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radionette: How do I know which tube is bad?

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Forum » Radios and other type of sets (Physics) etc. » MODELS DISPLAYED » radionette: How do I know which tube is bad?
           
Christer Wærnes
Christer Wærnes
 
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24.Feb.19 21:38

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Hello

So I restaured this radio a while back and it has been working fine until this yesterday. When I turn it on, there's alot of crackles and pops in the speakers. It's like it takes a while for it to pick up the sound and  get going. The magic eye also seems to correlate with the problem, it doesn't turn on/close until the cracks and pops goes away and there's reception. It's working ok but these noises comes and goes. It's more of a problem right when I power the radio on. I am pretty sure this is a bad tube, but there's six tubes in this radio and I don't have a tube tester. I'm thinking maybe it's the preamp tube (EF86), but that's just a guess.

If someone has any ideas it would be much appriciated, Chris

Rolf Beckers
Rolf Beckers
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26.Feb.19 18:56

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Dear Christer,

Many other reasons could be the source of your problem. If tubes are the reason, I would first try to change the EL 84 and then the EABC 80. Again many other components could make such trouble.

Regrds,

Rolf Beckers

Christer Wærnes
Christer Wærnes
 
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26.Feb.19 23:11

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Thank you for your reply Rolf.

I am now pretty sure as you are suggesting, that the EABC80 tube needs to be replaced. When I tap this tube there's a microfonic noise in the speakers, the EL84 is new. Also there is no problem using the radio to listen via the phono input. I ordered a replacement tube and I am confident this will solve the problem.

Thanks again! Christer

Uwe Roose
 
 
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27.Feb.19 16:19

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Dear Christer,
if one of the tubes realy causes the problem and, as you wrote there is no cracking when you switsch the radio on after choosing the phono input, the triode system of the EABC80 seems to be o.k.
Than chose MW before switching your radio on. If the cracking does show up again, the cracking is caused in the FM path, for instance in the ECC85, EF86 or EF89 and - less orbable -  in the diodes of the EABC80, but the ECH81 can be excludet.
An other check might be: Remove the ECC85. After switch on you should hear only noise but no cracking if the ECC85 is the culprit.
Good success.
Ragards Uwe

Christer Wærnes
Christer Wærnes
 
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27.Feb.19 20:13

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Thanks for the reply Uwe

The crackling- and pop noises are gone now and the radio works only with the phono input. When I have my PC plugged in with music, there's music on all bands- FM, SW, MW, LW. But it sounds better on "G", which is the right one for phono. Another thing I should mention is that I replaced the 0.004uF capacitors with 0.0033uF. Maybe that's too much difference in value? It's hard to find .004. Also, the voltage in my appartment is sitting at approximately 236V and that's a little bit over the radio's 230V.

Maybe the different value capacitors from the originals and the voltage in my place being higher is causing problems?

Regards, Christer

Daniel Consales
Daniel Consales
 
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28.Feb.19 09:21

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Hello Christer,

if you can hear the computer sound on all bands your computer is most likely connected to the tape output instead of the input. If that is not the case, there has to be a short somewhere.

 

P.S.: the usual value to replace 4nF (0,004µF) is 3,9nF which is easily available.

This article was edited 28.Feb.19 09:27 by Daniel Consales .

Brian Underdahl
 
 
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09.Jan.21 22:37
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I am desperately seeking dial stringing information for this model. I have the version with the EM81, but am quite certain that the dial stringing details will be the same. Unfortunately, the drive belt is in very poor shape and the wire that moves the dial pointer is broken. I need to figure out how both the drive belt and the pointer wire are supposed to be run.

 

Best regards,

Brian

  
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