Shims for Philips N4404 speed correction
Hello, I thought the following info about speed adjustment shims on the N4404 tape recorder might be useful to some.
I have recently been renovating my old Philips N4404 (bought new around 1968) and have done some speed testing using a spreadsheet calculation including input of the time to complete 20 turns and the thickness of the tape (1.4 thou). The results agreed with an old 10 minute accurate timed recording and showed that even after replacing the two main drive belts, the 3.75 inch/sec setting was still running about 1.6% fast.
The original long V-shape belt around the pulley is no longer available so I have replaced it with a 2.6mm diameter round belt which seems to work very well.
For those who want to do an adjustment, the pulley that is fitted to the main motor shaft is in two parts, with thin shim washers in between the two parts. Adding a 0.2mm shim reduces the speed by about 1% I think.
After removing the leaf spring and screw that rest on the little plastic cap at the top of the motor pulley, and unscrewing the two small grub screws that fix the pulley to the shaft, the whole pulley can be pulled off of the shaft. Using a 10mm AF spanner at the top and a 14mm AF spanner at the bottom, unscrew the bottom collar. The original shims were 8.2 mm ID and 10.5 mm OD and about 7 thou thick. I could not find those exact dimensions on the internet but did find that Screws City Ltd on ebay) sell 0.1mm and 0.2mm thick shim washers of size M8 ID and 14 mm OD. I fitted a couple of extra shims and found that the extra diameter did not cause any problem as the belt does not go down the groove enough to touch the new shim edge.
Hope this is some use to any N4404 owners still out there.
Cheers
RDA
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