Help identifying IC in Smeg toaster - Page 1
Forum section: electronics / repair

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: May 15, 2024, 12:55:32 pm
content: Trying to debug faulty toaster - wouldn't usually bother but Smeg replacement price makes it worthwhile to diagnose. IC is labelled RT2602H and 8006 (presume this mfr date). Photo attached to show form, code hard to read here but I can confirm it's definitely RT2602H. The IC is modulated by three switches and a 250K pot. It's involved in activating a small electromagnet that holds the activating lever down while toasting (that's what's faulty). Everything else I've checked so far, including on the main board (power in and switching relays) comes up OK. So I suspect this daughter board might be bad. Can't pin IC down on web. A datasheet would help with function/s and testing.

author: fzabkar
author_rank: Super Contributor
timestamp: May 15, 2024, 08:34:32 pm
content: I suspect that it's a microcontroller. What are its supply and ground pins, and Vcc voltage? Do they match a PIC?This is an interesting blog:https://esalvage.blogspot.com/2016/04/toaster-controller-a0201d.htmlhttps://www.mouser.com/datasheet/2/115/PT8A2511-1350784.pdf(8-pin toaster controller)https://www.diodes.com/assets/Datasheets/products_inactive_data/PT8A2511.pdf

author: DavidAlfa
author_rank: Super Contributor
timestamp: May 15, 2024, 11:23:24 pm
content: That round logo seems to be Fuji Electric:But unlikely to be the cause? See:https://www.electro-tech-online.com/threads/kenwood-tcx750-toaster-solenoid-not-powering.158883/

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: May 17, 2024, 03:44:15 am
content: Thanks fzabkar and DavidAlfa for the quick advice and the links. I think you're spot-on with it being an MC. The surrounding circuitry looks pretty similar to the Application Circuit in the PT8A2511 datasheet. I've started sketching it out. I have both boards out of the toaster at present and disconnected from the heating elements, so have to work through connecting it up and testing voltages etc with it out of circuit. The datasheets will be really helpful in trying to work out pinouts on the MC.I did suspect either the relay or the electromagnetic latch but they both test OK. So I'm suspecting the relay is not getting the coil activation signal from the MC. That should be easy enough to test if I can get it all connected to some re real or dummy elements loads.Bit of effort for a minor appliance but I do hate sending stuff to landfill.

author: MathWizard
author_rank: Super Contributor
timestamp: May 23, 2024, 06:37:01 pm
content: As an adult, I've hardly used toasters anymore (IDK I just never bought 1). But wow, do most of them have chips in them these days ?

author: coppice
author_rank: Super Contributor
timestamp: May 23, 2024, 06:51:48 pm
content: Now that is a seriously application specific IC. I assume the chip is actually a tiny MCU presenting itself as a fixed function device. Many chips are these days.

author: Lorenzo_1
author_rank: Regular Contributor
timestamp: May 23, 2024, 11:56:21 pm
content: I think coppice is correct on this one - it's some sort of proprietary MC. I roughed up a schematic of both boards and it certainly doesn't look like this chip is one of the 8-pin toaster controllers that fzabkar pointed me too. Circuitry doesn't look remotely like illustrative circuit in datasheet. Looks like it's running on a 5V DC supply, but I really have little idea of pin functions. I did get the toaster to come back to life briefly after soldering the main board back into place, but then part of one main element stopped turning on despite having continuity and a sensible low resistance. That again looks like a problem with switching the right relays, which is controlled by this daughter board MC. In the end I decided to can it - it will take more time than it's worth to diagnose and more expense to fix than it's worth.I think this shift to microcontroller based switching is greatly impacting the working life of appliances. I've had failures on a whole range of items and most have come down to MC-related problems. Seems to me the lifespan of these MC appliances is perhaps 3-4 years then you have to throw them out. I can think of only one (a mate's coffee machine) where the fixable fault was a bad diode and relay on the main control board. In contrast, I have a completely analogue-switched expresso machine that's been going strong for near 20 years and I've fixed several times without drama. Hopefully I can buy a non-digital toaster to replace this expensive dud.

author: Clear as mud
author_rank: Regular Contributor
timestamp: May 25, 2024, 10:34:35 pm
content: Quote from: MathWizard on May 23, 2024, 06:37:01 pmYeah, mine is just a cheap one, but it came with a "bagel" button and one other custom setting, and some LEDs to light up the buttons. I assume there's a microcontroller in there for all of that.But even if it's just a one-function toaster, they usually have at least a timer IC and an electromagnetic latch to hold the bread down. I am not sure if anyone still makes them with the bimetallic strip and no electronics, the way they used to.