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grundig: Loudspeaker swap from Grundig 8042 to 9040

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Forum » Radios and other type of sets (Physics) etc. » MODELS DISPLAYED » grundig: Loudspeaker swap from Grundig 8042 to 9040
           
Xavier Lemercinier
 
 
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02.Apr.21 12:04
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Over the last few years, I’ve been slowly rebuilding a Grundig 9040

And I now just got a 8042W/ 3D whose cabinet is unfortunately beyond repair ( at least for a radio hobbyist with reduced wood work ability ) so decided to salvage it …

 

My 9040 needs a replacement speaker and I have three questions regarding a possible loudspeaker changeover   

  

1) Are the front loudspeakers the same on both 9040 and 8042 ?  can they be swapped from one to the other model ? ( Both the dynamic and static )

They look the same on both models and bear the same mark ‘Grundig 287’

2) Second question is about the working conditions and electrical characteristics of the static tweeters

On the 9040 schematics

 

 

I wonder what does ‘120v ‘ indication mean ?

I guess it’s not a DC measured voltage? could it be a rating for a possible maximum audio voltage – but it seems to be huge?

Given the static loudspeakers are connected to 350 volts supply via the divider R237 and R238

one would expect their operating bias voltage is 290 volts; but the measured bias voltage will strongly depend on the instrument used.  

 

3) About the instrument used to measure voltages ... on the schematics it says:

What is a ‘ UVA ‘ ?  is it a multimeter , like an ‘ordinary’ 20kohms/volt – or a valve voltmeter ? Forgive me for my poor understanding of german

Thanks

Kind regards

X Lemercinier

 

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This article was edited 02.Apr.21 13:55 by Xavier Lemercinier .

Eilert Menke
 
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02.Apr.21 14:56
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Hello,

I don't want to say anything about the speakers because I don't know this radio. But, however in my opinion, nothing speaks against the interchangeability. The principle of operation should be the same.

The measuring device in question is a normal multimeter, either this or that.

EM

Daniel Consales
Daniel Consales
 
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03.Apr.21 11:50
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Hello Mr. Lemercinier,

as you said the real voltage at that devider is about 290V (if ua = 350V). The 120V value is only a 'number' to help finding errors. The mentioned "UVA" is used at 600V range - so the internal resistance is only 500k !

If you calculate the voltage devider again now (500k in parallel th R237) you get about "110V".

But in this case, even if you use a DMM with 10 Megohms internal resistance, you'll read about "270V" - which is not real, too ;-)

Regards,

D. Consales

BTW: the fatal thing is: if R237 is broken, you can hardly find the errror with an UVA ... it will show "117V" then.

This article was edited 03.Apr.21 12:00 by Daniel Consales .

  
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