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audioson: Information about component

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Forum » Radios and other type of sets (Physics) etc. » MODELS DISPLAYED » audioson: Information about component
           
Georges Van Campenhout
 
 
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28.Mar.20 17:27

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Dear Forum members,

I just uploaded a hand drawn circuit diagram for this model.

There is one component that bothers me:

it is C1: I unsoldered it, and it doesn't seem te be a capacitor.

It has a green stripe on top, and one wire has been cut.

It measures 9 x 12 mm.

When I measure the C-value, it gives about 12 nF, but when I measure the resistance it gives 3400 Ohms. I suppose it is a R-C combination.

Can anyone tell me more about it, please?

Thank you!

 

 

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Steffen Thies
 
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28.Mar.20 20:59

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Dear Mr. Campenhout,

sorry I can't open the schematic on this computer, so I can't verify if my guess makes sense. But that looks either like a voltage dependent resistor or more likely a NTC / PTC. VDR have definitely a large parasitic capacitance, for thermistors I don't know. But they're ceramic, so maybe...if it's not the resistance irritating your meter.

Regards,

Steffen
 

Giovanni Cucuzzella
 
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29.Mar.20 01:51

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Hallo Herr Thies,

die Datei läßt sich über den "Umweg" Unterlagen-Alle Pläne heruterladen und öffnen. Warum das wie gewöhnlich durch anklicken nicht funktioniert weiß ich nicht.

Freundliche Grüße

Giovanni Cucuzzella

 

Steffen Thies
 
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29.Mar.20 12:55

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Hallo Herr Cucuzzella,

warum's nicht geht, ist klar: Win98! Ihr Hinweis ist aber spitze, da kann ich noch ein wenig mit dem Dinosaurier weitermachen. Danke!!

Mr. Campenhout,

you're right to expect a capacitor at that position in the circuit. I also searched for a thermistor as stabilizer in such an oscillator, but couldn't find anything, and I don't remember this also. 
So perhaps it's just a damaged capacitor. Actually why did you remove it, does the radio refuse to work?

Regards,

Steffen Thies
 

Giovanni Cucuzzella
 
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29.Mar.20 13:32

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Hallo Herr Thies,

die Ursache dieses Problems sehe ich eher Serverseitig. Gestern hat es auf meinem Smartphon (Samsung S4 Android 5.01, Mozilla Firefox-App) nicht funktioniert. Auch auf meinem PC unter Windows 7 hatte ich das Problem. Heute nochmal probiert und festgestellt, dass es auf dem PC funtioniert und auf dem Smartphone weiterhin nicht. Ich denke, dass es nicht an Ihrem PC mit Win 98 liegt. Dieses seltsame Verhalten habe ich schon häufiger beobachten können und bin also schon früher auf oben beschriebenen "workaround" gekommen.

Freundliche Grüße

Giovanni Cucuzzella

Georges Van Campenhout
 
 
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29.Mar.20 14:49

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Dear mr. Thies,

thank you for your answer.

The reason why I unsoldered the component is following:

As I mentioned in my first post, I tried to draw the circuit diagram of the EK80. I was unable to read the value of a number of components because they are very densely mounted on the pcb.(they do not have a value written on my diagram), amongst them C1.

If you look carefully at the picture of the component, you'll see that there are 3 connecting wires, one of them has been cut. This was so in the circuit, I did not cut it.  The two extreme wires A and bB are at one side, and the middle one C at the other side.

I measure (using a Voltcraft LCR meter LCR-9063) between A and B ca. 3400 Ohm/ 12nF, and between B and C equally 3400 Ohm/ 12 nF.

Between A and C: nothing!

I am almost sure that the capacity measurements are faulty, since the instrument indicates a value only at the range 200 nF. Nothing at the other ranges!

Strange!

Any thoughts are welcome.

Best regards

 

 

 

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Giovanni Cucuzzella
 
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29.Mar.20 16:52

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Hello Mr. Campenhout,

it could be a double ceramic capacitor, but only half of it was used. If so, it is defective because of the measurable resistance of 3400 ohms. The connection between A and C should be low-resistance. However, you write that this connection does not exist. Can you check that again?


I found here htt  ps  :   //  books  .google.  de  /books?id=iSUDAAAAMBAJ&pg=PA202&lpg=PA202&dq=double+ceramic+condenser&source=bl&ots=hPTBoy4VRT&sig=ACfU3U0VxHZ8DcRdXmmQD-RtHn9PnLSk0Q&hl=de&sa=X&ved=2ahUKEwjki8Dr6r_oAhWIyKQKHWwXAtMQ6AEwDXoECAsQAQ#v=onepage&q=double%20ceramic%20condenser&f=false

beginning on page 197  a circuit with a double capacitor (C4a, C4b).
 

Also here htt  ps  :  //  www   .murata.  com/~/media/webrenewal/products/emc/emifil/knowhow/20to22.  ashx

another information sheet regarding such a capacitor from Murata.

Note: Please remove spaces in the given links

regards

Giovanni Cucuzzella

This article was edited 29.Mar.20 16:53 by Giovanni Cucuzzella .

Georges Van Campenhout
 
 
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29.Mar.20 17:39

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Good afternoon mr. Cucuzzella,

Super!

This is indeed the correct answer: it is a double ceramic capacitor, where point A and C are the same conductor.

I join a picture where I added in a dotted line the conductor, an I included a schematic drawing of such a component(source: Murata leaflet)

It is clear that my item is defective.

I guess that its value should be 50 nF, referring to the green strip on top.

Thanks again and best regards.

 

 

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Georges Van Campenhout
 
 
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31.Mar.20 20:08

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Good evening dear forum members,

I have to come back to the subject.

The component is not a singe capacitor. I replaced the supposed defective one with a ceramic capacitor of 50 nF: no result.

Then I tested the set with a 3k3 Ohm resistor in parallel with a 50 nF capacitor, and the radio plays well.

This was easily possible, since the pcb has provision ( 2 times 2 holes ) for the two components.

This is good visible in the detail picture.

Last test: I mounted the original component again, and the radio is OK.

Conclusion: the component is a parallel mounting of a 3400 Ohms resistor with a 12 nF ceramic capacitor.

 

P.S. Please compare with the Maro WX3: there is the same component, but with a red marking on top.

The Maro uses also other HF transistors .

 

 

 

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This article was edited 31.Mar.20 20:18 by Georges Van Campenhout .

Steffen Thies
 
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31.Mar.20 21:04

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Dear Mr. Campenhout,

you proved nicely that the resistance is part of the circuit. However I can't believe that such a cheap set uses a special component when a standard R plus a C do the job. Did you check if resistance changes when warming the part with your fingers? I strongly suspect this is a temperature stabilization for the oscillator.

Regards,

Steffen Thies
 

Günther Stabe
Günther Stabe
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31.Mar.20 21:03

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Hi all,
all the days I thought on a R/C combination like in this schematic with one this coupling / biasing methodes (schematic is from this radio) - but I am not a professional expert so I kept quiet...
G.S.

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This article was edited 31.Mar.20 21:06 by Günther Stabe .

Georges Van Campenhout
 
 
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01.Apr.20 17:47

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Dear Mr Thies

Upon your suggestion,  I unsoldered the component and measured the resistance under following conditions:

  • cooling down till freezing with Kälte Spray: very small change
  • warmed up with fingers: no change
  • room temperature: no change

I think we can assume that it is not a thermistor.

Best regards

 

Steffen Thies
 
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01.Apr.20 20:48

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Thanks a lot for checking again!
 

  
rmXorg