Im currently trying to repair a board and I found this SOT23 component marked as A1⌐ (last symbol is a 7 but rotated 90 degrees to the left, I think).


In the board is marked as D15 so I assumed should be a diode, besides the "A1" mark, according what I have found on the net, is a BAW56 component that is a double diode.

But the problem is that the readings I get from de component out of the board, don't match with the expected for the device. (I have more than one of these on the board and all give me the same readings)

Obviously we may think that is a burned out component. but all of them burned out?, I don't think so.

So I believe is a different component. The rotated 7 is the thing that give me doubts. could it be a manufacturer code? if it is does anyone knows it?

I'll appreciate very much any thoughts on this.

As asked, here is a pic of section of the board where the component is located. enter image description here

Is a series of active filters based on OP AMP. This is the last stage and takes as input the TANK2 signal (coming from a previous OP AMP circuit)

  • 1
    \$\begingroup\$ If you are measuring in circuit, you won't get accurate readings \$\endgroup\$
    – Passerby
    May 28, 2016 at 1:21
  • \$\begingroup\$ This type of problem is usually only solved with context. Explain where it seems to be in the circuit, or include a zoomed out picture of the area of the board with labeled inputs or outputs. \$\endgroup\$ May 28, 2016 at 1:34
  • \$\begingroup\$ Thank for your reply. Yes, I know that I can't get a good read with the component connected on the board. but I believe than one of the pins it's unconnected (meaning that if this is a dual diode there is only one diode being used in the circuit) Is in this unconnected terminal that I get mismatching readings with respect to the others. (it should be read as a simple diodo) \$\endgroup\$ May 28, 2016 at 2:08

1 Answer 1


Well, a quick Digikey search for "baw56" does turn up double diodes in a SOT-23 package. Of these, at least Fairchild and NXP sell them with A1* case markings. I'm not certain exactly which manufacturer made that part, but they're a general component in the same way as a 1N4001 diode. For this diode pair, typical specs are Vr=~75V, If=200mA, Vf=~1V.

As Passerby points out, you can't typically measure components within a complete circuit and expect to get the isolated component values. In this particular case, I can see a capacitor with a few millimeters of the component you're measuring that could easily mess with your test equipment. If you wanted, you could desolder one and measure it in isolation, but unless one shows signs of obvious damage, I wouldn't immediately suspect the low-power signal diodes as being the probable cause for your board failure.

  • \$\begingroup\$ Sure, i know I can't measure the component on the board and to expect a good reading, but this component has a disconnected pin that should be the cathode of one of the diodes and I should be able to measure without a problem the drop voltaje of the diode from anode to cathode. and that's the reading I don't get \$\endgroup\$ May 28, 2016 at 2:26
  • \$\begingroup\$ @AlfredMoreno What do you get? \$\endgroup\$
    – Owen
    May 28, 2016 at 7:24
  • 1
    \$\begingroup\$ I realize that the problem was a bad battery on the multimeter i change it and now i get the right readings thanks to all for your answerds and comments \$\endgroup\$ May 28, 2016 at 13:21

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.