grundig: 57; UKW-Concert-Boy compoents identification and

Dear RM members:

I am trying to restore my Grundig UKW Concert Boy 57, when play on line supply, sound is weak and distorted, the supply voltage is very low, measured on EL95 plate 135V (Normal 180V), on C56 170V (Normal 225V).

 I carefully checked and found R18 looks like burnt, it is marked as NSF 1810-212, I checked its risistance, it is initially 18Kohm and goes up,  seems to be stablized at 25Kohm.  Anyone know what R18 is,  a special resistor? How does it cause the problem? Where could I find a replacement?

Thank you very much for attention and looking forward to your help.

• Power supply (22 KB)
• R18 (45 KB)

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Hello Grundigfriend

The searched component is a „NTC"  (negative temperature coefficient resistor)

His Voltagetropout on 30 mAmp. is 21 volt's you must use a Type they have 700 ohms (worm) at 25 C° Roomtemp.   U / I   Values see Diagram.

I think, today only 470 or 1000 ohm's available. You can make a combination with a 470-ohm’s NTC in series with 220 normal Resistor, or 1000 ohm’s NTC and parallel a 420 (470) ohm’s resistor.

I cannot find any Data for this 50 years old original element from Grundig.

1973 VALVO offers the type:   2322 636 01473 , with 47 Kohm at 25°C and when a current of  42mA flows,  a resistance  of  800 Ohm and a  max. Powerconsumption of 1,5 Watt. I dont now, how can deliver this.

Best results!
Hans

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Hello Hans:

Thank you very much for your information, that helps a lot, I am searching for an exact replacement at this moment, if anyone knows where I can find one, please kindly let me know.

Best Regards

Songping 

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