Quad ESL57 EHT unit rebuild...

So I finally got around to rebuilding my ESL57 EHT units. I bought some 57s from eyebroughty a year back, then aybee kindly donated some old EHT units he had replaced. Many thanks to both, and apologies for taking so long to put them into use...the joy of a young family


The old EHT units from aybee - 2 different revisions, early and late;




Whack them in a pyrex bowl and into the oven at 150 degrees c for around an hour to melt away the beeswax (they have around 6kV at the end of the diode rail...);


Afterwards they look like this;




Different size boxes for different age;


First one done (takes ages!);




Newer board done too (using 16 diodes instead of original 8 - more reliable!);


With beeswax pured back in (still need to top up);


Topped up , but still less than before (hopefully this will be OK though - anyone know if this is enough?);





Many thanks again to both eyebrought and aybee!

Tomorrow I will either pull apart the 57s, clean and fit these...or get my valve hybrid monoblocs up and running - undecided so far, the joys of having wife and kids stranded in Egypt (there are considerable downsides too!).

Hopefully the 57 panels are OK - when I first listened they sounded great, but there was a definite volume difference between each unit. I'm hoping for a failing EHT unit...

Richard

Hhhmmm - lots of info on the net on how to do this rebuild, not one of the sites tells you how to clean old beeswax out of a Pyrex jug I need to get a new one before my wife gets home, LOL!

Richard

That bit's easy. Take it outside and get some petrol on a rag. Wipe it until the wax has dissolved, then take it back indoors and wash it thoroughly.

Or: soak it in caustic based oven cleaner or similar with hot water.

Or: Use Jif and labour mightily

Or: stick it in the dishy on a hot wash for a couple of cycles, hoping for the best.

Hi,

When I did mine the most noticable thing was more and bass that went deeper.
Its fun putting your electronics in the oven, I temper blades in ours!

Pete

What are those things?

If you need to ask what they are then that means you should never go anywhere near one

Remember the days when your telly got fixed by someone coming round your house? well they are similar to the reason you wouldn't mess with an old TV - very high voltages.

Its essential in an electro static speaker, which attract the film with very high voltages but the circuit for speakers doesn't need a lot of current, which is good or it would be difficult to build (see bottom)

The circuit is something like this one. AC goes in, DC out but at a higher voltage depending on the number of repeating stages.



And here's what a really big one looks like!


You could if you wanted use a 9V AC transformer and get a much higher voltage, but with low current. But defo a circuit to take care with

Wikipee info here, for reference only though, take care of you and yours.
http://en.wikipedia.org/wiki/Voltage_multiplier

I was just curious. Thanks for the info

Pete MB&D said:

Hi,

When I did mine the most noticable thing was more and bass that went deeper.
Its fun putting your electronics in the oven, I temper blades in ours!

Pete

Click to expand...

Absolutely my experience too - mid-range and bass is now incredible, but in comparison to my SF Concertinos (I only listened to the ESLs once at very low volumes, and noticed a channel inbalance). Going from my SFs to the ESLs is like going from a standard subchassis on LP12 to a Sole, except I didn't know I had one-note bass from my SFs! I keep hearing new things in the mix.

See my thread in Classics for the refurb story - I could do with some advice on what is causing treble panel mid-rangeish distortion at high volumes.

Cheers, Richard

stevec67 said:

That bit's easy. Take it outside and get some petrol on a rag. Wipe it until the wax has dissolved, then take it back indoors and wash it thoroughly.

Or: soak it in caustic based oven cleaner or similar with hot water.

Or: Use Jif and labour mightily

Or: stick it in the dishy on a hot wash for a couple of cycles, hoping for the best.

Click to expand...

Just saw this - thanks Steve, and DOH, petrol should indeed do it. Mind you, I have another set that need a rebuild now

Richard

its a shame the forum doesn't have a way to load and store pictures in threads in perpetuity since the info is timeless ... maybe someone could direct me to an equivalent information source if they know of any?

Jonathan said:

its a shame the forum doesn't have a way to load and store pictures in threads in perpetuity since the info is timeless ... maybe someone could direct me to an equivalent information source if they know of any?

Click to expand...

I think I recommended this already in the other thread. But if you haven't looked at the information at quadesl.com, you will find as much good information about rebuilding the 57's there.

oh - which was the 'other' thread? thanks for the link

Tom Bonjour said:

I think I recommended this already in the other thread. But if you haven't looked at the information at quadesl.com, you will find as much good information about rebuilding the 57's there.

Click to expand...

Sorry all, the original photos went with the demise of fotopic.net. Issue for Tony to host photos locally is one of cost.

there Must be other websites with photos on a 57 EHT rebuild? It’s really not hard, I’d just advise getting some extra beeswax blocks from eBay before you start, you lose quite a lot with the stuff that gets stuck to the Pyrex bowl

I do have copies of the photos somewhere if strictly required....somewhere