Spot the difference. Or one of them. Simple pcb repair?

[leavemetogetonwithit]

Re: Spot the difference. Or one of them. Simple pcb repair?

George, I asked,
“Wonder if you can guess what the problem was and find the evidence that pointed to it?”
Where is there any evidence in my first post that points to a, “defective pressure switch, defective heater.” ?
There isn’t any. So that leaves the other three you mentioned.
Thinking about what causes those faults you might be able to figure out what connection I missed making when I made my first approach to the machine. A mental connection that would have saved me an hour or more of faffing about.
One thing in my defence: the machine had already been pulled out before I got there so it was only when I was talking with the customer (about the job) after I had finished that the real cause came to light.

Ah, so Graham has got there.
It was actually 2 wires broken at the insulation displacement point of the motor plug. Only found them by continuity checking the loom.
When I carefully cut the plug open about four wires came away and 2 more were weakened. So I had to re-fit them all and keep them in their rightful places (not at all obvious.)
So the evidence was….
Mike.

[eastlmark]

Re: Spot the difference. Or one of them. Simple pcb repair?

life’s too short so I’ll give it a long shot. Back panel screw (removed obviously to service appliance) chaffed motor harness and shorted out, possilby the tacho wire which may not have caused it to trip/fuse/blow?
Anyway, Bosch motor in a Servis?

[leavemetogetonwithit]

Re: Spot the difference. Or one of them. Simple pcb repair?

I don’t think you read the whole thread, Mark.
Anyway, congratulations to Graham. No prizes, as success is its own reward 😆 .
What I was looking for was for someone to spot that the broken earth wire to the heater and the connector pulled off the ntc were pointers to a machine that had been jumping around. (“Oh yeah,” said customer, “it had been doing that for some time – I knew I should have adjusted the feet.”)
Also the one brush worn down twice as much as the other could indicate that one of the wires broke a long time ago and the motor had been running in one direction only(?)
Bosch motor on a Servis. Yes, I’ve seen that a few times. I wouldn’t wonder they might be factory rejects?
Mike.

[eastlmark]

Re: Spot the difference. Or one of them. Simple pcb repair?

leavemetogetonwithit wrote:I don’t think you read the whole thread, Mark.
Anyway, congratulations to Graham. No prizes, as success is its own reward 😆 .
What I was looking for was for someone to spot that the broken earth wire to the heater and the connector pulled off the ntc were pointers to a machine that had been jumping around. (“Oh yeah,” said customer, “it had been doing that for some time – I knew I should have adjusted the feet.”)
Also the one brush worn down twice as much as the other could indicate that one of the wires broke a long time ago and the motor had been running in one direction only(?)
Bosch motor on a Servis. Yes, I’ve seen that a few times. I wouldn’t wonder they might be factory rejects?
Mike.

Read the whole thread Mike, aside from your previous post which was posted as I wrote. I think, and most would agree, you already checked the harness at the motor end and confirmed it as ok. What it boiled down to is that it had to be the harness as there is nought else between the module and motor. As for a wire breaking causing the motor to turn in one direction? That cannot surely be the case (can it?) as, afaik, direction is reveresed by changing polarity of either the armature or field coils, hence a broken wire could only possibly give no motor action, wouldnt it?
Good post though, if only more of us had the time to mess around so much!

[leavemetogetonwithit]

Re: Spot the difference. Or one of them. Simple pcb repair?

eastlmark wrote:

I think, and most would agree, you already checked the harness at the motor end and confirmed it as ok.
I didn’t check it thoroughly until I had done all those other futile checks. I had prodded the area with a stick (power on, belt off) but that had not made it kick into life so I had assumed it was OK.

eastlmark wrote:
As for a wire breaking causing the motor to turn in one direction? That cannot surely be the case (can it?) as, afaik, direction is reveresed by changing polarity of either the armature or field coils, hence a broken wire could only possibly give no motor action, wouldnt it?
Good post though, if only more of us had the time to mess around so much!

Probably right about direction change. It’s the eight wires that made me think there might be more coils I suppose, but two are probably to the toc(?) Anyway, thinking about it further, I can’t really see any reason why unidirectional operation should wear down one brush more quickly. Must have just had my sleeping cap on when I thought that one up.
Messing around is what I do best.
Mike.

[eastlmark]

Re: Spot the difference. Or one of them. Simple pcb repair?

I have had the uneven wear on several machines, Miele notably- where one brush is worn and gone yet the other is almost as new- but its only the odd one and completely baffling to me.

[Allsorts]

Re: Spot the difference. Or one of them. Simple pcb repair?

The ‘short brush’ syndrome may be caused by a segment of the commutator being lifted on one edge but not the other. This would cause a shaving effect on the brush.

George

[leavemetogetonwithit]

Re: Spot the difference. Or one of them. Simple pcb repair?

George, that’s kind of how I was thinking at first when I suggested it might be going in one direction only. But thinking on it more that makes no sense because both brushes should meet exactly the same situation with your raised segment.
I wonder if somehow the worn brush has been subject to greater spring pressure by the spring catching on an imperfection in the brush holder instead of extending evenly up the “tube”.
Mike.

[jag-12]

Re: Spot the difference. Or one of them. Simple pcb repair?

Would the brushes wear unevenly if the customer did a lot of spin only cycles, so that the motor was rotating in one direction to a greater degree?

[leavemetogetonwithit]

Re: Spot the difference. Or one of them. Simple pcb repair?

Jag, I don’t think it can be about direction for the reason already stated. Anyway, all machines rotate much more in the spin direction, whether or not customer chooses, don’t they?
It’s kind of strange, when you think about it, how little we all know about washing machines.
Mike.

[eastlmark]

Re: Spot the difference. Or one of them. Simple pcb repair?

possibly the raised segment is only a tiny amount on one edge of the segment as George suggested, hence “shaving” the brush in one direction.

[leavemetogetonwithit]

Re: Spot the difference. Or one of them. Simple pcb repair?

But why wouldn’t it shave both brushes the same?
Mike.

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