Hi all,
I'm trying to troubleshoot issues with my mc2105 amp and want to check the filter caps. The caps I purchased are new mundorf 47,000 uf caps. When I attempt to measure them with my fluke 107 multimeter I get a reading of .00nf or .07nf. After awhile the reading changes to OL. I understand that the limit of this meter is 1000uf (I believe). However, I would expect the uf to increase to 1000 before hitting OL when measuring rather than it sitting close to 0nf. Perhaps this is expected? How would you suggest I measure these caps? Is this an indication of something wrong with the caps?
Thanks!
I'm trying to troubleshoot issues with my mc2105 amp and want to check the filter caps. The caps I purchased are new mundorf 47,000 uf caps. When I attempt to measure them with my fluke 107 multimeter I get a reading of .00nf or .07nf. After awhile the reading changes to OL. I understand that the limit of this meter is 1000uf (I believe). However, I would expect the uf to increase to 1000 before hitting OL when measuring rather than it sitting close to 0nf. Perhaps this is expected? How would you suggest I measure these caps? Is this an indication of something wrong with the caps?
Thanks!
The meter behavior is normal. It's just going through its auto ranging, and only the final result matters. I have a Fluke 110 with a 10,000 uF limit that does the same thing.
The OL does however indicate that the cap is not shorted. If you really need to know the capacitance, you can use the RC time constant principle to estimate it.
https://en.wikipedia.org/wiki/RC_time_constant
And keep in mind the tolerance on electrolytic caps is typically +/- 20%.
The OL does however indicate that the cap is not shorted. If you really need to know the capacitance, you can use the RC time constant principle to estimate it.
https://en.wikipedia.org/wiki/RC_time_constant
And keep in mind the tolerance on electrolytic caps is typically +/- 20%.
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Take a 9 V battery, a 1 kohm resistor, a digital multimeter set to the 20 V DC range and a watch. A calculator can also be handy.
Connect the multimeter to the capacitor. Connect the battery via the resistor to the meter and capacitor. The capacitor will now be slowly charged to about 9 V.
After 15 minutes, read of the voltage, disconnect the battery, put the resistor in parallel with the capacitor and meter.
Measure the time it takes until the voltage has dropped by a factor of e = 2.7182818284... The time in seconds is the capacitance in thousands of uF.
Connect the multimeter to the capacitor. Connect the battery via the resistor to the meter and capacitor. The capacitor will now be slowly charged to about 9 V.
After 15 minutes, read of the voltage, disconnect the battery, put the resistor in parallel with the capacitor and meter.
Measure the time it takes until the voltage has dropped by a factor of e = 2.7182818284... The time in seconds is the capacitance in thousands of uF.
There are available graphing type meters, and also digital meters, with capacitance function.
Do a search, the price is modest, buy one if you feel it will be useful.
Do a search, the price is modest, buy one if you feel it will be useful.
Hello all,
Thank you for your guidance and suggestions. My main concern is that the caps were shorted. based on techtools response, it appears this is not the case (thanks!). My fuse keeps blowing pretty much immediately after powering on the amp and I'm trying to hunt down a short somewhere. My first step was to replace the original filter caps with these mundorfs, but the fuse keeps blowing. I then replaced the output transistors...and the fuse keeps blowing. So with the "usual suspects" replaced, I'm trying to check component by component for a short.
Thank you for your guidance and suggestions. My main concern is that the caps were shorted. based on techtools response, it appears this is not the case (thanks!). My fuse keeps blowing pretty much immediately after powering on the amp and I'm trying to hunt down a short somewhere. My first step was to replace the original filter caps with these mundorfs, but the fuse keeps blowing. I then replaced the output transistors...and the fuse keeps blowing. So with the "usual suspects" replaced, I'm trying to check component by component for a short.
Did you heck the power supply diodes for shorts?
And sorry, I stand corrected on the Fluke OL.
My 110 does read OL with a short.
I have another brand meter that reads zero with a short and overload with a too large cap, so it does depend on the meter.
You can check the cap for short with a resistance measurement when it's out of the circuit.
And sorry, I stand corrected on the Fluke OL.
My 110 does read OL with a short.
I have another brand meter that reads zero with a short and overload with a too large cap, so it does depend on the meter.
You can check the cap for short with a resistance measurement when it's out of the circuit.
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That makes me wonder how a meter can tell the difference between an empty capacitor with an exceedingly large value and a short.
I use a simple analog meter in resistance x1 scale to check capacitors, the meter goes towards short as the cap charges, and back as it discharges.
It tell me if the cap is working or not, but not the value, for which I have to use another meter.
https://www.ebay.com/itm/2542827007...customid=eeeb35c4-7548-11ee-88e2-333936323039
This seller is selling part kits, and says the original caps are under rated, which may be bull excrement.
So, find the manual, put the original rated caps if needed.
And use a series lamp, and if the other members agree, put a NTC resistor in series to limit surge inrush, and a MOV across the supply as well, it will provide arcing and high voltage protection.
Also, tell us more about the issues you faced, which made you decide to attempt servicing the unit...it was not sold in large volumes, and is expensive.
May not be a simple repair...
It tell me if the cap is working or not, but not the value, for which I have to use another meter.
https://www.ebay.com/itm/2542827007...customid=eeeb35c4-7548-11ee-88e2-333936323039
This seller is selling part kits, and says the original caps are under rated, which may be bull excrement.
So, find the manual, put the original rated caps if needed.
And use a series lamp, and if the other members agree, put a NTC resistor in series to limit surge inrush, and a MOV across the supply as well, it will provide arcing and high voltage protection.
Also, tell us more about the issues you faced, which made you decide to attempt servicing the unit...it was not sold in large volumes, and is expensive.
May not be a simple repair...