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Old 10th Jan 2019, 6:30 pm   #1
Dorian27
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Default Grundig TK120 deluxe

Can any one help please. I have a Grundig TK120 deluxe, and R38 4.7 resistor is overheating. Can any one direct me what might cause this please.
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Old 10th Jan 2019, 7:48 pm   #2
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Default Re: Grundig tk120 delux

Which schematic are you using for the component references, just checked my paper version and an online version neither tie up with your component value.
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Old 10th Jan 2019, 7:55 pm   #3
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Default Re: Grundig TK120 deluxe

I am using a schematic i found on the GRUNDIG web site up
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Old 10th Jan 2019, 8:18 pm   #4
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Default Re: Grundig TK120 deluxe

Ok I've read looked at schematic and it says tk120manual but on printed circuit diagram it says TK140 I don't understand this when I get round to it I will upload pics of the circuit board with faulty resistor
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Old 10th Jan 2019, 9:40 pm   #5
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Default Re: Grundig TK120 deluxe

This is for a TK140, have you reformed the main smoothing capacitors.
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Old 10th Jan 2019, 10:22 pm   #6
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Default Re: Grundig TK120 deluxe

No I have not touched anything as I was not sure what my be causing the resistor to heat up the TK20 is identical in look to the 140 so I guess it is the same main board
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Old 10th Jan 2019, 11:30 pm   #7
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Default Re: Grundig TK120 deluxe

Hi Stephen could you tell me what capacitor I should use to change this what value and voltage etc I think I am a bit out of my depth if you can help thanks and thanks for your help so far
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Old 10th Jan 2019, 11:36 pm   #8
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Default Re: Grundig TK120 deluxe

The schematic I'm looking at for a Grundig TK 120 de luxe shows it's a transistor job.

Lawrence.
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Old 11th Jan 2019, 1:03 pm   #9
Dorian27
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Default Re: Grundig TK120 deluxe

No it's valve I have pics for you hope this helps the resistor is red something something gold thanks
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Old 11th Jan 2019, 1:26 pm   #10
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Default Re: Grundig TK120 deluxe

There appears to be different versions of that model number.

The stressed resistor could be 2.2k

Lawrence.
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Old 11th Jan 2019, 2:13 pm   #11
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Default Re: Grundig TK120 deluxe

The resistor is 68k according to the valve version circuit diagram. see extract below.

I would be checking the rectifier and associated caps in the first instance.
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Old 11th Jan 2019, 2:26 pm   #12
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Default Re: Grundig TK120 deluxe

The 68k is bleeder across the HT, it's a 1 watt job lurking behind the "unidentified" resistor in the photo.

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Old 11th Jan 2019, 2:34 pm   #13
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Default Re: Grundig TK120 deluxe

So R38 is not the one that is overheating it would seem. R28 IS 2.2 Meg and is connected to one of the grids of what looks to be an o/p stage valve. Maybe this?
To the OP: can you trace the heating resistor on the circuit board underside or post a photo? we need to see what it connects to in order to give more specific help.
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Old 11th Jan 2019, 3:45 pm   #14
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Default Re: Grundig TK120 deluxe

I have taken pics of underside and pointed to each end of resistor to where it leads
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Old 11th Jan 2019, 4:04 pm   #15
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Default Re: Grundig TK120 deluxe

That's R37 on Grundigs' TK120 schematic sheet (not titled "deluxe") which shows the board layout as well, 4.7k on the schematic but yours might be a different version....On the same bunch of schematics I have it shows the schematic for the TK124 as well but someone has written on it TK120 also, in that schematic R37 is shown as 2.2k. The source of the schematics I have is elektrotanya.

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Old 11th Jan 2019, 4:42 pm   #16
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Default Re: Grundig TK120 deluxe

For comparison (TK124)...approx. 2:46 mins. in:

https://www.youtube.com/watch?v=v7azvs3vu0Y

Lawrence.
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Old 11th Jan 2019, 5:28 pm   #17
Dorian27
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Default Re: Grundig TK120 deluxe

I have had a look on you tube and yes it looks like that .what might have caused it to heat up I wonder thank you all the the very appreciated help I just don't now where to go next thanks
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Old 11th Jan 2019, 5:32 pm   #18
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Default Re: Grundig TK120 deluxe

c15, the 50uF part of the can by the look of it is the likely cause. Change it for a 47uF. Ensure it is rated for around 400v
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Old 11th Jan 2019, 5:38 pm   #19
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Default Re: Grundig TK120 deluxe

Quote:
Originally Posted by Dorian27 View Post
I have had a look on you tube and yes it looks like that .what might have caused it to heat up I wonder thank you all the the very appreciated help I just don't now where to go next thanks
It depends on what it's feeding, maybe a leaking capacitor, or, if it's feeding the ECL86's screen grid a disconnection between the ECL86's pentode anode and HT, or a short within the valve itself.

A full view photo of the board underneath and topside might help to clear things up schematic/circuit wise.

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