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Old 8th September 2013, 06:45 PM   #21
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Hi all,
once again, my ML CLS is finally working, but i will like to know
1- what should be the HV, i measured 1370 Vdc
2- one speaker is sounding weaker then the other, taking in consideration the age about 27 years what should be replace? the capas from the input filter, resistors, high voltage components, ect?
cheers,
Williams
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Old 8th September 2013, 09:24 PM   #22
tyu is offline tyu  United States
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tyu...posted

An for the bias V........i was told buy Mr Jim Powers.... who worket at ML........ at one time CLS were at 4,5k........but then ML rolled them there panels down to 3.6k......an thats were thay are today..........
John65b may have put more bias on his re-worket CLS panels an thay worket fine.........right john??


jhon65...posted
I ran Acoustat Interfaces on my used CLS II panels and sound was very good - higher bias (~5kv) and better transformers than the CLS II I/F. Much better SPL and bass too.

My original CLS panels are being re-mylared...a project that keeps getting pushed back.

I think ML reduced bias for reliability reasons. I do not know if my higher bias would shorten life of my panels.


............As for the caps an res.......yes thay can be upgreaded...but get the bias UP!
...have fun...good luck
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Old 9th September 2013, 12:21 PM   #23
john65b is offline john65b  United States
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Yes, I think the CLSII bias was reduced to 3.5kv from 5kv. I am using over 5kv now with Acoustat interface, but they are in storage.

Check bias on both interfaces to see if the same. If bias is the same (and 3.5kv), you can rule out bias and look to step up transformers, stator leaks, bad bias charge ring, coating...

You Are you using a high voltage voltmeter?

Are your panels starting to separate? Mine were separating real bad. As you know, the when the stators start to separate, they lose spl as the stators are further apart...
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Old 18th September 2013, 09:09 PM   #24
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Hi all,
thanks a lot for the advices!
it is correct the HV bias is about 3.8kv, i had to make a voltage divider to test it.
now it works fine,,,,,, it is detailed, but sounds a bit too strident.
do you think is worth to try changing or tuning the equ. filter?
Cheers,
Williams.
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Old 19th September 2013, 12:55 PM   #25
tyu is offline tyu  United States
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Thanks for your findings...................let us know your thinking as you move on with the setup....................
i setup a bias that i can set....4k-7k............if to much bias.......... it can make the sound strident..................might pull back..............like 3k-3.3k......i know you got what 15m ohms.....are more at the end of the diode string........... right befor the panels?

good luck
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Old 19th September 2013, 05:22 PM   #26
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hi all,
yes are 2 resistors of 15 mega ohms, i think are in serial connection
i think that increasing this resistance will reduce the current and the high voltage applied to panels.
how it will affect the HV bias the sound, from your experience?
is any smart to readjust the input filter?

cheers,
williams
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Old 22nd September 2013, 10:31 PM   #27
X83 is offline X83  United States
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Quote:
Originally Posted by Williams Audio View Post
hi all,
yes are 2 resistors of 15 mega ohms, i think are in serial connection
i think that increasing this resistance will reduce the current and the high voltage applied to panels.
how it will affect the HV bias the sound, from your experience?
is any smart to readjust the input filter?

cheers,
williams
Don't omit the resistors at the end of the output of the supply! It is there for three reasons. First, it insures that you can't get enough current out of the power supply to hurt you. Second, it helps force the speaker to operate in the "constant charge" mode. Third, it helps minimize damage to the speaker in the event the diaphragm comes into contact with one of the stator panels.

If you need to calculate the voltage & current output, just use an ohms law calculator: Ohm's Law Calculator

I just ordered a few Vishay VR68 1W 10kV metal film resistors in various M-ohm values to experiment with my Monolith-III speakers which have four 15M-ohm 1/4W resistor in series.
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Old 23rd September 2013, 12:13 PM   #28
john65b is offline john65b  United States
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Just put another cap/diode in the chain. It will add another 750v.

Whoops - the power tranny secondary on the Acoustat interface is 750v - I don't remember what it is out of the CLS interface...whatever that secondary voltage is, adding another diode/cap will raise Bias voltage by that much.

If I remember correctly, there are places already on the PCB that you can add another diode and cap. The diodes in that power supply PCBs were 1N4007 (doubled up?)
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Old 5th October 2014, 12:48 PM   #29
Studley is offline Studley  United Kingdom
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Hope I will be forgiven for reactivating this thread and taking it in a new direction. I am looking at the possibility of DIYing some CLS 11A or Z. I would obviously be forced to buy new panels from ML. The the other tricky bit is the transformers, particularly the audio transformers. ML charge a lot of money for a set of transformers so I was wondering whether I could identify the manufacturer and buy them direct as I suspect they would be a good deal cheaper. Can anybody help me identify the manufacturer?
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Old 5th October 2014, 06:26 PM   #30
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Hi,
My model is the oldest CLS
i made some measurements with a voltage divider and
1- the audio TRAFO ratio is 1:100 nominally, frequency depended.
2- the HV supply to panel is 3800vdc
3- Plitron Canada and Elliot projects from Australia have some TRAFOs for this.
Maybe this will help a bit.
Cheers,
Williams
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