Quad ESL57 service

[Firebottle]

I thought it was time to inspect the ESL57s, it has been many years ago when they were fettled. I also had a feeling the high voltage multiplier boards were a bit tired - more of that later.

I got the left speaker down from its supports and laid it on a dust sheet on the floor:

http://i601.photobucket.com/albums/tt97/Paramotorpilot/ESL57%20service/P1030698.jpg

I then removed the rear grill:

http://i601.photobucket.com/albums/tt97/Paramotorpilot/ESL57%20service/P1030699.jpg

Not too much dust, just a little vacuuming required.
I then removed the side cheeks, revealing the staples holding the sides of the front grill. High tech or what?

http://i601.photobucket.com/albums/tt97/Paramotorpilot/ESL57%20service/P1030700.jpg

Once the front grill had been removed it revealed pretty mucky panels:

http://i601.photobucket.com/albums/tt97/Paramotorpilot/ESL57%20service/P1030702.jpg

As the panels are covered with a thin plastic dust sheet I thought the best approach was to just sponge them down with a damp sponge to remove most of the dirt. Here is the after view, they don't look particularly clean but I didn't want to start replacing dust covers :eek:

http://i601.photobucket.com/albums/tt97/Paramotorpilot/ESL57%20service/P1030705.jpg

http://i601.photobucket.com/albums/tt97/Paramotorpilot/ESL57%20service/P1030706.jpg

The inside of the front grill showed a bit of discolouration/muck so this just had a vacuuming with the brush nozzle:

http://i601.photobucket.com/albums/tt97/Paramotorpilot/ESL57%20service/P1030703.jpg

Once the front grill was refitted I checked the high voltages coming from the EHT block and my suspicions were realised:

http://i601.photobucket.com/albums/tt97/Paramotorpilot/ESL57%20service/P1030707.jpg

The voltages are well down on what they should be, particularly the bass panels, so I'm going to replace both EHT blocks shortly.

I'll post the result when I've done it.

:cool: Alan

[Gordon Steadman]

Aha..... unless you have discovered the secret of the Star Trek transporter..........I assume this means you are home:)

Nice to see you back to work. Its astonishing that such basic looking stuff can work such magic. I remember being somewhat surprised at how they were held together. I'm hoping mine are good for a few years yet. One Thing rebuilt them about twelve years ago and they have had a pretty quiet life since we've been here. Busy busy busy!!:doh:

Those stains look like they could be coffee or cat!!

[Ammonite Audio]

I have an unused pair of these HT boards for the 57, if you are interested:

http://quadesl.nl/en/quad-esl-parts/eht-power-supply.html

[Firebottle]

Definitely Hugo, PM sent.

Alan

[dowser]

If the EHT units are wax potted then its pretty simple to rebuild them yourself.

Richard

[Audio Al]

If the EHT units are wax potted then its pretty simple to rebuild them yourself.

Richard

Any details on how to do the rebuilds ?

[dowser]

I did a write up on PFM when I did mine a few years back, including Farnell part references & pictures I think. Melt wax in oven, replace caps and diodes, melt wax again and pour back in - best to have some spare wax off eBay too, as some sticks to whatever container you use in oven (& ruins it :)).

Richard

PS: baby nappy wipes are great for cleaning dust cover membranes

[Firebottle]

Thanks Richard, I have rebuilt the rectifier assembly before but I thought ready made this time.

For a couple of guides to refurbishment try these:
http://www.keith-snook.info/loud-speaker-stuff/QUAD-ESL57/QUAD-Hi-Fi-ESL57.html
http://www.f2s61092.f2s.com/html/refurbish.html

:cool: Alan

[Firebottle]

Many thanks to Shuggie for a very quick response to buying the replacement EHT boards.

I have now replaced them in both speakers and discovered I had a seriously leaky bass panel in one.
The ESL Labs boards have a very useful extra feature, there are 3 neon indicators which show the relative health of the treble panel and both bass panels.
With a small leakage current the neon flashes every few seconds, on one bass panel it was lit continuously and quite bright.

I removed the offending bass panel and stripped off the tape holding the dust covers on. With care it is possible to do this without damaging the thin plastic of the dust cover itself. I rigged up a temporary high voltage test setup on the dining room table as shown:

http://i601.photobucket.com/albums/tt97/Paramotorpilot/ESL57%20service/P1030718.jpg

There was a particularly corroded rivet at the bottom of the panel which I succeeded to remove without problem. I then tested one side of the panel (centre and right terminal) and the EHT was OK. When I tested the other side (centre and left terminal) it definitely was not :doh:

A lot of fretting and nashing of teeth followed, thinking I will have to take the panel apart, with the associated time and effort to make and fit a new diaphragm.
I took a little time out to think what could be causing the excess leakage, but without internal inspection of the diaphragm and through holes for all the rivets I thought I was stuffed.

With one of the wires disconnected to the middle diaphragm I had a eureka moment. As I was leaning on the dust sheet covering the table the EHT voltage was varying :scratch:

The connections to the rear side were in contact with the sheet (dust cover off, remember) and the very small dampness of the sheet was causing the EHT leakage.
I stood the panel on its side to test again and voila, no leakage :)

http://i601.photobucket.com/albums/tt97/Paramotorpilot/ESL57%20service/P1030719.jpg

I dusted every thing off and refitted the dust covers with some new tape all round:

http://i601.photobucket.com/albums/tt97/Paramotorpilot/ESL57%20service/P1030720.jpg

Now back to the carcass of the speaker for resoldering, a very good idea being to cover the dust cover against solder splashes with some cardboard:

http://i601.photobucket.com/albums/tt97/Paramotorpilot/ESL57%20service/P1030721.jpg

Once refitted and tested the EHT holds up well but the one panel is still a little leaky, the neon glowing almost continuously, but dimly.
This condition shows a leakage of around 40 uA, far more than a new panel, but the best I could achieve without panel surgery.

All 4 panels show raised leakage compared with new but then the speakers are 40 years old!
Although it seems that only one speaker was particularly down on EHT, it sounds now like the bass is back, so quite happy for now.

:cool: Alan

[Ali Tait]

Love the tape!