Grundig TK23

[OliverWestby]

I have a grundig TK23 reel to reel tape recorder, I have replaced all the capacitors, yet the erasing head doesn't work. I have checked the wires using a scope, and came to the conclusion that there was no signal being produced.

Does anyone know how to fix this problem, and where I can get a schematic from.

Thanks
Oliver

[Roy]

Hi Oliver,

I repaired a TK23 a while ago, and if I remember correctly, the EL95 has a dual function - erase/bias oscillator for recording, and output for playback. If it plays back satisfactorily, the valve is probably OK.

There is a switch which disconnects the erase heads when the "superimpose" function is selected - this operates when the record button is turned. Have you checked this switch, and the track selection switches?

The TK23 is listed in Paul's "service data by email" facility at http://www.service-data.com/

Hope this helps,

Roy

[AndiiT]

Hi,
I had a similar problem on an Elizabethan LZ 29 some years ago - check the electrolytic capacitor that decouples the screen grid of the EL95 (which presumably is the audio output valve on playback and the oscillator on record) the capcitor will probaly be in the order of around 22uF; In the event of it being faulty the erase function will not work and the audio output will be reduced on playback but not to a noticable effect, at least not until you replace the capacitor and hear the difference (which is what happened in my case )

Andrew

Whoops just read your original post and realised that you have already replaced the capacitors....doh!

[DOFFERY]

Hello Andrew, Does the machine attempt to record, best tried with a blank tape, there will be distortion without bias but a recording will take place.

Have you checked the osc.? A VTM or good anologue meter on the variable capacitor top right(adjacent take up spool, any AC readings on record, about 40/50 VAC??/ one side/200 plus other side. I presume erase head OK

If you get a reading but still no erase, check the slider(squirt of lubricant & operate rapidly) Erase head is fed direct from a tap on the osc. coil., hence possible contact problem.

If no reading on the vari, capacitor, hence no record /erase, check the simplex cap. across coil, also coil itself.

Best of British.

Doffery

[mitajohn]

Hi all,

I own a TK24 (1959 model), a four track machine. I think TK23 is the half track model. The electronics are very similar and there are separate EL95 for the audio output and the bias/erase. My suggestion: check the record relay and the contacts of the mechanical switches for recording/playback and input selection, if they are not deformed they need cleaning.

John.

[DOFFERY]

Regret to say the TK 24 & TK 23 are quite different in their circuitry, there is no relay in the TK 23 & it is indeed a four track mono machine, however there is no seperate osc. valve unlike theTK 24. The TK 24 however was a much better machine, albeit much earlier.

Doffery

[mitajohn]

Yes you are right!
I had in mind the TK20 which was the half track version of mine. I have been informed that the later model TK23 is a rather compact design with push-buttons (no rotary switches) and not very easy for servicing.

John.