3035 USA


Home Up 3035 W/3D USA 3035 USA 5088 5088 w/EM34

 

 

This is the second of two featured 3035s.

 

3035 w/3D USA 

 

IM000102.JPG (75879 bytes) As received IM000101.JPG (74642 bytes)Look left IM000100.JPG (72284 bytes) Look right IM000099.JPG (61969 bytes) Broken Ferrite Antenna support quickly repaired with Hot Melt glue gun.  Replacing and stringing the dial cord was a different matter.   
IM000103.JPG (75529 bytes) Out of the cabinet shot.  IM000109.JPG (64857 bytes) I ALWAYS store the dial glass separately.  I do not want an accident and have to find a replacement! IM000106.JPG (84954 bytes) The blue capacitor just under the left side of the switch enclosure was shorted.  You can also see the burnt (open) 1k ohm resistors that the short took out.  IM000107.JPG (80720 bytes)The yellowed paper capacitors can be seen under side.  The blue capacitors are also paper inside.  
IM000128.JPG (305335 bytes) Restored and working.  Products on the left used to shine the knob brights and treat the plastic.  Glass cleaner took care of the dial glass.  TEST the paint before cleaning. IM000129.JPG (178357 bytes) No flash and  Light Out shot. Sorry.  I did not take a picture of the restored under chassis.  I will post one if I disassemble the unit again.  All the paper and blue capacitors have been replaced with yellow tubular caps that are considerable smaller in size but all rated at 630 volts. In the picture directly above,  between the two horizontally oriented blue caps, is a dark circle with three wires.  Two electrolytic capacitors mounted to a new terminal strip replace the chassis mounted can capacitor.  The wires were moved to the terminal strip and the can cap left in place for appearance sake.  Again sorry for not taking an after picture. See the Capacitor Page for an example. 

 

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.

 

bridge start.JPG (227543 bytes)  This is the flat pack selenium rectifier bridge removed from the radio.  A screw driver, pliers and a soft touch will slip the cover off. inspect diode.JPG (357921 bytes)  Once the cover clears the bottom metal container the top flies across the table and little square metal pieces shower back down on your bench.  Those are the selenium wafers.   Drill .JPG (58982 bytes)  Trim the contacts so one pad per solder contact remains.  Drill two holes in each to receive the 1N4007 lead wires.
lable install diods.JPG (131963 bytes)  I tapes and labeled the solder pads in accordance to the stamped terminal identifiers in the metal cover plate (the one that shot across the bench).   4 diodes.JPG (509973 bytes)  Install and solder all four diodes. bridge done.JPG (474160 bytes)  Reassemble making sure all the insulating materials are returned inside the metal enclosure or a high voltage short will occur.  That's it!

 

Also see the bottom half of the Electrostatic Tweeter page for the 3035 tweeter repair.

 

 

DIN Switchbox

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.

DIN switchbox.gif (4816 bytes)  Schematic Diagram. IM000151.JPG (192704 bytes)  Front view. IM000152.JPG (198152 bytes)Rear view of switch box. IM000153.JPG (192541 bytes) DIN connector in the Grundig 3035.

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.

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