Magnetophon 85 Idler

[Silicon]

I have little previous experience with the mechanical side of tape recorders.

The take-up turntable (platter) on this recently acquired reel to reel machine is slow/weak and the tape is looping on play mode.

The problem seems to be due to a stiff idler pulley.
I removed the idler and disassembled it.
Someone has worked on this before - it shows signs of rough handling.
Under the plastic retaining clip were 2 small washers, a curved washer and a larger plain washer.
These were all above the idler pulley but I think the sequence is incorrect.

My preferred arrangement is shown on the attached photo.
It avoids the axle bracket rubbing against the bottom of the pulley.
The curved washer at the bottom. The larger washer fits inside the recess next to the sintered bushing.
I will adjust the number of washers at the top to allow for some clearance.

Can anyone advise the correct assembly sequence of these parts?

I intend to add a little Wahl clipper oil to the sintered bushings. Is that O.K.?

I don't like the plastic 'circlip'. Is this original?

[Silicon]

The correct description of the faulty unit is the 'Drive pulley for slipping belt'.

I have found a metal circlip that could replace the plastic retainer.

[electrostelios]

Originally Posted by Silicon

I have little previous experience with the mechanical side of tape recorders.

The take-up turntable (platter) on this recently acquired reel to reel machine is slow/weak and the tape is looping on play mode.

The problem seems to be due to a stiff idler pulley.
I removed the idler and disassembled it.
Someone has worked on this before - it shows signs of rough handling.
Under the plastic retaining clip were 2 small washers, a curved washer and a larger plain washer.
These were all above the idler pulley but I think the sequence is incorrect.

My preferred arrangement is shown on the attached photo.
It avoids the axle bracket rubbing against the bottom of the pulley.
The curved washer at the bottom. The larger washer fits inside the recess next to the sintered bushing.
I will adjust the number of washers at the top to allow for some clearance.

Can anyone advise the correct assembly sequence of these parts?

I intend to add a little Wahl clipper oil to the sintered bushings. Is that O.K.?

I don't like the plastic 'circlip'. Is this original?

Hi there, i can guess that it is the Telefunken 85 model tape recorder. The very first point to start is to download the service manual for this machine. You can find it to electrotanya site. There is a detailed scheme about what you asking for.

[DMcMahon]

A shame the Service Manual does not show/list the washers.

Can be difficult when there are several washers of different types, profiles and materials to really know the correct placement order/location, quite common to have mixed washers on idler, spool shafts etc.

When a machine has been previoulsy stripped down by someone else there is probably a good chance that they did not refit the washers as they were when removed. The quantity of a particular type can vary (from same type machine to same type machine) for height adjustement and reel table clutch tension etc.

So often it is just guess work and experimentation to see what works best.

Your preferred arrangement looks good to me.

The sintered bushes may well have dried out so no problem adding a little oil I would say.

David

[Silicon]

The drive pulley is now back in the machine and the fast forward function works OK.
The play speed looks OK. There are no valves in it at the moment.

However fast rewind works initially but stops when the lever is latched on.

The motor pulley continues to rotate but the motor belt is stationary.

I suspect that the motor belt has stretched, It has certainly distorted over the last sixty years.

Are there any tricks to renovating rubber belts such as soaking in hot water?

I will probably reassemble the machine with valves and see what works.
This model, Magnethophon 85 KLB has only a few paper capacitors. They are mainly Polystyrene.
I have reformed most of the electrolytics.

[DMcMahon]

I have heard some people say soaking in boiling water can help a streteched belt, never tried it myself.

Also heard of cutting a small section out then rejoin the cut ends with super glue.

David

[wd40addict]

Boiling idlers definitely works. Did it once on a Tandberg, never tried it on a belt however.

[Silicon]

I cleaned the motor belt which was slipping and then adjusted the motor mounting to give maximum tension.
It is still too loose and the recorder sounds a bit like a washing machine.
I definately need a new belt or a miracle cure.

After reassembling the machine I found it will play and fast forward OK.
Fast rewind is still poor.

The shaft of the Bass tone control and another potentiometer shaft are both incredibly stiff.
I'll see what lubrication can achieve.

[DMcMahon]

Had a look inside my Telefunken Magnetophon 76KB thinking it might be similar to your 85, to check out the idler washer arrangement.

But after looking at it and comparing the drawings for both machines, mine looks different and does not appear to have the "Drive pulley for slipping belt'.

I see that my flywheel flat belt has a split across it so probably will not last long and the other rubber flat drive belt is broken so need to find some suitable replacements.

David

[Silicon]

I have been looking for suitable drive belts. I can't find any part numbers or specifications for them.

I noticed on a German website that a Magnetophon 85 was fitted with green coloured belts.
These could be industrial drive belts with a fibre core to eliminate stretch.

I don't remember seeing any form of tensioner on the motor drive mechanism.

Is it essential to use a stretchable rubber belt in these machines?

[TIMTAPE]

Unless the machine incorporates some type of spring powered belt tensioning system, yes the belt must have some elasticity or maintaining consistent tension becomes difficult.

[DMcMahon]

Some people use rubber O-rings as alternative to rubber drive belts (round section) with good results, O-rings typically can have less elasticity, I personally have never used O-rings on tape recorders.

OEM service data for domestic recorders provide little if anything on drive belts dimensions etc typically.

My Telefunken 76 service manual does list the Telefunken stock numbers for the drive belts but this is of no real use now.

Many makes & models drive belt sets can often be found for sale (NOS & New) online (such as eBay) but many of the Telefunken models belts seem more difficult to find.

David