Blue box issues

[jimbob]

I have built 6 effects in the last week and only one wont work. The blue box. I used 2n5089's since i didnt have any of the reqired 2n3904's. No matter what I do/change I cant get it going. Im getting power to all the right places..and still.. I hate making a thread about simple issues that i have control over.

I was just wondering if there are any problems that others have had with the values or parts or schematics...Im using the layout from the Tonepad site. Since the search is down I cant use that as a reference.

[octafish]

I had no problems with tonepad's bluebox, l'm sorry to say. I had a few teething problems because I drank a six pack over the course of the build but the schematic should work. I'm assuming you checked the pinout, ground connections, and for cold solders. It might be time to check for stuffed pots and broken wires.

P.S. I seem to remember changing the value of the blend pot, but that was just a personal preference not because it wasn't working.

[KORGULL]

No problems here with the Tonepad layout either - built one on PCB and one on perf.
Are you getting any sound at all?
Did you actually use 56K resistors where specified, or did you sub different values? That could be a problem since there are so many 56Ks - alot of little changes in values could add up and the circuit might not operate correctly.

I tried several different transistor types and they all worked - some better than others though. I like the higher gain ones better than 2N3904. MPSA18 sounded best to me, 3904 were the worst.

[jimbob]

I actually used a lot of 47k instead of 56k. I didnt think that would make much differece..but who knows.

[KORGULL]

I was remembering what MartyMart said in this thread: http://www.diystompboxes.com/sboxforum/viewtopic.php?p=241054&highlight=#241054 about how he used 47K resistors and then switched to 56K and the sound improved.

But I guess your pedal is completely non-functional at this point.(?)

[jmusser]

Man, I wouldn't think you could be that far off on those values, and end up with it working correctly. That's 9K off, times every resistor and it's tolerance. I would think it would cause misbiasing big time, but I'd be guessing on that. For some reason, that whole area around the mixing pot uses all 56Ks, and I'd guess there would be circuit balance issues with lower values. I used a NJM4558D, and a CD4013BCN. I had two bare ground busses on the bottom of my board, that every ground got tied to, and then came off with a ground wire to the pots and jacks. I only ran one ground wire to the buss from the 4016, and all the rest of them were daisy chained together. I also used the 2N3904 transistors throughout. Mine seems to have pretty good volume, because I can only stand to have my amp on 3 with the volume all the way up. The output is not splatty (misbiased) sounding at all. It just hunts around for the octave note on several places on the neck, and sort of warbles back and forth between the fundamental squarewave, and the down octave. I have some MPSA18s, so I may go ahead and sub them out to see if there is a significant difference in the performance.

[jimbob]

For my grounds i just made a hole throuout different places around the outside of the board and then ran them to whatever needed a ground-I really didnt have 1 particular place they all grounded to.

[jmusser]

However you did the grounds is fine, as long as they're all together. I was just giving you a play by play of my building style. I'm really hoping Mark takes a look at this and renders a verdict on whether you could get by with 47Ks or not. If you have proper voltages, that's about the only thing I could think of, except for your jacks or bypass switch being wired wrong.