anderton bi-filter again

[thomas2]

someone tell me what is wrong!
i used the audio probe on it and found out the guitar signal doesn't get far.. in fact it only goes into the first opamp input and doesn't get out anywhere.. i tried a bunch of different opamps and i'm pretty sure they can't all be bad.. the pedal acts like a wind simulator at the moment.. i can hear the sweep when i turn the knobs.. also when i touch the opamp with my finger.. it oscillates very loudly and i can hear some of my guitars signal trough it..
i had to substitute some parts to it.. (caps, opamps, diodes) and i used the led/ldr in a shirnk tube instead of the optoisolators..

sorry about my crappy english btw  :shock:

[niftydog]

which op amps are you trying?

[thomas2]

i used 4558's and TLO82

[niftydog]

checked voltages around op amps with a multimeter? check supply pins. Make sure there's not lots of DC on the inputs / outputs etc.

make sure the 10k pot is wired correctly.

(as a quick check, I might try this; turn off the circuit, temporarily short the 2.7uF cap and read the resistance from the op amp output to ground - Just to make sure I hadn't done anything stupid! Should read a little less than 10k I guess.)

[thomas2]

oops.. i just noticed that i had substituted the 2.7uf cap with 2.2uf.. i think i haven't ever even seen a 2.7uf one... could that be the problem? well.. i will try checking the voltages later today. thanks for the help man..

[niftydog]

that's unlikely to be the problem.

Sorry, gotta go, I just finished work, it's 10pm where I'm at!

Good luck!

[thomas2]

:evil:  i checked the voltages.. everything seems to be like they should.. also checked the pot wiring.. again everything is like they are on the layout.. i just can't get the damn thing working..

[Mark Hammer]

1) Is this a PCB or perfboard build?

2) Are you certain about the orientation of ALL electrolytic caps, including those in the power supply?

3) Are you certain about the orientation of the CLM6000's?  Dot should go to ground.

4) Are you certain that all appropriate parts go to inverting and noninverting pins on op-amps?

5) Are you sure you're getting an envelope signal (check with AC or DC voltmeter at  output of envelope-follower section.

6) Have you wired up the "Initial" pot correctly?

[thomas2]

i used the pcb layout from generalguitargadgets.. and i corrected the mistake on the layout..

i'm absolutely positive about the orientation of the caps.

i don't have clm6000's at all.. i can't get those here where i live.. so there's led's and ldr's in a shrink tube.. the led's light up when the power is on.. (i checked before putting on the shrink tube)

all three pots have been wired correctly.. i doublechecked.

still doesn't work..  :shock:

[thomas2]

maybe i'll just call it  "mysterious wind simulator thing" and let it be.. kinda tired of trying to debug the damn thing.. i've tried for over a week already.

[Mark Hammer]

A week, and you're quitting!!?  It took me a year to find out what was wrong with the first Doctor Q I made (fractured wire inside the insulation to the switch leads), and almost a month to debug the 1st Doctor Quack I made (the board was etched backwards).  

I realize it's frustrating, but you need to have faith Brother Thomas. I promise you, the rewards are well worth it.  This is a nice sounding pedal, and not many others (if any) sound exactly like it.

When you say the LED's light up, I assume you mean they light when you play, or when you turn the Initial/Sweep control up, right?  Unlike the Dr Quack's bias-setting LED, these should not be on all the time.

There *should* be something coming out of the first op-amp.  Probably somewhere in the neighbourhood of a few hundred millivolts.  If you have changed op-amps without any change in this condition, then there are a few things to consider (and my apologies right now if some underestimate your intelligence):

1) You used the wrong op-amp type (e.g., a single where a dual ought to be) or have it oriented wrong.

2) The PCB was etched backwards (i.e., mirror image; bending the pins backwards so that the numbers face down will actually let you stick the chip in the socket and have the circuit work if this is the case).

3) There is a crack in the circuit board such that eiother signal or power is not going where it needs to.  I had this happen to me several times.

4) There is a short produced either by a blob of solder or else a connection between IC pads that looks "normal" when you inspect it.

5) The input jack lug carrying signal or a battery lead is not the one you think it is. (easily identifiable by having a single battery completely die on you overnight without plugging anything in).

[thomas2]

i don't remember how the led's were..  i should take them out from the shrink tube and look. i did take care when i made the pcb.  i already doublechecked the solder joints and made sure there's no shorts with a sharp blade.. but what if? what if the led's do light up even without signal? i don't know how i would fix that either.. i really should have taken something easier in the first place but i have no use for a distortion pedal or something like that..

[Torchy]

Link to schematic ?

[thomas2]

http://www.generalguitargadgets.com/v2/index.php?option=displaypage&Itemid=104&op=page&SubMenu=

[thomas2]

i checked the led's.. they light up when i turn the power on.. the 10k sweep pot changed the brightness. but guitar signal had no effect on them.

[Torchy]

Thanks  :wink:

If the signal dont go past the first op-amp I would suspect a short around that chip. I take it you made your own pcb as you mention fixing an error ... check the pcb in font of a strong light for whiskers or unetched copper. You certain you got + and - on the chip (not + and 0v) ? Check D1 and D2 in case one has gone o/c. Sounds like a power problem to me but Im probably wrong (again  :oops: ) Isnt learning fun  :lol:

[thomas2]

no it isn't  :wink:

[niftydog]

when you're checking voltages and probing audio, are you making contact with the actual pins of the op amp or the tracks, pads and wires of other components?

Basically, if the signal isn't getting out of the op amp then there's a finite amount of things that it could be.

- There's a wiring error aroun the op amp

- Power is not getting to the op amp

- There's damaged or incomplete tracks or bad soldering around the op amp

- There's a short circuit on the output of the op amp

- The op amp is dead


My approach would be to isolate the op amp from the circuit. that is, if you can, disconnect the components attached to the output pins and try again with the audio probe.

The input op amp should have about 0V on pins 5,6 and 7, +9V on pin 8 and -9V on pin 4.

[thomas2]

can you tell me what could be the problem.. i checked it yesterday.. as i told you before.. i used led's and ldr's instead of the clm6000's in the circuit.. both of the led's light up when i turn the power on. guitar signal seems to have no effect to them.. only the sweep pot.

i did check the voltages.. there's power where it should be.
there's no breaks in the pcb and no solder blobs at all..

[thomas2]

i used ic sockets btw.. i checked the voltages from the ic socket pins.