......

For checking an electrolytic capacitor, you can get a good idea of its condition using a capacitance meter on a digital multimeter and a can of freezer spray.

Connect the cap under test to the meter. If the capacitance reading is well below the nominal value then it's faulty. If, however, the reading seems to be right, spray the capacitor and observe the reading.

With a faulty electro cap, you will see the reading decrease rapidly. Continue to apply freezer until it is approximately 75% of what it should be, if it goes that low it is definitely faulty.

Works every time for me when I don't have the ESR Meter to hand.

Best Regards,
Julian (Fozzy The Bear)
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