Bosch WFK2200GB/11 – Violent spin to begin with followed by Error 4.

[Rhothgar]

electrofix wrote:you have to host photo’s off site and post public link. Its all down to server cost as we are a free site

as for the tacho if there is not output on a low ac volt scale then thats not good

Dave

OK. I’ll try again.

I do get a voltage reading. Like you said, you don’t even need to spin it fast to get a reading. Spinning fast by hand gives 1.1-1.4 AC volts so it is fine.

[electrofix]

Rhothgar wrote:

OK. I’ll try again.

I do get a voltage reading. Like you said, you don’t even need to spin it fast to get a reading. Spinning fast by hand gives 1.1-1.4 AC volts so it is fine.

as long as you are on the tacho connections as you will get the same output from the armature

Dave

[Rhothgar]

I shall double check but I am pretty sure I was on the right pins. With it not having actual wires, it is hard to trace where the pins go to.

I know I didn’t get anywhere near the same output from some of the other pins.

I did the check without the brushes in though I don’t fully
understand how motors work.

Presumably the brushes just drive the motor in which case if the brushes are out, it would still be possible to get a reading from the armature?

[electrofix]

with brushes out you will get no reading off armature

you can easily find out which wires going to the armature by doing a reading between the brush wires and the connecter

the field coil somtimes have 3 connection so your left with 2 for the tacho. this is assuming your motor has 7 pins. if only 6 then you have 2 armature , 2 field and 2 tacho. the pair with the highest resistance is normally the tacho

Dave

[Rhothgar]

electrofix wrote:with brushes out you will get no reading off armature

you can easily find out which wires going to the armature by doing a reading between the brush wires and the connecter

the field coil sometimes have 3 connection so your left with 2 for the tacho. this is assuming your motor has 7 pins. if only 6 then you have 2 armature , 2 field and 2 tacho. the pair with the highest resistance is normally the tacho

Dave

Excellent. Thanks. That explains what those two spade connectors are that appear to go to nowhere. So they have continuity with Pins 4 and 5 on the connector that goes back to the main board. The free hanging spade connectors plugged into the carbon brush housings.

I only get 0.048VAC when spinning the pulley by hand as fast as I can. The resistance is 2.9-3.0 Ohms across Pins 4 and 5.

Pins 6 and 7 are the tacho-generator pins and I have doubly confirmed this. I get a healthy looking reading of 0.2VACs with a very spin hand spin and up to 1.4VAC when I really wang the pulley around. The resistance is 15.3 Ohms across the pins so this meets your criteria above.

However, if the voltage reading from the tacho should be say 0.2VAC at say 60 rpm but, let’s say, 240VAC at 1100rpm then how do I know whether it is in spec or do they not go out of spec?

There is also a thermal cut-off switch within the motor and this connects to one of the carbon brush housings.

I have to admit that the carbon brushes I fitted were only £6 on Amazon on 1st May this year and I’ve just been back on and the reviews are atrocious. I question whether these have actually caused the issue with the power board. Buy cheap! Buy twice!

Seriously considering investing in some genuine Bosch brushes now and do wonder if they have stronger springs to press the brushes more firmly onto the commutator. Your thoughts on this would be much appreciated. I could kick myself. One review on Amazon says that the quality was so bad it caused the commutator to exhibit burn marks and require a motor replacement.

[Rhothgar]

Detached earth cable from element. Pretty sure this does not affect anything other than heating of water.
https://1drv.ms/u/s!Ar8AkvzZJWl9-ksYldGGOR-SFGlE

Connector to motor: Looks almost burnt but I think it is carbon dust. Could this be causing tracking of current or voltage?
https://1drv.ms/u/s!Ar8AkvzZJWl9-k1YdY6n9Z5DoNHY

Plastic frame for picking up tacho and feeding to pins 6 and 7
https://1drv.ms/u/s!Ar8AkvzZJWl9-kw7HesiDWndDQ6j

Ignore most of what is said in here but you can see the commutator at 49 seconds in. Also, beginning of video I go on about how the top can be rotated 180 degrees out and ponder whether I’d put it on right. NOTE: This video was taken last night and before today’s findings.
https://1drv.ms/v/s!Ar8AkvzZJWl9-wIXJcRXEuPFLOa0

Video to show testing of tacho generator. Might be useful for others in the future:-
https://1drv.ms/v/s!Ar8AkvzZJWl9-n4OPaIszoebpzPp

[electrofix]

links dont seem to work. Are they public links ?

Dave

[Rhothgar]

electrofix wrote:links dont seem to work. Are they public links ?

Dave

Oh damn! They should be. They are hosted on my MS OneDrive account. It does state anyone with a link can view them. They open for me when I click on them but I am not sure if that is because I am on the PC that I generated the links on.

Maybe worth trying again just in case there was a glitch?

Maybe try this one too. I’ve just quickly generated one for email transmission:-

Please let me know if it works and I will redo all the others.
https://1drv.ms/v/s!Ar8AkvzZJWl9-n4OPaIszoebpzPp

[electrofix]

that works and that looks fine so scrap another idea

Dave

[Rhothgar]

Morning Dave,

I have now updated all the other links in the post above if you wouldn’t mind looking at them and particularly the other video where it shows just how worn the commutator is.

So where do you suggest I look next?

Presumably I should trace the power board and the connections for pins 4, 5, 6 and 7 and see where they end up? Perhaps the issue actually lies with the front controller panel. I took it off yesterday but have not yet removed it from the plastic housing so I cannot see all the PCB components on that. The side I can see is just copper PCB tracks and under looks fine with the naked eye. I’ll check it over with a jeweller’s loupe to make sure all solder joints are intact and no dry joints perhaps.

Think it is a good idea if I actually take all the cabling out between the motor and the main PCB and the front panel and carefully inspect it. On cursory glance, it all looked OK apart from either the carbon dust or burn marks on the motor connector.

There have been times when it smelled as though something was burning. I recognise I need to be very careful with that yellow connector as it could be very fragile having been subject to heat.

[electrofix]

from vids re field coil

i always run a felt pen down the motor before i start

probably cant be reversed as the field may have extra high spin tappings so it may be your problem

Dave

[Rhothgar]

electrofix wrote:from vids re field coil

i always run a felt pen down the motor before i start

Fantastic and obvious idea! Why didn’t I think to do that?

electrofix wrote:
probably cant be reversed as the field may have extra high spin tappings so it may be your problem
Dave

So I probably need to replace the resistors and try it again and, if that doesn’t work, it will no doubt burn out those two resistors again, which I will then replace and then rotate 180 degrees and try again.

Do you think that sounds a sensible plan of action?

Presumably as those two resistors are burnt out will get the same result irrespective of whether the end cover is the correct way around or not if I just plug it back in now?

[Rhothgar]

It seems to be going from bad to worse.

Stripped it again and rotated cover 180 degrees. Machine span really quick as before but without any vibration. Maybe because there was nothing in it?

Stripped again and cleaned brushes and commutator with isopropyl alcohol. Now the motor won’t even spin! I’ve had the motor in and out about 6 times this afternoon. I’m getting quite proficient at it…

https://1drv.ms/v/s!Ar8AkvzZJWl9-yXJpDgSjNK_3k6_

I’ve just been pondering as I watched this video. The above must be correct but the central portion on the motor can ALSO be rotated 180 degrees out so I am going to strip it yet again and go from there.

Just wondering if I will ever get to the bottom of it.

If the tacho is fine, could it be the front controller panel that is somehow faulty. I think all the microprocessing is done on the power board? Could the front controller on this machine actually cause the programmes to not do what they should?

In my mind, I am thinking that the fault cannot lie in the power board because the original one blew two resistors and the new one did also. Never say never but the fault cannot lie in the power board. Could a short be occurring within the tacho generator under load for example ie it’s fine by hand but under load the reading might not be in spec or somehow fail?

[Rhothgar]

Latest update on this:-

I did change both resistors and they haven’t blown. Cleaning up the motor housing with compressed air presumably helped. Issue still persists though regarding the spin.

Apparently, the control board on the front of machine with the dials cannot be faulty. So if the fault now lies in the power board where do I go from here please?

I have traced the copper traces back to what look like Zener diodes. They are absolutely tiny so much so that it is difficult to get a reading from them with the DMM probes I have (which are standard probes). I cannot really get onto the copper pads it seems unless there is a fault.

Question is could Zener diode cause this fault? I fear almost it is the end of the line for the machine because I am getting down to a level that I do not have the equipment to readily see what I am doing visually.

[electrofix]

short answer dont know

you cant know what a blown component can do unless you know its function. zenners are normally power supply components or anywhere you need a reference voltage

dave

[Author]

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