Electronics > Beginners
Soldering station Quicko T12-943 no power
Specmaster:
The T12-952 controller is same one I have in my stations and I’m happy with their performance.
Haggis McHaggis:
--- Quote from: floobydust on May 24, 2019, 01:52:04 am ---You want a TVS that does nothing at 20V (or 24V) yet clamps below the point of damage to the controller. SMD marking code SYTB I couldn't find, it might be an LM2841 max. 45V input. So a 22A or 27A TVS is OK.
Notice app. note 88 also shows adding a bulk capacitance 47uF 35V works very well.
I would put in both the TVS and capacitor, like this schematic.
--- End quote ---
Thank you very much for the schematic. Much more than i could ask for.
draza:
Sorry,
I was very busy these days.What I found was that S4 Schottky diode is
shorted, I do not have a suitable replacement. No voltage on CPU.
The SYTB is step-down DC / DC regulator chip (LM2841XBMKX).
Does anyone know what this 541IG ic is?
Specmaster:
I did a google search and cannot find any data on this IC at all so I did a image search and came up with this test of a USB charger meter that uses the same IC and there author seems to think that this is indeed an op-amp ?
https://lygte-info.dk/review/USBmeter%20RD%20Tech%20USB%20Meter%20AT34%20UK.html
EDIT
I just did a search for 5411G (thinking that the I could be a badly printed 1) and bingo, I have the data sheet for this IC which would appear to a voltage detector with built delay circuit and is set at 4.1V.
floobydust:
Buck-converter diodes failing short has been talked about in this thread: https://www.eevblog.com/forum/projects/interesting-failure-of-buck-converter/
SMT marking "S4" is a Schottky diode SOD-123 package, like a 1N5819 (B5819) or SD103AW 40V 0.2A
These controller boards have the absolute minimum capacitance to just work, and this PCB does not look so great especially the ground pour and putting a high gain op-amp next to the noisy buck converter. I can't see the temperature reading being stable.
Other controller designs use a buck-converter then a 3.3V LDO for quiet power.
The SOT23-5 IC is the thermocouple amplifier, usually a LM321-clone op-amp like SGM8551.
SMT marking "541I" I could not find SOT23-5 parts, it might be a clone of AD8541 (A4A marking).
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