Help - could In have shorted my pedal?

[Rick1114]

I was modding my small clone this weekend (I added a depth pot and delay time pot) and everything was working as expected.  Then I went to reassemble the pedal and had some trouble gettiing eveything to fit inside the chassis. After I re-assembled the pedal, the depth pot was making scratchy noise for a few seconds and the pedal was no longer functioning. The pedal LCD light ups and I hear sound, just no chorus and the knobs have no effect.  I opened the pedal back up and it looked like one of the lugs from the delay time pot were touching the metal chasis - all the other wiring seems to be hooked up properly. Could I have shorted the pot or one of the chips?  How do I troubleshoot this with my multimeter?

Thanks,

Rick   

[swal]

The first thing I would do is unhook your mods and see if the pedal works then. If not go over to general guitar gadgets, they have schematic and the voltages for the ic's under the project secton. See if the voltages are close to what they should be.

[Rick1114]

Thanks Swal,

I will unhook the mods tonight.  I guess that will tell me right away if I may have shorted the pot.  I have not been able to find a schematic for a EH Small Clone reissue, only the tonepad schematic, but the PCB layout are different enough to make my head spin!

Thanks,

Rick 

[Rick1114]

Can anyone tell me how to properly check the voltages on the BBD chip pins with a multimeter?  I have found these repair notes and I have a suspicion that the BBD chip is Fried (I get no chorus sound but the original sound come through intact).  He supplies the voltages for the pins here, but I'm not sure how to test them correctly.

http://www.axecentral.com/forums/effective/93126-small-clone-repair-notes.html

Thanks,

Rick

[swal]

What you need to do is read what Aron wrote here http://www.diystompboxes.com/smfforum/index.php?topic=29816.0
Answer all the questions like this person did http://www.diystompboxes.com/smfforum/index.php?topic=70355.0
I did the same mod that you did to the small clone and it worked perfectly. Good luck

[Rick1114]

Swal,

Thanks again for your help!  I backed out of the mods and realized the delay time pot was hooked up incorrectly.  Now everything is working fine.  I have one question about the delay time pot.  Mine seems to have a subtle effect, and not quite the range I expected. It does seem to "tighten up" the chorus a little bit, but I would like more range!  I have some other mods in place, like a 100pf cap (instead of 150), and a 1uf cap in place of the 2.2uf (I did these mods to slow down the rate knob and make the chorus more "vibey").  Is this why my delay time pot seems so weak?  Can I experiment with another resistor on the 100k pot to increase the range?

Thanks,

Rick         

[swal]

What I did was put on a dpdt toggle switch that changed between using the original  switch and a pot. The pot goes  slower then original switch in the slower mode and faster then the original switch in the faster mod. It seems that 1/4 turn equals the original slower mode and 3/4 turn equals the original faster mode. Therefore, I think it is the change of the 1uf cap is the problem, I don't think the 100pf change would make that big of a difference, but I could be wrong. I would put in a spdt switch that would choose between the orginal 1 uf cap or the orginal 1 uf cap and another 1 uf cap making a total of 2uf. This will allow you to get the vibey chorus when you want and the original when you want. Happy to hear the pedal is working.

[Rick1114]

Swal,

Thanks for your input regarding those component changes.  I tried changing the 100pf cap to 250pf and there was no difference in the sweep of the delay time pot - so I think you are right on that point. I will try the SPDT switch to come up with the 1uf / 2uf settings you recommended - I think that will do the trick!  (why not? I've got the hole for the switch sitting there already doing nothing)   

Thanks,

Rick