Control Board LED weirdness (poli) [solved]

Not sure the poli part matters and man does this thing have some growl. I didn’t expect so much fuzz until overdrive filter is turned on.

At any rate, When I select the first (or first/second - not the second only) Osc to adjust all leds light (dimly). This also occurs when switch s5 is set to bottom (no led should be lit but all are). The s5 light up happen whatever setting is going on. Everything else works fine and I’ve swapped 595s and no difference. Ideas?

Maybe a short somewhere around the resistors for the leds?

I have checked for resistor shorts or bad values, led forward voltages and everything looks normal. It only dimly lights things up on Osc 1 or when both Osc lights are to be lit, doesn’t matter if its shifted to top or ‘bottom’ controls and it only happens on Osc 1. Perplexed.

Any other suggestions anyone? I’ve double checked, reflowed solder points, exchanged ICs, reflashed the 644p, just can’t figure it out.

What kit are you building?

It’s a Polivoks

Do you have 5V on the active port of the 74HC595? Have you checked the polarity of the leds and the value of the resistors R2-R9?

yes and yes.

Strange, it almost sounds like the 74HC595 shift register is receiving and shifting in some data on the serial line when it shouldn’t even be enabled or something like that. If you can try swapping the 74LS165 as they share some signals and try probing the led outputs from the 74HC595 with an oscilloscope. This could also be a bug… I don’t think the filter setting in the firmware could affect this but you should double check that as well if you haven’t.

The Filter settings (and the Programmer Settings) are pushed thru the onboad LED 595 so if this one is faulty or simply to slow some Bits might not to the right Place…

Yes, I just saw that some of the lines to the 595 are the same as for the UI_EXP.

Same issue. Swapped 165 and MCU- nothing changed.

This was down to faulty 595s and can be considered solved.

Yes indeed, thanks lindeborg, you must be a mod. But yes, it is solved. Unfortunately Tayda will not be rectifying the situation. Blurg. Oh well, it’s only a few dollars.