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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 28th Jan 2020, 11:57 am   #1
nmiddlemass
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Default Grundig TK121 - No Sound

Good Morning

I have a Grundig TK121 Reel to Reel Machine. It is in great cosmetic shape and mechanically it functions well.

The issue with the machine is there is no sound output from it.

When I raise the volume, you can hear the volume of speaker hum increase.. It is as though there is no audio reaching the volume slider.

Visually the boards and components look OK and there are no broken wires etc..

Could anyone suggest what the issue may be? I have read elsewhere that other machines could have issues with the record switch..

Alternatively, if anyone could suggest a work flow order of things to check I'd be grateful..

Thank you for taking the time to read the post.

Regards.

Neil
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Old 28th Jan 2020, 4:38 pm   #2
DMcMahon
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Default Re: Grundig TK121 - No Sound

Hi Neil,

A silly question maybe, but are you happy that there is recorded sound on the tape you are trying ? if any doubt than if possible prove tape is OK on another machine and/or try doing a recording and then playing back.

Maker sure the Playback head is really clean and that the tape is making proper contact with the Playback head surface, also make sure you do not have the tape back to front ( I have done it and wondered why there is no sound, so easy done !).

Regards

David
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Old 28th Jan 2020, 11:34 pm   #3
Welsh Anorak
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Default Re: Grundig TK121 - No Sound

If you remove the top cover and select 'play', you shuld get a pretty loud hum at a reasonable volume setting if you touch the record/play head's connections with a wet finger. If that's the case then David's advice is very sound, speaking as someone who only recently wound a tape backwards! If you've got a clean head and there is definitely a good recording being played, then it's possible the head's open circuit. I have a 141 which has this problem, unfortunately. It seems the heads used on these transistorised machines weren't as robust as the ones for the valved ones (TK120, 124 and so on).
Of course if there's no buzz, then it's time to investigate the early AF stages.
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Old 29th Jan 2020, 10:24 pm   #4
DMcMahon
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Default Re: Grundig TK121 - No Sound

Good input from Glyn above, be careful not to try that in Record mode, the fairly large HF record bias signal going to the record head may possibly bite a little.

Another possible thing to try Neil is the following (Note I am not sure if your TK 121 works the same as my TK 141/146s (have not had time to compares the circuits).

Setup the recorder for recording using a microphone or music source connected into the DIN input. Press the record button and select Pause (the record button should then stay locked down).

By either playing music into the DIN input or speaking into the microphone adjust/increase the Record level slider and you should see the record signal on the VU meter.

Then by increasing the volume control slider you should hear the record signal through the loudspeaker, i.e. you are monitoring the source. If this works, at least it proves that the later stage (s) of the Playback amp are functional. This is the bit I am unsure about if the TK 121 has this Source Monitoring functionality, the same as the TK 141 /TK 146, if you have the User manual for the 121 it will reference monitoring, either explaining the same as what I have just explained or otherwise it will say something like monitor via earphone/headphone connected to the headphone DIN socket.

Then you can switch from Pause to Play and it will record, you can then playback the new recording to see if any sound played back, if the source monitoring through the speaker works during Paused record it will also work during actual recording.

Note - If doing microphone record tests, then if the microphone gets too close to loudspeaker area and volume is set too high then you will almost certainly get loud feedback howl.
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