TG 1020 Tape Speed Modification

[DMcMahon]

My TG 1020 has had the 4.75 cm/s speed push switch modified, so that it functions as 38 cm/s speed.

I see that there is an additional push button switch that has been added on the left side of the 4.75 cm/s switch and it is glued to the 4.75 cm/s switch body.

The additional switch has been mechanically coupled (by a twisted/soldered wire) connecting from the 4.75 cm/s switch operating shaft to the new switch operating shaft, so when the 4.75 cm/s switch is operated, it also operates the additional switch.

Does anybody have any more details on this modification please ?

David

[raimund54]

Hi David,

I have no idea what these modifications can be.

I myself tried several things to get the TG 1000 to 38 cm/s speed. But with the original capstan and 24 V voltage you never get 38 cm/s. You can modify the electronical circuits by changing resistors and their values. But without increasing the 24 V voltage beyond 30 V you will kill the capstan. My cousin tried another way. He installed a wheel with a bigger diameter on the capstan and then he could manage to get 38 cm/s. This worked with the 24 V supply.

Second problem is to change the record and playback curves in the record and playback amplifiers to get an overall flat record/playback frequency response.

regards,

Raimund

[DMcMahon]

Hi Raimund,

Thank you very much for your reply. The 4.75 cm/s speed button has been marked as "38" and it certainly runs very fast. I have not done any tests to see what sort of speed it actually runs at. I am away from the machine for several days, so cannot do any speed measurements or measure the 24V supply or see if the capstan motor runs hot or noisey at that speed. But I will check those things once I am able to.

Best Regards

David

[DMcMahon]

Hi Raimund,

I tried to remove the Speed PCB to check out the modification more, but was only able to partially remove it, as many soldered cables stopped it being fully removed and it looked very difficult to remove and reconnect all the soldered connections.

Have not been able to attach photos to make things clearer, when I select "Insert Image" I cannot then see how to insert the image/photo ?

I noticed that all 3 internal glass fuse holders are heavily tarnished and one of them the fuse was loose, when I touched it the fuse holder broke so I need to replace the fuse holder before I can power up the machine to do some speed tests.

The capstan/flywheel diameter is around 110mm.

David

[DMcMahon]

On my TG 1020 the outside diameter of the capstan motor pulley (which drives the flywheel via the capstan belt) is around 33mm, on my TG 1000s the motor pulley outside diameter is around 19.5mm.

David

[raimund54]

Hi David,

then someone used the same modification as my cousin did 40 years ago with a pulley with higher diameter to increase the rpm of the spindle that drives the tape.

Regards,

Raimund

[DMcMahon]

Hi Raimund,

Unfortunately I was not able to check the value of the 4.75 cm/s R3013 resistor but assume its value must also have been changed.

Also assume that the larger pulley would increase the speed of the other 2 speeds, assuming no changes to the electronics.

Best Regards

David

[raimund54]

Hi David,

of course you have to change values in the electronic circuit to adjust the speeds of 4,75, 9,5, 19 and 38 cm/s. Furthermore you have to change the frequency curves for record and playback to match the specified ones for tape recording. Otherwies you won´t get a flat overall record playback frequency curve.

Regards,

Raimund