> From: Jim Carroll > > RH drive doesn't take up - doesn't appear to be the belt
Can't comment on the suggestion of repairers by others, as I digitised my own R2R recordings over a decade ago, and anyway have always done my own repairs. Many of the simplest repairs can be done with little more than common sense.
To begin with, note the sources of movement in such systems. In cheap machines like the Sonys we are discussing here, there are only two: a motor and the muscle energy of the user in twisting the control knob to its various positions, which with my Sony consisted of a big twistable knob with four positions: << (rewind), a square symbol (stop), > (play/record), and >> (fast forward).
For our purposes here, the motor can be considered to be spinning all the time (though on my model there was a switch which depended on the tape being taught through the heads - when the tape run out at the end, this switch would cut the electricity supply to the motor). All rotational movement must be somewhow derive mechanically from the motor itself.
Take-up spools, like everything else in such a system, are usually belt or pulley driven. At their simplest, there is a metal or plastic drive pulley (a 'source' of rotation, which may well be mounted directly on the motor) and a metal or plastic driven pulley (a 'destination'), a rubber belt or 'idler' pulley to link the rotation of source to destination, and a mechanism to engage and disengage the link as required by the current position of the control knob.
In actual practice, there may be a drive chain between the motor and the take-up spool. If this is the case, most probably all but the last will be permanently engaged, and only the last will be controlled by the user via the control knob.
All drive mechanisms work by friction, so it is essential that the pulleys and belts involved are clean and free from oil, grease, or dirt. If dirty, they can be cleaned, but I can't remember for certain what I used to use - white spirit I think, but at any rate it would have to be something that would leave the rubber of the belt or intermediate pulley and the plastic or metal of the drive(n) pulleys clean without adversely affecting the composition of any part involved.
It is also essential that belts have sufficient tension to grip the pulleys, and rubber 'idler' pulleys are truly round and do not have 'flats' from being left engaged for long periods without the motor running.
However, the mechanism to (dis)engage the link is just the opposite, and usually needs lubrication to work properly. Over time the oil or grease can get clogged by dirt and dust, and the mechanism begin to fail. Old lubrication can be removed with white spirit on an old toothbrush or similar, dried off with kitchen roll (don't leave any bits behind) and then replaced by new lubrication of the correct type. If the correct type is not available, probably light machine oil such as Singer Sewing Machine oil will do for oil, Vaseline or other light grease for grease. An intermediate composition can be obtained by mixing the two.
Note that the (dis)engagement mechanisms also often rely on spring catches, and in time the springs begin to fail. Sometimes stretching a spring further can effect a temporary repair, but really failing springs need to be replaced. I keep a container of old ones from junked machinery against such eventualities.
Note that the (dis)engagement mechanism must be connected in some way to the control knob that that sets the tape moving and stops it. The entire chain of mechanical linkage back to this knob needs to be checked to ensure that the drive to the take-up spool is engaging as required.
Note also that the take-up spool is trying to turn anti-clockwise to spool the tape coming out of the heads WHENEVER THE CONTROL KNOB IS IN ANY POSITION OTHER THAN 'STOP', REGARDLESS OF WHICH OTHER POSITION. Think about the implications of that for a moment. Even when the LH feed spool is pulling the tape backwards to rewind it, the take-up spool is still trying to pull it in the 'wrong' direction, forwards, because this keeps the tape taught and under control.
Also, in normal recording and playback, as the take-up spool fills, the radius of the filled spool is constantly increasing, yet tape is being fed to it at a constant rate, so the take-up spool has to spin slower as it fills.
Therefore there must be a deliberate slippage mechanism, between the drive source and the take-up spool, and indeed there is. It's part of the spool pulley, which consists of two halves. The lower part of the spool pulley is driven as described above, while the top is 'free', but between the two there is a ring of felt that is trying to impart drive from the lower to the upper part, but will do so only as far as the upper part will allow itself to be driven. This way the tape is kept taught without the take-up spool damaging it by stretching it. You need to ensure that there is sufficient friction between the two halves of the pulley to impart movement from the bottom half to the top, but not so much as to stretch the tape. In time the felt may get covered with oil, grease, or dirt or just wear away, and need to be replaced.