Ferrograph 4A Capstan Motor won't run

[SteamingRichard]

My machine ran very well until one day the capstan motor wouldn't run. I changed the motor cap but to no avail. Forward and rewind motors both run ok. Please can any one advise me on how to diagnose the problem? Maybe check the motor windings? I am amateur at electronics . Many thanks in advance .

[Uncle Bulgaria]

Hullo Richard. Welcome to the forum!

Do you have the book 'Manual of the Ferrograph'? You may do as it sounds as though you've had and used this machine for a while. If not, there's the possibility to download an average scan here, but it's well worth getting a copy of the hardback book itself if you intend to keep the machine.

It's good to be able to look at the same diagram and use the same terminology when trying to diagnose a problem at a distance. I've attached a circuit diagram and parts list.

I am no electronics expert, but I have a 4A and have dismantled it down to every nut and bolt (including the motors) and so have some experience with the nitty gritty of this model. I have also put it back together again.

By 'motor capacitor' do you mean C2? The first thing to do would be to ensure continuity within the capstan motor circuit, which is safe as it's done with the power disconnected. Assuming you have a multimeter with continuity/resistance measurement, you can check for the obvious first: that there is no break in the circuit between the transformer and the motor (via P4/S4 etc.)

If it was working very well then stopped, it's likely to be something simple and age-related rather than a complex fault associated with some bizarre series of events. There were no smells, smoke, other symptoms or sudden changes associated with the motor not running?

[SteamingRichard]

Hello Uncle Bulgaria!
thankyou so much for your help! I do have the book thanks, and it is indeed C2 I am referring to. There were no noticeable smells or anything . Just next time it wouldn't work. The selector dial locks in position ok . I've lost track of where I'm up to regards checking if I'm honest so I'll do as you suggest and check through the continuity side of things first. Once again, many thanks

[TIMTAPE]

Unless occasionally cleaned and oiled the capstan motor's top and bottom bearings can become stiff enough to stall the motor. With the mains power disconnected try gently spinning the motor by flicking the fan blade at the bottom. It should spin easily. If it doesnt, a clean and oil with a light sewing machine light oil is probably needed. From memory there are felt reservoir rings surrounding the bronze bearings. A syringe with suitable oil makes it easier to direct the oil to only the felt pads and bearings.

If it's really stuck the motor might need to be disassembled and the shaft and bearings cleaned properly before reoiling and reassembly.

[Uncle Bulgaria]

Good idea! Mechanical problems shouldn't be overlooked. If it is seized, dismantling is possible - it surely can't be as horrid and gunky as the ones I had to service!

If you get confused as to where you are with your checks, I find it helpful to keep a notebook with drawings and tables of what I've done. Going through the circuit diagram with a coloured pen and marking off junctions once tested is a good aide memoire as well.

[SteamingRichard]

Thank you Timtape and Uncle Bulgaria.

Thank you you both for your advice. The motor is free to spin but appreciate you suggesting it. I will take on board your suggestion, I'm sure it will be better to make notes. I'll print out the circuit diagram and mark it up as I go along as you suggest.

Thank you both- Richard.

[Uncle Bulgaria]

It does sound like a broken connection somewhere. Make sure to check continuity all the way between the plugs and their terminations - I've had several odd failures traced back to the tag strips on the deck where the interconnecting wires terminate. Opening and closing the deck can stress them to the point of cracking, but the rigidity of the wire sleeving makes it look to the cursory glance as though all the wires on the tag strip are still soldered in position.

[SteamingRichard]

I have been busy! I have traced through the wiring I hope correctly and can't find any faults , please see attached .

Also I have taken some figures from the windings (meter in continuity mode) , not sure if this is correct way. pleased see attached .

More importantly , I can feel a non rotating field in the motor when I spin the fan , does this point back to the cap?
It measures ok on value but I don't have an ESR meter. 0.75uf 450v . I did replace it with attached advertised as a motor start cap , have I fitted the wrong sort do you think? It didn't rectify the problem.

Once again I am grateful for any assistance , many thanks

[SteamingRichard]

Originally Posted by Uncle Bulgaria

It does sound like a broken connection somewhere. Make sure to check continuity all the way between the plugs and their terminations - I've had several odd failures traced back to the tag strips on the deck where the interconnecting wires terminate. Opening and closing the deck can stress them to the point of cracking, but the rigidity of the wire sleeving makes it look to the cursory glance as though all the wires on the tag strip are still soldered in position.

Many thanks, I have put some further info up. I would be very grateful for your thoughts? Thankyou very much

Thankyou , I have removed the motor but I'm getting a bit confused how to test the windings. Would appreciate any help. Thankyou

[DMcMahon]

The replacement motor run capacitor should be fine.

As the motor windings appear to measure good continuity and the motor is not mechanically seized or stiff, then it sounds like the motor supply voltage is not correctly reaching the capstan motor winding connections.

According to the schematic the common side of the motor windings is permanently connected to the 205V tapping on the mains transformer (TR3) via terminal strip connection 7 and socket SK4 / plug P4 pins 3.

The 0V tapping on TR3 connects via pins 7 of P4 / SK4 then to terminal 8 of the terminal strip and from there to the motor start switch SW3, which when switched on, connects the 0V connection to the motor main winding and to one end of the motor run capacitor C2.

The other end of the motor run capacitor provides a phase shifted connection to the upper end of the motor auxiliary winding.

So the next recommended step I suggest would be to use your multimeter switched to AC volts and measure across the motor connections when the machine is switched on and the motor run switch is switched on.

So would expect around a nominal 205VAC across the main winding and probably a little higher voltage across the motor on the phase shifted motor capacitor connection to the auxiliary winding.

BUT you should only do this if you are competant and can do it safely with confidence. If you are not sure then you need to get someone more experienced to help with this measurement. You have to be very careful as there will be higher AC and DC voltages present in the machine when powered up.

Your safety should be your number 1 priority.

David

[DMcMahon]

Make sure that the motor run switch lever is staying down when pulled down, i.e. not being reset by the auto stop operation/stop button.

David

[SteamingRichard]

Thankyou very much David, I will try that .

Regards
Richard

[SteamingRichard]

I should've also have said that I have 'OL' across the motor terminals . thanks

[DMcMahon]

I assume this is an indication on your multimeter, if so what was the meter switched to ? it could mean overload or out of limit or open loop etc.

David

[SteamingRichard]

Hi David,
I had it set on the continuity setting. thanks

[DMcMahon]

In that case it could mean open loop which is effectively open circuit.

You should get a low resistance across each of the 2 motor windings, in your marked up schematic drawing above you had written 0.841 and 0.863 which I thought were probably the 2 resistance readings (in Ohms) for the 2 windings.

If you cannot get a resistance reading across each of the 2 windings then that is incorrect.

David

[SteamingRichard]

Thankyou very much David, I have ordered a replacement motor so fingers crossed!

[DMcMahon]

Would be an unusual failure for a motor, especially as it was working fine, good luck.

David

[SteamingRichard]

Replacement motor has sorted the problem! All working now, so thankyou to everyone who offered assistance. Much appreciated - Regards, Richard

[DMcMahon]

Well done, that is good news.

David