Slow loss of sound in the CLS panel... - solved.

[Martynka]

Hi,

A few months ago I started hearing an imbalance in the soundstage. The soundstage was moved to the right side. I checked and adjusted the BIAS in power amplifier, I checked the same in the preamplifier and everything was OK. I thought maybe there was something deeper in the preamplifier and I started listening to music with the balance knob into the left.


Everything changed when I bought a new integrated amplifier. One big piece of tubes, Ayon Triton with 8 x KT150, only direct sound, without... a balance knob. Because my favorite source is my custom DAC that I built, I started using software balance. I saw on the computer screen that the soundstage is centered when the right side is turned down to 70% (oh f*** ). I didn't expect such degradation. It's time to get ready to change the foil (but my foils are not old at all). Since the foils are waiting to be replaced, why not experiment, I won't lose anything, if I kill them, I will replace them faster.

In the same time my friend had the same problem with Odyssey, His ML were after refoil and few month later sterted to lose power in one panel. He resent it to workshop in Germany and panel was repaired with description " problem was with oxydation ". I started to connect this two, CLS and Odyssey problems and....

1) I disconnected the electronics from the panels and swapped them. Problem was still in left panel. Transformers and all passive elements inside "black box" were ok.

2) I checked 2 wires ( green and black ) from connector to the panel stators. No problem in this part.

3) Red wire - from PCB conector to the foil... I checked continuity of the wire from the connector to the foil entrance (multimeter probe with a thin and sharp tip inserted into the wire insulation). No problem.

Problem was in foil sourface or red wire - foil connection. I started to search how it is connected inside and... this wire is only wrapped in foil.

( photo from internet )

I thought that maybe here is problem, maybe oxidation and problem with connection.

I dissasembled panel from the frame and decided to deoxide red wire connection.

I checked red wire installation, probably the same like on internet photo because I can move wire about half inch fom inside to outside.

I put inside stator near red wire, thin pipe with deoxidant and spray it,

after this I use in the same way isopropyl electronics cleaner. Few minutes later when cleaner flowed out and evaporated I put inside one more time contact spray.

Asembly everything, connected and... I was shocked. Sound started to back to left panel. First to 80% anfter one day to 90%....

One week later I repated it. First contact spray, after that I moved wire up and down, after that iso cleaner and moved too, and finish with contact spray. I rotated slightly wire to give more contact to the foil and assembly everything.

I gave time for evapurated sprays and few days later start measured sound with db meter... OMG I repaired CLS panel. sounds perfect. Clear hi tones back to left panel and soundstage is balanced and huge.

 

[Jazzman53]

It's always better to solder the bias supply wire to the copper foil charge ring. Here's how I do it:

 

[Martynka]

It's always better to solder the bias supply wire to the copper foil charge ring.

But only when you removed front stator. My method can be use with fully assembled panel

 

[Jazzman53]

But only when you removed front stator. My method can be use with fully assembled panel

Question (just curious, since I've never worked on a ML panel):
Do you know whether or not the front stator can be removed without damaging the diaphragm, or is it too well bonded to allow that?

 

[Martynka]

Do you know whether or not the front stator can be removed without damaging the diaphragm,

On earlier CLS, yes but nobody give you 100%. On CLS II is harder to remove stator without damaging diaphragm ( my friend tried 2 times without succes.

 

[Robert D]

Question (just curious, since I've never worked on a ML panel):
Do you know whether or not the front stator can be removed without damaging the diaphragm, or is it too well bonded to allow that?

Russ Knotts that does lots of panel rehab told me my Prodigy panels were bonded too much and chances were high he'd damage the mylar trying to separate them. Mine were made in 2000.

 

[Jazzman53]

Thanks for the info. I'm asking because I will be remotely assisting someone with refurbishing a pair of dead panels. I have extensive experience building wire-stator ESLs but I've never worked on ML panels. I figured the CLS panels would be fully bonded because they appear to have a compound curvature(?), whereas the hybrid ML panels appear to simple curvature, in which case there is no compelling reason to bond the entire periphery--- just speculating.

 

[Jazzman53]

But only when you removed front stator. My method can be use with fully assembled panel

My point was that the problem would not have occurred had the bias supply wire connection been soldered rather than wrapped. There's really no reason not to except that it would add several labor-minutes to the fabrication.

 

[Robert D]

My point was that the problem would not have occurred had the bias supply wire connection been soldered rather than wrapped. There's really no reason not to except that it would add several labor-minutes to the fabrication.

I wonder if ML newer panels are like that?

 

[Jazzman53]

I wonder if ML newer panels are like that?

I doubt that ML is soldering the wire lead to the foil strip--- but I'm just speculating (I don't know that). Apparently it's not a huge problem or we would hear about it more often.

As an ESL builder, I consider it a no-brainer to solder the wire to the foil strip, and also extend the strip around the entire periphery of the panel.

At least ML adds a copper foil contact strip now to increase the contact area (apparently they didn't always do that).

Below is a ML build video posted eleven years ago. I don't see a copper foil strip at all-- just a stripped wire taped onto the diaphragm.

At 1 minute 26 seconds into the video you can see the technician attaching the bias supply wire to the diaphragm.