Fridge Freezer Board Repair - Transistor

[Wobbly0199]

Hello everyone.

Hope you can help.

My fridge freezer controller board wet faulty. Eating from tins and packets (DOH!).

Problem: i cannot find anywhere the transistor needed to repair.

Any idea as to a equivalent replacement?

The board was semi working i.e. intermittently but the Transistor has burnt out slightly.

Any help really appreciated.

It's 240v input to the board. Bulb 240v.

THANKS.

IMAGE>>>





 

[themadhippy]

Problem: i cannot find anywhere the transistor needed to repair.

maybe because the mac97a8 isnt a transistor

https://uk.farnell.com/ween-semiconductor/mac97a8-116/triac-0-6a-600v-to-226aa/dp/2902394

[Wobbly0199]

Yes, my bad.... BUT i still cannot find that particular Triac. So cannot look up it's specs.

So finding an equivalent replacement is a tough.

[themadhippy]

BUT i still cannot find that particular Triac. So cannot look up it's specs.

try clicking the link i posted,not only are there 5197 available to buy,but also the data sheet.

[Wobbly0199]

Hi, Yes i did that, but it's not listed.
i tried;

"MAC97A8 WJ62"

"MAC97A8-WJ62"

"WJ62"

Etc

[themadhippy]

The WJ62  aint important,its often just a code for manufacturing location or date of manufacturer,the important bit is  MAC97A8

[Wobbly0199]

Oh.. ok...

So buying a "MAC97A8" would be a direct replacement or are there variants i need to look at?

Thanks

[floobydust]

Yes MAC97A8 (is rated 600V) 0.8A triac or alternate Z0107MA (600V), NA is 800V will work, they are sometimes easier to find. Z01 datasheet

[Wobbly0199]

Cheers for that.

i did notice the gate trigger voltage can vary, i.e. 1.5v to 2.5v.

i have no idea what the original is.

Any advice on that at all?

Cheers.

[MathWizard]

Yeah it shouldn't matter too much, IDK the circuit or those triac's, but the circuit should be designed for some worst case scenario. If the gate was auto-biased, so with the gate on one of it's input power pins, it only takes 894micro-seconds for a 120VAC sinewave to go from 1.5V to 2.5V

[Wobbly0199]

You are right. i tried the 1.5v version and it worked fine. it didn't solve the original fault of intermittency doh!

[ozcar]

In what way is the operation "intermittent"?

How did you know that component had "burnt out slightly"?

With some insight from a view of the other side of the PCB from the second photo at http://ridzip.ru/shop.php/2/1/0/1020?n_str=0&k_str=1, maybe that triac is used to turn the lamp on, but in that case failure there would not obviously cause the whole fridge to stop working.

Given it is only a single-sided board, it should not be too difficult to trace out the circuit.

[floobydust]

The controller IC might be toast, the burn marks on the PCB at little triac, or if there was a ground-fault.
Providing the make/model of the fridge would help others.
The big triac BT137 I think drives the compressor contactor, the little one the lamp.
The capacitors do fail on these boards as well.

[themadhippy]

if its intermittent id start by looking for a dodgy solder joint or wire connection.

[floobydust]

Intermittent operation of fridge control boards can be the dropper cap aging, as well as the 470uF going bad.
"Eating from tins and packets" I'm not sure what that means, tinfoil everywhere, beer being splashed on the board? 
Isn't the board covered or something?

[Wobbly0199]

Hi, Yes i have resoldered most of the joints. Cleaned the POT etc.

[factory]

Intermittent operation of fridge control boards can be the dropper cap aging, as well as the 470uF going bad.
"Eating from tins and packets" I'm not sure what that means, tinfoil everywhere, beer being splashed on the board? 
Isn't the board covered or something?

I read it as this;
"My fridge freezer controller board went faulty. Eating from tins and packets (DOH!)."
Presumably they are eating tinned food & dry food from packets, as fridge is "intermittent".

"Providing the make/model of the fridge would help others."
Make is given in the picture, Servis are now just another zombie brand these days.
https://en.wikipedia.org/wiki/Servis
The Quartz washing machine on the wiki page looks very familiar, we had one for several decades, the much newer replacement Servis was a PoS, lasted barely a year before the bearings failed.
This fridge/freezer could be either Italian or Turkish (Vestel), board doesn't look old enough to be from the original company.

David

[floobydust]

No idea WTF the fridge is doing, OP could communicate better and elaborate on "intermittent" or why the little triac area on the board looks to have soot there. I thought it was just for the lamp?

Posting the make/model/board number helps others as the search engines will index the thread. Also to find the fridge schematic for the connector pin wiring.
I looked at Servis and found many different board. These appliances are made by some mega-conglomerate and the same board used in many different brands.

pic looked the same on reddit p/n 546089001.

[factory]

Looking at the back off the board in this video, I would say the small triac is only switching to the lamp too. Don't do what they have done, the resistor before the capacitor dropper should be the same rating as the original.  Also seems to be a different version, as it's got some different parts populated.



Date codes on the older boards are consistent with the Italian maker, could be anywhere from 10 to 16 years old, have you verified the capacitive dropper based power supply is good? if it isn't then there is no point looking at the other parts.

David

[Wobbly0199]

"capacitive dropper based power supply" - Which component is that? i assume it's the blue rectangle (in my image).

NOTE to all:

The intermittence issue is that the compressor sometimes starts normally, sometimes it attempts to start and stops within half a second. Fiddling with the temperature control turning up/down sometimes makes it come on when it has stopped.

[floobydust]

High failure rate parts on these kind of boards are the capacitive dropper cap, the filter cap and the zener diode.
What do you have for test equipment- something that can read capacitance or DCV? Borrow a friend's multimeter etc.

Check the big blue boxed cap for going low value. Same for the 470uF black electrolytic cap.

[ozcar]

I'm sort-of wondering if the compressor is OK.

I see that there are two LEDs on the board, "DL1" (green) and "DL2" (yellow). What do those normally indicate, and what do they show when the fridge is misbehaving?

Uncle Google suggests that the green one might simply indicate that the power is on, in which case you'd expect it to be on steady, not flickering or dim. As for the yellow one, well. who knows, perhaps that means "too darn hot" (and compressor should be running) but still not having the fridge model number makes it hard for us.

Floobydust deserves an award for figuring out that the larger triac is a BT137 - I certainly can't read that in your photo (nor in any other photo I could find). I get tantalisingly close to be able to read the markings on U1, but no cigar there either. Clear photos of both sides of the board please.

[factory]

I'm thinking U1 is a custom part. The board has what looks to be a thermistor, this goes to the IC.

The interior lighting switch is external to the board in this model (hence the extra pins on the connector), the video found last night has reed switch fitted to the board instead.

Maybe the LEDs are for fault codes? No way of knowing without full model number & a manual, if they are even mentioned in the customer manual.

David

[ozcar]

I'm thinking U1 is a custom part. The board has what looks to be a thermistor, this goes to the IC.

You could be right about U1, and then the numbers on it probably won't help. Perhaps eagle eyed floobydust could see that already, but I'd still like to know.

I turned up a variant of the board where the incandescent lamp was replaced by a daughter board with LEDs on it, and where U1 is not visible (perhaps changed to an smd on the other side of the board?). That board was marked "www.erselettronica.it" and what could be a part number, but that did not yield anything useful.