Clone Boss SG-1 Slow Gear Sabrotone doesn't work

[Elijah-Baley]

Hi guys. I'm trying an unusal pedal effect: Boss SG-1 Slow Gear, but it gives me just a clean sound at any setting. I got no swell effect.

Layout: http://www.sabrotone.com/?attachment_id=4246
Schematic: http://topopiccione.atspace.com/pjimages/BossSG1Sch.gif
None mods.

My voltages with pot at noon.

T1
C: 9.50v
B: 2.98v
E: 3.00v

T2
D: 5.65v
G: 2.75v
S: 5.65v

T3
C: 9.50v
B: 4.24v
E: 6.78v

T4
C: 6.07v
B: 3.00v
E: 3.30v

T5
C: 5.35v
B: 1.25v -> 0v*
E: 1.25v -> 0v*

T6
C: 5.75v
B: 1.00v -> 0v*
E: 1.00v -> 0v*

IC
1: 0.13v
2: 3.20v
3: 3.85v
4: 0.00v
5: 0.13v
6: .4.73v
7: 7.62v
8: 0.00v

* This voltage start around 1.40v-1.10v and low to 0v.

I really need help this time.

Thanks a lot!

[anotherjim]

That schematic won't show, and Malwarebytes thinks it's host is a nasty place.
On the layout, I think there is a hidden track cut under R5, between T2 & T3.

There is no direct connection between the JFET and any BJT.

[blackieNYC]

The slow gear is a one trick pony, but also a one-setting pony. With both lots at 10-11 o'clock, I get a short fade in. And technique-wise, with a short attack like this, you need to palm mute after each note. 
The gator for ex. has a longer attack and shuts off quicker, both of which seem to require less playing technique. I love my slow gear, but I thought it wasn't working at first.

[Elijah-Baley]

That schematic won't show, and Malwarebytes thinks it's host is a nasty place.
On the layout, I think there is a hidden track cut under R5, between T2 & T3.

There is no direct connection between the JFET and any BJT.

Sorry for the bad link!

I made all the cuts, even the hidden ones.

The slow gear is a one trick pony, but also a one-setting pony. With both lots at 10-11 o'clock, I get a short fade in. And technique-wise, with a short attack like this, you need to palm mute after each note. 
The gator for ex. has a longer attack and shuts off quicker, both of which seem to require less playing technique. I love my slow gear, but I thought it wasn't working at first.

Strange. My Slow gear really seems not to do anything, even the trimmer. Zero effect!

[PRR]

> That schematic won't show

topopiccione.atspace.com is known to have an anti-linking script; you can't display their images in a link from another site (probably to conserve network bandwidth). Copy the URL and paste into a new tab, it usually works.

Or just link to the project page, not direct to the image.  http://topopiccione.atspace.com/PJ03BossSG1.html

I can't find any evidence that topopiccione.atspace.com has malware. It is however hosted on a shared server, many websites (42!) on one IP. It is possible one of the other sites has malware, and your anti-mal app over-reacts.

EDIT-- atspace.com is a "free website" host. Looks like a fair deal and a square outfit. While they say no bandwidth cap, it is possible the free plan does not allow external linking to limit runaway network costs (i.e. not Alessandro's decision).

[Slowpoke101]

Are you using a 2SK30A as T2? If you are make sure that it is installed with the correct orientation. Your voltage measurements show that the gate of T2 is about 2.7V which is correct for the effect to be in an un-muted or semi-muted state. But I suspect that your meter's input impedance is about 1M which would pull this voltage down since the FET's gate is connected via a 1M resistor. Not to worry.

The voltages on T4 and T5 collectors are correct for the FET to mute the audio, but there is no muting action. To make sure that the side chain is doing something set sensitivity to 12 O'clock and attack to minimum (fully counter clockwise). Also adjust TR1 to mid-range. Measure the voltage on T5 or T4 collector (this can be measured on the attack pot's centre pin) and pluck a string on the guitar. The voltage should drop from about 5 volts and vary to as low as 2 volts (TR1 sets the how low this voltage can go). As the plucked note decays this voltage should rise back up to the voltage initially indicated.

If you are using a different FET you will have to make a few changes.

Have a look at the 'Critical parts substitutions' section of http://topopiccione.atspace.com/PJ03BossSG1.html

I have a Slow Gear replica that I built from the info on General Guitar Gadgets and it works well. I did use a 2SK30A and had no real problems getting the effect to work. Adjusting TR1 is not hard to do with good test gear, but you can adjust it fairly well just by ear.

[Elijah-Baley]

Here's the layout:


T2 is a 2SK30A, (K30A is printed on it). The orientation is like the layout image and the notes. The BC549s (T1, T2, T3 ,T6) have the round side looking to te right, only T5 is reversed.

Sensitivity was linear 100k. A mistake. I replaced it with a log 100k. Of course the circuit still doesn't work properly.

[...]
To make sure that the side chain is doing something set sensitivity to 12 O'clock and attack to minimum (fully counter clockwise). Also adjust TR1 to mid-range. Measure the voltage on T5 or T4 collector (this can be measured on the attack pot's centre pin) and pluck a string on the guitar. The voltage should drop from about 5 volts and vary to as low as 2 volts (TR1 sets the how low this voltage can go). As the plucked note decays this voltage should rise back up to the voltage initially indicated.
[...]

I made the test and it works exactly how you said. But I can't hear any effect.

I a 2N5457 as T2. The pinout is different, but I twisted the legs. Nothing's changed.
There must be something wrong, but where? 

[Slowpoke101]

The layout appears to be correct (it has been verified by others) so no worries there.
The orientation of the transistors are also correct.
Make certain that the cut under C7 is correct and does not have any bits of copper hanging on. Make sure that R8 and R10 are 1M. Also make sure that R6 is 470K and that R7 is 47K.
The voltage that you noted on T2's gate may be valid and not due to loading effect of your voltmeter. If it is actually around 2.75V then the audio signal can pass with no muting effect. The gate voltage must rise above 4V (at least) for muting to occur. So something is causing T2 not to turn on.
Any chance you can take some close-up pictures of both the component and solder sides of the board and upload them? This would help a lot.

[jimilee]

There are mods floating around to make the effect more prominent, I don't k ow what they are though.


Sent from my iPhone using Tapatalk

[Elijah-Baley]

The layout appears to be correct (it has been verified by others) so no worries there.
The orientation of the transistors are also correct.
Make certain that the cut under C7 is correct and does not have any bits of copper hanging on. Make sure that R8 and R10 are 1M. Also make sure that R6 is 470K and that R7 is 47K.
[...]

Cuts and resistors are ok.
Soon the pics.

[Elijah-Baley]

Some info:
C6 Cap is on the socket for some experiment.
The board has one more empty row. It doesn't count.
Some components could have the legs bended for problem of spacing, but the position should be right. If someone has some doubts just ask.

I had just used 10uF cap suspected of damage, so C18 cap is on socket, already replaced with another one with no changing. I have still some doubt about C11 and C16.
Until now nobody named those caps. Could be there the problem?

Here's pics, I did my best.







Thanks for helping!