Trouble shooting a new CTB16PC

[Powers_Ronald]

I have finished two CTB16PC's and one of them has a problem with channel 10 (not coming on). I have checked and re-soldered the components, but nothing. I did notice a voltage difference on pin 1 U13(8.5 vac) verses U12 and U14 (1.5 vac) and on pin 5 (0 vac verse 120 vac). Without a schematic, I am not sure where to trace the changes. Does anyone have access to the schematic for this board? If so, what pins from U2, U5 and R18 drive channel 10?

Thanks,

Ron

[-klb-]

Without digging deeper, the first thing I would suggest checking the orientation of the Fairchild Opto isolator chip for that channel. For some reason, with the white cased version of the chip, the F logo looks more like the pin 1 mark than the actual pin 1 mark to me when I am populating the board. I know to be really careful with it, because I had put one in backwards on one of the boards I had designed in the past, and almost did it twice assembling my kits.

[Powers_Ronald]

Thanks. U13 is oriented with pin 1 (notch) in the upper left. I agree with you that the little notch and the dark print on the optos make it hard, but all the chips are facing the same direction.

[-klb-]

Unfortunately, I don't have one here off the heatsinks, or I would trace it back and come up with more solid suggestions. But I would double check the solder joints for the resistor network, opto isolator, and that octal latch.

[Guest guest]

Doubtful it would affect only one channel, but just to eliminate it, have you reset the board?

Opto orientation would have been my first suggestion also....I've had a couple on my boards flip themselves after I soldered them in..:X

I'd lean towards what klb is saying...orientation on the chip, solder joints on the chip, resistor network, etc. If its that one channel, and a brand new kit, more likely it is a construction error than a component failure.

Can you send a close pic of the board around channel 10, both top and bottom? Might be worth a look.

You've got a working board with the other one you built, I assume...thats a perfect troubleshooting tool as far comparing voltages, etc.

I did ask about a schematic for these long ago, and the answer I got from Dan was that one doesn't really exist:

We do not have a schematic available. This board was so simple it was simply drawn directly to the PCB (gerber files) with no need for a schematic.

[Powers_Ronald]

Hmm, U13 was bad. I pulled the Opto out and checked it with an ohm meter. It was open both directions, which for a diode is not good. Went to Frys and found a NTE replacement part (NTE3048). Placed it in and it all works.