Quad ESL 57 panel refurbish: DIY or not?

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Franz Gysi

Member
2007-10-28 9:29 am
Since about 10 days I am a happy owner of two Quad ESL 57 loudspeakers in very good optical condition (including dust covers).

Serial numbers 30509 and 30510!

I replaced the diodes in the HV supply in both panels .

One speaker is now working very good considering its age: 38 years.

The other speaker has one bass panel not playing. The second bass panel of this speaker is very low in level.

I will investigate further.

Here a picture of both panels on new stands (not finished, one panel still has the original feets attached and the "old" horn speakers are still ready for backup...)

An externally hosted image should be here but it was not working when we last tested it.


When I now decide to use this speakers for the rest of my life, I have to make the decision:

Should I save money to let refurbish the panels by Quad Musikwiedergabe in Germany? They use the original equipment to do this job.

Or should I learn to refurbish ESL panels? Build a rig and all this stuff?

Will I have a stable and consistent result from my diy work? Will it be worth all the effort?

@Calvin: did you receive my two mails from oct 13th and 14th, about replacing the diodes? It was the first step for me, to really be in contact with the innerts of this speakers, believe me!

BTW: I drive the ESL 57 actually by an F5, it seems to be an ideal amplifier for this speakers. I will later compare the F5 as driver with the two Quad II monoblocks I also own.

And the ESL's are supported by a professional JBL 350W subwoofer (the black box behind the left panel).

Regards
Franz
 
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hafp

Member
2008-02-05 10:17 pm
DIY Quad ESL rebuild

I have had good results with DIY rebuilds on Quad ESL's.
There are several companies that sell good all in one panel rebuild kits, as well as parts; or you could probably source them on your own.
There is many Quad ESL DIY websites, which you probably are aware of.
IMO - the best company I've delt with in the past 10 years for repair kits is ER Audio in Australia. They sell a complete rebuild kit and have great support, but they don't use the exact same materials that Quad did 40+ years ago.
Good luck.
 
My experience is that the bass panels seldom fail. They might not get the 6 kV polarizing voltage, or there is a loosy terminal-to-diaphragm contact.
I permanently connected small wire lead neon bulbs in series with the polarizing voltages on the PSU block (both on 1.5 kV for the treble and on the 6 kV for the bass - the latter could be done separately to each bass panel) so I can visually detect any leakage as neon light blinking.
 

Franz Gysi

Member
2007-10-28 9:29 am
Yes, I also plan to install blinkers to control leakage.

My intention was to use the same circuit as used in the ESL 63: a bulb with a cap in parallel and inserting a protection resistor.

What type of neon bulbs do you use?

I agree: it is hard to believe, that the bass panel failed.

I will investigate further.

One bass panel of this speaker is playing on low level, the other is silent.

Franz
 

Franz Gysi

Member
2007-10-28 9:29 am
I replaced also the two resistors by new ones and double checked the wiring and soldering points.

It is hard to believe, something should be failed in this panel, when I look the nearby mint condition:

An externally hosted image should be here but it was not working when we last tested it.


But, there is an UFO inside the dustcovers:

An externally hosted image should be here but it was not working when we last tested it.


I will now take the HT-supply out of the working speaker and test the faulty speaker with this HT-supply.

Franz
 
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In my experience, the diaphragms themselves rarely fail, but the coating on them is often gone or marginal. The soluable nylon they used as a conductive coating wasn't particularly good and dissipates over the years. I've seen many bass panels where the bottom half charges and the top doesn't.

I also second the recommendation on the ER audio kits.

Sheldon
 

hafp

Member
2008-02-05 10:17 pm
In my experience, the diaphragms themselves rarely fail, but the coating on them is often gone or marginal. The soluable nylon they used as a conductive coating wasn't particularly good and dissipates over the years. I've seen many bass panels where the bottom half charges and the top doesn't.

I also second the recommendation on the ER audio kits.

Sheldon

Franz,
Since you already tore into the 57's and seem to know the layout pretty well, it would be best to do the complete panel rebuilds now and save time and effort of putting them back together and breaking them down every time you hear an issue...

Sheldon (stokessed) is the man (IMO) when it comes to Quad ESL's, so take his advice as word.
I don't have any association with him, but have owned Quads that he rebuilt the panels, and his work was top notch.
Once you get the panels completely rebuilt, you will not have to worry about them for years, unless you get too crazy with the power amps.
The neon light circuit adapted from the 63's sound like a great idea too.

Good Luck.
 

Franz Gysi

Member
2007-10-28 9:29 am
Franz,
Since you already tore into the 57's and seem to know the layout pretty well, it would be best to do the complete panel rebuilds now and save time and effort of putting them back together and breaking them down every time you hear an issue...

Sheldon (stokessed) is the man (IMO) when it comes to Quad ESL's, so take his advice as word.
I don't have any association with him, but have owned Quads that he rebuilt the panels, and his work was top notch.
Once you get the panels completely rebuilt, you will not have to worry about them for years, unless you get too crazy with the power amps.
The neon light circuit adapted from the 63's sound like a great idea too.

Good Luck.

Yes, I think so, it would be the best solution to do all work at the same time.

BUT: there is also a financial aspect.

I could refurbish both Quad II amplifiers I own, sale it and use the income to refurbish the speakers.

BUT: I also want to compare the Quad II to my F5...

I am also aware, that I have to take the advice from Sheldon as an expert advice.

Thanks for all advices up to now in this thread, Guys!

And still: I am a DIYselfer and I try to find the fault. Maybe it encourages me to do panel rebuilds by myself.

Another good contact is Jan-Arend, I heard his Quad ESL57 at the ETF 08 and they are very good.

Franz

/Edit
At the moment I am listening to Roger Waters "The pros and cons of Hitchiking" from Vinyl, Eric Clapton on Guitar, Salas RIAA pre, F5, 5/6 Quad ESL: Great! I will stick with this ESL for a long time, I am sure!

/Second Edit:
Any idea from where the UFO could origin? Some small ring, obviously made from metal.
 
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Yes, I also plan to install blinkers to control leakage.

My intention was to use the same circuit as used in the ESL 63: a bulb with a cap in parallel and inserting a protection resistor.

What type of neon bulbs do you use?

I agree: it is hard to believe, that the bass panel failed.

I will investigate further.

One bass panel of this speaker is playing on low level, the other is silent.

Franz
Franz,

I used NE-2 type bulbs without any resistor or capacitor, same as depicted here:

Neon lamp - Wikipedia, the free encyclopedia

Did you try swapping the HT block from the working to the non-working unit? You wrote that you replaced the diodes (why was it necessary?), so you never know...

I have one other idea. Since the stator of the bass panels is metallized outside (unlike the mid/treble panel that is metallized inside), you can test the continuity from the left/right binding posts and the front/back surface of the stator. You just need to remove the dust cover and scratch the grey paint a bit. Or you can puncture the dust cover with a needle at the top corner, easy to undo. The metallization is on "islands", it is missing where the HT goes to the diaphragm (from the red wire on the middle binding post).

BTW the dust covers in my original units were painted grey. Since it is transparent on your units, could it be that yours have been already repaired? This could explain the small washer. Anyway, you are lucky if the mid/treble panels are OK, since they are much more difficult to repair than the bass panels.
 

Franz Gysi

Member
2007-10-28 9:29 am
I have one other idea. Since the stator of the bass panels is metallized outside (unlike the mid/treble panel that is metallized inside), you can test the continuity from the left/right binding posts and the front/back surface of the stator. You just need to remove the dust cover and scratch the grey paint a bit. Or you can puncture the dust cover with a needle at the top corner, easy to undo. The metallization is on "islands", it is missing where the HT goes to the diaphragm (from the red wire on the middle binding post).

Many thanks for this explanation!

Now, I understand how the stators are built. What material are they made from?

I changed the diodes in both speakers I own and it is the planned next step to take out the HT supply from the working speaker and test it on the faulty one.

After that, I will examine the faulty panel in more detail.

No, I dont think they are repaired before, as it seems that the front cover was never removed.

Franz
 

Franz Gysi

Member
2007-10-28 9:29 am
Thanks, very informative link!

I can imagine a contact problem with the rivets connecting the signal/polarizing voltage to the stators.

Specially when I know now, the stator panels are made from some kind of thermoplast.

Could the UFO be a part from this rivet/contact assembly?

Next weekend, when I have free time, I will first move the HT supply from the working speaker to the faulty one. Before I punch the dustcovers.

And when this does not cure the problem, I will check the stator connections as you described, punching the dustcovers with a needle.

Kind regards
Franz

/Edit
do you think, it is better to make the needle hot to melt a hole?
 
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Franz,

I used NE-2 type bulbs without any resistor or capacitor, same as depicted here:

Neon lamp - Wikipedia, the free encyclopedia

Did you try swapping the HT block from the working to the non-working unit? You wrote that you replaced the diodes (why was it necessary?), so you never know...

I have one other idea. Since the stator of the bass panels is metallized outside (unlike the mid/treble panel that is metallized inside), you can test the continuity from the left/right binding posts and the front/back surface of the stator. You just need to remove the dust cover and scratch the grey paint a bit. Or you can puncture the dust cover with a needle at the top corner, easy to undo. The metallization is on "islands", it is missing where the HT goes to the diaphragm (from the red wire on the middle binding post).

BTW the dust covers in my original units were painted grey. Since it is transparent on your units, could it be that yours have been already repaired? This could explain the small washer. Anyway, you are lucky if the mid/treble panels are OK, since they are much more difficult to repair than the bass panels.

I confirm that bonding between metallized zones can fail. This happened to s.o. I know.

What do you mean by much more difficult to repair a treble than a bass panel ?
Indeed it requires more weights. And some heat setting can be applied as an option. But basically it is the same process isn't it ?
 

Franz Gysi

Member
2007-10-28 9:29 am
Quad fan !

I subscribe immediately this statement.

When I come back tired from work and other things :confused:

I switch on my ESL's and relax.

Even with one bass panel not working but the very low level supported by the JBL sub (yes, the soundstage is not perfect, yet, but I dont sit in the sweet spot anyway).

Such a clearness and without any coloration, absolutely no listening fatigue.

Relaxing and reactivating long forgotten emotions...

And my cat: she never turned the ears to my old speakers so many times as with the Quad's. Specially human voices are always attracting her (she worries about unkown people in the flat as she is very very shy).

Franz
 

Franz Gysi

Member
2007-10-28 9:29 am
Today, I had time to work with the faulty basspanel.

I've built a completely new high tension supply (covered with bees wax later):

An externally hosted image should be here but it was not working when we last tested it.


This supply includes neon bulbs, one for the treble panel and for each bass panel one separately.

Immediately after switching on the first time, I have seen the two bass panel bulbs flashing several times with decreasing frequency.

After one or two minutes, no more flashes could be observed.

I turned on music. In the first moment, I thougth having solved the problem: both bass panels where playing at very low level, while the treble panel still was silent.

After 10 to 15 minutes, it was obviously not having solved the problem as the left bass panels gots louder and louder while the other one remaines at very low level.

The treble panel is still charging with a the bulb flashing about once per minute and is playing now at good level.

I give it time to charge till tomorrow. Should the problem with one bass panel not be solved then I will start to investigate the panel and possibly perforate the dust cover to do some measurements.

Franz
 
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Franz Gysi

Member
2007-10-28 9:29 am
BTW:

I measured the originial (but revised) power supply and compared it to the new build.

To do the measurements, I made a voltage divider 99Meg / 1 Meg and I fed the circuit by 6VAC instead of about 600VAC.

Both measurements showed about the same results:

0,14VDC for the treble panel and 0.32VDC for the bass panels.

I think this is in the green area, with the voltage divider 1:100 (to be exactly, 1:99).

The Cockroft Walton cascade is to heavy loaded and therefore showing the voltage drop in the higher voltage output of the psu.

Franz
 
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Use a digital VOM and measure the drive voltage to the panels. Set the amplifier to 1VRMS. You should measure approximately 280VAC across the bass stators. If this voltage is low, disconnect 1 wire from the stator and remeasure. If the voltage is normal, the stator has a problem...perhaps the conductive coating has failed. Otherwise the problem is the transformer or a series resistor.
 
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