I think that confirms TR9 is dead. Even if the package contained two Schottky diodes rather than an N-FET, you shouldn't get the same reading both ways.
Good catch. I think you're right. The meter test results in post #20 are consistent with the meter probes being connected between Gate and MT2 of a triac having the pinout MT1,MT2,G ( instead of a mosfet with pinout G,D,S). So, TR9 could well be functional.Perhaps it's a triac?
I've just noticed that in your photos the left-hand and right-hand pins of TR9 have nearby board markings 'CM' and 'G' respectively. If those stand for 'Common' and 'Gate', that would imply TR9 is not a MOSFET with the usual pinout, so maybe I've been barking up the wrong tree? I haven't come across any FETs in that (TO-263?) package with the pin order S,D,G, but perhaps someone knows of some?
Perhaps it's a triac? (Which also has a gate terminal)
Nonsense, I never have schematics for my repair work. Sure they help but its not that big of a deal for most repairs.Board level repair without a schematic and/or service manual is effectively impossible. Maybe not impossible for a well-tooled electrical engineer, but not worth the time.
> i replace U4 VIPER17H Switching Converter and nothing
"nothing"? Power is going in? Switching converter is switching
or not? Output is low/high/overloaded?
There's the difference between guessing which part(s) are bad vs
measuring and thinking it out.
Guessing can be very fast but doesn't work in many cases. I lean more
toward measuring/thinking (perhaps with a guess as what to measure first).
Knowing how a triac is used to switch AC power and looking at the overview
circuit diagram from post #7 (which I'm not sure is for this specific
washer?) I see some likely typos:
- J9 pin 5 6 7 seem like typos
pin 5: there's no triac for the cold valve
pin 6: drives the dispenser valve
pin 7: has a triac driving a -5? Huh?
Ignoring these, the diagram seems to indicate that the triac
CM is directly connected to the AC line neutral.
The triac from post #28 datasheet says that this triac only has
specifications for 3 quardrants of operation
(see pdf page 1: Triggering in three quadrants only and page 2.)
Since switching AC you would need the LD+ and LD- cases which implies
you need G- drive (LD- G+ the missing quadrant the triac doesn't
So there has to be a negative power supply referenced to CM
which is AC neutral.
Beware: It's likely that at least some of the DC power on this circuit board is
referenced to the AC power line.
The overview diagram shows a -5V existing...
I'd verify that the triac terminal is connected to AC line neutral and
I'd trace down what the gate and LD pin of that triac is connected to,
perhaps there's a problem elsewhere...
Anyway, it seems likely to me that the microprocessor is on that
circuit board and it drives the triac's (possibly via some buffering
transistors?). Possibly the microprocessor is toast, which might make
the circuit board unrepairable without a specific programmed replacement.
It would take more circuit tracing to check this out.
I'd also test the removed triac as a triac, not a resistance measurement
to see if it is really dead.
I looked at:
It says the warranty is only for one year so it's out of warranty.
Also the reviews of that washer are terrible so even if the circuit
board was fixed it doesn't sound like a washer I'd want.
My Maytag washer is also out of warranty. It's first service was when
it was 10 years old and the problem was that the drum drain hose had
slipped off. That was in the 1970s. It's had more service since then
but there haven't been any electronic circuit board failures, it has none.
Then its likely where voltage gets converted. Have you checked the transformer, those diodes where it first comes in, are there any shorts on the board?their is not a centel of volts across anywhere in the board but at the 120v input from the main after that nothing anywhere
I doubt the mcu is bad. I think its just a power issue. Most of the time if the mcu is software failure you would still see the lower voltages even if nothing else works. Usually if its partial hardware failure some things will still work, if its full hardware failure the mcu would be getting extremely hot.when you say microprocessor is toast, i also agree but shouldn't be some voltages somewhere in the Power circuit?
Yes, it should be straightforward to trace out the input power path. Looking at the viper17 datasheet page 13 the "typical"
circuits show a bridge rectifier at the AC line input. Looking at your pictures of the circuit board I don't see a bridge
rectifier. Is your power 120VAC or 240VAC? Assuming 120VAC (normal for the United States) and seeing the
two (and only two) power diodes near the power input (d26 d28, picture is a bit fuzzy) I'd suspect a voltage doubler
at the input (along with c70 and c71). See https://ec.kemet.com/blog/voltage-doublers/ section "The Full-Wave Voltage Doubler.
View attachment 197124
Likely the AC netural goes to the middle of the series capacitors and the AC line goes to the diodes.
So with no power connected, check out each trace/part between the power input and the main capacitors. At the same
time compare what you find on the circuit board with this model (just so you know if this is really how things are
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by Robert Keim
by Robert Keim
by Cabe Atwell