Author Topic: Replacement hard to find (Read 3128 times)

Slapt0p · « **on:** July 29, 2019, 12:15:31 pm »

Hello,
I have a blown dishwasher PCB.
My uninformed assessment is a 48ohm +-5% that tests zero continuity and has a visible crack. See pic.
But I can't find a 48ohm replacement. So am I wrong? Also, I don't know the rating.
Can't get a replacement PCB. So I'd like to fix it.
Any help appreciated.
Bill

Psi · « **Reply #1 on:** July 29, 2019, 12:22:52 pm »

It's an odd value, you might have to make it up with two resistors in parallel.
Stack one on top of the other.

capt bullshot · « **Reply #2 on:** July 29, 2019, 12:34:52 pm »

Most probably it's a 47R resistor, not 48R.
Anyway, 47R is well within 48R +/-5% (and vice versa), so just use a 47R resistor. What you should watch out for is some other specs of that resistor (such as fuseability and power rating). Sometimes such resistors are rated "fuseable" and serve a dual purpose (as resistor and fuse).

Psi · « **Reply #3 on:** July 29, 2019, 01:02:54 pm »

What makes you think its 47R when the colors clearly say 48R?

However, good point about it not really mattering, considering its 5%

brabus · « **Reply #4 on:** July 29, 2019, 01:06:07 pm »

Needless to say, if you change it, it will probably burn again immediately. There may be a short downstream the resistor, which needs to be addressed before searching the exact replacement.

capt bullshot · « **Reply #5 on:** July 29, 2019, 01:07:26 pm »

Quote from: Psi on July 29, 2019, 01:02:54 pm

What makes you think its 47R when the colors clearly say 48R?

Clearly? I can't recognize the second ring colour at all, looks rather burnt - so I'd assume it's 47R.

Psi · « **Reply #6 on:** July 29, 2019, 01:13:05 pm »

Looks grey to me, definitely nothing like purple or what purple would look like if burnt.

Mechatrommer · « **Reply #7 on:** July 29, 2019, 01:19:14 pm »

Quote from: brabus on July 29, 2019, 01:06:07 pm

Needless to say, if you change it, it will probably burn again immediately. There may be a short downstream the resistor, which needs to be addressed before searching the exact replacement.

buy few more than needed might not hurt as those are cheap. power resistor like that usually burnt and cracked overtime until it disconnected electrically, failure due to other component usually resulting in magnificent explosion. but anyway it may or it may not. after installation of the new part and if it suddenly explode, then its sure other component damaged as well. if its me, i will try resistor about the same size (will likely to be the same power rating or there about) and closest to the resistance value, over engineering maybe possible by paralleling 2 100 ohm of that 1W resistor. i wont concern value accuracy to much as this is not precision device, 5-10% off maybe still ok, so maybe 45-56 ohm maybe ok. ymmv.

Slapt0p · « **Reply #8 on:** July 29, 2019, 02:13:12 pm »

Thanks for your thoughts. Yes the grey originally looked a shiny silver to me.
Here is the board in different outdoor lights. On the bench in the shade and lounging completely naked in direct sun.
Does that help?

Bashstreet · « **Reply #9 on:** July 29, 2019, 03:53:41 pm »

Well yes it is 48 Ohm resistor and it do not matter if you use 47 ohm one of suitable speck.

I would look for shorts as it is likely something broke as result of a short and something else may be source of the problem.

1.Inspect carefully the board for any other visible damage.
2.Look for shorts if you do not know how to there is few good guides online and on boards(?).
3.Get spare(s) of the component(s) you order.

Post here if you find any shorts etc and we can try help further.

Cheers

picburner · « **Reply #10 on:** July 29, 2019, 04:12:25 pm »

I found a pcb pic on the net with a 47 ohm resistor, but there are others with 49 ohm values too.

Slapt0p · « **Reply #11 on:** July 29, 2019, 05:35:05 pm »

Thanks everyone, for the thoughts so far.
Can anyone tell me how to determine the rating?
@mechatromma mentioned 1W, but I don't know how serious that suggestion was.

Mechatrommer · « **Reply #12 on:** July 29, 2019, 05:51:52 pm »

Quote from: Slapt0p on July 29, 2019, 05:35:05 pm

@mechatromma mentioned 1W, but I don't know how serious that suggestion was.

sorry, rechecking my inventory of 0.1-10 ohm resistors of that size, my resistor speced as 2W, ymmv.

Kleinstein · « **Reply #13 on:** July 29, 2019, 06:40:07 pm »

The resistor looks like a fusible one that did it's fuse job. So chances are high there is another fault that caused the resistor to blow. So I would check a few more parts, like the diodes and SMPS chip.
Chances are the resistor ring just changed color on overheating. Any way the slightly off value is the least problem.

I just last week had a similar case - with the SMPS chip blown, and not good way to replace it.

Rollin Hand · « **Reply #14 on:** July 29, 2019, 07:10:08 pm »

I have had some similar experiences. Unless you have a lot of free time and nothing better to spend it on my guess is that chances are you will waste much time and not get far. From a practical point of view I would suggest finding a pro.
A new dishwasher with extended guarrante will be the solution.

Rick Law · « **Reply #15 on:** July 29, 2019, 08:35:13 pm »

Quote from: Rollin Hand on July 29, 2019, 07:10:08 pm

I have had some similar experiences. Unless you have a lot of free time and nothing better to spend it on my guess is that chances are you will waste much time and not get far. From a practical point of view I would suggest finding a pro.
A new dishwasher with extended guarrante will be the solution.

Besides purchasing a new dish washer with extended warranty... Here is one more option:

If your problem is just the control board and not the other fun stuff like your motor or valves or whatever...

Look on ebay for parts - not the resister but the whole control board. You could probably replacing the whole control board a lot easier than purchasing a whole new machine, removal the old one, and reinstall the new one. Just getting the damn thing from the kitchen to the driveway for pick up is an adventure, and then you have to get the new one from the driveway back through the door - this time a lot more carefully because while you may not mind scratching or dropping the old, you certainly don't want to do that to the new.

I have managed to kept my old dish washer running for years by replacing only the broken part(s) from ebay. It was only until the darn thing cracked at the base and begun leaking that the whole thing had to be junked...

shakalnokturn · « **Reply #16 on:** July 29, 2019, 09:29:14 pm »

I've seen to these before on Whirlpool, Bosch and others with similar LNKxxx based SMPS.

They're usually an easy fix unless lightening hit them.

The resistor: 47 $\$\Omega\$$ 3W fusible is there for inrush current limiting and fusing...
You'll also need to replace the LNK304GN, you can even tell on your photos that it has spat it's guts out. (Small hole in the top and spew between D-S pins.)
It can be worth checking secondary side electrolytics but they're usually ok.

fzabkar · « **Reply #17 on:** July 30, 2019, 12:08:36 am »

An example of a successful repair (U3 and R70):

https://www.elektroda.pl/rtvforum/topic3039338.html

Rick Law · « **Reply #18 on:** July 30, 2019, 02:08:39 am »

Quote from: shakalnokturn on July 29, 2019, 09:29:14 pm

I've seen to these before on Whirlpool, Bosch and others with similar LNKxxx based SMPS.

They're usually an easy fix unless lightening hit them.

The resistor: 47 $\$\Omega\$$ 3W fusible is there for inrush current limiting and fusing...
You'll also need to replace the LNK304GN, you can even tell on your photos that it has spat it's guts out. (Small hole in the top and spew between D-S pins.)
It can be worth checking secondary side electrolytics but they're usually ok.

Re: "...you can even tell on your photos that it has spat it's guts out..."

That must be a Japanese resistor made by The Samurai Inc. or something like that. Samurai spirit lives on. That resister died but died with honor intact.

shakalnokturn · « **Reply #19 on:** July 30, 2019, 05:59:14 am »

The only stain made to rōnin resister's honor was a questionable second-band color. This is drifting O.T.

fzabkar · « **Reply #20 on:** July 30, 2019, 06:22:17 am »

The LNK304 has a 170mA output rating.

http://www.mouser.com/ds/2/328/lnk302_304-306-179954.pdf

There is an application circuit on page 4 of the PDF. ISTM that the LNK304 would only be supplying the analogue and digital circuitry on the PCB, not the solenoids, etc. The circuit has a fusible resistor, so that would tend to confirm the suspicions re R70.

I wonder what would happen if the LNK304 failed with a short between D and S? Does the PCB have any overvoltage clamp?

shakalnokturn · « **Reply #21 on:** July 30, 2019, 07:12:15 am »

Quote from: fzabkar on July 30, 2019, 06:22:17 am

I wonder what would happen if the LNK304 failed with a short between D and S? Does the PCB have any overvoltage clamp?

A clamp on the primary side? There's the "VDR1" MOV, not sure about clamping the across the switch itself.
The LNK do fail with shorted D-S, the result is the I.C. fusing a hole in it's top (faster than the fuse resistor of course...). Why the LNK fails in the first place though?

fzabkar · « **Reply #22 on:** July 30, 2019, 07:19:36 am »

I would want a clamp on the load side so that everything downstream from S doesn't get whacked by D.

paulc · « **Reply #23 on:** July 31, 2019, 09:07:23 am »

1. Colors of a burned part (resistor) change.
2. Value is not very critical.
3. First find why it failed!

Electro Detective · « **Reply #24 on:** July 31, 2019, 10:33:13 am »

If OP does source another board, taking measurements from the good one may help getting the broken one fixed,

rather than going the easy route and wacking in a resistor,
and blowing it out because of other component drama up/downstream


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Author Topic: Replacement hard to find (Read 3128 times)

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