Sir cjcharles . . . . . . .
Thanks to this thread and the post by 73's de Edd, I managed to fix my Bosch SMS69L22GB/55 dishwasher. I had almost discarded it and ordered a new one as it was 8 year old. After reading your post and another fellow's post on uk whitegoods forum, I decided to have a go. I found that 100 ohm resistor was burned. TNY264GN had no obvious damage but pins 3 and five were short, telling me it needed to be replaced. Replaced both the components and dishwasher is working as before. Thanks to you guys, saved me £500-600.
Raj
Did you give back info on the RED circled area . . . as I view it, it possibly just might be some ferrite beads on a wire.
I CAN make out a 200 and 100 ohm surface mount resistor and a centered transistor.
Notice that they make no effort to assign designations to any components on the board.
Since this unit is typically being mounted in an enclosed " sarcophagus " for shock and humidity / water protection, one can only SEE the board when it is exposed . . . such as you now have it.
SURELY that TNY unit is bad . .at 36 ohms . . . D to S and the open supply resistor that feeds the power supply for it.
If you want to confirm the proper value of that open metal film resistor, try this.
I am reading it as brown black brown and a gold or silver tolerance band. . . . with an insignificant very end band.
That would make it 100 ohms . . .totally realistic.
To test, take a single edge razor blade and VERY carefully scrape away a bit of the paint cover in the very center of the resistor.
Take ohmmeter in a suspected 100 ohm range scale and touch one meter lead to the wire lead at either end of the resistor and then see if a reading is obtained with the other leads probe as it is touched onto the very center, of the just scraped area.
If no reading, then move from one resistor end lead to the other , in reading to that central area.
With the next paint scraping . . or another . . . if required.
A reading should eventually show up from one of those ends to the center. Double that value and you have the value of the blown resistor.
Here is how I am " reading " other areas:
Main AC power input at A connector and then as activated, power relay B or B' feed power down to A' as either a motor or water heating element supply.
AC line from A also gets line filtering with C series of X and or Y cap types. AC then passes thru dual AC inductive line filter for EMI / RFI at D.
AC line from D makes its way down to J ( now open resistor ) passes thru and then needs to find its way to a usual used Full Wave Rectifier Bridge * to get DC voltage for the main B plus storage capacitor H.
I can't see it * in the picture.
Also you need to test K and L to see if they are two power diodes or ferrite shielded feed thru lines . . .which would test out as shorts.
Back up at E is your shorted TNY which is relying on its B+ supply from cap H . . .I can read 100 ufd . . .is its voltage rating on up around 400 VDC ?
If E was working, it would drive low voltage power transformer F which then supplies its voltage to be rectified and feed into G storage capacitor. That meets the low voltage DC supplies for the circuit board .
Check the part numbers and give feedback on items M and N, as M looks like it could be a power dual Schottky rectifier, or and looks like N could either be a 3 terminal regulator or power FET.
Need more picture coverage of P, as some SERIOUS " bidness " is going on over there, possibly power and adjustable speed control of main motor.
BTW . . . . don't you realize that YOUR problem is deviating from the norm . . . . . with the USUAL failure mode, being one of the high current handling terminals on B , B' or the other like big relay nearby having developed into the condition as is being shown on inset A below..
PCB MARKUP :
View attachment 29198
73's de Edd
in my case it's the only thing burned on the board. do you think replacing only this part would be enough for the beginning, or should i, just in case, replace also other components?
