Martin Logan CLS IIz -- capacitor replacement

There is potential to replace the HV capacitor in the CLS IIz speakers.

There is one Electrocube brand high voltage capacitor in the CLS IIz speakers -- in different units I've noticed there are either a set of 0.005µF capacitors in parallel (to equal 0.01µF) or a single 0.01µF unit.

side note:
For high frequency use (e.g microwave, over 1GHz) there are advantages to using capacitors in parallel, such as reduced ESR. For audio -- well, it's something you could try.

The specs for the Electrocube capacitor:

electrocube miniature HV capacitors, 520-series

If you care to replace this capacitor, here is one option:

Allied Electronics -- ASC 16kV 0.01µF

$10.82 each. They also have 0.02µF units in stock for $12.93 each.

Manufacturer website

Vendor datasheet - X675 series metallized polyester tape wrap and epoxy fill case

Web searches for other HV capacitors show that there might be other brands with similar capacitance and voltage rating that may be suitable for substition. Note that placing multiple lower voltage value capacitors in series can increase the voltage rating of the string but good engineering practice would include equalizing resistors -- which may adversely affect the ESR rating of the string.

Mon Aug 25 16:32:33 CDT 2014

Another suitable capacitor:

Illinois Capacitor 103MWS103KT -- 0.01uF, 10kV

This is stocked via several distributors. It is approximately the same size as the Electrocube unit that it is replacing in the CLS IIz.

Again note, there is no bleeder resistor on the 10kV circuit. I used a 100x voltage probe to check voltage prior to start:

My meter indicated 1400V for a speaker that was previously plugged in but not in use. I discharged this down to zero prior to working on the speaker. If you do not have the ability to measure and discharge I would suggest leaving unused speakers unplugged and disconnected for at least two hours prior to starting any work. If the speakers have been recently run, I would wait significantly longer. Even then, check with your regular voltmeter on the highest voltage setting to ensure that the capacitors are discharged to zero volts prior to starting any work.

This modification required minimal disassembly. I used the Metcal to heat the connection to the existing capacitors and used a solder sucker to remove the initial solder. Once the capacitor was removed, I again used the solder sucker to clean the via. Note there is some aggressive double-stick tape under the original capacitors. Due to the plastic label the original capacitors can carefully be removed cleanly and the original double-stick is sufficient to hold the new capacitors down.

The black Solen capacitor is completely bypassed in the 'flat' setting or with the jumper installed and has no effect on audio.

This page last modified Mon Aug 25 21:36:59 CDT 2014 by timc!

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