Acoustat - Can it be saved?


Has anyone out there encountered this? I have a pair of Acoustat electrostatic speakers - they are prototypes developed at Rockford Fosgate around 1990 so no model type associated. They are 6' X 2' flat panels with built in power supply. Recently one of the power supplys went down. The circuit board was badly damaged. The worst thing is after extenstive digging it appears that the capacitors and resistors used on the board are no longer made. The capacitor is .01 UF 6000 V. The resistor is 100K OHMS. It seems the only way to save it would be to locate a similar boards somewhere but it is looking doubtful. Anyone think there is a chance to outfit the panels with a more modern power supply? I hate to give up on this speaker. As a pair they have provided remarkable sound.
donmallonee
Wow...this is a really old thread.  The link I posted above no longer is active, but here is a current one:

https://www.diyaudio.com/forums/planars-and-exotics/183168-acoustat-answer.html

This is ran by Andy and has a lot of excellent info.

I rebuilt/modified/updated my pair of 2+2's with lots of help from the above site. 

They do indeed sound fantastic as everyone who has heard them can testify...
Donmallonee

The main thing you need to remember is that there are the earlier Acoustats and there are the later, Rockford Spectra Acoustats. Most of what you will encounter out there will be the older Acoustat stuff, with the panels having three wires. The later Spectra series panels have five wires and the transformers/circuits look entirely different. The earlier design is much simpler and easier to deal with, as far as finding individual pieces and as far as doing a repair. The Spectra, not do much. To be fair, I don't have much Spectra experience. At any rate Spectras are complicated. Nothing will interchange between these two different designs.

 As far as the 6k capacitors, you won't find high voltage stuff at any current retailer I am aware of. Surplus is the only practical way to go that I know. We have an electronic parts surplus store locally and I have obtained most everything I needed from them. The 3k or 6k stuff isn't always there but, more often than not, I can find what I need. I find individual parts, that is, although no HV power supply capacitors.

You'll have more trouble finding the resistor.

Re-engineering the circuit would take a real engineer with HV experience, for practicality and especially for safety. This 6kv stuff will seriously shock you, if you give it a chance. There is less and less high voltage stuff out there, as we go. I have found several people who are qualified to do this sort of thing but I have found no one who is sufficiently interested to take on such a project. What we really need for Acoustat is someone to do what Kevin Gilmour, and a few others, have done for Stax earspeakers, aka headphones. He/they have very beneficially modified several Stax amps and have designed ground up new amps for Stax headphones. The Stax community has several guys who have published schematics, and made circuit boards, for Stax amps. These are substantial improvements on the original Stax amps. There are people who will build these modified, modern amps for electrostatic headphones. It would be great if some individuals would take on such a project for Acoustats. I simply can't imagine it happening. To a Acoustat guy, this is a sad paragraph.

This probably isn't the place, you asking about Spectras, nevertheless, for a long time, I have been toying with the idea of commissioning a production of the capacitors in the high voltage supply of the Acoustat Servo amps. I haven't checked into doing this for a long time so I don't know the exact state of this sort of thing at present. Those are electrolytic capacitors from the mid 70s. My amps appear to work fine - but - those are 40 year old electrolytic capacitors. If someone out there would join in, and split the cost, and motivate me a bit, I'd get serious about making this happen over the winter.

A properly set-up Acoustat, with appropriate modern sources, particularly a 2+2, or a 6, with Servo amps, remains, at this point in time, about as good as it gets.

Tom
Posting Date : January 14, 2008

For unparalleled service and expert upgrading of :
Acoustat Interfaces
(Magne-kinetic and Spectra Types),
Acoustat Trans-Nova power amplifiers,
and Acoustat Trans-Nova preamplifiers

Contact: Roy A. Esposito
email: soundslikenew@prodigy.net

Roy was an original member of Dr. Strickland's team
at Acoustat Corporation
when our company was located in Fort Lauderdale, Florida
I just visited that audio Circuit site. For Acoustat it has been 3+ years since I checked them out. Finally, some real good on the amps!

thanks for starting this thread. I have already learned alot and I hope it is of some value to you.
Here's an interesting forum with postings by both Roy Esposito of Sounds Like New and Andy Szabo:

http://www.audiocircuit.com/A-HTML/AA-Structure-STR/Content-CON/905-STR-CON_Brand___-A01.php?Code=ACO&Circuitcode=941
This website may be helpful to you.

http://www.integracoustics.com/MUG/MUG/tweaks/acoustat/
The capacitor is .01 UF 6000 V. The resistor is 100K OHMS.
.

I know next to nothing about capacitors, resistors etc, but just wanted to say that there was a time i needed a transformer that was no longer made, but someone i knew was able to wire two transformers that were available, to equal the one i needed and I wonder it something similar could be done in your case.
Yes. I own a pair of Acoustat X that match your description. My power supply went out and I took them to a local fellow who was able to examine the working twin and he replaced both power supply components. Of course, my circuit board was not damaged as the fuse saved me. If you do multiple searches on 'Acoustat' you will find referances to a couple of people who are still servicing and upgrading these amps. I misplaced my notes but the answer exists in the Audiogon Archives Discussion forums. If you find them, please post here so I can refresh my own database.
Try this link below:

http://www.audiocircuit.com/A-HTML/AA-Brands/A/Acoustat-ACO/941-ACO-GEN-AS_BIA__-F-A02.htm#int

Also Andy Szabo probably knows more about Acoustat than anyone. His info can be found at the above link...