Hi all, i have a BOSS SD-2, and this is the problem i have, id like some help to solve this if possible please.
ok here goes.
1st) the pedal will not activate bypass mode when it is pressed, so it will not give a clean signal...i have replaced the switch and nothing is different.
2nd) the check light is green/red all the time no matter what position i have the mode witch in, and again the switch is fine, replaced it with a known working switch.
any ideas are welcome
thanks in advance
luke ???
Maybe this can help:
http://www.geofex.com/Article_Folders/bosstech.pdf
thanks ill take a look then post my results ;D
hi i have looked at the link its helped me understand a little better but still not sure on what i need to test and what i should be getting?
link to schematic (http://www.aronnelson.com/gallery/main.php/v/KHE/Boss_SD2_schematic.jpg.html?g2_imageViewsIndex=1)
This pedal is a bit more complicated than the average Boss pedal:
- it has the normal footswitch
- it also has a remote switching possibility
- and it has a mode switch.
The mode switch leads the footswitch and remote switch levels to a switching IC (TC4011 (http://www.datasheetcatalog.org/datasheets/208/495230_DS.pdf)).
This switching IC then controls the FETs at the input and output of the effect circuit. The IC also controls the LEDs.
So what you could do is to try and modify the inputs of the switching IC (the footswitch, the remote switch and the mode) and see if changing any of these switches makes any difference.
If it doesn't make any difference, you may want to start investigating if that IC is still working ok. (does it have power, does it see voltage changes on its inputs, does it act upon these voltage changes?).
hi thanks for your help so far as you may have guessed im not much good with electronics....im a mechanic so have a very basic understanding, what would i need to modify the inputs of the switching IC or to test to see if its working?
thanks
A few things to try:
- try the footswitch: does it change the LEDs or the sound?
- try the mode switch: does it change the LEDs or the sound?
- do you have a remote switch? Does it change the LEDs or the sound?
If the answer to these three questions is NO, then probably something is wrong with the IC.
If the pedal is younger than 2 years it may have warranty on it, maybe your shop can help.
Otherwise if you don't feel comfortable measuring/soldering the pcb of your pedal, you can bring it to a tech or ask in the Lounge whether there's a forum member in your area that's willing to have a look at it (probably for a small compensation).
hi the answer to all of your questions is no.
i found a scheme of the IC and tested against the pins...here were my findings?
pins
1+2=0v
1+3=4.98v
2+3=4.98v
4+5=4.39v
4+6= -0.59v
5+6= -4.98v
8+9= 0.01v
8+10=4.72v
9+10=4.71v
11+12=4.98v
11+13=4.98v
12+13=0v
do these findings mean anything to you?
thankyou
Measurements on the IC should be made relative to ground.
In other words: your black ground probe should remain on pin 7 (Vss= ground of the IC).
Did you measure this way?
I would expect pin 14 to be at power supply level (Vcc = power supply for the IC). (about 9 Volts?)
- are you using a battery? Does it still supply about 9 Volts?
no thats not how i done it. told you i was no good lol
..but heres the results of your proper way
battery used...V of battert is 8.51v
terminals 7 & 14 the way you sugested....supplies 8.50V ???
you guys on here are a gr8 help ;D
8.5 volts is close enough to 9V.
So your supply voltage is good.
http://www.bossarea.com/loadpage.asp?file=boxes/sd-2.xml
So if I understand the mode switch correctly:
1. LEAD mode: pedal footswitch toggles between LEAD on and bypass.
2. LEAD/CRUNCH mode: the pedal footswitch toggles between LEAD and crunch.
3. CRUNCH mode: the pedal footswitch toggles between bypass and effect. Extra remote footswitch toggles the effect between CRUNCH and LEAD
Can you test 1. 2. and 3 and post your results?
Since everything doesn't work, it's pretty safe to say the Gate IC is bad. It isn't surface mount, is it?
hi thanks for your speedy replies ;D
i have tested as you asked, and the answer to all of your questions again is 1-2+3= no they do not do as you asked...they all do nothing. each mode produce the same tone and pressing the pedal does absolutely nothing. ???
thanks luke
oh and when you say surface mounted, i have no idea...but if you wish to view the circuit board i have uploaded 3 pics at this address just click on them to enlarge them,
and dont worry the link is not anything bad...just my bands website.
http://paradoxmuisc1.webs.com/apps/photos/album?albumid=11138727
thanks ;D
Can you read schematic? Can you locate the componments from the PCB?
In the right bottom corner of the schematic, that part is called flip-flop, you can also see the foot switch there.
If you connect youur meter like that: black lead to gnd, red lead to one side of the R10( the side that connect to the rotary switch).
When you push the foot switch, it should be from 0 V to around 4.x V, or from 4.x V to around 0 V , and again... -----if the flip-flop part works
This is the HIGH or LOW signal to controll the bypass/channels.
If it is not working like that, try disconnect the wire that is connectted to the rotary switch, and try to measure again.
Post what you found, other people will help you.
hi located r10...here are my findings:
with wire attatched to ratary switch v were.....
at brown end of r10 gave 8.38V no change when momentary switch was pressed.
at red end of r10 gave 7.35 V no change when switch pressed
AND with wire to momentary switch disconnected, the results were the same.
thanks luke ???
Sorry that if I can not descripe this cleary.
The foot switch need to be always there, the rotary switch means: the channels setting switch. One side of R10 has
lead or trace connect to another PCB that has the rotary switch.
I made some mistakes when I write the above post. The side(connect to thr rotary switch) of R10,
should be 8.x V or 0 V, when you push the foot switch. ( not 4.x V or 0 V)
(Push switch once, 0 V, push again 8.x V, push again, 0 V, push again 8.x V........)
You should get that when it works normally.
Or you need to disconnect the side(connect to thr rotary switch) of R10, make it connect to nothing,
( dis-solder the solder joint,and take that side of the R10 out of the PCB)
and put you red lead there. If you still can not get 8.x V or 0 V, when you push the foot switch. That means
the flip-flop part is not working.
If the flip-flop part is not working, check all the traces and solder joints of the flip-flop part, and try to replace parts,
try the 2 transistors first, then caps, then.... Good luck.
sorry my mistake not yours, i removed the wire for the mode switch as you described, but i replyied saying i had removed the foot switch one...sorry...yes my results were that it was about 8v, but when the pedal was pressed it stayed the same voltage, and it also done the same when the wire was disconnected.
thanks
According to the schematic posted by geertjacobs and the pictures you have shown, the TC4011 is a standard DIP (dual inline package - not surface mount) quad NAND gate similar to the RCA CD4011 or the Motorola 14011 of which various versions are available from a lot of suppliers. The SD-2 has the usual transistor flip-flop and the NAND gates are used to select which channels are enabled. The first thing to determine is whether the flip-flop section consisting of the pair of 2SC2459GR transistors, the associated four capacitors and six resistors and the switch debounce circuit consisting of R2, C2 and R12 are actually capable of changing the state of the flip-flop each time the effect on/off switch is pushed. This can be determined by checking the voltage at pin 12 of the board. If this is toggling i.e. changing state each time the button is pushed, then that part of the circuit is OK. If not, fix it. (How's that for helpful advice?) Then check that the mode switch and level switch connections are good and the signal on pin 12 gets transferred to pins 10 and 11 when the switches are connected.
If this is OK, then the logic surrounding the TC4011 is the next thing to check. For a NAND gate, if both inputs are high, the output is low and any other input combination results in a high output. Two of the gates are connected as inverters with the inputs connected together, so the output is the opposite of the input. The output from pins 4 and 10 go to the transistors and at this point, the schematic must deviate from reality because it shows the PNP emitters connected to high voltage and the NPN emitters connected to ground, so your voltage supply is loaded down to two base-emitter diode drops. Check what happens there - there may be some resistance in the bases of these transistors which would make everything work.
(voltage of battery is 8.8v)
hi AMPTRAMP that last quote has confused me a little with the indepth technical terms used...how ever, i checked at pin 7(ground) and pin 12 when pressing the foot switch and nothing changes in the voltage, it just stays at 5v
Then the mode i checked the voltage at 12 to see if it transfered to 10 & 11 when the mode switch was switched between modes...my findings were as follows...
#switch position at right side, crunch mode pin, 12 had 5v, pin 11 had 0v and pin 10 had 0.25v
#switch position at middle, lead (remote) mode, pin 12 had 0v, pin 11 had 4.20v and pin 10 had 4.20v
#switch position at left side, crunch/lead mode, pin 12 had 5.00v, pin 11 had 0v and pin 10 had 0.25v
??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ;D
Make sure there is no misunderstanding. Push the foot switch each time (push and release),
the side(connect to thr rotary switch) of R10, should be 8.x V or 0 V.
Let me quote the words from amptramp , these are the same as what I mean, in a different way.
"The SD-2 has the usual transistor flip-flop and the NAND gates are used to select which channels are enabled. The first thing to determine is whether the flip-flop section consisting of the pair of 2SC2459GR transistors, the associated four capacitors and six resistors and the switch debounce circuit consisting of R2, C2 and R12 are actually capable of changing the state of the flip-flop each time the effect on/off switch is pushed. This can be determined by checking the voltage at pin 12 of the board. If this is toggling i.e. changing state each time the button is pushed, then that part of the circuit is OK. If not, fix it. (How's that for helpful advice?) "
" changing the state of the flip-flop each time the effect on/off switch is pushed. " = Push the foot switch each time (push and release), the side(connect to thr rotary switch) of R10, should be 8.x V or 0 V.
If your measurement is right, it is obvious, the flip-flop part is not working. Change the 2 trainsistors.....
"If the flip-flop part is not working, check all the traces and solder joints of the flip-flop part, and try to replace parts,
try the 2 transistors first, then caps, then.... Good luck."
hi yes my answer is right from what i got, with no miss understanding i pressed and released the switch as it would if i stood on it to select bypass mode etc, you say to change the 2 transistors, but can you tell me which numbers i need to change as i dont wanna do the wrong ones ???, i have checked all solder joints and none of them are dry.
thanks you guys are real helpful ;D
According to the schematic, the transistors are Q1 and Q2. On the third picture on your own site, you can see Q2 at the lower left of the picture and Q1 is probably under the jumble of wiring to its left. If you move up one row of components from where Q2 is, you can see a row of components that include C7 just below the white shielded wire. Two components to the left of C7 is another transistor. Although I cannot see the designator in the picture, this is probably Q1. On photo 1 of the series on your site, this appears to be the upper left. The soldering looks OK from here, so I assume there is a component failure. Incidentally, Boss redesigned the circuit to take both transistor emitters through a single diode to ground in some of their other pedals - maybe the switching was not reliable enough at high temperatures or something like that.
Incidentally, the problem may not necessarily be transistors - that is just the most likely item. If C2 was shorted, you would also never switch, so make sure what has failed before you do anything. If you try a wholesale replacement of the parts in that circuit, you may burn the board or lift traces.
so what would be your suggestions then replacing q1-q2 and see how it is?...where would i get them from and what would i ask for?
are they a specific thing i know nothing about transistors etc so wouldnt know what to get lol :icon_mrgreen:
i have found some on ebay...with the same numbers on ....heres the link these ar the right ones yes?
http://shop.ebay.co.uk/i.html?_nkw=c2458&_sacat=0&_odkw=transistors&_osacat=0&_trksid=p3286.c0.m270.l1313
cheers luke
In your second picture, left top, you can see Q1,Q2.
Troubleshooting a flip-flop circuit might be extremely easy, also might be extremely hard.
In some cases, even the bad componment is replaced with a good one, the flip-flop might not work.
Google " flip flop" you will find a lot links like:
http://en.wikipedia.org/wiki/Flip-flop_(electronics)
http://talkingelectronics.com/FreeProjects/5-Projects/Page16.html
...
Then you should learn how to test a tranisitor, capacitor, and resistor....
If you want to save the hassles, ask a friend in electronic field to do it.
Quote from: wordstep on March 09, 2011, 09:18:01 PM
In your second picture, left top, you can see Q1,Q2.
How did I miss that? Absolutely correct. It might be easier to check with a DC scope - you would be able to see voltages move when the button is pushed. The problem with DMM measurements is that the pushbutton is capacitively coupled into the flip-flop, so the voltage at the base that does the switching only appears briefly.
ok well thanks for your guys help, i think i will read up about doing it but may put it to a specialist to test, keep checking to see my progress and ill post how i get on in a few days or something...you guys have been great. cheers.
luke