Seamoon Funk Machine troubleshooting

[akm]

I'm doing a second attempt at one of these and first test is very fuzzy; any hints from hearing this?

Sample audio: https://soundcloud.app.goo.gl/yfMgqqVjFK8kLbe36

[akm]

Photos, and using 2N3904 and 1458.

Going off this info: http://effectslayouts.blogspot.com/2015/11/seamoon-funk-machine.html?m=1 and only difference I know of is the 1M pot is log.

[iainpunk]

have you continuity checked all traces? some look a bit shoddy,
what are the voltages on the IC's and trannies?
do you have the schematic which the layout is based on?
cheers, Iain

[PRR]

> do you have the schematic

Sometimes it is worth reading the Comments on the effectslayouts.blogspot.com site.

Google is your friend...
http://bit.ly/1X1bAL8

Which just pulls a lot of images including this likely-looking one:
http://files.effectsdatabase.com/docs/schematics/seamoon_funkmachine.gif

Also:
DEBUGGING - What to do when it doesn't work

[PRR]

> only difference I know of is the 1M pot is log.

I do not see two '741 opamp chips. We like to say "opamps are all alike" but in this plan, it may make a difference, because "normal" is slammed to the rail which is not normal for opamps.

[Mark Hammer]

The Funk Machine is largely equivalent to the EHX Dr. Q, with one mode instead of two.  While Jack Orman's clever mods to the Dr. Q in the form of the Dr. Quack and its cousin NUrse Quacky, without those mods, a standard DR. Q and Funk Machine, need either a pair of 741 op-amps or an LM1458 dual op-amp to sweep properly.  I've tried out a variety of dual op-amps on the stock Dr. Q, and the only one that yielded usable sweep was the 1458.

[iainpunk]

he uses a LM2904 (basically a LM358), which is not that different to a 741, its dual, quite a bit faster and can work on lower voltages.


yes, google is a freind, but is this particular schematic that google spits out used to design the layout?

have you replaced that 2M2 with 2K2 like the comments say? it/they are the upright pair, one is 180 ohm, i can't read the other but i guess its somewhere near 2k, try to replace the pair with a 2M2.

cheers, Iain

[akm]

Thanks for all the replies!

After reflowing the traces I am getting some almost autowah sound out: https://soundcloud.app.goo.gl/m7THWAXxY9gyo1Aq9

I also did see the 2.2M comments in the meantime too, going to swap that out.

[Mark Hammer]

There is an error in the drawing you are working from.  That "2K2" resistor needs to be at least 2M2, and possibly even higher, like 2M7 or 3M3.  The 50k sensitivity pot allows for "taming" the sweep, but does not allow for getting MORE sweep when the input signal is modest.

Note that:

a) You will be hard-pressed to find a 5M pot.  A 1M pot will be much easier to find, and still provide a reasonable range of adjustment.  If you feel a need to achieve different filter ranges, use a toggle to add a second set of .005 (4700pf) caps in parallel with the existing pair to lower the filter range by an octave.

b) As that feedback resistance is increased, the output and emphasis will increase, but the center frequency of the filter will lower.

c) Increasing that feedback resistance needs a volume pot on the output, rather than leaving that .0047uf cap "hanging".  Use a 100k log pot.  That termination of the free end of the cap will also reduce switch-popping.

d) You are welcome to use a 1k and 12k resistor in series, since 13k resistors may be near impossible to find.  Use of a 12k resistor won't really interfere with the functioning, though.

[akm]

Mark thanks for your reply too.

I put another 2M in series there and it seems to be working now: https://soundcloud.app.goo.gl/VUxJdV6gEQs4XUSq6

Will look at your other suggestions as well, thanks for all the help!

[Rob Strand]

d) You are welcome to use a 1k and 12k resistor in series, since 13k resistors may be near impossible to find.  Use of a 12k resistor won't really interfere with the functioning, though.

There was a thread on FSB about this pedal.    The 13k was in fact 33k.
Whether that's the right value is another matter but it does make some sense.
The 33k gives more opportunity for the rectifier opamp to work in a linear range.


There's what looks like 33k behind the 10k and 100R in the mid ground.
You can also see 47k and 2M2.



More pics here,
https://www.diystompboxes.com/smfforum/index.php?topic=66002.0

[Rob Strand]

I've got a very strong feeling the output cap should be 47n.    You can see two 50n's in the pic.

Also the schematic has 2x5n  so why would you have an almost identical but different value 4.7n!
   

These schems capture all,

[Mark Hammer]

Nurse Quacky has a 100nf cap on the output.  The Dr. Q and Dr. Quack both use 50nf (47nf).  So clearly use of a 4n7 cap on the early Sea Moon drawing is an error.

Good eye, Rob! 

[Rob Strand]

Nurse Quacky has a 100nf cap on the output.  The Dr. Q and Dr. Quack both use 50nf (47nf).  So clearly use of a 4n7 cap on the early Sea Moon drawing is an error.

I can see the motivation in building a Seamoon - the prices now are just ridiculous.   The truth is they are pretty rough around the edges.   The DIY designs smooth off some of those rough edges.


EDIT:  Another observation,  Nurse Quacky was specifically hard wired to the Doctor Q (or Dr Quack) Bass mode.   However the Seamoon is in fact hard-wired to the Doctor Q (or Dr Quack) Normal mode.

[Mark Hammer]

TWO good eyes! 

In the original Dr. Q (I own one), I find the Bass mode settles back down faster and more comfortably than the Normal mode, which has a tendency to linger up high longer than I want.  In the late '70s, I persuaded our band's keyboard player to buy a few effect pedals, so he bought a Dr. Q and a Small Stone, for $29Cdn each...brand new.  The Normal mode was next to useless on the piano because of the very quality I described.

[Rob Strand]

In the original Dr. Q (I own one), I find the Bass mode settles back down faster and more comfortably than the Normal mode, which has a tendency to linger up high longer than I want.  In the late '70s, I persuaded our band's keyboard player to buy a few effect pedals, so he bought a Dr. Q and a Small Stone, for $29Cdn each...brand new.  The Normal mode was next to useless on the piano because of the very quality I described.

The Normal mode is a bit over the top and has a garbled character.   The Normal mode is a band-pass filter presumably motivated by a wha pedal.   It doesn't really emulate a wah pedal since the Q gets larger (more narrow) as the frequency sweeps up.   The Bass mode is a low-pass, so it has the MXR character.   I guess that's why it tends to be more appealing to most people.   I use these things mainly for bass and I'm not a fan of the Seamoon band-pass sound (... and yes I know, a lot of bass players like the Seamoon).

[akm]

Rob thanks for that tip on the output cap; I'll swap that out too.