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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc. |
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12th Oct 2020, 12:12 am | #1 |
Triode
Join Date: Jun 2020
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 33
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Radiomobile 104 8 Track Player - Motor Starting Problems
Hello all, I'm after a bit of help please.
I'm refurbishing a Radiomobile 104 8 track player. I've got the radio working correctly. I've cleaned and lubricated all the mechanical parts, including the capstan shaft, making sure the capstan itself is clean, and it turns freely. I have a problem with the motor developing enough torque to start. Once it's going it's ok and the cartridge plays, but it does have problem starting. If I remove the belt it's the same. Once I give it some help the pinion will turn under power. If I connect 12v to the motor drive board without the drive belt I still have the same problem, the motor will start with some help. The motor spins freely with no power. Is there a component on the motor drive board that's shot or is it the motor? Any help greatly appreciated, Many thanks, |
12th Oct 2020, 10:59 am | #2 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,846
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Re: Radiomobile 104 8 Track Player - Motor Starting Problems
It does sound awfully like a "dead spot" on the motor's commutator.
Can the motor be carefully dismantled? N. |
12th Oct 2020, 3:36 pm | #3 |
Triode
Join Date: Jun 2020
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 33
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Re: Radiomobile 104 8 Track Player - Motor Starting Problems
Thanks Nick,
I think you may be right. I have stripped it down and had a look, couldn’t see anything, put it back together and then reinstalled it. Same result I’m afraid. Before I “hand start” the motor and rotate very gently, I can feel the “electromagnetic force” of each segment. Once running, the motor’s great, but it really struggles with starting. Cheers. |
12th Oct 2020, 9:19 pm | #4 |
Hexode
Join Date: Jan 2013
Location: Wigan, Lancashire, UK.
Posts: 372
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Re: Radiomobile 104 8 Track Player - Motor Starting Problems
This is similar to problems I have encountered with model train motors. It can mean that one of the armature windings is defective, one of the connections to the commutator has come adrift, there is a build up of carbon in the commutator slots or a breakdown in insulation.
If you have access to a multimeter, do a resistance check across each segment of the commutator, Each segment should give a similar resistance reading if the armature windings are okay. Next check for any short to the armature body by touching each segment and the armature shaft in turn. A reading here indicates that the insulation has broken down. Make sure that the slots between the commutator segments are not clogged with carbon, if he motor uses carbon brushes. |
12th Oct 2020, 10:40 pm | #5 |
Triode
Join Date: Jun 2020
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 33
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Re: Radiomobile 104 8 Track Player - Motor Starting Problems
Thanks Fidelity, will do.
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13th Oct 2020, 9:38 pm | #6 |
Triode
Join Date: Jun 2020
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 33
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Re: Radiomobile 104 8 Track Player - Motor Starting Problems
I’ve had a look at the motor and it is a permanent magnet unit so is driven by transistors firing and not brushes....could I have a dodgy transistor that’s causing this?
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