CJ's Plus-Dist - a little help (FIXED!)

[Bret608]

Hi everyone,

I recently finished populating CJ's Plus-Dist board. Last night, I hooked it up to my test box (yes, I'm finally rocking before boxing!) and wasn't getting any sound.

So, here's what I've done so far. I've checked for bridges/cold joints (may reflow an iffy one or two), checked my in/out and power wiring, checked continuity across the wiring and board with the schematic's help, and confirmed correct parts values.

I have not had a chance to check power and ground on the board with it plugged in, but I anticipate this will be okay due to the continuity checking out. I also have not tried swapping the ICs yet.

I have a TL071 I could try--would that work? Also, what's the best next step after checking power and ground on the board?

Thanks,

Bret

[timbo_93631]

Do you have a pic of the pcb you could post? I have built a number of these now and would be happy to look.

[Bret608]

I haven't taken one yet, but I can do that tonight or tomorrow. Thanks!

[Bret608]

Hey Tim, thanks again for offering to help out on this. I still haven't taken any pictures--I got a chance to poke around a little further on the board, but ran out of time (i.e. kids' bedtime!).

Here's what I found though--there is power on the board, and it does get to the IC. The ground points are all good too. When I crank the volume and gain, I get a little hiss and radio interference. There is a very faint crackle if I hit the guitar strings hard. I changed out the IC and nothing changed.

Looking at the solder joints on top of the board, esp. the pots, some of them are not looking good at all (my home iron has a fat tip, and my hands were a bit shaky due to fear of burning up a component). This is particularly true of lug 2 on the volume pot, which goes straight to the output if I remember correctly. I'll touch them all up today and report back.

Cheers,

Bret

[timbo_93631]

It is always good to double-check your resistor and cap values, seeing you have done that maybe make sure your electrolytics, IC socket etc. are in the right direction.  Other thing would be to make sure the clipping diodes are pointing in opposite directions.  Good luck!

[Bret608]

Thanks man! I checked all those orientations and they're good to go. I reflowed some joints, and also grabbed a few spare caps in case one of the ones on the board are bad. When I populated the board, I tried to be cool and scrounge for parts in the electronics lab where I work, but I have no idea how old their parts are, so the electros I used could be problematic (particularly the 1uf tantalum).

[juansolo]

Well whatever you've done, I've done it too. On both my boards I have exactly the same issue. Good power, good grounds, seemingly solid builds, no output.

Bizarrely, if you swap the out and in, it actually works... Sort of... It shouldn't, but it does. It's a headscratcher!

[jimilee]

This isn't the issue.I'm sure,but when I built my multiplex I was goin nuts then I checked my test rig out,yurns out the issue was with that and not my actual build. Duh moment for me.

[juansolo]

Yup, nailed it, duh moment...  

Had my loop box plugged in arse backwards. I'm a plonker.

[chordball]

 

I was just about to reply and then it notified me of your post. That's good to hear. In my reply I mentioned it was probably going to be one of those things you're embarrassed to admit. Ha!

Good job man.

[Bret608]

Good times, eh? I was just about to chalk this up to my test rig too!

I'm glad Tim encouraged me to look at the resistors again. I got most of the resistors at work, and since their parts bins can be a bit mixed sometimes, I checked all of them with a DMM before I soldered them onto the board. But, there were two resistors I had grabbed at home, and I did not check those with the DMM. I just read the color codes and made a pretty big mistake. For R8, I grabbed 100k instead of 1m! 

Anyway, this thing is rocking hard now. I will always check resistors more closely in the future! I even sacrificed an electro or two thinking I had a bad one on the board.

I've got a 1n270 and a 1n4148 for the diodes at the moment. What other combinations have all of you enjoyed the most?

[timbo_93631]

Good to hear you have it going!  I like OA1160 in this but I have mine built to OD250 specs