Grundig TK40 TK46 Replacement Idler

[Phantomrose1999]

Hi all,

As you know i kinda love the old grundig R2R's. The TK40 i have had the usual metal disintegration problem with the main idler that drives the play take up spool.

A very common problem with these. And the best new is there is a solution !

I was wrecking 2 Tanberg 3300X units, to get the motors and transformers, and i saved the rubber idler in them.

Through magic and with a little sandpaper, the Tanberg 3300X idler fits the TK40 and TK46 units and the unit can drive the play spool like new !!!

Please see my video on this.

https://youtu.be/UH_YhY0n9W8

Unfortnatley the brake mount just fell apart while testing it, and i am not sure the head is working, as i tried a tape and there was not much !! But i did learn a great lesson.

David

[Phantomrose1999]

Just a quick update

fixed the disintegrating idler support with JB weld, stuck it an coated the whole thing in it and now its solid !

The FF was not working welll, and i found the main drive wheel that has a belt form the motor, had dropped lower into the chassis and not correctly engaging the idler to drive the FF spool. Added a few shims under the main drive wheel from the motor and its silent and works well

please see

https://www.youtube.com/watch?v=XbXxhs5SQ20

https://www.youtube.com/watch?v=5PQ8h1Ey-Lw

I noticed the motor is weak and stops easily, maybe the motor cap is going.. Also the head is worn through corrosion, and the sound is bad, but it does make some noise. At least the head coils are not open...

[ricard]

Excellent work regarding the idler! We should start compiling a database of this kind of interchangeable parts.

As for the idler support, I think that over time the disintegration of the original will continue, causing it fall apart somewhere else. At least that has been my experiencing when die cast parts like this start falling apart; it's not just some internal tension that needs to be relieved, but a process that sees no end.

[ben]

Good to see you got a 'salvage solution'!

Personally I'd be more interested in doing this the other way round - the Tandbergs being a far better machine than the Grundig. The Tandberg idler rubber tends to go hard, I have an early series 15 waiting for one here.

[Phantomrose1999]

Ben, I like the Grundigs because they are all valve and built to withstand atomic blasts. The Tanberg 3300x was so light in comparison it was amusing and finally the Tanberg 3300x are all transistor units.

Whats interesting with the Tanberg 3300x is that all the transistors are commercial units with identification that i know, such as the BCxxx and BFxxx. I kept the motor as its a beautiful 240v unit, and all the electronics, so i can strip it one day.

[Phantomrose1999]

Originally Posted by ricard

Excellent work regarding the idler! We should start compiling a database of this kind of interchangeable parts.

As for the idler support, I think that over time the disintegration of the original will continue, causing it fall apart somewhere else. At least that has been my experiencing when die cast parts like this start falling apart; it's not just some internal tension that needs to be relieved, but a process that sees no end.

Richard, JD Weld turns to a solid metal like substance, and given i covered the whole piece in it, (which has crumbled into 3 pieces) its like casting a new piece with the old former inside it. There is no way it can break again, even if the original inside it totally disintegrates, the outer shell i add will keep it together. Great way to restore the poor castings from Grunding.

The original idler was around 62mm, the replacement was a 58MM unit. The hold is around 3-4M. I think there may be turntable idlers that also fit.

[ben]

Originally Posted by Phantomrose1999

Ben, I like the Grundigs because they are all valve and built to withstand atomic blasts. The Tanberg 3300x was so light in comparison it was amusing and finally the Tanberg 3300x are all transistor units. .

Well, the top frequency response of the Grundig is 18khz with w&F at 0.1%, while the Tandberg goes to 22khz with W&F at 0.07% - I know which one I'd prefer! For me, the sound quality is the first consideration. Build quality is important but it isn't everything.