Help Identifying Components

Brent Hilpert bhilpert at
Sun Dec 24 14:04:37 CST 2017

On 2017-Dec-24, at 10:27 AM, Rob Jarratt via cctalk wrote:
> I am continuing work to reverse engineer the schematic for my H7826 PSU. I
> have removed one of the daughter cards in order to draw its schematic, but I
> can't identify some of the surface mount components on it. I have posted a
> picture of it here:
> The ones I can't identify are:
> 1.       The component with two wide pins that looks like an IC
> approximately in the middle of the board. It is marked M106 (or it might be
> AA106) and 91813 underneath. I think it may be a resistor, but I am not
> sure.
> 2.       Just to the right of this is another much thinner two-pin component
> which is black on top with a kind of white notch. I have no idea at all what
> this is.
> 3.       The three 3-pin black components to the left of the first
> component. Two of them are marked "2T L" (or is that "ZT L"?), one appears
> to be marked "2X I" (letter "ih", not letter "el"). I guess they are
> transistors, but they may not be of course, and I don't know their pinout.
> Any help with identifying what these are would be very helpful.

SMD codes are a mess as the same code is often used by different manufacturers for different devices.
Resolving them is often an effort working between the multiple code possibilities, what makes electrical sense after reverse engineering the circuit topology, and ohmmeter measurements of the device.

2: Try measuring the resistance, if it's a low resistance perhaps a fuse as Chuck suggested, but considering the precision reference on the board, if it's a higher resistance perhaps a precision-trimmed resistor.

3: As per Chuck's suggestion likely bipolar transistors, and probably:
	2T: PNP
	2X: NPN
with pinout (hopefully this renders unambiguously):
	B		E

Try drawing it out presuming the above and then assess whether it makes sense electrically for polarity, current flow and control.

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