Quad ESL-63 fault, please help

[tatchoune]

Hi,
I've a pair of Quad ESL-63; they sound very well, but one of them gives a lower sound (about -10 dB) than the other.
I've no experience with those loudspeakers, have you an idea about the reason of the fault ? I tried at different frequencies and levels, and the symptom is the same.
Thanks in advance.

[ramallo]

Probably you have a failure on a high voltage supply, this link can help you

[tatchoune]

Thanks for the reply.
But I forgotten to tell that when power supply is "off", the ouput volume of the defect loudspeaker is also lower than the other. Naturally, there's a big distorsion without the high voltage but the difference of volume stays.

[woodturner-fran]

Most likely you have a dead panel that's pulling down the high voltage....

[tatchoune]

When I disconnect the power supply, sounds remains a very long time. When I try to find a defect pannel with my ear near the grill cloth, I don't find any difference on any pannel...

[Mike Beck]

For the speaker that has low output: Remove the rubber plug that sits close to the mains power socket. Beneath this plug is a small neon lamp that flashes every time the panels pull more charge from the power supply. The normal flash rate is around 1 flash every couple of seconds to as long as once every 10 or more seconds. if the lamp is flashing faster than once per second or is on continuously, high voltage leakage is occurring indicating a problem panel.

[tatchoune]

I measured the high voltages and they're the same on the 2 power supplies (a little difference of about 7 %).
I tried to see if some pannels are defect, by sending 2 hz square signal at a low level; while looking with a focused beam coming from a big Maglite LED torch, I can see the reflexion moving in relation with the signal. On the "good" loudspeaker, I can "see" a big signal coming from the right pannel, and a much lower signal from the other pannels. On the "bad" loudspeaker, a signal can bee "seen" on the right pannel too, but lower than from the "good" loudspeaker, and a very little signal coming from the other pannels.
I'm thinking all the pannels aren't rather good to replace only one or two. When I would have replaced the bad pannel(s) on the bad loudspeaker, there is a good luck that it would sound better and louder that the other... and the probleme would be reversed.
The pressure level is very very low with 60 watts rms in the input. Less than 95 db I think.
Does anyone know the price for a complete replacement of the pannels ?
I looked too at the neon lamp, it flashes rarely (15-20 sec).

[Mike Beck]

2 Hz is too low for a practical test since this is nearly DC. The ESL63 rolls off in the 30-40Hz range so not much signal will get through. 100Hz would be a good test frequency since all panels will be driven in phase at this point. You could use an SPL meter to see if any panel were defective and for comparison to the good speaker.

[ramallo]

If the power supply are ok, maybe the problem is a panel.

95dB SPL is the max level you can achieve.

P.S. In one of my Quads (2805) I had a problem with the resistor-capacitor input filter, the resistor was incorrect and due this problem the level dropped, but was a factory mistake

[woodturner-fran]

I have a service manual for the 63s - drop me an email if you want it.

Its worth going over all the connections and making sure that each is intact. I understand that its usually the bass panels that go, rarely the centre panels. You could also see what output you are gettiing from each panel - that might point you towards the bad one.

I think also the panel can look fine, but have degraded and become "leaky".

Can I ask how you measured the voltage? Do you have a HV probe?

Fran