Swedish Chainsaw too tame - Grind Customs Helvete (Boss HM-2)

[the_crowing]

Hey guys,

I'm a bit out of my depth here and would appreciate any advice from people with more experience. I've got a Boss HM-2 inspired circuit built on a Grind Customs Helvete using his build doc. The only substitution were 2x 20K's in parallel when I ran out of 10k's. The thing works, meaning it's got some of the character, but compared to my original MIJ HM-2, it doesn't provide nearly the same amount of EQ boost and grind that makes the HM-2 so unique. It's a tame "Swedish Chainsaw", which is kind of an oxymoron.

Here's a link to the build doc:
https://www.dropbox.com/sh/200s6g8gdclno0a/AADbezf-LsBKdZmkjSRrODina?dl=0&preview=HelveteBuildDoc.pdf

And here are my voltages:

Q1 - 2N5457
D:9.41
S:5.83
G:4.28

Q2 - 2N5089
C: 3.88
B: 0.6
E: 0

Q3 - 2N5087
C: 4.5
B: 7.89
E: 8.52

IC1 - 4558
1: 4.47
2: 4.5
3: 4.5
4: 0
5: 4.7
6: 4.73
7: 4.73
8: 9.41

IC2 - TL074
1: 4.72
2: 4.72
3: 4.68
4: 9.4
5: 4.67
6: 4.72
7: 4.72
8: 4.72
9: 4.72
10: 4.67
11: 0
12: 4.73
13: 4.73
14: 4.73

D1 - 1N4148
A: 4.23
K: 4.5

D2 - 1N4148
A: 4.46
K: 4.24

D3 - 1N4148
A: 4.5
K: 4.46

D4 & D5 - 1N34A
A: 0
K: 0

D6 & D7 - 1N4148
A: 0
K: 0

D8 - 1N4001
A: 0
K: 9.4


Now, I don't understand much of what's going on, but I'm assuming there's something weird going on with Q2? And what about D4-D7 all being at 0V?

Thanks guys!

[PRR]

Welcome.

> something weird going on with Q2? And what about D4-D7 all being at 0V?

Q2 is just about where it should be. Collector anywhere near half of 9V, emitter essentially at zero, base 0.6V higher.

The diodes are sitting idle waiting for some signal they can clamp. No signal, no voltage on them.

Working, but "tame", suggests the connections are right but some part is wrong. A popular error is a 220 Ohm where should be a 22 Ohm, or something similar. Done it many times myself.

[the_crowing]

Thanks for your reply!

Glad to hear Q2's fine, but now I don't know where to look for the culprit... I had already checked for wrong values visually, but could have missed something once more.

[willienillie]

Where did you source your (active) components?  There are a lot of fake ICs and JFETs out there these days.  Some don't work at all, some work but don't sound quite right.

Posting pics often helps.

[ElectricDruid]

Sounds like it might be time to get an audio probe on it, and find out where things start to go wrong. If you test the output of each stage in turn, you should be able to hear if the sound is "tame" or not. As soon as you find a stage where the previous one was ok, but the output of this one sounds a bit off, you're narrowing down the search area for the problem.

HTH

[the_crowing]

Where did you source your (active) components?  There are a lot of fake ICs and JFETs out there these days.  Some don't work at all, some work but don't sound quite right.

Posting pics often helps.

2N5457 and 4558 were from Small Bear, 2N5087 and 2N5089 were from Tayda and TL074 could be from either, I can't recall.

I'll try to post pics.

[the_crowing]

Alright, so here are the better photos I managed to take. Bad lighting and one-handed due to shoulder surgery... Here we go:

[the_crowing]

Where did you source your (active) components?  There are a lot of fake ICs and JFETs out there these days.  Some don't work at all, some work but don't sound quite right.

Posting pics often helps.

Swapping the TL074 did it! It grinds and grunts beautifully now!

Thanks for your help!

[willienillie]

Good to hear!  The one in your pics looks real to me, maybe it was just defective instead of fake.

[the_crowing]

Good to hear!  The one in your pics looks real to me, maybe it was just defective instead of fake.

Yeah, sure looked real to me!  Then again, it did work, just out of spec.