Electrostatic Tweeter repair and restoration.
This is a German made electrostatic tweeter. It has failed like so many others of this vintage. This tweeter is from a 1959-60 Emud Junior 196 six tube AM/FM radio. There were three choices involved with this speaker, leave it in the unit dead, find a replacement that works or repair the existing speaker.
If one wiggled the positive contact while playing the radio the sound would cut in and out. It was a quite subdued sound but present none the less. So see below the steps to restoring this Electrostatic Tweeter speaker.
Note below the three main problems that contributed to the failure of this speaker. All caused by deteriorating foam.
GRUNDIG 3035 w/3D USA
This is a flat square electrostatic tweeter from a Grundig 3035. It had a corroded contact that is press fit against the conductive vibrating membrane. Disassembly and sanding off of the corrosion where the contact touches the membrane is all that was needed.
A new Tweeter failure mode
I came across a new failure that I have not seen. The conductive coating has been ruined. Almost like eaten away. This essentially disconnects the conductive film from the positive solder lug rendering the tweeter silent. Simple replacement of the foam is not the solution. I had to find a replacement conductive film to fix this problem
After spending a day researching the internet and talking to technical sales people I discovered there is little hope for a simple cost effective source of materials. The Chinese manufacturers want a minimum order of four metric tons. Well they can forget about that. US based distributors have to contract out the coating of Mylar to make one side conductive. But I was not satisfied.
I came across some Mylar model airplane covering on the internet. So I headed to my local hobby shop with a micrometer and DVM in hand. They did not have anything that was conductive on one or both surfaces. I left defeated.
On the way out of the parking lot I stopped at a Dollar General for a pop (soda pop). While inside the Dollar General I spotted the Mylar balloons floating at the ceiling. A buck fifty for a cartoon character and a buck for a plain silver star. I bought the star.
At home I let out the gas (did not inhale it) and cut the star open. The exterior was conductive. I got around 20 ohm per inch and a half. The interior was an insulator. Yreka! The original conductive layer is near zero ohms. I figured with such high impedances in this tweeter system what do I have to loose?
I reopened the tweeter with the fresh foam and pulled out the diaphragm. Traced around it and cut it out. Once inside the tweeter housing I connected the B&K digital cap meter and heard the familiar little buzzing tone and read about 600 pf. Connected it up to the radio and WOW. A dollar fix!
Enjoy the pictures below on how I facilitated this repair.
Remember after the next Birthday party save some of those Mylar floating balloons. It is up to you what you do with the helium.
To see other Tweeter restorations see:
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