Author Topic: Identify chip L7c - Siemens kitchen appliance (oven) repair  (Read 540 times)

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Offline pplaninskyTopic starter

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Identify chip L7c - Siemens kitchen appliance (oven) repair
« on: September 11, 2024, 05:44:57 pm »
Hello,

It’s a control PCB from an kitchen oven.
The issue it lost comms with the user interface board on the front panel.

The chip is on the TX path of the data line (single wire for TX/RX running on 50Hz clock, generated from the mains).
The obvious purpose is to buffer that line as the other side is pulling the same wire to ground when transmitting.
[At least it’s what I think.]
However, it seems that at the moment this chip pulls down the line constantly to 2.3 volts, which is too low compared to the 5 volts level observed otherwise.

However, I couldn’t find any datasheet that matches the pinout.

Anyone - can you help me identify this chip?
 

Offline suntime

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Offline pplaninskyTopic starter

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Re: Identify chip L7c - Siemens kitchen appliance (oven) repair
« Reply #2 on: September 11, 2024, 08:21:43 pm »
Seem to match the pins and purpose.
Thank you.

I am wondering, if I can just temporary shunt the buffer - just to test the functionality of the PCB.

My guess is that if you connect just 2 devices, the sink current on the MCUs should be good enough.
This buffer is probably for over voltage protection and when you chain more devices
 

Offline pplaninskyTopic starter

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Re: Identify chip L7c - Siemens kitchen appliance (oven) repair
« Reply #3 on: September 15, 2024, 02:51:09 pm »
As I couldn’t find such replacement chip, I bodged a 7407 and used one of the six buffers from it.
Works perfectly.
 

Offline fzabkar

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