Take a moment now to check your previous solder joints for “opens” where the solder did not completely flow around the connection, or solder bridges between closely spaced pads. It seems the best time to identify these problems is now when you’re focused on this section of the board, saving you time trying to retrace your steps later.
14. Install R2, the PC mount 1K ohm potentiometer (marked 102). It only fits on the board one way; just be sure it is seated flat before soldering.
15. Install D17, one of the 1N4148 diodes (small glass diode with black band). This part will be mounted in a
16. Install R8, 10K ohms
17. Install Q1, the 221334 PNP transistor. This transistor appears to have two flat sides, one with writing on it and a larger flat side without writing. The pin orientation of Q1, the 2N3906 (221334) transistor, is incorrect on your LABC1 circuit board The larger flat side with no writing is the one pictured on the silkscreen; orient the part using this as the correct flat side. with the flat side (no writing) facing the front of the board towards the D5- D14 diode matrix. Solder all three pins.
2 2 1 3 3 4 |
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o n b a c k | B |
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Q 1 |
| B | |
Q 1 |
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| C | ||
| C | ||
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| E |
| E |
E B | C |
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18. Install R1, 270 ohms
19. Install the last jumper wire, JMP1. Form and solder as you did the other jumpers. You can start throwing away your clipped off leads now!
20. Install R4, 18k ohms
You’ll see a designation on the silkscreen for R5. Now that I’ve brought it to your attention, ignore it. This part is not needed for your LABC1.
21. Install R7, 820 ohms
22. Install R9, the last 820 ohm resistor
Next we’ll install a group of identical parts, the diodes D5 through D14. They all must be installed in the correct polarity but if you can get the first one in
