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Old 15th April 2011, 08:53 AM   #11
audiom is offline audiom  New Zealand
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You cannot be certain the fault is in the speakers until you have eliminated everything else. Your first test should be to swap the speakers from one channel to the other and see if the perceived lack of treble follows the swap.If it does then the fault lies in the speaker.If the fault stays in the same channel regardless of whether you swap or not, clearly identifies the problem as in the amp/pre-amp area.
It is absolutely pointless in trying to fix a problem (in the speaker) if the problem actually isn't there! The above test will confirm the above.
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Old 22nd April 2011, 06:41 PM   #12
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Quote:
Originally Posted by wolfiesn View Post
1. The wiring had been replaced with a flat copper cable (brand unknown)
2. There was (in the vicinity of the treble centre panel) a series of coronal arc discharges upon powering up.

Again, no damage to any panel is evident.

The arc discharges you observed is your evidence of panel damage. How can you say that no damage is evident when you can't see inside the panels? I'll bet you that if you split that treble panel open, you'll have a nice arc through the diaphragm that has blackened and melted both stators in that region. Look for darkness in one of the stator holes in that region. The outside of the treble panel is not the "business end", it's what's going on inside that matters.


Sheldon
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Old 23rd April 2011, 08:46 PM   #13
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I agree with sheldon, it sounds like your treble panel has a short circuit. You can actually measure this. Unsolder the brown and blue wires from the bottom of the step-up transformer (remember which goes where). Measure the resistance between the two brown wires and between the two blue wires. One of them will probably read a low value (they should read open circuit).
If you find no short there hook up a capacitance meter. Between the brown wires you should measure something like 160-180 pF and between the blue something around 300 pF.
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Old 24th April 2011, 10:39 AM   #14
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Too many unknowns here. Were the discharges inside the treble panel, behind the covers? Were the arcs seen from the "flat copper wire" to some other point near the treble panel?

I think - sort out the wiring with good HT leads, check the HT supply and then try the speakers. This is really easy to do. Dismounting a panel or order a new one might not be the first to go for.

Of course, switching the speaker wires from right to left speaker and left to right speaker, would be my first try, as was mentioned earlier.
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Old 5th May 2011, 09:34 PM   #15
tmblack is offline tmblack  United Kingdom
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Is there a diagnostic test to determine which panels are bad (woofer, treble, woofer)?
Any simple tests we can do without opening the speaker up to determine if HVS, transformer is bad?
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Old 6th May 2011, 10:32 PM   #16
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There is no reliable test without opening the speaker, but what you can do to find out "big problems" can be:

- Listen to all four bass panels (stereo set) at the same distance - say 4 inches away. They should sound equally loud regardless of panel and at which location on the panel you put your ear.

- Listen to the middle section, i e treble section and mid section. Since it will be very difficult to judge if there is a problem with the mid sections or treble section, you can be fooled to think the panel is ok, but it is not. Listen at various heights from bottom to top of the speaker. The sound should be equally loud from each position.

If there is a large difference in sound level when you move your ear around over a panel, you probably have a severe short-cut inside the panel. Typically, the bottom of the speaker is working while the upper top parts of the panels can be "dead". The other way around is not very likely since the panels have there connections at the bottom.

Also note that the active panel surface does not extend all the way up to the top of the grille - it typically ends two inches down. So, don't be alarmed if not the entire area has a good sound level.
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Old 9th May 2011, 04:47 PM   #17
tmblack is offline tmblack  United Kingdom
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I will try to open up the panels to get to the supply. Can this be done by just removing the back?
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Old 9th May 2011, 05:32 PM   #18
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Yes
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Old 9th May 2011, 06:36 PM   #19
tmblack is offline tmblack  United Kingdom
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I'm considering rebuilding the treble panel. Would this work?
Electrostatic Speaker Membrane Dupont Mylar C 12um 20M
Electrostatic Speaker Membrane Dupont Mylar C 12um 20M on eBay.ca (item 120630202315 end time 02-Jun-11 08:48:21 EDT)
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Old 9th May 2011, 06:39 PM   #20
tmblack is offline tmblack  United Kingdom
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What capacitors should be in the HV block?
The schematic shows 0.01uF but some sites recommend 0.001uF?
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