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Old 6th December 2018, 01:53 PM   #2101
TJG55 is offline TJG55
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How about LF transformer? Anything else I can do?
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Old 15th December 2018, 09:33 PM   #2102
bolserst is offline bolserst  United States
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Do you(or a tech friend) have access to a signal generator you can hook up to the amplifier driving the speakers and a DMM(digital multimeter)? If so, I would recommend measuring the output of your HF & LF transformers and the mixer at 100Hz. Based on what you measure, the fault should be narrowed down to the mixer parts or a particular transformer.

With the interface unplugged from the wall and the wiring to the panels disconnected, apply a 100Hz signal @ 1Vrms to the audio input binding posts using signal generator and power amplifier. If possible measure the voltages on the “good” interface before the “bad” so you know what to expect. The voltage values shown in the attachment are ballpark numbers, but they won’t be far off.

Let us know what you find out.
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File Type: png Acoustat_LF_Interface_Test.png (403.0 KB, 273 views)
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Old 7th January 2019, 11:21 PM   #2103
Audio Adrenaline is offline Audio Adrenaline  Australia
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Hi Andy My Acoustat Spectra 11s have started making a small crackling noise when playing piano but with all types of other music its fine including at good volume levels-im not flogging them any ideas? im a bit puzzled
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Old 8th January 2019, 12:34 AM   #2104
2bdave is offline 2bdave  United States
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My 2200's crackled on one panel; turned off the transformer 24 hours , tapped on the corner it crackled at, blew it with my leave blower downward, plugged in the transformer and the dust particle had fallen to the bottom outside of the charged field. No Crackling. Now then, my 1100s could not be fixed as the gray magnetic coating painted on one side was delaminating; I replaced the panels with some from a Spectra 11, fixed.
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Old 12th January 2019, 07:26 PM   #2105
pforeman is offline pforeman  United States
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Default High voltage connection to diaphram

Hello,
I moved about a yr ago and finally brought out my Acoustat 2+2's which were 2" too tall for my basement. So new frames made from steel. I removed and cleaned the panels in shower and dried them off and found that 3 of my panels had a ~.75" tear in the diaphragm right through the tab of conductive paint that connects to the red wire. 2 of the 3 have only a very thin crescent of conductive coated mylar going to the red wire.
I bought some copper adhesive tape and went over the hole with approx. 1 inch long piece ( more to ensure bias voltage to panel, than support against further tearing). The copper tape is no closer than about 3 mm from any of the stator wires.
Now I am afraid to plug them in for fear of corona discharge from the copper tape.
Should I remove the tape, leave it alone, or maybe cover it with silicone caulk.
The copper tape seems quite well "stuck " onto the mylar and its coating.
Thanks,
Paul
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Old 17th January 2019, 01:06 PM   #2106
pforeman is offline pforeman  United States
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Default charge ring insulation

Thought maybe I'd re-word this for a possible answer.
\
Can a charge ring in an electrostatic speaker be exposed to air without being insulated.
Thanks,
Paul
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Old 17th January 2019, 08:44 PM   #2107
bolserst is offline bolserst  United States
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Is the copper tape you are using the type with conductive adhesive? If not, you will most certainly generate corona/ozone between the edges of the tape and the conductive coating you have it stuck to. You will likely hear it (and see it if room is dark) as soon as you plug in the power cord. Over time, operating in this many will eat away at the coating around the tape and eventually cease to charge up the panels.

If it does have conductive coating, the other concern would be ozone generation from exceeding the voltage gradient for ionization between the insulated stator wires and the copper tape. You mentioned a 3mm separation distance which should be more than adequate for the voltages involved. The only way to tell for sure is to play some bass heavy music at high volume in a darkened room and look for purple corona glow around the copper tape pulsing to the music. If it does, I am skeptical as to whether silicone would help…maybe some corona dope.
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Old 19th January 2019, 08:44 PM   #2108
zetterstroem is offline zetterstroem
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Default bias transformer mk-141

hello all

(i tried searching this thread but lost patience)

I'm in the process of restoring my old beloved model 1 MK-141C speakers

I have the schematics and part list. But one of the bias transformers is damaged.

Anyone know the specs (A) ??
... (I know they're 750 VAC)

Thanks... can't wait... haven't heard them in 25+ years
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Old 23rd January 2019, 06:40 PM   #2109
AcoustatAnswerMan is offline AcoustatAnswerMan  United States
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Quote:
Originally Posted by zetterstroem View Post
hello all

(i tried searching this thread but lost patience)

I'm in the process of restoring my old beloved model 1 MK-141C speakers

I have the schematics and part list. But one of the bias transformers is damaged.

Anyone know the specs (A) ??
... (I know they're 750 VAC)

Thanks... can't wait... haven't heard them in 25+ years

I don't know the ampere output on the bias transformer, and in any case, it's highly unlikely that you would find an off-the-shelf replacement. You really need to find a genuine Acoustat part. Any bias transformer from MK-121, MK-131 or MK-141 will work, unless it's from a very early 3-diode multiplier model (most use a 5-diode multiplier). The most recent part numbers assigned to these transformers are TTA-100 (100 volt mains), TTA-117 (110-120 volt mains) and TTA-240 (220-240 volt mains).
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Old 7th February 2019, 01:31 AM   #2110
FishFast is offline FishFast
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Acoustat Answer Man is here
I'm in process of bringing a pair of Acoustat Model 3's back on line after 25+ years in storage. In my instance they worked for about a week and then one speaker went quiet. Likewise believe that it's the HV multiplier, but in my case the xformer is good. So I did search the entire thread.
In post 3631175 Acoustat Answer Man is here john65b generates an estimate that the xformer is "near 30ma - 40ma at best".

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