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[Closed] Electronics - resistor

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Guys, what resistance should this be?

I think it goes (L to R) blue, brown, silver/grey, red, brown and my multimeter has it showing 1.0 million ohms.
[img] [/img]
The switch tests as a closed circuit when pushed, but when checking continuity around the switch [i]and[/i] the resistor I cant get a closed circuit when button pressed. Is that because the resistance is very high, or because the resistor is borked? cheers.


 
Posted : 24/08/2009 3:06 pm
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Possibility it's a pull-up / pull-down resistor (especially if it's a MO or higher), so you wouldn't get continuity through the switch and resistor.


 
Posted : 24/08/2009 3:14 pm
 CHB
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Stoner, have a look here for the theoretical value of the resistor:
http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/info/comp/passive/resistor/colourcode/colourcode.html


 
Posted : 24/08/2009 3:15 pm
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pull-up / pull-down

sounds facinating. WHat is it? 🙂


 
Posted : 24/08/2009 3:16 pm
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What's it from? Those colour codes suggest a 61.8KOhm. Continuity tester wont beep with a 62K res in there, depending on the tester. Resistance through the whole circuit should measure the same as the resistor resistance obviously.


 
Posted : 24/08/2009 3:16 pm
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its a dishwasher start/reset switch.

resistance measurement across the resistor is 1m ohms with no continuity using my tester.

I have no idea what im doing, but all civilians are out of harms way....


 
Posted : 24/08/2009 3:20 pm
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http://en.wikipedia.org/wiki/Pull-up_resistor


 
Posted : 24/08/2009 3:21 pm
 CHB
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concur with coffeeking on the decoding, but thats a flippin weird resistance spec, I always thought they had even numbers (could just be my naivety?)


 
Posted : 24/08/2009 3:21 pm
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ditto what Flaperoon said, it's probably just a stupidly high resistance so that the rest of the circuit knows whats happening with the switch.

If it was just a switch connected to the +ve rail when the switch is open you'd imagine it would read 0V, in reality the IC will see it as anything it wants to see, so the big resistor just lets a trickle of a current either flow from the +ve rail, or to the -ve rail depening on where it is.


 
Posted : 24/08/2009 3:28 pm
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right, so its probably not borked.
thats what I thought.

cheers guys.


 
Posted : 24/08/2009 3:36 pm
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Well if the resistor IS a megohm you may have a borked circuit, but that depends if you were measuring it correctly (correct range) etc. Presumably the system simply isnt turning on? Was the connector to it a 2 or 3 wire connector? Have you scoped/metered out the leads to see what voltages are on the pins?


 
Posted : 24/08/2009 3:51 pm
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2 pins out.

have checked measurement across ranges from 200 Ohms to 200M ohms. Definitely 1 megohm.

The switch works but can be a bit of a delay. Engineer mentioned it should be replaced if its being flaky. I wasnt sure whether it was being flaky or the big PCB control unit reading the output from the switch board was being flaky. Since I need to change the control unit (that is def knackered on another function) anyway, I was wondering whether I should bother changing the switch board at the same time or assume that any problems with the flaky switch circuit might be solved by buying a new controller board instead.

EDIT: just put the phone down on the engineer. He agrees its probably more likely the main control board is causing the problems, not the switch board. Just ordered a new board...lets see.

In the meantime Mrs S is going to have to get used to being the "plongeur" round here for a few more days 🙂


 
Posted : 24/08/2009 4:03 pm
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if it reads what you say at the pins then its defo shagged, sounds part-open. just get a new one of similar rating and off you go. looks like a 1/2 watt metal film.


 
Posted : 24/08/2009 6:52 pm
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Woohoo!!!!

New PCB fitted to the dishwasher and its working fine.

Thats 3-0 to Stoner vs Whitegoods!

New belt on the 12yr old dryer (Old AEG=The Nuts), new element in the 6 yr old oven, and now new PCB in the 3yr old DW (Indesit=Shite)
Apart from the £35 for the engineer call out to identify the borked dishwasher PCB and the cost of new parts I've saved a bundle on what could have been a pricey year! (I reckon at least £1k)

Switch board up there ^ seems to work OK so I've left it alone.

*tucks willy back in*


 
Posted : 27/08/2009 8:28 am
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Nice one, white goods are generally pertty easy to sort out but everyone assumes the opposite. Glad to hear you've nailed a few!


 
Posted : 27/08/2009 8:32 am
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Whats most infuriating is that you can see the economics of disposable whitegoods.

The DW was cheap*, £200, and I can get a replacement now for about £175.

Tech call out was £35 and if they were to supply and fit the new board they would have charged something around £100+. at £130-150 vs £175 for a new one...who wouldnt consider dumping the old and buying new?

At £35 for the call out and £35 for the replacement PCB from online, fitted by me for free, the numbers make more sense to repair and reuse.

*In future I shall only buy Miele or Bosch from now on. Sadly AEG are no longer "AEG". Its by far and away the "greenest" and most economic approach.


 
Posted : 27/08/2009 8:38 am