Hi just beginning to strip my Quad ESL57 due to a burnt treble. I've run into a problem with the the removal of the 1.5Kv treble feed wire where it is connected to the EHT unit. There is thick rubber sleeve on the wire as it enters the EHT and I cannot see the solder post. Has has anyone seen this and what do you suggest. Of course I'm tempted to cut the wire further down and then remove the EHT to get a better look, but I thought I would ask first
Cheers
Cheers
Attachments
Thanks yes it looks potted, Does anyone know were I can get a suitable pcb for the EHT? I looked online and they wanted £150 for a pair, crazy the caps and zener will cost very little. Either that or reverse engineer the present boards and etch my own single sided pcb
Those are non-servicible epoxy style blocks. Do you want a bunch, free?
I unbolt the power supply and pivot it toward the back of the speaker and cut the wire or slice the tubing and unsolder the wire. Those blocks generally just get tossed out. I have a bunch that work if you want an old rickety circuit element that could fail any moment.
Sheldon
I unbolt the power supply and pivot it toward the back of the speaker and cut the wire or slice the tubing and unsolder the wire. Those blocks generally just get tossed out. I have a bunch that work if you want an old rickety circuit element that could fail any moment.
Sheldon
Thanks Stokessd, I've decided to make new ones. the circuit doesn't look complicated and it's probably best to do it while they're been refurbished. It the treble panel rebuild that's worrying me the most!
I've just noticed, are you the Sheldon who did the Quad Book? First of all thanks so much for the resource, a great contribution to ESL57 longevity. I found it when looking for a EHT PCB template. I have also found some Mitsubishi GDT's as alternative to the recommended CPClare GC3 in the book for the audio transformer and available in UK
I've just noticed, are you the Sheldon who did the Quad Book? First of all thanks so much for the resource, a great contribution to ESL57 longevity. I found it when looking for a EHT PCB template. I have also found some Mitsubishi GDT's as alternative to the recommended CPClare GC3 in the book for the audio transformer and available in UK
You probably missed this information:
“Original Quad ESL Treble Protection BoardsMonday, November 06th, 2017 | Author: stokes For a number of years, I suggested a gas discharge tube to protect the original Quad ESL treble panels. and they do work well, but I’ve had them get leaky over time and their striking voltage drops. I have reverted to the stock Quad ESL treble protection circuit. The original circuit is a rectifier bridge of 3000 volt diodes, where the input to the treble panel is applied across the AC inputs of the bridge. A stack of zener diodes is placed across the rectified outputs.”
Well spent a while today removing the audio transformers and the the EHT units. The burnt treble panel is out. I hope I'm not boring you all but I am doing this as any other novices are thinking of doing the same thing and as an "aide memoire" for me. The EHT unit are resin potted and new board will have to be made or bought if I can get a pre-made PCB. Never made a PCB but I believe that it can be done with a laser printer, heat transferred and etched. I going to do a little more research before splitting the treble panel and the job of removing the rivets. Can anyone recommend material for replacing the dust covers on the bass panels? Is thickness important? Thanks for everyone's help so far
Attachments
I've got new protection circuits and rectifier boards available on OSH Park:
OSH Park ~
OSH Park ~
Here's info about them here:
Sheldon’s World
Sheldon
OSH Park ~
OSH Park ~
Here's info about them here:
Sheldon’s World
Sheldon
Hi been looking at Fabien's ESL57 World website, says to use the same material for the dust cover as as for the diaphragms. Got all the rivets out the the damage treble panel this morning. While I'm waiting for the Mylar arrival I am going to look into the method of DIY PCB's for the EHT. There is a PCB design on Fabien's site for both EHT and Clamp boards. Any one done DIY PCB's before? Any tips?
Attachments
Thanks Sheldon, just seen your reply this morning. Going to to try to fabricate the boards, if not got somewhere to fall back on
Cheers
Cheers
Years ago, when it was more difficult to get boards made in small quantities. It was time consuming and tedious. It really only made sense because I was young and didn't have the money to do it any other way.
There wasn't much that was applicable to other pursuits, so other than learning something new, it wasn't that amusing.
Drilling a lot of precise, very small holes with carbide bits isn't a load of fun either. That was one of the more difficult parts of the process. Tear-out around holes and bit breakage were pretty common. A CNC I'm not.
At this stage, I'd gladly buy someone else's board before trying to make my own. Your amusement may come from different sources though.
The PCB is so simple you can even paint it with a suitable ink. Etching is best with hydrogen peroxide tablets dissolved in diluted hydrochlorid acid (in open area or near open window). Design the PCB only when you have all components at hand. I made it myself and it still works after 30+ years! I potted the lower part of the PCB in bee's wax. A Christmas market is a good source for bee's wax candles 🙂
2 spare PCBs
Let me know if you are interested, only postage costs to send them to you.
Kevin
Lapitude, where are you based? I needed 4 PCBs and received 6 from OshPark. These are Sheldon's latest PCBs. I am unfortunately based in South Africa, so this may not be an option for you.
Let me know if you are interested, only postage costs to send them to you.
Kevin
For DIY PCBs, you can use EasyEDA.
Even if cheap, this has a cost.
Then you need to buy diodes and capacitors, and postage is not free neither.
Then you need to solder and test.
Save time and buy a kit.
Even if cheap, this has a cost.
Then you need to buy diodes and capacitors, and postage is not free neither.
Then you need to solder and test.
Save time and buy a kit.
Thanks for the links. Could you confirm the neon lamps spec 500uA?. Are all 10nf caps 2 or 3Kv? diodes GP02-30 (marked on board) resistors all 1/2w ? What do you recommend for the 2 x 47nF?
Thanks again
http://getinthewoodchipper.com/wp-content/uploads/2017/08/57_eht_schematic.pdf
Thanks again
http://getinthewoodchipper.com/wp-content/uploads/2017/08/57_eht_schematic.pdf
Lapitude, I got the 3 kV caps some years ago, and the GP02-30s from Digikey, because I also ordered the Pomona HV cable. FWIW I would recommend getting the treble clamp boards, and some new HV cable. Depending on the age of the existing resistors in the transformers (x-over) it will probably be worthwhile replacing them and the caps at the same time. The neons recommended are these A1A Visual Communications Company - VCC | Optoelectronics | DigiKey
HV cable is: 6733-2 Pomona Electronics | Cables, Wires | DigiKey and 6733-0 Pomona Electronics | Cables, Wires | DigiKey
The SMD zeners I got from Mouser: BZG04-220-M3-08 Vishay Semiconductors | Mouser Europe and more neons A1A VCC | Mouser Europe
Regards,
Kevin
P.S. If you want a list of all the resistors drop me a PM, as I had to source them from both Digikey and Mouser. Neither carried all the resitors needed at the time.
HV cable is: 6733-2 Pomona Electronics | Cables, Wires | DigiKey and 6733-0 Pomona Electronics | Cables, Wires | DigiKey
The SMD zeners I got from Mouser: BZG04-220-M3-08 Vishay Semiconductors | Mouser Europe and more neons A1A VCC | Mouser Europe
Regards,
Kevin
P.S. If you want a list of all the resistors drop me a PM, as I had to source them from both Digikey and Mouser. Neither carried all the resitors needed at the time.
Last edited:
Yes I suppose you're right but as a retired widower on Covid19 lock down with nothing better to do? The do say you should never stop learning, It's been fun with the CAD package, laser printing on old Nat Geo pages and as an ex chemist, don't you just love the smell of acetone in the morning... Anyway latest development is it looks like a very kind Gentleman is going to send me his excess EHT and clamp PCB's if he can arrange shipment, what with the Pandemic...
Acetone smells pretty good, but THF . . . now that's the solvent that does it for me 🙂
With a chemistry background, you may find the etching process more interesting and familiar than the average person also.
As long as you're having fun learning new things, that's all that really matters. I wasn't trying to be discouraging, just providing my opinion on the experience.
The COVID lockdown seems to have sapped most of my energy and disturbed my focus, so I commend you on your gumption.
With a chemistry background, you may find the etching process more interesting and familiar than the average person also.
As long as you're having fun learning new things, that's all that really matters. I wasn't trying to be discouraging, just providing my opinion on the experience.
The COVID lockdown seems to have sapped most of my energy and disturbed my focus, so I commend you on your gumption.