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Infinity ServoStatik - high end stopped working on one panel

76.131.186.160
Posted on March 8, 2023 at 10:47:02
pyite
Audiophile

Posts: 3
Location: Colorado
Joined: March 8, 2023







Hello Inmates!

I have had an original ServoStatik for a few years, and used it quite regularly for awhile. Unfortunately the high end on one of the panels went out not too long ago.

It didn't just cut out immediately - the high end volume level on the bad panel got lower and lower until one day it stopped. The orange light still comes on. Mid-range still sounds excellent.

Luckily I found a slightly beat-up spare panel on eBay at the beginning of the pandemic, so I can use this for practice. Its high end is suffering the same fate - about halfway gone now.

I'm no EE but I'm pretty good with a soldering iron, so I want to try repairing the spare panel and if that goes OK I'll repair the nice one. I don't have a schematic but it looks like there are a couple of easy-to-reach transformers that are obvious candidates for replacements. There are what appear to be some resistors and small capacitors that are coated with some sort of wax, hopefully I can avoid dealing with this.

If anyone has any suggestions on how to proceed with troubleshooting, or maybe even a schematic, please let me know. It looks fairly straightforward though.

The image URL should have the two photos showing the electronics, and I attached one of them to this message.

Thanks!

 

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RE: Infinity ServoStatik - high end stopped working on one panel, posted on March 8, 2023 at 12:10:34
pyite
Audiophile

Posts: 3
Location: Colorado
Joined: March 8, 2023
 I guess step 1 is figuring out where to find the matching parts, such as a T-437.

 

RE: Infinity ServoStatik - high end stopped working on one panel, posted on March 8, 2023 at 13:57:12
kentaja
Manufacturer

Posts: 4531
Joined: March 26, 2001
 The RTR tweeters may be found on eBay. Rebuilding is not a DIY type of thing for most people. Replace the offending unit with another one.

The transformers are fine leave them alone.

Amazing the high voltage board(s) are working after all these decades. This is something that will need attention at some point.

Great speakers when working good luck!

 

RE: Infinity ServoStatik - high end stopped working on one panel, posted on March 8, 2023 at 14:33:00
pyite
Audiophile

Posts: 3
Location: Colorado
Joined: March 8, 2023
 Thanks for the reply. Should I test the individual blue drivers to see which one is bad?

If so, what is the easiest way to do this? There are three wires going to each one: orange, red, and green, and the 4 drivers are all parallel so presumably a single bad driver won't stop the others from working.


I found some technobabble in a thread over on Audio Karma which I should save for future reference:

"The tweeters use a TE 14023A 0r TE14023 after 73 , blue wire is 1:75 tap and red wire is 1:50 tap, If any problems with the IN4007 diodes wired in series replace with Varo V65 diodes, the bias voltage here is approx 1250V +- 10%, the overall system bias is 3750V +-5%, I've had a few sets of them many yrs ago"

and

"The midrange uses it's own transformers, either a TE14022 or T437 "1:125", main trans is a TE14184 or P8151 "

 

RE: Infinity ServoStatik - high end stopped working on one panel, posted on March 8, 2023 at 18:34:21
InfinityApogee
Audiophile

Posts: 232
Location: Sk
Joined: February 14, 2014
 yours look like the early model before 6-73, I had them as well, mine the panels delaminated, at the time there was no way to fix, some owners had problems with blowing the IN4007's transformers are tough, unless shorted, will never need them, just check tap voltages, I still have the dwgs I made of mine somewhere, with all parts and wiring diagram .

 

RE: Infinity ServoStatik - high end stopped working on one panel, posted on March 9, 2023 at 03:47:00
triamp
Audiophile

Posts: 748
Location: USA
Joined: August 6, 2008
 Play something like FM radio interstation hiss- some broadband noise. Put your ear next to the front of each of the blue tweeters. If they ALL sound low in output, the problem is likely the high voltage "bias" supply is no longer producing the voltage that it should. Note that this is a charging voltage for an electrostatic panel and not a high voltage supply like your have for a neon lamp or a transmitter - this is a very low current supply since all it has to do is supply charge to the tweeters, not current. Therefore you need a somewhat special meter to measure the voltage, a regular DVM won't work. There are ways to measure this voltage; consult one of the electrostatic speaker forums for advice. My point is, don't just stick a DVM on the supply and expect to get any kind of accurate measurement. But once you have a method of measuring the high voltage bias (special meter or special setup for a regular meter) you'll want to compare the GOOD speaker's bias voltage to the bad speakers. As I recall the RTR tweeters use about 7,000 to 8,500 volts - something like that. Note that even though the current is quite low, 8 thousand volts can still knock you on your ass, so unless you know what you are doing, it's not advisable to monkey around in there. I'll bet that the diodes in the ladder voltage multiplier have broken down. Find someone who can sell you a rebuilt high voltage multiplier board if you find that the bias voltage on the "no highs" panel is not up to snuff. The parts used on these voltage multiplier boards are not exotic and are readily available, so I would guess that you would be able to find some electrostatic speaker guy someplace who can either rebuild yours or sell you a rebuilt one.



====================================
Science doesn't care what you believe.

 

RE: Infinity ServoStatik - high end stopped working on one panel, posted on March 9, 2023 at 13:42:22
kentaja
Manufacturer

Posts: 4531
Joined: March 26, 2001
 Be very careful when testing there are lethal voltages involved.

I've only seen one pair of ServoStats a factory produced stacked pair. Only 2 were made this pair belonged to Cary Christie. The other was for Arnie Nudell.

With this pair I removed all the drivers and tested them one at a time. The RTR tweeters were in great shape but the midrange drivers needed to be rebuilt.

 

RE: Infinity ServoStatik - high end stopped working on one panel, posted on March 9, 2023 at 13:47:45
kentaja
Manufacturer

Posts: 4531
Joined: March 26, 2001
 The midrange panels have about 4.4kV on the diaphragm. The tweeters are around 1kV.

 

RE: Infinity ServoStatik - high end stopped working on one panel, posted on March 9, 2023 at 13:49:02
kentaja
Manufacturer

Posts: 4531
Joined: March 26, 2001
 This pair has the later black midrange panels which were built in-house. The earlier grey version were built by another supplier.

 

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