mxr blue box Help

[whomeno]

built from this




bypass works nothing when turned on

voltage power 9v power supply

IC 4558
1  5.60
2  4.38 and drops
3  5.73
4  0
5  5.78
6  5.52
7  7.03
8  6.16

IC cd4013
1  7.01
2  5.72
3  5.73
4  5.73
5  5.72
6  5.73
7  5.73
8  5.73
9  5.72
10  5.73
11  6.91
12  5.72
13  5.73
14  7.03

Q1 2n222
E  5.73
B  1.97
C  1.63

Q2  2n222
E  1.19
B  1.62
C  5.73

Q3  2N222
E  Swings from 4.80 to 5.20
B  swings from 4.58 to 5.60
C  swings from 6.42 to 6.60

[Govmnt_Lacky]

Right off the bat I see that your 4558 chip has bad voltages. Why is Pin 7 higher than Pin 8? Pin 8 should be close to 9VDC (if your battery is not drained) and even so, Pin 7 should not be higher than Pin 8.

Also, where is the 0V ground on the 4013? Should be on Pins 4, 6, 7, 8, and 10.

You might want to look for shorts on the Ground rail somewhere. Most likely close to all the ground connections on the 4013. Also, check your voltage protection diode to make sure it isn't backwards or blown.

(BTW.. I cannot see your link so I am basing this off the Tonepad Blue Box project)

[Slowpoke101]

You have missed a number of through the board connections to the main ground link.
Solder these then test your voltages again.

[whomeno]

The links are there. I will go back and see what is going on

[Slowpoke101]

Now having looked at the solder side more closely, the links are there but in the wrong position.
Also I am not sure that you have got the link starting points under IC1 in the correct positions either.


Here's a picture that may help.

[whomeno]

4558
1  2.34
2  2.37
3  1.15
4  0
5  2.53
6  2.13
7  3.25
8  4.62

4013
1   4.59
2  0
3  0
4  0
5  0
6  0
7  0
8  0
9  0
10  0
11  2.30
12  0
13  0
14  4.60


q1
e  0
b  .02
c  .14

q2
e  0
b  .39
c  0

q3
e  0
b  .40
c  2.38

i had gr and power off on under 4558

[whomeno]

I will move all connections and post new v

[whomeno]

4558
1  3.58
2  3.61
3  1.79
4  0
5  3.46
6  3.35
7  3.96
8  7.15

4013
1 4.79
2  3.57
3  7.20
4  0
5  6.94
6  0
7  0
8  0
9  2.70
10  0
11  swings from 3.44 to 6.0
12  swings from 2.00 to 6.0
13  7.01
14  7.16

q1
e  0
b  0
c  .05

q2
e0
b  .25
c  .42 
q3 
e  0
b  .45
c  3.33

[Slowpoke101]

Check the connection between pins 9 and 12 of IC2 (4013). They should be the same voltage.

[whomeno]

9 & 12 are 6.97

[whomeno]

4013
1  4.79
2  3.58
3 6.98
4  0
5  3.58
6  0
7  0
8  0
9  7.10
10  0
11  3.61
12  7.10
13  .09
14  7.13

[Slowpoke101]

I can't see any other problems at the moment so give the effect another test.
Turn the blend pot fully counter clockwise and plays some notes. See if you can hear anything. The turn the blend pot fully clockwise and again play some notes. At one extreme of the pot you should hear the guitar - clean. The other extreme may be silent or just sound weird. The Blue Box sub-octaving effect usually works best with notes played above the 8th fret and terribly with complex waveform shapes such as chords.

[whomeno]

Tried it nothing at all do the voltages look right?

[Slowpoke101]

The voltages around the op-amp look OK. It's harder to tell with the 4013. It is set up as a divide by 2 / divide by 4 divider, so the pin voltages on it are dependant on what logic state the 4013 is currently in.
The voltages on the transistors Q2 and Q3 are also not a constant value but Q1 should be. Q2 and Q3 are powered by a charge pump formed by D1, D2 and the two 47uF capacitors. The charge pump output voltage varies depending upon what you are playing and the input level. Nothing being played = almost no voltage.
Grab your audio probe and see if you have any signal on pin 1 & 7 of the op-amp and the base and collector of Q1.

[whomeno]

it is fixed.. it was a bad switch.. got it on both octives now.
Thanks for the help!!!!

[Slowpoke101]

Works ! Good Job 

If you do a search of the forum you should find some info that Mark Hammer posted on the Blue Box recently (last 6 months or so). He has made some improvements to it that I thought were quite good and worthwhile doing.

Here's the link;

https://www.diystompboxes.com/smfforum/index.php?topic=119645.msg1117163#msg1117163

Hmm....More than 6 months ago...Time certainly does fly when you're wondering what happened.

There are other mods on the forum, just do a search for "blue box" and quite a few postings will show up.