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Old 22nd June 2011, 07:17 PM   #31
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Hi All.

I have the same problem as the topic starter:

One of my ESL 57's has a reduced output.

First i though it was the EHT unit.
I rebuild both power supply's an they work like a charm.
Unfortunately this didn't solve the problem. Still one panel has a much lower output.

I measured the voltage on the power supply. When the the treble panel is connected, the voltage drops to 225V instead of 1200V.

My first conclusion: the problem is in the treble panel.

I measured the resistance of the treble panel:
Both blue and brown measure with one multimeter nothing, with the other between 1,5Mohm and 2,5Mohm.
The capacitance is 160pF and 280pF.

I Also measured the bass panels: no resistance and around 550pF.

i am confused....

Does anybody know what the issue could be?
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Old 22nd June 2011, 08:55 PM   #32
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If the voltage drops when you hook up the treble panel to the power supply then the logical conclusion would be that it has a short between the charge ring and the stators. So between the red wire and one of the blue/brown wires. Did you measure those resistances?
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Old 22nd June 2011, 09:15 PM   #33
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Yes i did, al of them have a to hi resistance to measure
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Old 22nd June 2011, 10:31 PM   #34
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Here's a quick and dirty trick to see where the short lies. Unbolt your audio transformer and flip it over in place (assuming your treble leads are long enough). Unsolder your blue and brown treble wires one at a time, and watch your HV. Also if you don't have a HV probe, hthen you can just bring your unsoldered wire to the terminal slowly. The non-shorted wires will produce a small arc just before touching. The bad section will arc much more loudly and farther away.

Sheldon
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Old 24th June 2011, 07:43 AM   #35
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Thanks for the tip. I will check that today.

I double checked and the problem lies in the treble panel.
When the treble panel is disconected from the power supply, the low panels preform excelent.

This will probable end up in a revision of the treble panel
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Old 27th June 2011, 05:28 PM   #36
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So.

I did the suggested test, and with result:

When the bleu wire is desoldered from connector 12 (the bottom connection point with the resistor and capacitor parallel) the voltage is around 1200V as it should be.

I measured the components and windings of the audio transformer and they look ok.

conclusion, bad high section. Time for some refurbishment, or am i missing something?
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Old 8th July 2011, 03:21 PM   #37
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I'm willing to put money on it that your treble panel has arced somewhere. Perhaps if you look very carefully (peep through all the holes from all angles, using a torch) or perhaps it's not visible from the outside.
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Old 11th July 2011, 08:22 AM   #38
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I am going dismantle the panels next week an the plan is to get them refurbished next month (i don't have the time, and gear to do it wright).

The other panel (the working one) has a black spot on the dust cover, so this one has a clear arcing trace.

I will get both panels refurbished, also keeping the matching of the two panels in mind.

Thanks for all the help.
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Old 14th July 2011, 06:19 PM   #39
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hello there in diy land.... i'm sitting here listening to my new/old Radford sta15 valve amp (original/unmolested/good condition) and Quad esl57(last serviced by quad in 87), just delivered to my door for 750 all in.... wonderful sound, plenty of bass (i'm used to PMC tb1 monitors/musical fidelity a3 amp). whats all the nonsense... i.e. bass light, small sweet spot, need large room?

i've got the volume set at the loud side of just right (so maybe a little louder would be needed sometimes. but that little bit louder is where one speaker starts to break down, slight crackle/pop... then a rasping clicking (seemingly a bass panel.. cos bass heavy passage brought it out).. for now i'll keep the volume at the perfectly usable volume where the sound/bass/treble are all fine/great really.

any comments?...

i know they need work... but they should be ok for a while ? they sound so good/even as they are.
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Old 14th July 2011, 11:03 PM   #40
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done a bit of reading and....these symptoms are more like treble panel?
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