As bolserst suggested, you need to start taking voltage measurements and comparing the "good" unit to the "bad unit". Randomly swapping parts is a tough way to troubleshoot, and eventually you'll damage the board with so many parts pulled and re-soldered.
I also suggest you check and compare the output of the wall transformer. I've seen them go bad.
I also suggest you check and compare the output of the wall transformer. I've seen them go bad.
Adjusting bias voltage on acoustat spectra 11s
Hi Andy, I've read both in this thread and also on on the Audio Circuit site about adjusting the bias voltage on the Spectra 11s I've looked around google and your site and can't find a procedure that describes how to safely do it-obviously you unplug the speakers adjust the potentiometer on the circuit board but do i need to discharge the panels first similar to when you take them apart to move them by touching the red wire on one of the other pin connectors or anything else I'm not worried about getting an exact match of level by using a multi-meter so im not going to have them plugged in when I do the adjustment- but I still want to make sure I am performing the procedure correctly.
Hi Andy, I've read both in this thread and also on on the Audio Circuit site about adjusting the bias voltage on the Spectra 11s I've looked around google and your site and can't find a procedure that describes how to safely do it-obviously you unplug the speakers adjust the potentiometer on the circuit board but do i need to discharge the panels first similar to when you take them apart to move them by touching the red wire on one of the other pin connectors or anything else I'm not worried about getting an exact match of level by using a multi-meter so im not going to have them plugged in when I do the adjustment- but I still want to make sure I am performing the procedure correctly.
how do I adjust the Bias voltage on the spectra 11 model?
I'm not sure if my last post went up so im putting this up as well my apologies if I doubled up was wondering the procedure to do this ? i looked on the audio circuit site and any other sites I could find -obviously you adjust the potentiometer and could not find anything I'm not going to use a multimeter or anything but I would like to know whether I need to discharge the panel same as when you take them apart to move them? obviously you unplug them lol I've worked on a few different audio things before but not electrostatics so I want to make sure I do it right
I'm not sure if my last post went up so im putting this up as well my apologies if I doubled up was wondering the procedure to do this ? i looked on the audio circuit site and any other sites I could find -obviously you adjust the potentiometer and could not find anything I'm not going to use a multimeter or anything but I would like to know whether I need to discharge the panel same as when you take them apart to move them? obviously you unplug them lol I've worked on a few different audio things before but not electrostatics so I want to make sure I do it right
An update on the Spectra 11 with low bias. I did the diode bypass mod mentioned by Chamberman,
and I finally got the bias back up! Woo hoo! I was able to adjust the trim pots so both are stable at around 75V. I recapped the large crossover electrolytic caps while I had them opened up. Thanks for the help! They sound super, just like I remember from years ago. Has anyone tried a modern replacement woofer? Any links suitable 8 inch woofers would be great.
and I finally got the bias back up! Woo hoo! I was able to adjust the trim pots so both are stable at around 75V. I recapped the large crossover electrolytic caps while I had them opened up. Thanks for the help! They sound super, just like I remember from years ago. Has anyone tried a modern replacement woofer? Any links suitable 8 inch woofers would be great.
Since an 8-panel Spectra was never contemplated, I cannot say how suitable the MK-2146 would be at driving 8 panels. If you try it, the extra panels would be added to the low frequency segment only. You will likely end up with too much bass. You'd also want to change the LF sector resistor to compensate for the added panel capacitance, if you want to keep the transition frequency the same.
Sounds like a lot of work to me, with the potential for results you may not like. A six panel Spectra is already one awesome speaker.
Do not attempt to adjust the bias without a means to measure the voltage. Yes, the panels must be discharged and disconnected from the interface before adjusting the bias. Instructions for adjusting the bias have been posted in this thread numerous times. See post #1999 for the most recent.
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Now its back to mid winter with rain in SW Australia.
Did you find a fix for the distortion in damp weather?
Yes, rebuilt the interface, gave them a good vacuum, sound better in summer, but not by much.
Thanks. I suspect regular cleaning of the panels might be a good idea given they are like a giant electrostatic dust machine. Did the vacum cleaner suck dust off the membrane? I wonder if blowing air would be quicker and better then vacuming. Beside its more macho
Maybe something smaller that wont tear the mylar for 30bucks
Seriously has anyone compared using a compressor vs a blower?
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I have always used Air.....
But if the panels have low output...only thing I have ever found ...is low bias...or bad leeking of bias....even with a bad interfaces trans..get the bias right....thay well play..I have had about 50 Acoustat panels now....an 10 pr of MK 121 interfaces or more....99% of any low output is Bias...buzzing...if not lose inside panel wire..Bias !
Ezey fix..Less than $30. US.
Low Bis makes people sale Acoustat For low Cash.....
I have panels...near 30 years old...never been clened....put 5k bias on them...thay can be driven to full output with 50-70 tube watts..
Good luck...have fun an great sound with Acoustat ESLs
But if the panels have low output...only thing I have ever found ...is low bias...or bad leeking of bias....even with a bad interfaces trans..get the bias right....thay well play..I have had about 50 Acoustat panels now....an 10 pr of MK 121 interfaces or more....99% of any low output is Bias...buzzing...if not lose inside panel wire..Bias !
Ezey fix..Less than $30. US.
Low Bis makes people sale Acoustat For low Cash.....
I have panels...near 30 years old...never been clened....put 5k bias on them...thay can be driven to full output with 50-70 tube watts..
Good luck...have fun an great sound with Acoustat ESLs
I can't recommend the use of "blowers" for cleaning your speakers. These blow unfiltered air, and are just as likely to introduce new dirt as they are to remove old dirt. Most air compressors have an intake air filter, and therefore have a better chance of producing a clean air stream. Both vacuuming and blowing with compressed air are effective, and the combination of the two is probably the most effective. Just be careful with the compressed air: don't hold the nozzle too close or use too high a pressure, as there's always a chance of damaging the delicate diaphragm.