weird 808

[Mugshot]

first off, i am so not a tech, so obviously i cannot debug.

the thing is, i have here in me a DIY 808 clone, with the board layout taken from tonepad.com. my friend made that, and he pledged that he will replace the circuit board. but while there is no replacement board yet, i'd like to know what went wrong (just for curiousity, and im eager to learn DIY stuff as im a pedalhead  )

ok, here's the problem, and im sure some of you here have encountered the same thing before.
bypass is fine, no prob btw.
when engaged, none of the controls (level, tone, drive to a certain degree) seem to work as it should.

a) the volume knob doesnt cut volume even when zeroed in. sure it boosts volume to a certain degree, but i was expecting it to cut at least to a very minimal level when turned all the way down.

b) i get cloudy-thundery sounds when tone is either maxxed or zeroed. i had to set it midway to prevent this. and doesnt change the tone either way.

c) i cannot tell if the drive knob functions, but i think it does. but the defects of the tone knob and the level pot overshadows it functionaility (if it IS functional).

so there. im just curious to know what could've happened, since im planning to build one for my kid bro sometime.


thanks,

sean

[oskar]

when engaged, none of the controls (level, tone, drive to a certain degree) seem to work as it should.

a) the volume knob doesnt cut volume even when zeroed in. sure it boosts volume to a certain degree, but i was expecting it to cut at least to a very minimal level when turned all the way down.

It is either wired wrong or, which sounds more likely, there is a problem with the reference voltage it is going to or the pot is broken or...

b) i get cloudy-thundery sounds when tone is either maxxed or zeroed. i had to set it midway to prevent this. and doesnt change the tone either way.

Resonance?... feedback somewhere, move wires around an see if it helps... ( reference voltage again?)

c) i cannot tell if the drive knob functions, but i think it does. but the defects of the tone knob and the level pot overshadows it functionaility (if it IS functional).

If you cannot tell if the function works then a good place to start is to find out if it does. It's important to know how the effect is supposed to sound really. I've spent hours on trying to help people with things that's really worked...

Happy engineering



oskar

[MikeH]

first off, i am so not a tech, so obviously i cannot debug.

First off, welcome!

Secondly, it's not as hard as it seems; there's a thread here: http://www.diystompboxes.com/smfforum/index.php?topic=29816.0 that will give you step-by-step instructions and all you need to start is a digital multimeter (which you can find for as cheap a $5 some places).  That being said, if you're eager to learn about DIY pedal stuff, it is essential that you learn some debugging skills.

Lastly, there's no way for anyone to know what's wrong with your particular build without some data provided debugging; all anyone can do is make 'shot-in-the-dark' guesses

Give it a try!

[Mugshot]

(didnt see any thread for forum newbies so i posted right away  )

update: by a stroke of miracle last night, i DID manage to correct the circuit, i know i did, because the level pot kills the signal when turned all the way down, and boosts volume when cranked  i can now hear the drive pot respond when i tweak it. the only prob i have now is the tone pot. i still get the crackle/thunder-y/cloud-y kind of interference.

what i did: out of "desperation" (i was actually having a "this is the last straw for you, you PCB!" moment) i "probed' the whole circuit using, among other things, a soldering iron. yeah, a soldering iron. i simply retouched the solder lines and blobs (i was reminded not to overdo the solder thing as it may damage the circuit). i plugged the whole thing and it worked! 

what i suspected: i think there is no connection among and between some of the components since the copper that remained after etching the whole PCB is very thin, which could have cracked causing discontinuity.

after making the whole thing work, i quickly replaced the opamp (a TL072) with the fabled JRC4558D which a local dealer had selling for approx. $1 (and it was the last jrc4558d in his stock, lucky me). i found the TL072 too "clean," and i wanted something dirty to start with (no, noisy caps and resistors are not welcome).

i informed my friend regarding the matter and he was excited. he promised to send in a back-up PCB with components already mounted just in case.

im inclined to think that the thin PCB could be the culprit. is there a better way to etch a board (i.e., preserve the copper part from the etchant better)?

sorry for making you guess, but out of excitement last night i immediately velcroed the OD to my board while i was inspired to do so  and forgot to take pics 

thanks for the help guys. im already getting some tools for DIY stuff this week.

(i guess i DO have to get a multi-meter too. that's next in the agenda.)