My second modolus 60 counter is counting wrong. The first one works fine and it's the same design. The tens alternate from 4 to 5 and 5 to 4 with up and down settings. The up/down switch is wired correctly. I checked for countinuity integrity of the parts connection on the board with R *1 ohms with my meter and it shows OK. On a second cycle an extra pulse is needed to change from 4 to 5. I think there's a loose connection or a short somewhere. Does anyone know of any idea, my troubleshooting skills are poor. I have a logic probe I bought recently, can someone tell me what to test for? I replaced the ICs and I still have the problem so the ICs are good. There is inversion occurring at the collector of the transistor when zero is reached with the units cd4510 so that's fine.

 

My first guess is that the counter outputs are being too heavily loaded. Worst case source current is 0.51mA @ Vdd=5V, with 1mA typical. That's affecting the decode logic.

Schematic in question:

 

I'm sorry I wasn't clear dl324, the Q outputs are not going to LEDs but to cd4511 decoders which drive 7 segment led displays. There is no high level at Q 2 for the tens cd4510 up or down (the one that is supposed to count 0 to 5 and reverse). 0 to 3 is not showing on that counter but only 4 and 5. When the units cd4510 reaches 0 the tens display show only 4 and 5 and 5 and 4 only and alternates both ways whether the dpdt switch is up or down. The 0 to 9 units display is okay up and down. I tried uploading a 3gp video file less than 10mb but my file type was not supported. I am pretty sure the cd4511 decoders and displays are okay but then again I could be wrong. Maybe the tens 2^1 input of the cd4511 is shorted.

 

Can you post the schematic for the circuit?

EDIT: Check pins 13 and 14 on the 10's digit for a short.

 

The counter is okay now. The tens cd4511 decoder waz faulty so I replaced it. There was no short between pin 13 and 14 of the cd4510. There was a low resistance between pins 1 and 2 of the decoder. Thanks for your consideration.