Opus 8


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This is a Telefunken Opus 8.  A beautiful sounding radio utilizing push pull EL-84 output tubes driving six speakers.  Two of the six speakers are electrostatic speakers driven off of the plates of the final audio output tubes.  Full specs are listed by Radiomuseum.org.  

The circuit restoration is similar to the Grundig line of radios.  The electrostatic tweeters are serviceable on the bench or in the cabinet.  The electrostatic speaker restoration is featured below.

 

IM000173.JPG (1069598 bytes)Four bands IM000173.JPG (1069598 bytes)FM, AM, SW and Long wave with phono pickup and tape recorder input. IM000171.JPG (1276742 bytes) This is a big radio. IM000020.JPG (779392 bytes)Six speakers IM000021.JPG (559877 bytes)
IM000024.JPG (929914 bytes)Similar to Grundig.  Space for new electrolytic under chassis. IM000025.JPG (803267 bytes) That is NOT rust on the dial scale reflector.   IM000022.JPG (448373 bytes)Mark the electrostatic leads.  IM000023.JPG (431938 bytes) IM000142.JPG (987239 bytes)Bench disassembly.  Twist lock tabs.
IM000143.JPG (969869 bytes)Be Gentle.  Open up the assembly.  IM000144.JPG (1012658 bytes) There is the deteriorated foam.  It turns to crumbs when touched. Brush it off.  IM000146.JPG (967048 bytes)Gently remove the diaphragm. IM000147.JPG (1035308 bytes) Mark up a new section of foam rubber.  IM000148.JPG (1054582 bytes) Clean the tarnish from the press fit contact points. 
IM000152.JPG (1141764 bytes)Clean the diagram contact point only.  You can rub off the metal leaving unconductive plastic.  IM000153.JPG (708884 bytes) I rebuilt the left side tweeter in the cabinet.  IM000154.JPG (720325 bytes) IM000155.JPG (570465 bytes) 'Brush off the old foam rubber.  IM000156.JPG (651897 bytes) Insure it is clean no rust.
IM000157.JPG (879427 bytes) Separate the insulator and the diaphragm.  IM000159.JPG (944021 bytes) Hot wire cut a new ring of foam.  The 100w lamp is in series with a length of salvage wire wound resistor wire.  IM000160.JPG (823877 bytes)  IM000163.JPG (877443 bytes) Use rubber cement to secure the new ring. IM000164.JPG (893873 bytes) Glue a little square of foam rubber opposite of the lead wire contact to insure good contact with the diaphragm.
IM000165.JPG (855403 bytes) Reassemble the diagram lining up the area that you cleaned with the contact.  IM000166.JPG (833062 bytes) Push it all back together. IM000167.JPG (829263 bytes) Twist lock the tabs.  IM000170.JPG (1061460 bytes) Alligator clip lead the tweeters to the chassis for a test! Check you work.  You will not hear overwhelming treble like modern tweeters.  The German engineers designed this tweeter to compliment the whole acoustic compliment. 
IM000173.JPG (1069598 bytes) Looking good. Sounding great.         

 

 

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