Acoustat Answer Man is here

[hella356]

Originally Posted by Reefin Dude

Glad to see you are still around Andy. you helped me once before on my Monitor 4's disabling the auto turn off circuit. worked like a charm. unfortunately i now have an odd whistling sound coming from one of my servo amps. i have tried to get it fixed by two people local to me, but within 6 months the sound comes back. it is definitely in the amp and not in the panels. the last person i took the amp to replaced nearly all of the caps except the 1microfarad 3000VDC one, because they were not able to source it. i have replaced both of the monster transformers in the units many years ago. do you have any ideas on where to start to try and find remove the whistling, or to find a place that would fix the problem for more than 6 months? i guess i could hunt down a set of interfaces, but would rather keep the servo amps.

thanks,

G~

Have you tried Mike Savuto at Analogue Associates? He specializes in Servos.

[Reefin Dude]

i just came across their email last night after posting this. i was trying to hunt down some more info about them to see where they are located before emailing them, but will probably go ahead just to be sure.

when i first got the Monitor 4's i had Sounds Like New rebuild one of them, but when i tried to contact them again a few years ago, they no longer seem to be around. i was really happy with their work.

Thanks,

G~

[AcoustatAnswerMan]

Originally Posted by Reefin Dude

i just came across their email last night after posting this. i was trying to hunt down some more info about them to see where they are located before emailing them, but will probably go ahead just to be sure.

when i first got the Monitor 4's i had Sounds Like New rebuild one of them, but when i tried to contact them again a few years ago, they no longer seem to be around. i was really happy with their work.

Thanks,

G~

Sounds Like New (aka Roy Esposito) is still servicing Acoustat products, but I've heard numerous times that he can be difficult to contact. According to his posts on The Audiocircuit website, he is still in business. Roy is probably your best bet when needing repairs on Acoustat transformer interfaces and amps/preamps.

I would heartily recommend Mike Savuto for any servicing needs on the servocharge amps. He does repairs, but also makes upgrades that will improve the reliability of the units. Good luck!

[hella356]

I really don't know anything about what Roy Esposito offers, although everything I've read about him has been positive. I've spoken and emailed with Savuto a number of times; he's very helpful and informative. His upgrades (which I've not experienced myself) are supposed to be outstanding, according to some of his customers who've posted their results around the web. Some of Savuto's upgrades are for reliability, others for sound quality, some seem to cover both areas. I'm hopefully starting a new (higher paying) job soon, and I'm planning on buying a full set of mod parts from Savuto when I save up enough. Four Servo amp total rebuilds will not be cheap, but if they live up to the hype it will be money well spent.

[bear]

Originally Posted by Reefin Dude

Glad to see you are still around Andy. you helped me once before on my Monitor 4's disabling the auto turn off circuit. worked like a charm. unfortunately i now have an odd whistling sound coming from one of my servo amps. i have tried to get it fixed by two people local to me, but within 6 months the sound comes back. it is definitely in the amp and not in the panels. the last person i took the amp to replaced nearly all of the caps except the 1microfarad 3000VDC one, because they were not able to source it. i have replaced both of the monster transformers in the units many years ago. do you have any ideas on where to start to try and find remove the whistling, or to find a place that would fix the problem for more than 6 months? i guess i could hunt down a set of interfaces, but would rather keep the servo amps.

thanks,

G~

You can do a few things at home.

1) switch power tubes from one amp to the other
2) making sure the charge is gone from EVERYTHING in the amp, desolder the blocking caps from one amp and place into the other.
3) check the PCB for solder cracks - best to touch up as many of the HV connections as you can.
4) look for DUST and grime on the boards, and wires (clean with denatured alcohol - use a rag that leaves no residue behind or similar means ) (make sure no voltage remains!!)

Whistling sound can be generated by HV leakage!

Get the room DEAD DARK and let ur eyes adjust, you may see some purple glow... that is leakage.

Silicone rubber or "Corona Dope" can tame that, if you find the source.

Sounds like leakage.

_-_-bear

EDIT: 4,2, 3, 1 is the best order to do these things, I just wrote off the top of my head...

[tyu]

Bear
thanks for your info..

[bear]

Nope: 4, 1 , 3, then 2... got that wrong in the original post.

On 4) I mean to say make sure there is no residual voltage IN the amp, so before putting your hands or anything else there be certain there is no voltage - and discharge the panels too.

There are DANGEROUS voltages in the servo amps.

_-_-bear

[john dozier]

Also remember that the panels themselves are giant capacitors and can retain a charge for some time. I would let them discharge overnite. Even then I would not touch the bare plugs that go to the panels. Handle them only by the plastic handles. Regards John Dozier (former original Acoustat owner)

[bear]

Bah, just short them out, they drain fast!

Use an insulated jumper. If ur squeemish use a jumper (clip leads are good) with a resistor like 1kohm range in series, that will reduce the initial spark, if that scares you...

Myself, I am bold, I grab the insulated wires and touch the stator wire to the center pin (diaphragm) connection. Use an insulated pliers to undo the screw down on the stator wires, and DO NOT HOLD THE CHASSIS WITH THE OTHER HAND!!

_-_-bear

[Atom666]

Andy
Do you know the type/brand of high voltage resistors used in the Spectra 44 for the panel equalization?
Thanks
Andrew