Author Topic: Zombie ticks after all three separate bias mods!  (Read 1039 times)

Peter

Zombie ticks after all three separate bias mods!
« on: April 18, 2006, 02:19:51 PM »
Hi everyone,

As you allready know ftom the title the Zombie I built still ticks! Prior to populating the PCB I performed the LFO separate bias mod!
After completing I tested the circuit and was realy pleased by the effect! Wery crisp and clean but with thick that is at very low level but still can  be heard when I stop to play. Then I performed the separate MN3007 and Op Amp's bias mods as sugested by Mark Hammer. To my big dissappointment there was no any positive change!Thicking was at the same level. Capacitors up to 470 uf with every of the bias networks do not help at all  too!
I was not able to check up  the MN chip by changing it with another one because I solsdered it directky to the PCB (without socket).
It sounds great with distortion before it though something very interesting happens- the ticking stops completely! Can this be clue to the problem?

All suggestions are wellcome!

Regards!

Peter 


Mark Hammer

Re: Zombie ticks after all three separate bias mods!
« Reply #1 on: April 18, 2006, 02:41:05 PM »
Not sure why ticking would be contingent on input signal tone, but one question worth considering is whether the source of the ticking is more from the wiring layout of the pots and any switches you might have, rather than from the decoupling.

gez

Re: Zombie ticks after all three separate bias mods!
« Reply #2 on: April 18, 2006, 02:42:56 PM »
I second Mark's concerns, probably a wiring issue...
"They always say there's nothing new under the sun.  I think that that's a big copout..."  Wayne Shorter

Peter

Re: Zombie ticks after all three separate bias mods!
« Reply #3 on: April 18, 2006, 03:42:43 PM »
Hi Mark,

Thank you for your  reply!

Here are some more details: At my request a  friend designed and made for me new PCB that is more compact and can fit into a Hammond 1590B box. I think this is the right size for this circuit. It is 2 1/4  by 2 1/4 " and leads for pots and the mode swich come out from the top side of the PCB like the original PCB.First I tested the finished circuit without box. Then I petformed the last two mods and put it in the box and there was no any change in ticking at all. The PCB was made the wrong way - mirror image of what it should be so I put chips and few caps on the copper side, the rest of the caps and resistors + mods on the other one ( where they  should realy be ). There is no "part over part" and there are no parts  on the spots  where the chips are on the opposite side of the PCB.Can something be wrong with the desingn of the PCB( my friend is a proffessional PCB designer)? Chips are placed horizintaly on the PCB(with the above mentioned orientation) this way: Up left U3, up right U1, down left CD4046 and down right MN3007.

I am looking further for more comments!

Regards!

Peter

chunks717

Re: Zombie ticks after all three separate bias mods!
« Reply #4 on: April 18, 2006, 04:29:54 PM »
hello.........I fought this circuit tooth and nail, and in the end, it was the cap I added between pin 1 of the lower left op-amp (on board, comp. side, with off-board facing up) and pin 3 of the BBD. (that long trace). I initially used a 1uf, and then a 10uf, but it needed a 47uf(in mine) to kill the tick..............neg. side toward bbd..............I even removed my bias points, and LFO wire shields just to see and it was still quiet.....so in my experience, that was the tick-et (smirk)

puretube

Re: Zombie ticks after all three separate bias mods!
« Reply #5 on: April 18, 2006, 07:27:40 PM »
you`re all talking riddle language to me...  :icon_question:

btw.: anybody mentioned: Welcome to the forum, Peter?  :icon_wink:

Peter

Re: Zombie ticks after all three separate bias mods!
« Reply #6 on: April 20, 2006, 12:49:03 PM »
Hi Chunks 117,

Thanks for sharing your experience!

Unfortunately enlarging the cap didn't help!

I'll build another one when I receive the new properly made PCB. Then I'll make anoder post!

Rregards!

Peter

Peter

Re: Zombie ticks after all three separate bias mods!
« Reply #7 on: April 20, 2006, 01:37:06 PM »
Hi Purerube,

Thanks for wellcome!

Regards!

Peter

Peter

Re: Zombie ticks after all three separate bias mods!
« Reply #8 on: April 20, 2006, 01:46:15 PM »
Sorry Puretube,

 I wtote the wong your name!

Regards!

Peter