Need help with Boss SD-1

[jn777]

Hi im modding a friends SD-1 with this instructions http://www.geocities.com/overdrivespider/SD1/stepfour.htm  Ive only changed D6, R6, C3 and R30(for led brightness)
Im using DPDT switches to change between stock and mod values in D6, R6, and C3.

When i connected the pedal to test, the distortion and tone pot didnt work, only level pot is working(bypass or engaged). I get the same sound in bypass and effect engaged like if the effect wasnt engaging with the switch, the led works fine with when the switch is pressed..
Here are the voltages on the Ic and transistors.

IC1  4558
1-2.87
2-2.86
3-2.84
4-0
5-2.59
6-2.85
7-2.85
8-14v    ( i was using an unregulated power supply)

Transistors i measured and numbered watching the pins in front(left to right, 1 to 3) and the flat side facing upwards.

Q1       K30A
           Y  4F
1-0
2-0
3-0


Q2     K30A
         Y  4F
1-0.11
2-0
3-0.11

Q3    C2458
   
1-0
2-0.68
3-0.73

Q4    C2458

1-0
2-0.01
3-0.64

Q5    C2240

1-2
2-14
3-1.86

Q6   C2240

1-1.89
2-14
3-1.4

Maybe Q1 is burnt because of the voltages.  Is this part easy to find? which one is a substitute?

Thanks in advance!

[jn777]

Do you think these parts could get easily damaged by desoldering the other parts? with a crappy soldering iron 
Ive found a place to get those transistors, do you recommend changed them all using sockets?

Thanks in advance!

[oskar]

edit! Oops! I hit post before I was done writing. I'll look into this tomorrow.

[oskar]

EDIT! I see now that the reference foltage ( +4.5V )voltage, which in your case should read ~7V, is too low. IC pin 123567 should give you +7V ( or really 4.5        ) I have no explanation for this. The flip/ flop isn't connected to the +4.5V and nor is the LED. The R6, C3 pair is however...

http://www.freeinfosociety.com/electronics/schemview.php?id=169

You modified two functions in there and it sounds a bit to me like you've got two errors. And you're using strange voltages... so make that three.
Running it from 14V may be super cool but since something is not as it should you need to, as a first step put in a normal 9V
battery before you do anything else.
And don't change any components by chance, until we know what's wrong... OK?

1. Bypass or not... The volume pot shouldn't be active in bypass, should it?
2. Gain stage. The first OP-amp ( triangle on the schematic ) is where the distortion happens. There is no reference to a schematic on the homepage you refer to and the one i post don't have reference numbers.
I think R6, C3 from the mod is the equivalent to the 4k7/47n   R/C-couple going from the clipping diods to a +4.5V ref voltage to the left of the gain stage.... ( Drive pot left... 33k resistor... keep going left! ). if there is a broken connection here, the OP- will start working as a buffer letting through a unity gain clean/cleanish tone and perhaps you wouldn't notice the tone pot because there where no highs to filter out?
Try it with a distorted signal at the input to see if the tone pot really is out!

On the drawing, down left is a flip/flop( 2 2sc1685 transistors with R's and C's around them ). It first flips and then it flops. When you push the on/off switch. It's doing both!? ( They should not be both "on" or both "off" at the same time, they turn on and off Q1/Q2. )
Q4 is upset with base at ground level... anyway both 2sk30's are turned on at the same time. That's why the level pot has influence on the clean volume. Since the distortion is fed audiosignal all the time, if the gainstage was working we now would have a mix of clean and distorted signal. So this is how we know there are two errors.

Double check the value of R30... what was it from start and what was it when you were done?
The on/off problem is probably from the LED-brightness mod. And the lack of distortion from an open connecton bad solder joint( likely )...

Plan of action
1. What was the LED brightness mod? Changed the 3k9 resistor from the schematic above?
    Make sure R30 isn't absurdly low...
2. Put in a battery.
3. How is the soldering on/around the R6/C3 net?

Damn I'm good!



Oskar

[jn777]

Thanks a lot for your replys!!    maybe it was some kind of bad soldering around r30 that ive changed to a 330ohm resistor, and R2 that ive change from stock 470k to 1Mohm.
Ive replaced that ones to stock values using sockets to change values laterand it worked  .   Then ive put again the mod values and it worked also, so maybe was a bad solder around those 2 parts.
Here it is a picture of the modded SD-1.


Thanks everyone!

[oskar]

Thanks a lot for your replys!!    maybe it was some kind of bad soldering around r30 that ive changed to a 330ohm resistor

Not soldering, current. You increased the current throught the LED tenfold. That disturbed the switching logic.
I'm glad it worked out well.