Tandberg 64 - PAPST motor - help needed

[Chris Don]

Hi all,

This is a sketch of the synchronous PAPST motor HSZ 32.50-4-440, that one can find on Tandberg 64 tape recorders (made in 1965).

I have seen that a few guys here have significant knowledge about these motors, as appears in an old thread: https://www.vintage-radio.net/forum/...t=90880&page=2

As is common with PAPST motors, the bell-shaped rotor is outside the stator.
Two sleeve bearings guide the axis.
Downward, the rotor is held by a thrust (1 ball) bearing.
Upward, the rotor movement is limited by a steel washer in contact with the (stator's) sleeve bearing.

My problem is: the thing (marked with ? on the drawing) that used to maintain this washer has completely deteriorated, and I can't figure out what it was. Couldn't figure out if what remained was dust (from some kind of felt?) or rust. Looked like rust, hard and brittle.

Could anyone familiar with these motors tell me what this mystery element was? Felt or spring?...

Without this, the motor runs smoothly when vertical (gravity holds the rotor in contact with the thrust bearing) but not when horizontal (and yes, these tape recorders could be used vertically i.e. with motor horizontal).

I have contacted the EBM-PAPST manufacturer in Germany in the hope that they can still unearth a documentation of their antique motors, but I guess there is little chance they do...

Thanks for your ideas 8)

[ben]

I'm sure someone more knowledgeable will correct me, but I'd imagine there would be felt possibly to aid oil retention. I will see if I have any photos of the motor in my series 12 which dates from a couple of years later.

[DMcMahon]

I also thought possibly a felt oil retaining pad maybe.

Not sure if same end of the motor, but Post 22 in Post 1 link above refers to cork or other material washer that had disintegrated.

David

[stevehertz]

I used to do the PR work for Papst in the UK and they were very high quality units, with many innovations and firsts. I would be surprised if Germany didn't get back to you.

[Cathovisor]

Agreed - a good few years ago I contacted Papst over a motor made by a company they had taken over and they were really helpful; even though the actual motor itself was long discontinued, they even suggested alternatives.

[Chris Don]

Originally Posted by DMcMahon

I also thought possibly a felt oil retaining pad maybe.

Not sure if same end of the motor, but Post 22 in Post 1 link above refers to cork or other material washer that had disintegrated.

David

Yes, that's the one

[DMcMahon]

I had a look at a 1959 Papst motor from one of my Grundig TK 20s, it is a different model to yours, I would guess yours is physically larger.

The assembly is different to yours, no sign of the cork/other material washer.

On mine I cannot separate the rotor from the stator, something several mm down the shaft is solidly holding the two together.

David

[DMcMahon]

There was a black circular hard rubber/fibre washer that was fitted into the circlip groove in the shaft.

David

[Richardgr]

I see second hand ones over here in Sweden quite often, where Tandbergs are 10 a penny (there was one in every school classroom once upon a time).

Good place to look is Tradera

I also have 4 players (5B, 74, 74B, 64), and I was thinking about using the guts of the 64 for a Phono preamp. So potentially will have a spare motor from that? (Or is that project sacrilege?)

[Richardgr]

Tandberg motor

Is this a candidate?

[ricard]

Of the older (i.e. the classic “yellow” and “grey” ones), it was only the model 6 that had Papst synchronous motors. Most of the others used asynchronous motors from Engel (like the one in the picture above), I believe the 14 and 15 used B&O.