This is a 3055 with 3D sound USA Version. This case is in Excellent shape. Nothing needs done with the wood finish. The plastic parts were cleaned and treated with Glayzit. The Dial glass cleaned and the red line on the FM indicator repainted.
The original Eye tube is an EM-85 (6DH7). This has been replaced by an EM-81 that looks the same but with different pin outs. The specs of both tubes closely compare. The EM85 is hard to get and very expensive tube, if you can find one. Both popular vintage radio vendors that I do business with do not carry it. And I do not want to risk the likely probability of a re-marked or fake eBay purchase.
This is the second of two featured 3035s.
Selenium Bridge Rectifier retrofit with 1N4007.
Selenium rectifiers loose their efficiency over the years. It is common practice to replace them with silicon diodes of similar capabilities. I use 1N4007 diodes with a 1000 volt PIV. That stands up easily in a tube type radio B+. Some applications a series resistor is added to compensate for the much lower voltage drop of the silicon junction diode. This is to bring the B+ back down to specifications. Below is a pictorial of how a flat bridge rectifier was retrofitted.
Also see the bottom half of the Electrostatic Tweeter page for the 3035 tweeter repair.
I wanted to hook up some external audio sources to the Grundig. So I took a Radio Shack switch box modified the circuit board and added video quality dual shielded coaxial cable terminated with a three pin DIN. It works well.
The output of the Grundig is routed to the two RCA output jacks on the switchbox. This provides for recoding off of the air programs on AM, FM or SW bands. The signal seems a little weaker than standard line output so the recorder's manual gain had to be set high.
Three inputs can be selected with the three push buttons. I have hooked up a DVD player playing Shania Twain "UP" album, A cassette tape deck (I tested the off the air recordings) and a monaural source, my FM amateur radio transceiver. All three sounded GREAT through the Grundig.
Use the tape button on the front panel of the Grundig to play the source going through the switch box.
I was curios to the frequency response of this modification. There are a lot of people rightfully concern with audio losses due to cable losses. So I preformed a little test.
Unfortunately, I did not own an Audio Generator so I used the lower end of my RF generator (HP-606a) along with a 100mhz B&K Oscilloscope and a 100k ohm termination resistor (as in the Grundig).
I found no frequency roll off between the frequencies of 56khz and 20 mhz. Therefore, I can conclude frequencies below 56khz down to DC are also unaffected.
This is a third 3035 restored.
It came in non functional with an open line fuse. Putting a new fuse in and using a DBT the radio came to life. Not much life but hearing some weak stations on all bands is a quick check of all the important parts that contain "Unobtainium"( Illusive material, substance or construction method no longer available on the planet Earth).
See the photos below:
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