Conway,
Do you have the heat sink in place? If so, the most probable failure is
a short due either misplaced thermal pads or a bit of metal entrapped in
the pad.
If the heat sink is removed, then you are correct in your assumptions.
Try first removing T3 - then check again. If still present, remove T4.
If you still have the low resistance to ground on the base and
collectors, the fault might be with Q7 and Q8 themselves.
As an alternative, you could remove Q7 and Q8 first if you have the
means to do that without damaging the pads and thru-plated holes. That
will allow you to measure the base to emitter and base to collector
resistance of the transistors, and also measure the in-circuit
resistances to see which may be at fault.
73,
Don W3FPR
Conway Yee wrote:
> I have just finished the basic construction of the RF board.
>
> Both the base and collector of Q7 fail resistance checks, being near
> shorted out (0.1-0.2 ohm). I must have a solder bridge SOMEWHERE,
> otherwise unidentified. No obvious bridges noted.
>
> Logically, it should somehow be associated with T3 and/or T4.
>
>
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