On Tue, Mar 1, 2022 at 10:29 AM, Colin Herbert wrote:
A2Q9 base-emitter junction shows infinite resistance one way and
452K the other.
Ideally if you have "diode check" mode on your DVM that is what you need to use with the transistor off but all indications point to a faulty A2Q9.
Both A2Q8 and A2Q9 were Motorola SM4713 originally and it looks as though a
2N3251 would be an equivalent now, though they are ?2.40 each.
For now you can use widely available 2N3906 to get your debug going. I don't have this equipment and didn't look at the design carefully so there may be better equivalents recommended by group members.
Ozan
