Wrong LED pattern on first booting

Uh-oh! First and subsequent powering of control board attached to the filter board gives me only an LED pattern of: On off On off On off On off.

I have RTFM troubleshooting following step 14 in the assembly instructions. I’m pretty sure I didn’t make a contact between the two boards. The 165 and the 595 are in the right place and correctly oriented and my solder joints look OK if not beautiful. Any suggestions for remedies.

And, by the way, wouldn’t it be better if the 165 and 595 were socketed rather than soldered directly?

Despondent but not defeated. Any help most gratefully received!

Standard Failure #3

Your Shruthi thinks it is in Firmware Update Mode (RTFM again…) which means Switch S6 is pressed while it is booting. Check the Resistor Network if its aligned correctly (the Dot indicates Pin 1) and check all solder joints on the Resistor, 165 and if there are shorts around S6.

Is the resistor network soldered correctly? Check for shorts between pairs of pins on the S6 switch.

Thanks for these really prompt responses. Will check this out in the near future and report back. Cheers.

Hi. I’ve checked everything mentioned. Resistor network is aligned correctly and I can see no obvious shorts where one soldered joint is touching another that it shouldn’t. I’ve redone the solder connections on the 165, the resistor network and even, after temporarily taking out the IC, the solder joints on the socket for the ATMega chip. Still the same result.

Would it help if I desoldered, say, switch six and reinstalled it? Am I right in thinking that there is no correct/incorrect positioning for the switches? (I’m assuming that switch six is the one on the right looking down on the board.)

Hi ho. And thanks.

Please measure between the pins of the switch if its damaged (hence conductive between all 4 pins in any combination). If its not and you are confident with your soldering the 165 is defective.

Thanks fcd72. I’ll test the SW6 just as soon as I can find a replacement battery for my meter!

Hi. I’ve tested the switch and it seems fine - behaves exactly like all the others and is not conducting between all pins so I assume it’s the 165 that’s defective. Would it be wise to socket this once the current IC is removed? Can I get a replacement from Mutable or would be easier to buy on line (e.g. Farnell in the UK where I’m based).

Thanks for the continuing help.

74hc165 is such a common chip that you might even find it at Maplin & co. I think local options will be cheaper and give faster delivery.

Will do. Thanks for the suggestion. I’ll report back once I’ve got it and installed it. Thanks.