Egodrive not working

[cdicker]

can someone help me. I am a total noob and I can't figure out why my egodrive won't work. No sound at all.  The LED lights up but that is the only thing that works.  I checked all the solder joints and values and they seem to be correct.  I tried to trouble shoot from a different post (the egodrive problem one) and I have voltage but when I go to the IC, I only get .66 on each one (other that 4 which is 0).  I know he got values of 4.4 but I don't.  I am lost where to even begin troubleshooting.  Please help.
Thanks

[desmoben]

Have you checked to connect directly the guitar input to the OCD input?
Maybe your switch wiring is incorrect?
BenoiT.

[cdicker]

I have bypassed the whole 3pdt switch  and everything is wired directly to the PCB.

[gtr2]

Do you have 9v at pin 8?

[cdicker]

Nope.  I have .75 V and the rest are .60 V ish other than 4 which is 0V.

[k.rock!]

Make sure you have all the correct resistors, caps, polarities of caps and diodes.

If all of them check out, check for short circuits to ground. You do this by setting your DMM into continuity check mode, place a test probe on a ground point, and with the other one start touching joints and if it beeps and you're certain it should not be connected to ground, then you've found the area where the problem component is.

Can you post pictures of your board? That would help us a lot to help you better

-Kaleb

[bigmufffuzzwizz]

Have you checked the power to makes sure you have 9 volts coming in? If it is and your not reading 9 volts at pin 8 I would then check to see if 9 volts is flowing through the components connected before pin 8. It could be a bad IC but there's other stuff to rule out first. I would try to measure 9 volts across R13 or you might have to take it from ground. Also double check to make sure you actually used a 100 ohm for R13. With metal film, 10k and 100R have the same color code but backwards!

[cdicker]

I tested the voltage coming in and it's 9V. I checked R13 and it's 9V to ground and it is 100R.  I checked connections and nothing is touching other than all the grounds.  Do you think it's the IC?  I will try to take a pic today also.

[cdicker]

Ok wait, I measured the wrong resistor.  It is a 100R but the side furthest away is .7V.  When you measure it, it comes out as 100R though so could that mean that it could be a bad resistor even though you can measure it? May be a dumb question.

[k.rock!]

Ok wait, I measured the wrong resistor.  It is a 100R but the side furthest away is .7V.  When you measure it, it comes out as 100R though so could that mean that it could be a bad resistor even though you can measure it? May be a dumb question.

You shouldn't measure impedance on the circuit because that could give you the wrong reading. For example, if you have two 220R resistors in parallel you will end up reading around 110R on either one and you would think you have the wrong ones. The best you can do is either measure off the board or check the color code if you don't want to desolder it. Honestly, just check the color code. It should be brown-black-black-(tolerance stripe) (for 4 stripe resistors) or brown-black-black-black-(tolerance)(for 5 stripe resistors)


-Kaleb

[cdicker]

It is the correct color stripe.

[cdicker]

I didn't clarify whether it will help but R13 at the one side reads 9V and the other side reads .7V.  Bothe from ground.

[cdicker]

Here is the pic. Sorry it's blurry, I'll try to get a better pic but hopefully this can help a bit. And here is a random question kinda.  Why if I test the voltage for R12 do I get 9V on both side to ground and when I measure R13 I get 9V on one side and .7V for the other to ground.  And I did change out the resistor and nothing has changed.

[attachment deleted by admin]

[bigmufffuzzwizz]

R12 is there as a current limiting resistor for the LED and after the LED it goes straight to ground which is why your seeing the full 9 volts. When your measuring the junction of R13 that connects to IC pin 8, there's not a straight path to ground. Since your measuring from ground I can see other components involved in the path. One of those is more than likely affecting the voltage. I haven't solved a problem like this yet but I can give you more suggestions until someone with more experience can chime in.
Try measuring the voltage across R13. Since its 100R it shouldn't be dropping more than 0.1v I would think. Also try measuring from the ground point of R15 across to its juction w/ R14 and across R14 and see if there's a chunck or most of the voltage sitting there. Looking at the schem, the positive voltage on the IC (called VB) must go through R14 (after going through R13) before it can enter the chip so that seems the next best place to check for problems. I would also double check the values of R14 and R15 and make sure they are 10K and not 100k.  

[oldhousescott]

It sounds for all the world like your protection diode is in backwards, but from your picture, it looks correct. Pull out your IC chip and measure again.