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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 18th May 2021, 4:56 pm   #61
reartech
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Default Re: Grundig tk 24

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Originally Posted by ms660 View Post
When the anode voltages are low what's the voltage measurements between pin 7 and ground and pin 8 and ground?

Lawrence.
These are following ratings observed in different pins

p-1 25v
P-2 4v
p-3-4v
p-4 0
p-5 0
p-6 10v
p7-1 v
p8-2v
p9 0v

Krishna
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Old 18th May 2021, 5:20 pm   #62
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Default Re: Grundig tk 24

Other voltages aside, pins 2 and 7 should be 0v or almost 0v when measured with respect to ground, any positive voltage on those pins will reduce the anode voltage, measure pins 2 and 7 again with the valve removed, if they still measure positive I would check the coupling capacitors to the control grids (C17, C18, C20)

Lawrence.

Last edited by ms660; 18th May 2021 at 5:29 pm. Reason: extra info
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Old 18th May 2021, 7:14 pm   #63
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Default Re: Grundig tk 24

[QUOTE=reartech;1375534]
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.

Now that problem solved its Capacitor issue i got same result in Record and play back.
Was it C10 as Lawrence suggested ?

David
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Old 18th May 2021, 9:18 pm   #64
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Default Re: Grundig tk 24

If you have not already done it, it is important also to check the Control grid voltage of the EL 95 output pentode at pin 1. As per the ECC 81 Control grids, if any +ve voltage then best to replace both C22 (0.1uF) & C26 (0.047uF).

David
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Old 18th May 2021, 10:07 pm   #65
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Default Re: Grundig tk 24

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Originally Posted by ms660 View Post
Other voltages aside, pins 2 and 7 should be 0v or almost 0v when measured with respect to ground, any positive voltage on those pins will reduce the anode voltage, measure pins 2 and 7 again with the valve removed, if they still measure positive I would check the coupling capacitors to the control grids (C17, C18, C20)

Lawrence.
Yes Sir I will Check And update
Krishna
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Old 18th May 2021, 10:08 pm   #66
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Default Re: Grundig tk 24

[QUOTE=DMcMahon;1375624]
Quote:
Originally Posted by reartech View Post
Quote:
Originally Posted by reartech View Post
.

Now that problem solved its Capacitor issue i got same result in Record and play back.
Was it C10 as Lawrence suggested ?

David
yes it is C10 as Lawrence suggested.
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Old 18th May 2021, 10:09 pm   #67
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Default Re: Grundig tk 24

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If you have not already done it, it is important also to check the Control grid voltage of the EL 95 output pentode at pin 1. As per the ECC 81 Control grids, if any +ve voltage then best to replace both C22 (0.1uF) & C26 (0.047uF).

David
i will check and update too.

Krishna
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Old 18th May 2021, 10:49 pm   #68
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Default Re: Grundig tk 24

Watching your video I find the point where you lift up the relay to get good playback sound confusing.

The relay is the Playback/Record relay (W) which is energised in Playback mode. It looks like you are lifting up the relay armature plate which is the same as the relay being de-energised which equates to Record mode but this seems to be when you get good volume, to me this appears to be the opposite of what you were describing ?

David
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Old 18th May 2021, 11:06 pm   #69
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Default Re: Grundig tk 24

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Watching your video I find the point where you lift up the relay to get good playback sound confusing.

The relay is the Playback/Record relay (W) which is energised in Playback mode. It looks like you are lifting up the relay armature plate which is the same as the relay being de-energised which equates to Record mode but this seems to be when you get good volume, to me this appears to be the opposite of what you were describing ?

David
Actually The problem was solved and system given good sound through Head but now in both mode Audio is too low earlier it was in record mode full sound but playback it is too low
Krishna
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Old 18th May 2021, 11:14 pm   #70
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Default Re: Grundig tk 24

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Quote:
Originally Posted by ms660 View Post
Other voltages aside, pins 2 and 7 should be 0v or almost 0v when measured with respect to ground, any positive voltage on those pins will reduce the anode voltage, measure pins 2 and 7 again with the valve removed, if they still measure positive I would check the coupling capacitors to the control grids (C17, C18, C20)

Lawrence.
Yes Sir I will Check And update
Krishna
Sir when i Remove Cap on Pin 2 i got 0 volt but audio signal on pin 2 and pin 1 and 6 have got their rated voltage ie 100 and 140 but pin 7 4 volt again i removed cap from pin7 i got 0v on pin7
cap leg removed from pin 2 shows 150v
cap leg removed from pin 6 shows 4 volts
What next ?
Krishna
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Old 19th May 2021, 6:42 am   #71
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Default Re: Grundig tk 24

Definitely replace C20, it is very electrically leaky indicated by the 150V measurement.

I assume your "cap leg removed from pin 6 shows 4 volts" should have read "cap leg removed from pin 7 shows 4 volts". The 4V (1V when connected) shows that both C17 and C18 are both somewhat electrically leaky so best also to replace C17 & C18, they will only get worse with age anyway.


David

Last edited by DMcMahon; 19th May 2021 at 6:49 am.
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Old 19th May 2021, 7:09 am   #72
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Default Re: Grundig tk 24

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Definitely replace C20, it is very electrically leaky indicated by the 150V measurement.

I assume your "cap leg removed from pin 6 shows 4 volts" should have read "cap leg removed from pin 7 shows 4 volts". The 4V (1V when connected) shows that both C17 and C18 are both somewhat electrically leaky so best also to replace C17 & C18, they will only get worse with age anyway.


David
Ok sir I will Do as per your instruction; and update the same Thank You very Much for valuable knowledge sharing, I was Totally 0 in Vintage Equipments especially Valve technology where as both of you guided me a lot
Regards
Krishna
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Old 19th May 2021, 7:36 am   #73
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Default Re: Grundig tk 24

Still strongly recommend to check the output pentode Control grid voltage as per Post 64.

If C22 and C26 are electrically leaky or become leaky later then worse case scenario is that the output transformer could get damaged.

If you have an insulation tester/Megger then you could test the coupling capacitors (out of circuit) for their resistance. Test at their rated voltage or at least their circuit working voltage, you will see that new capacitors will be virtually infinite (> 100s MOhms) and old/bad capacitors will be much lower value.

David
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Old 19th May 2021, 7:40 am   #74
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Default Re: Grundig tk 24

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Originally Posted by reartech View Post

Actually The problem was solved and system given good sound through Head but now in both mode Audio is too low earlier it was in record mode full sound but playback it is too low
Krishna
Yes fully understood, it was just that my interpretation of the video at the point where you lifted the relay appeared to indicate the reverse but that is maybe just me being confused

David
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Old 21st May 2021, 10:07 pm   #75
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Default Re: Grundig tk 24

Quote:
Originally Posted by DMcMahon View Post
Quote:
Originally Posted by reartech View Post

Actually The problem was solved and system given good sound through Head but now in both mode Audio is too low earlier it was in record mode full sound but playback it is too low
Krishna
Yes fully understood, it was just that my interpretation of the video at the point where you lifted the relay appeared to indicate the reverse but that is maybe just me being confused

David
Dear sir I am unable to get old capacitors is there any alternative cap in present market i will update soon i replace caps
thank u regards
krishna
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Old 21st May 2021, 10:54 pm   #76
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Default Re: Grundig tk 24

You do not have to use old capacitors, even if you source NOS (New Old stock) due to age they can be bad as well.

Any good quality modern capacitors such as Polyester, Ceramic, Polypropylene etc will do.

I personally prefer Polypropylene Metal Film, I use 630VDC rated axials but not the expensive Hi-Fi audio grade type.

David

Last edited by DMcMahon; 21st May 2021 at 11:13 pm. Reason: Typo correction
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