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Chris55000 · 22nd Sep 2019, 3:55 pm

Hi!

These simple motor regulator circuits rely on the internal back–emf generated by the motor's armature due to it's rotation in the magnetic field provided by the permanent–magnet pole pieces, and they operate to stabilise the motor current rather than the motor voltage!

The usual cause of failure to stabilise or run correctly is either badly worn brushes or a badly worn/burnt centrifugal switch contact on the speed governor, assuming the motor uses one.

If there is centrifugal switch governor, there will always be a tiny screw for adjusting the motor speed accessible thro' a hole provided in the side of the motor casing, whereas an electronically regulated motor will not have a screw visible.

If you can't get another identical motor, you might be able to get similar tiny brushes from any of the small hobby motors sold for toys (look for one of about the same size and voltage) or it might be possible to get another Philips deck cheap with a similar motor & control board you
can try!

If you've got a steady hand and you're confident at dismantling the motor, try rubbing the commutator with one of those red fibre–pencils sold by RS etc., to remove as much as the black deposits from the brushes as you can, then make sure you wipe the commutator surface with IPA etc., afterwards to get rid of the fibre particles left over!

If the motor runs in the wrong direction after reassembly you've reassembled it 180 degrees out!

Chris Williams

PS!

I think Mr. Michaelis wrote an article on the principles and faults assosciated with battery–operated motor speed control in the later 1966/1967 issues of P.W., have a look on American Radio History for them!

PPS!

Might be worth looking to see if you can get a replacement brushless d.c. motor that's compatible with the N2205 mechanics, altho' you'd need a variable – speed one!

22nd Sep 2019, 3:55 pm	#12
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,868	Re: N2205 Running slow and wobbly Hi! These simple motor regulator circuits rely on the internal back–emf generated by the motor's armature due to it's rotation in the magnetic field provided by the permanent–magnet pole pieces, and they operate to stabilise the motor current rather than the motor voltage! The usual cause of failure to stabilise or run correctly is either badly worn brushes or a badly worn/burnt centrifugal switch contact on the speed governor, assuming the motor uses one. If there is centrifugal switch governor, there will always be a tiny screw for adjusting the motor speed accessible thro' a hole provided in the side of the motor casing, whereas an electronically regulated motor will not have a screw visible. If you can't get another identical motor, you might be able to get similar tiny brushes from any of the small hobby motors sold for toys (look for one of about the same size and voltage) or it might be possible to get another Philips deck cheap with a similar motor & control board you can try! If you've got a steady hand and you're confident at dismantling the motor, try rubbing the commutator with one of those red fibre–pencils sold by RS etc., to remove as much as the black deposits from the brushes as you can, then make sure you wipe the commutator surface with IPA etc., afterwards to get rid of the fibre particles left over! If the motor runs in the wrong direction after reassembly you've reassembled it 180 degrees out! Chris Williams PS! I think Mr. Michaelis wrote an article on the principles and faults assosciated with battery–operated motor speed control in the later 1966/1967 issues of P.W., have a look on American Radio History for them! PPS! Might be worth looking to see if you can get a replacement brushless d.c. motor that's compatible with the N2205 mechanics, altho' you'd need a variable – speed one! __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed! Last edited by Chris55000; 22nd Sep 2019 at 4:09 pm.