[chinsettawong]

You should go and ask the experts here: https://www.diyaudio.com/forums/planars-and-exotics/

 

[WallofHooligans]

What you recommend to do to fix old speakers that I trying to restore.
Qued esl 57
makes a lot of scratches noise on middle and high volumes.
though about:
1- check the bias voltage
2- check the electricity
3- recoat the diphrgm with antistatic spray
4- Try to open it and Strach the diaphragm better, or put another one.
may glade for any suggest where to start
thanks for any help =D

Whoa. Uhhhhh Do us a favor and be really careful with that stuff- 1 because these are nice rare speakers and 2 because they are biased with speaker voltages which are quite high and dangerous.
I would honestly suggest that you start smaller and work your way up. Find success in easier projects then move up to something like this.

 

[XLR8]

What you recommend to do to fix old speakers that I trying to restore.
Qued esl 57
makes a lot of scratches noise on middle and high volumes.
though about:
1- check the bias voltage
2- check the electricity
3- recoat the diphrgm with antistatic spray
4- Try to open it and Strach the diaphragm better, or put another one.
may glade for any suggest where to start
thanks for any help =D

Look for any obvious holes and patch with scotch tape.
Aside from that, if it's voltage related and again the voltages are dangerous with quad electrostats, then unless you have someone local who does refurbishments, then it's time to get rid of them sadly.

 

[legopart]

Look for any obvious holes and patch with scotch tape.
Aside from that, if it's voltage related and again the voltages are dangerous with quad electrostats, then unless you have someone local who does refurbishments, then it's time to get rid of them sadly.

In the most bad case I can strech another cheap membrane for all of 6 speakers (Buy I dont know how to measure the streching force).
I can even glue the old membrane while streching it.
and I can try to remove one of dust membranes/filters and spray the original membrane, If they only dried from the first coating.

I not have any measure tools to measure the bias voltage of 6000v (the regular voltmeter works up to 1000v)
I dont know where to measure the bias

< the red part is covered by wax cube
I can test each capacitor and each diode.
I sure that they fine.
this data is from the company restoring book https://www.quadesl.com/origRefs/quad_book.pdf

And thank!, I'll be very carefull!

as I know screching sound may causes by:
- bad streching of the membrane or damaged membrane
- bad bias voltage

as chinsettawongone suggested, I will post the message in speakers furom too.

 

[WallofHooligans]

In the most bad case I can strech another cheap membrane for all of 6 speakers (Buy I dont know how to measure the streching force).
I can even glue the old membrane while streching it.
and I can try to remove one of dust membranes/filters and spray the original membrane, If they only dried from the first coating.

I not have any measure tools to measure the bias voltage of 6000v (the regular voltmeter works up to 1000v)
I dont know where to measure the bias

< the red part is covered by wax cube
I can test each capacitor and each diode.
I sure that they fine.
this data is from the company restoring book https://www.quadesl.com/origRefs/quad_book.pdf

And thank!, I'll be very carefull!

as I know screching sound may causes by:
- bad streching of the membrane or damaged membrane
- bad bias voltage

as chinsettawongone suggested, I will post the message in speakers furom too.

Okay, but seriously do be careful. These sorts of voltage multipliers "cockroft walton multipliers" are quite simple, but the actual parts themselves can't be measured in circuit if I remember correctly. Look for burnt diodes, they will be discolored and harder to read. Make sure all the capacitors are intact, no cracks. If the old membrane is loose, it will probably look loose. Under a light you should check the edges, see if the diaphragm is still taut. Check the center of the diaphragm by blowing on it gently. If it moves a lot it's probably too loose. I wouldn't patch any holes with tape as the above user suggested, but I would check for holes. You can definitely replace full diaphragms, but you will have to think of a clever way to mount the plastic in order to pre-stretch it.

 

[qu1en]

In the most bad case I can strech another cheap membrane for all of 6 speakers (Buy I dont know how to measure the streching force).
I can even glue the old membrane while streching it.
and I can try to remove one of dust membranes/filters and spray the original membrane, If they only dried from the first coating.

I not have any measure tools to measure the bias voltage of 6000v (the regular voltmeter works up to 1000v)
I dont know where to measure the bias

< the red part is covered by wax cube
I can test each capacitor and each diode.
I sure that they fine.
this data is from the company restoring book https://www.quadesl.com/origRefs/quad_book.pdf

And thank!, I'll be very carefull!

as I know screching sound may causes by:
- bad streching of the membrane or damaged membrane
- bad bias voltage

as chinsettawongone suggested, I will post the message in speakers furom too.

I would do the easy stuff first. It looks dirty so try and clean it without damaging anything. Listen to the type of crackling you’re hearing. Check for bad capacitors etc.. I can’t imagine a bad bias is causing crackling. If there is no bias it will be very quiet or not work at all. It is also unlikely to be the voltage at the stators but you can measure it with a scope with a very low volume. Does the crackling change with different volumes? Is it possible to inspect the diaphram by removing the stators? how does it look? just don’t do anything complicated until you are confident something is the issue first. Start with the easy stuff first, and make as many observations as possible.

 

[legopart]

I would do the easy stuff first. It looks dirty so try and clean it without damaging anything. Listen to the type of crackling you’re hearing. Check for bad capacitors etc.. I can’t imagine a bad bias is causing crackling. If there is no bias it will be very quiet or not work at all. It is also unlikely to be the voltage at the stators but you can measure it with a scope with a very low volume. Does the crackling change with different volumes? Is it possible to inspect the diaphram by removing the stators? how does it look? just don’t do anything complicated until you are confident something is the issue first. Start with the easy stuff first, and make as many observations as possible.

To reveal the diaphragm I have to remove the element first and then to cut the dust filter from the corners

This sopeaker have 2 very heavy tranformers with all the electric elements (one for the speakers bass/tweeter and one for the bias) the speakers too heavy because of them, I want to remove them from the speakers and connect each element separate with longer wires, out side of the speaker.

I plan to test the option to connect each speaker element with a portable amp and Stax Srd-4 energizer (I think that its rate is 1:25).
the bias still use the original transformer of 6000v.
^ I must to chek if this option is actual becoas Stax Srd-4 using better transformer.

I will afford on this speakers some thing like several hours a day or a week. can't fix or check them by once.
Because of it I have to seperate all the transformers and the elements.

 

[legopart]

---
Sorry mistake the bias is function good, after it charges the diaphrasm several minutes, and I unplug it, the speaker still function the same.

Yes as I wrote, one of them function the same with/without the bias voltage (external power)

Another new about it.
I accidently removed the power plug from bias supply...
and what I discovered?
they sounding the same with cracking noises, and with the same volume.

I can explain this only as: something goes wrong with the bias functionality

The bias connection not affect the sound == there is some problem with bias producing

​

two explains:
-maybe I not dischaged from the last connection
-maybe the transformer/bias circuit not function

the second one function without screch noises up to high volumes
the first with the bias problems function bad on the middle volumes

 

[chinsettawong]

Quad 57 isn’t that easy to fix. The stators are riveted together. If you want to remove them, you’ll need to use a drill press to drill all the rivets out. And then you’ll need to check if the stator surface is damaged. The stators are first coated with conductive paint and followed by insulation paints. If you need to remake the diaphragm, you’ll need to know what tension you need to get to first. You can buy a diaphragm repair kit from eraudio.com. They’ll tell you exactly what tension you need to achieve. Overall, it’ll take quite a lot of time to fix. And you need to do a lot of studies before you start fixing it. Don’t forget that you’re playing with extremely high and lethal voltage. Be very careful!

 

[legopart]

Quad 57 isn’t that easy to fix. The stators are riveted together. If you want to remove them, you’ll need to use a drill press to drill all the rivets out. And then you’ll need to check if the stator surface is damaged. The stators are first coated with conductive paint and followed by insulation paints. If you need to remake the diaphragm, you’ll need to know what tension you need to get to first. You can buy a diaphragm repair kit from eraudio.com. They’ll tell you exactly what tension you need to achieve. Overall, it’ll take quite a lot of time to fix. And you need to do a lot of studies before you start fixing it. Don’t forget that you’re playing with extremely high and lethal voltage. Be very careful!

Do you have some guide to make some straching machine or where can I buy one ?
I hope not to touch the paint on the stators, do I have to buy it too ?

 

[bui501-tech]

Why don’t you read through he threads in this forum just like everyone else has and like the other members have suggested half a dozen times before already?

 

[legopart]

Why don’t you read through he threads in this forum just like everyone else has and like the other members have suggested half a dozen times before already?

I tried but I can't find what I searching for inside this 200+ pages
lots of people here show the final product and I cant understand from it how to do it by myself

 

[legopart]

Quad 57 isn’t that easy to fix. The stators are riveted together. If you want to remove them, you’ll need to use a drill press to drill all the rivets out. And then you’ll need to check if the stator surface is damaged. The stators are first coated with conductive paint and followed by insulation paints. If you need to remake the diaphragm, you’ll need to know what tension you need to get to first. You can buy a diaphragm repair kit from eraudio.com. They’ll tell you exactly what tension you need to achieve. Overall, it’ll take quite a lot of time to fix. And you need to do a lot of studies before you start fixing it. Don’t forget that you’re playing with extremely high and lethal voltage. Be very careful!

eraudio.com not function anymore.
I thought from the guide that I read about the conductive paint use inly for the part where I connect the membrane and the bias.
so the stators made of plastic too, and they just coated with condactive paint that protected with isulation paint.

new I can understend why the bass panels on the front side covered by black/blue paint.
to isulate the electric charge from the user. (if I right)

this condactive paint for example is fine: ?
https://www.ebay.com/itm/Conductive-Carbon-Paint-3ea-30-grams-SPRAY-FORMULA/280448195257?epid=1955725924

cant find isulated paint (one of the bass plate front without it.)

drill is not a problem.

I still hope that the problem is from some electric elements.
I cant belive that speakers membrane that stored uselessly many years will unstrach.
for example, stax headphones works fine after all this years.

If I will open the plates, I plan to try and keep the membrane and try to restrech it and glue it again.

someone suggested to try shrink the membrane with heat-gun (shrink gun).

I still need some suggestion for the condactive and isulate paint.
And some suggestion how to regulate the straching of the membrane.

thanks for help!

 

[quintile]

usually the problem with the old quad ESLs is the diaphragm is damaged by them being overdriven.

i would buy or make a high voltage probe and check the EHT voltage. if that is ok check the stator drive voltages. opening the panels should be the last resort.

there is a huge amount written on the net about repairing ESLs, most of it sensible but there are some rather silky ideas about (this is always true on the net).

i suggest you read widely from many different sources on esl57 repair before attempting any serious disassembly.

-Steve

 

[WallofHooligans]

I really have a bad feeling about what's happening here.

On the note of tensioning a diaphragm, I think a heat gun would be a bad idea. Assuming that the plastic is even slack and could be reformed with heat, you would probably be better off putting it in an oven with carefully selected temperatures, and only if the frame is able to withstand that heat without warping. I really think you need to slow down and read more before you go full hog on it. Like you would never take apart your car's engine if you didn't know how to reassemble it. The bit about exchanging the transformers for stax voltages makes it clear that you don't know what you're doing. You're messing with stuff that you shouldn't until you know more.