Deathklaw - Half of delay pot is usable [SOLVED]

[Ralfg]

Hey Guys,

Built the Deathklaw and I notice that the delay pot really only is functional on the first half of rotation.  Everything else seems to work.  About half way up the delay time gets to be pretty long and a bit distorted, which I think is probably normal, but at the half way point it starts to click and makes a crazy knocking sound.  I double checked all my values and made sure all the resistors were correct and they look right, voltages are a bit different than the BOM, but not really too far off as I think it has to do with my 9v adapter which measures at exactly 9 volts whereas the voltages in the BOM is from a 9.25 or something like that power supply.  I also switched out the ICs to make sure they were not the problem. 

Is this a function of the delay?  I would assume not.  I checked the resistance of the pot too and it seems to be working fine.  So a bit of a loss here as to what might be happening.  Everything else works, including the ghost switch.  I did use 550c transistors, but I don't see how that would affect anything other than the volume of the delay. 

What do you guys think?  Cold solder joint somewhere?  I re-flowed most of it.  I can include pictures if it helps.  Thanks in advance. 

[madbean]

Using 550C should be fine. First thing I would suspect is R26, 27, 28 or 29 are incorrect leading to the long delay time. Can you post a clear picture of the top of your build?

[Ralfg]

Thanks for the help!

Its pretty crowded on this board, so I took 2 angles.  You can't see R27, but I measured it and it is 618R, should be good.  R26, R28, and R29 measured ok...  shoot...

[Ralfg]

Doh!  I've been looking at the schematic while eating breakfast before work, thinking what could I have done wrong?  And there it is, possibly, right before my eyes...

I switched diodes 1 and 4.  I'll have to swap them out later tonight to see if that is actually the problem.  Its right in the area where you pointed out Madbean where there might be a problem.  Thanks for that tip which helped me catch my error.  I'll post an update when I get a chance to do the swap.

[Ralfg]

And it was the diodes.  My bad, delay works great now. 

[cajone5]

How do you like it?  I'm really considering this delay with added modulation for my next delay build (likely in a big multi for my acoustic).

[Ralfg]

Too soon to tell. So far it's just been wanking on my testing rig. It's definitely worth boxing and giving it real go in my band. I'm big into tap tempo based delays, but they can get a little much in solos, so I'm hoping this fits the bill as a straightforward clean delay. I'll post an update when I get a chance to really try it. But so far so good!