Attached is the schematic of the circuit I am working on, which is basically
a 555 timer running (IIRC) as a multivibrator, clocking the 4027 chip
mentioned, which drives a simple transistor tester with Q1 and not-Q1, and
alternating the configuration of the tester with Q2. This is the basic
model, which I am trying to get working so I can expand it. Frustration is,
I had it working at one time, but can't remember what I changed that made it
stop working. It was constructed as shown on a breadboard but got shoved up
under the bed for a while due to more pressing concerns. I am trying to
dust it off, and pick it up again. Any help would be greatly appreciated.

OPERATION is supposed to be as follows: Q1 and not-Q1 alternately bias the
transistor pluged into the E/B/C sockets as a PNP or NPN device, indicating
which polarity the device is by illuminating one of the two LEDs in the
schematic. When the transistor successfully turns on, it shorts out one of
the two LEDs, so that one LED flashing indicates the polarity of the device
under test. Two LEDs flashing mean no transistor, or one that will not
conduct when biased appropriately. Neither LED flashing indicates a shorted
transistor. And yes, it does work. PROBLEM arises when I try to use the
74HC4053 in the lower left corner to change the configuraton of the E/B/C
sockets for a transistor with E/C/B pin configuration (like an NTE199)
rather than standard E/B/C pin configuration (like a 2N3904 or 2N3906). To
make this happen, I use Q2 to alternately send the "Select A/B/C" pins of
the 74HC4053 high and low, which alters which of the a/b/c (lowercase) pins
are connected to the A/B/C (uppercase) input/output pins that are in turn
connected to the E/BC sockets of the basic tester. And, yes, I can make
this happen too. But not with the shown schematic. To make this last part
happen, I must disconnect Q2 from the Select A/B/C pins, and connect not-Q2.
With this change the project tells me that the NTE199 under test is
functional as an NPN transistor. But it will not tell me anything about the
2N3904 or the 2N3906. To re-establish that functionality, I must disconnect
not-Q2 and reconnect Q2 to the Select A/B/C pins of the 74HC4053. And this,
if I am not mistaken, is *not* the way it is supposed to work. If I am to
understand correctly, Q2 going from high to low (logic 1 to logic 0?) should
do it all. Someone please enlighten me. What am I missing?

Ignorantly yours...

Dave

PS: For whatever mistakes I have made in my description of the circuit or
its operation, I can only ask patience. I am not a degreed individual
(nobody was wondering about that, right?) and I do not have any cookbooks
under my belt. I am merely a tinkerer trying to produce something
worthwhile. As I said before, any help is greatly appreciated.