Dirtbag MN3005 - No Delay

[eldanko]

Howdy friends -

I'm finishing up my second Dirtbag, and I'm not getting any delay whatsoever.  The "Level" control is functional (with clean signal), but from what I can tell with my probe, my signal is not making it to the MN3005s.  I know that my chips are good (tried them in my other Dirtbag, which works), and visually everything on the board checks out against my functional build.  The only difference I can see is that I used TL072CPs here and TL072CNs on the other.

Where should I be looking for a signal drop?  I've tried tracing via the instructions and I keep getting lost/frustrated.  Any help would be appreciated.  Thanks!

[Scruffie]

You should start with... Voltages!

[eldanko]

Can do!  Which chip?

[Scruffie]

Can do!  Which chip?

All of them would be the best way to go about it, I know it's a hassle but it helps to gauge the area alot of the time.

[gtr2]

Dane,

Here is my working voltages from another post...

The input voltage is 14.75V.  I omitted IC7 since thats the modulation section.

Josh

IC1
1) 7.14
2) 7.14
3) 7.12
4) 0
5) 7.07
6) 7.14
7) 7.14
8 ) 14.74

IC2
1) 1.18
2) 1.78
3) 1.78
4) 0
5) 1.78
6) 1.78
7) 10.12
8 ) 1.78
9) 1.78
10) 7.73
11) 6.02
12) 1.78
13) 14.74
14) 1.78
15) 1.78
16) 0

IC3
1) 7.14
2) 7.14
3) 7.12
4) 0
5) 7.12
6) 7.14
7) 7.14
8 ) 14.74

IC4
1) 14.7
2) 7.29
3) 6.28
4) 6.27
5) 0
6) 7.29
7) 7.82
8 ) 0

IC5
1) 14.7
2) 7.29
3) 7.33
4) 7.33
5) 0
6) 7.29
7) 8.94
8 ) 0

IC6
1) 8.95
2) 8.83
3) 8.8
4) 0
5) 6.96
6) 6.98
7) 6.83
8 ) 14.74

IC8
1) 7.14
2) 7.14
3) 7.12
4) 0
5) 7.66
6) 7.73
7) 7.73
8 ) 14.74

[eldanko]

Alright, here we go.  I included all ICs for the sake of being thorough.  Input voltage is 14.7.

IC1
1) 8.6
2) 8.6
3) 8.6
4) 0
5) 8.5
6) 8.6
7) 8.6
14.7

IC2
1) 1.0
2) 3.2
3) 3.2
4) 0
5) 2.6
6) 2.6
7) 13.9
3.3
9) 3.1
10) 13.9
11) 10.9
12) 3.1
13) 14.7
14) 3.1
15) 3.1
16) 0

IC3
1) 8.6
2) 8.6
3) 8.6
4) 0
5) 8.6
6) 8.6
7) 8.6
14.7

IC4
1) 14.7
2) 7.2
3) 7.0
4) 7.0
5) 0
6) 7.2
7) 8.2
0

IC5
1) 14.6
2) 7.2
3) 7.1
4) 7.1
5) 0
6) 7.2
7) 8.2
0

IC6
1) 8.2
2) 8.2
3) 8.2
4) 0
5) 9.4
6) 9.4
7) 10.3
14.7

IC7
1) Varies
2) 7.5
3) Varies
4) 0
5) 7.5
6) 7.5
7) Varies
14.7

IC8
1) 8.6
2) 8.6
3) 8.6
4) 0
5) 13.7
6) 13.9
7) 13.9
14.7

IC9
1) 7.9
2) 6.7
3) 6.8
4) 14.7
5) 14.7
6) 14.7
7) 0
0
9) 0
10) 7.2
11) 7.2
12) 0
13) 7.9
14) 14.7

There you have 'em.  The only thing my untrained eyes noticed was that I had much higher voltages on lugs 5-7 of IC8 than you did, Josh.  So... you guys see anything?

[eldanko]

Side note: now I see why you had a space in your "8 )" in each list...

[Scruffie]

Side note: now I see why you had a space in your "8 )" in each list...

So... those readings aren't just cool? 

IC8 is looking bad on the output post NE570, voltages are far too high for pins 5,6 & 7

NE570 voltages are a bit odd too... look around there for wrong values, solder bridges etc.

[eldanko]

After re-checking all of my resistors and solder joints, I decided to try swapping in the NE570 from my other Dirtbag... it worked.  Looks like I got a bad NE570 chip.  Got it biased up now, and it sounds killer with the exception of some nice lo-fi clock noise at the longest delay setting.  That's normal, yes?  Either way, I'm happy - it's giving me longer times than my other Dirtbag.

Thanks for the help in narrowing that down fellas.

[djaaz]

I did have to troubleshoot my dirtbag and fought with a bad ne570 as well.

Do you mind sharing where you ordered it from?

[eldanko]

It was an NOS Philips from SmallBear.  The other one I got from there was good, as was the spare that I swapped in after discovering the failure. 

Mods: If sharing that isn't cool, feel free to edit/whatever.  No ill will towards SBE... 

[gtr2]

Glad you got it solved!

Josh