Electrostatic Tweeters

What is a good way to repair, or rather bring back to life these tweeters that were wsed in table radios in 50's and 60's.

Does blowing air help?

How about replacing the foam backing?

How should one fix these type of tweeters?

Omer
 

Added by EE 6th Sept. 2008:
Here is a very good article about Electrostatic Tweeter Restoration.
By our member Paul Pinyot. He shows methodically and with explaining pictures how you can bring to life a dead Electrostatic Tweeter.
 

To thank the Author because you find the post helpful or well done.

Dear Omer,

first of all: the carrier pidgeon is on it´s way to Los Angeles !

Back to your inquiry: I don´t know your german language skills but there are already a few artikles dealing with this subject, I´d suggest following this link: http://www.radiomuseum.org/dsp_forum_post.cfm?thread_id=18685#post18682

One of the most important issues: These tweeters need high voltage to operate and  it is essential to fix the membrane-film correctly.

To thank the Author because you find the post helpful or well done.

BIG THANKS Hans for your time and efforts promoting our hobby by helping us with the forum, vacuum tubes, etc.!

I did go to the forum, and with the aid of Babel Fish, translated everything roughly into English.

Sending tweeters for repair might be a solution, but if someone has any homegrown suggestion those are welcome too.

Jan Wuesten (AskJanFirst) was telling me about someone in the Netherlands that has the myler film used in these tweeters.

I was wondering if there are web sites, etc dedicated for the repair of these types of tweeters.

Or maybe methods used ot get more years out of these tweeters.

Omer

To thank the Author because you find the post helpful or well done.

I have rebuilt the two tweeters in my Emud T-7.

The foam I used was sold in a hardware store as a replacement airconditioner filter. (It was a rectangular piece of foam approximately one-quarter inch thick with no frame.) This foam seemed to provide a proper pressure for the mylar diaphram and it had an appropriate structure of large open cells.

The treeter was originally held together by melted plastic. I drilled and tapped these locations in the plastic tweeter body for 2-56 screws, one-quarter inch long. I used a tap drill that was one size undersize to give better threads in the plastic.

The + connection in my tweeters was different from the tweeter on Paul Pinyot's web page.  This connection was made by a strip of metallized mylar that was rivited to the + terminal and pressed against the back of the tweeter diaphram so the metallized surfaces touched. The pressure was provided by the foam behind the diaphram. There was a problem that the metallization on the mylar connecting strip had a broken connection caused by voids in the metallization. (This may have been caused by the current flow over many years or corrosion.) I was able to repair the metallization using a conductive copper paint that I found in an auto parts store as part of a kit to repair the rear-window defogger grid in a car. This kit was made by Loctite. (I would avoid using the conductive paint on the tweeter diaphram since this would substantialy increase the moving mass.)

The rebuilt tweeters sounded fine when they were outside the radio, but when mounted in the radio cabinet they were difficult to hear. I believe the grill cloth and plastic grills reduce the sound output. I cannot tell how the rebuilt tweeter performance compares to their operation when new.

To thank the Author because you find the post helpful or well done.

I understand that you can check these speakers by temporarly disconnecting the paper cone speaker(s)and then turning up the volume and treble.

Omer

To thank the Author because you find the post helpful or well done.