obselete washing machine motor problem

[mab2]

hello all,

my ancient washing machine has developed a fault: the motor doesn't turn. The motor itself including the brushes seems fine - though i haven't yet tried it with a direct connected supply to confirm.

I think the fault is with the 'digital module' - a Remco 5525 (attached pic). The big resistor (also in the pic) was open cct (>2Mohm) and looks like 120K to me, but as this is the 230v to 5v dropper resistor that seems like a high value to me (120k, 240v and 1/2 wave rectification says ~1mA to me, and my substitute hasn't cured the problem).

When Googling Remco 5525 I turned up a few pics that look identical, one with a resistor that looks like 12K, and poor quality pics that look more like 120ohms which is obviously far too low.

Could anyone please suggest what a plausible value would be? the 5v(?) is regulated by the zenner DZ1. and I assume there needs to be enough mA available to turn on the Triac?


Thanks.

 

[rjenkinsgb]

That looks to be a very basic controller, not much more than a "light dimmer" style circuit.

Can you post a good photo of the other side of the circuit board, so it's possible to follow the connections and see where that resistor comes in to it?

See the first schematic in this thread for the concept it likely uses:

Reuse a Washing Machine Motor, Make an upcycled multi-tool!

The last three videos have all been about using old washing machine parts! Two have shown the de-construction and upcycling of the bearings and frame, into...

www.floweringelbow.org

 

[mab2]

it is a very old washing machine, but it does have a large ic on the other side.

can post a pic of the other side, but this big resistor is in a fairly simple part of the circuit:-

starting from the live 230v terminal (bottom left), via R1 (small 100ohms), D1 (400v rectifier top left) to R7 (the big resistor - now removed and the two substitute resistors in its place, to the -ve of C3 and DZ1. +ve of C3 and DZ1 to neutral.

 

[mab2]

 

[rjenkinsgb]

OK; it's a bit more sophisticated than it appeared to be from the top view!

The one below uses the same concept, but a different IC; in that, the feed resistor is 6.8K
12K is not unreasonable, if yours uses a bit less current than this, or this is a 115V one; it's not clear from this diagram..

Can you read the rest of the type number on the zener, or is it underneath? I can only see "BZX".. The voltage and power rating of that should give a clue to to reasonable resistor values.

 

[mab2]

It looks like BZX 55C - 1/2 watt? To see any more i'd have to desolder it.

 

[rjenkinsgb]

OK; guessing at 15V, the maximum permitted average current would be ~30mA
Or 60mA at 50% duty cycle.

For a 240V input, that would mean a 4K resistor.

So, either 12K or 6.8K would be safe & not overload the zener, as long as it is no more than 24V; what is actually needed depends on the current used by the rest of the circuit.

I'd try the 12K; it should not cause any harm & seems reasonable for the circuit, plus fitting in with the photos you found.

 

[MaxHeadRoom78]

The TDA1085 was developed by Motorola specifically for washing machine using a Universal motor.
It does have to have a simple low-res tach on the motor however.

 

[mab2]

Thanks for that - I'll try 12k 1st as that fits with one of the internet pics and the 1st two colour bands on the original resistor - maybe the orange has heat-faded to yellow?

Don't know what the chip actually is - didn't come up on an internet search - but the motor is a universal type and does appear to have some sort of tacho on the tail end.

 

[Nigel Goodwin]

Thanks for that - I'll try 12k 1st as that fits with one of the internet pics and the 1st two colour bands on the original resistor - maybe the orange has heat-faded to yellow?

Over heated resistors commonly change colour with age, so it's quite plausible.

Don't know what the chip actually is - didn't come up on an internet search - but the motor is a universal type and does appear to have some sort of tacho on the tail end.

Probably an in-house number, these boards aren't supposed to be repaired, hence no circuits or spares for them - you're supposed to simply replace the board (tough luck when it's no longer available!).

 

[mab2]

To tell the truth i did find a new one for sale:- £102 + postage + vat.

But as a matter of principal I'd rather repair/get it working some other way.

 

[mab2]

Fixed! Lacking a 12k resistor of suitable power rating i found a 20k and 30k and put them in r7 and r8 for about 12.5k.

And it's washing again

One wonders how many washing machines get thrown out for the sake of a 2w resistor.

Thanks very much for the advice:- in hindsight it ought to have been obvious that 120k was wrong but i was thrown by the fact that the old resistor doesn't look burned at all, and the third band is properly yellow whilst the red, brown and gold don't look faded at all.