Author Topic: fixing my electrostatic loudspeakers  (Read 2760 times)

Offline Andrew Wildman

  • Full Member
  • ***
  • Posts: 165
  • Country: 00
fixing my electrostatic loudspeakers
« on: October 10, 2015, 04:03:50 PM »
About 15 years ago I made some electrostatic loudspeakers.  They have survived quite well but recently one of them gave up the ghost and took out the right channel of the bass and treble amp (I have an active crossover in the system and a separate stereo amp for sub, bass and tweeter).  The amps should be easy to fix as they are quads and the output transistors always go first.  The speakers should be easy as I made them but I am struggling to find anything wrong  :doh:

The speakers existed (as far as I was concerned) before the wife, I don't think she would let me make these now as they are 6' tall :borg:

Here is an old pic of the speakers in our old house


Here is the gubbins inside the speaker, essentially a hv power supply and two big old step up transformers.

Anyway better carry on measuring things to see if anything looks screwed up.....


Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 6415
  • Country: gb
  • East Sussex, UK
Re: fixing my electrostatic loudspeakers
« Reply #1 on: October 10, 2015, 06:37:15 PM »
Problem is obvious. In the first picture they are lying on their side, as is the rest of the room,  :scratch: :scratch:

Now you have them upright, so obviously gravity is affecting the electrons  :lol:

(In case it doesn't show in your browser the first picture is rotated 90 degrees)

Later edit : ..ello ..ello they're back upright again  :scratch:
« Last Edit: October 11, 2015, 08:47:22 AM by awemawson »
Andrew Mawson
East Sussex

Offline Jonny

  • Hero Member
  • *****
  • Posts: 781
Re: fixing my electrostatic loudspeakers
« Reply #2 on: October 10, 2015, 08:23:43 PM »
Assume you have done the obvious swap over the L R output from pre amp non working side, take it from there.


Offline BillTodd

  • Hero Member
  • *****
  • Posts: 790
  • Country: 00
  • Colchester Essex (where the lathes were made)
Re: fixing my electrostatic loudspeakers
« Reply #3 on: October 16, 2015, 06:41:17 PM »
Hmm they look a bit like martin Logan's :-)

Ah you said quads , 405s?  If so, they can self destruct if the o/p gets  (thyristor protected output to protect their speakers)

Sounds  like a flash over. What bias volts are you running?

Bill
Bill

Offline Andrew Wildman

  • Full Member
  • ***
  • Posts: 165
  • Country: 00
Re: fixing my electrostatic loudspeakers
« Reply #4 on: October 17, 2015, 04:19:06 PM »
Well after a bit of fiddling one of the plates to the membrane is measuring about 6 Meg ohms but only at hv. Should be hundreds of Meg. At multimeter voltages it shows open circuit. Indicates that there is something like a cremated harvest mite in there! Time for a rebuild.
Bill the bias voltage is about 6 kV. I am running a 405 for the bass and a 306 (I think) for the treble. When I first got the 405 I had to repair it.

Offline krv3000

  • Hero Member
  • *****
  • Posts: 2075
  • Country: gb
Re: fixing my electrostatic loudspeakers
« Reply #5 on: October 17, 2015, 06:54:21 PM »
hi if I had that much mess on the living room floor I wood come home from work and find the lot in the bin   good work  :nrocks:

Offline tom osselton

  • Hero Member
  • *****
  • Posts: 956
  • Country: ca
Re: fixing my electrostatic loudspeakers
« Reply #6 on: October 17, 2015, 08:34:06 PM »
I'd like to see that much of my carpet!

Offline krv3000

  • Hero Member
  • *****
  • Posts: 2075
  • Country: gb
Re: fixing my electrostatic loudspeakers
« Reply #7 on: October 18, 2015, 08:10:44 AM »
Brill