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Author Topic: boss sd-2 effect won't turn off  (Read 6808 times)

nosaj

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boss sd-2 effect won't turn off
« on: July 28, 2015, 08:26:58 PM »
I've got and SD-2 the effect won't turn off.  Effect works as well as all the dials and crunch lead selector just won't turn off when you hit footswitch.  I hooked my meter up to the leads on the circuitboard push button meter moves to right let go goes back left so the switch is good.  Not sure where to go from here.

Nosaj

J M Fahey

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Re: boss sd-2 effect won't turn off
« Reply #1 on: July 29, 2015, 02:08:48 PM »
OK, you already checked the switch.

It's a manually (footally?  ;) ) triggered flip flop, to begin with:
* check that collector voltage at Q1 - Q2 switches high (close to 9V)  /  low (close to ground)
* if so, check that said voltages reach CD4011 legs,

There's a switch involved in the middle , it or its wiring can fail.
* check 4011 itself, voltage on pins 3 - 4 - 10 - 11 should change with footswitch action.
* AN1211 transistor array IC should receive , invert and output those DC signal changes.
* switching FETs (too many to mention, look at the schematic)  must receive varying (0V or +9V) switching signals at their gates.
* even if they receive them, they may not change state (dead :() , in which case they should be replaced.

As you see, they used a way more complex switching chain than actually needed (in my opinion) , but it's a chain after all, and should be followed link by link.

As Enzo says, do not suspect just bad parts, cracked tracks or solder or bad switches/connectors can be just as deadly.
« Last Edit: July 29, 2015, 02:12:24 PM by J M Fahey »

nosaj

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Re: boss sd-2 effect won't turn off
« Reply #2 on: August 01, 2015, 12:51:44 PM »
Ok no voltages at Q2  Will check r19 next. The arrow after r19 does that mean they ran out of room jump to other side of page to the power section? If so the 4.5v onr or the 5 volt one?

Voltages on 4011
pin1 5.14  hit switch 2.5
pin2 5.13                2.5
pin3  0                      0
pin4 4.5                 4.20
pin5 0                    0
pin6 5.09               2.5
pin7 0                   0
pin8 5.06              4.79
pin9 5.06               2.5
pin10 .28               .30
pin11 0                  0
pin12 5.07              4.79
pin13 5.07              4.79
pin14 8.71              8.52


What the heck are chip points?



Thanks for your help,
Jason

Enzo

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Re: boss sd-2 effect won't turn off
« Reply #3 on: August 02, 2015, 03:48:57 AM »
The arrows.
Lower left, the power comes in as 9v.  9v is used in many many places throughout the circuits, and if we drew a line from the 9v input to every place it was used, we'd have a spaghetti mess on the page.  This is a Very common convention.  That arrow pointing up just indicates a 9v connection.  All of them are just connected together.   The 9v is an open triangle pointing up.  Next to it is 1/2V, which is 4.5v here. Note the arrow is different, it is an actual arrow symbol instead of a triangle.  So through the schematic, the triangle is a 9v connection and the up arrows are 4.5v connections.   I don't see 5v anywhere.

Q1,Q2 form a flip flop.  When one is on, the other is off.  SO when the collector of Q1 is at 9v (or close to it), the collector of Q2 will be close to zero.  When the flip flop is toggled, then that reverses, and collector Q2 will be 9v and collector Q1 close to zero.

The footswitch grounds momentarily wire terminal 2, thus grounding R12, and discharging C2.   SO you ought to see about 9v at that point, going to zero volts when the switch is pushed.  You can/should verify that happens at the wire 2 terminal on the board, or for that matter at the terminals of the switch itself.

Please don't say "no voltages" at some points, zero is still a voltage reading.  If you have zero volts on the collector of Q2, look at Q1, is that also zero, or is there 9v there?  If so, does each push of the switch alternate the 9v and zero to the opposite transistor?

before chasing anything, verify the flip flop works or doesn't.  Ultimately look at Q2 and off to the right through R5 is its output.  You should see that going between 9v and zero with each push of the switch.  That ultimately (follow the line up the page) goes up to pin 11 of the ribbon over to the selector switch.  Note that the switch is wired to the selector switch in only some of its positions.  SO the setting of the selector affects if you will get changing readings down on the 4011.

CHip points?  I don't see that in the posts or schematic.

J M Fahey

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Re: boss sd-2 effect won't turn off
« Reply #4 on: August 02, 2015, 05:59:47 AM »
"Chip points" is what Enzo just got , going from 133 to 134   :cheesy:

Since we don't handle money here, not even Bitcoins, and sending a sixpack or a piece of Mom's delicious apple pie is not quite practical, Forum lets you express appreciation for help received by clicking the "useful" label just below each poster's name, call it a good karma action if you wish.
The counter will go up by one point  :dbtu:

FWIW Enzo's counter should be in the couple thousands by now, given the tons of help freely given, but most members don't know (so don't use)  that Forum feature.
So now you know (hint hint)  ;)

Back to the Tech problem, I'm somewhat worried that you are counting 4011 pins the wrong way (literally), as I stated you should see changing voltages on pins 3 - 4 - 10 - 11 , while you show changes on pins 1 - 2 - 6 - 9
Too sleepy now to open and recheck the schematic and chip pinout but do it yourself to save time, you *might*  be reading pin order backwards, because " seen from below pins are counted clockwise but from above counterclockwise  , a very common source of error.
Datasheets often (but not always, specially old ones)  show chip as seen from above, while you have the actual PCB in tour hand, may look at it from "below", the solder side, and so should count pins the other way.

Just sayin', and not sure it's happening, just a warning :)  so recheck that.

And repeating that since it's an unnecesarily complex circuit, check step by step thatb there is switching action, changing voltages with button pushes, step by step.

Start with first transistor pair , check, then next stage, check, and so on, until you get to the FET gates ... which should change voltage following button pushes.

Slow and boring, remember to take notes at every step, simply don't trust your memory, ... but the only way available.

Don't hurry, check a step and post results, then we check and go on.

Ok, a warm bed is waiting ..... aaaaaaajjjjjuuuuuuummmmmmm !!!!!

phatt

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Re: boss sd-2 effect won't turn off
« Reply #5 on: August 02, 2015, 07:50:38 AM »
You gotta watch those chippy points,,, they can be rather deceiving. 8|

Heck I'm the novice here and Enzo would be far more technically savvy yet I have more chip points than Enzo.

Go figure?  :o
Phil.

nosaj

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Re: boss sd-2 effect won't turn off
« Reply #6 on: August 02, 2015, 03:05:52 PM »
Ok. looking at bottom of board left to right

Q1  .03vdc 0vdc 4.41vdc hit switch 5.70vdc 0vdc .02 vdc
Q2  .61vdc 0vdc 4.42vdc hit switch .01vdc 5.42vdc 0vdc

4011 dc jack in North Direction measurements taken from bottom side left to right the slash between measurements will denote switch change. because I am really now confused as to pin numberings I will not number them at this time

Left side going down
9.15/9.02
5.31/5.01
5.31/5.01
0/0
.27/.29
5.30/2.63
5.30/4.99

Right side going down
5.29/2.62
5.30/2.62
0/0
4.67/4.39
0/0
5.27/2.61
0/0


Now Pin 11 on the ribbon cable  4.90vdc hit switch 5.11 vdc
Selector switch all the way to left.

I think the flipflop is working. But where you say Q1 and Q2 should have close to 9v getting about half that. I'm gonna zoom in on schematic and see

Thanks,
nosaj 

D12  8.93vdc
C44 8.90vdc
R61  8.90vdc other side 4.39vdc  this is the voltage divider?
r44 4.34
c45 4.34

So I guess now I need to trace 9v to q1 and q2 to see where it is dropping.  Would low voltage keep footswitch from disabling effect?
« Last Edit: August 02, 2015, 03:37:47 PM by nosaj »

Enzo

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Re: boss sd-2 effect won't turn off
« Reply #7 on: August 02, 2015, 06:33:51 PM »
I just assumed 9v, if the collectors reliably toggle between zero and 4.5v, that sounds OK to me.   The bottom line is this:  does that line coming from the flip flop up and over to the selector switch in the center of the schematic toggle up and down with the switch pushings?

I don't want to hear left and right, just learn for sure how to count IC pins.  Then we don't have to assume which side you are looking at.  On any IC there is either a notch at one end or a round dimple in a corner.  The dimple indicates pin 1, and the notch indicates the pin 1 end of the IC.  Look at the IC with the dimple or notch at the top.  The dimple will be upper left, or the notch top center.  That will mean pin 1 is the upper left corner.  We are looking at it from the top side, not the solder side.  Obviously if you are looking at the underside, pin 1 would be upper right instead.

Pins are always counted down the side from pin 1 and then back up the other side.  So the upper right pin will be the highest number:  8, 14, 16, whatever.

On your 4011, pin 14 should be power, so 9v, and pin 7 is grounded.

nosaj

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Re: boss sd-2 effect won't turn off
« Reply #8 on: August 02, 2015, 09:24:32 PM »
pin1 5.29/2.62
pin2 5.30/2.62
pin 3 0/0
pin4 4.67/4.39
pin5 0/0
pin 6 5.27/2.61
pin 7 0/0
pin 8 5.30/4.99
pin 9 5.30/2.63
pin 10 .27/.29
pin 11 0/0
pin 12 5.31/5.01
pin 13 5.31/5.01
pin 14 9.15/9.02

Enzo quote:  The bottom line is this:  does that line coming from the flip flop up and over to the selector switch in the center of the schematic toggle up and down with the switch pushings?

Yes it does, comes in pin12 of ribbon cable goes through mode and level SW1a and b comes out pins 10 and 11(I checked both sides of ribbon and am getting voltage change with the switch on the main board pins 10 and 11.

Thanks,
nosaj

nosaj

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Re: boss sd-2 effect won't turn off
« Reply #9 on: August 04, 2015, 06:06:34 PM »
Since there is no voltage on Pin3 of the 4011, my next guess is to follow it up to R6 D5 then Q9.  Will do that and post follow up.

Thanks,
Jason

Enzo

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Re: boss sd-2 effect won't turn off
« Reply #10 on: August 04, 2015, 06:23:03 PM »
It is a logic gate wired as an inverter.  If a logic hi sits on pins 1 and 2, then pin 3 will sit at zero.  Since R6 is 1 meg, I doubt anything further along will affect pin 3.  The problem is either at the IC itself of in the circuit driving pins 1,2.

With the selector switch in the center two positions, the toggle line from the foot switch flip flop is connected to pins 1,2 of the 4011.  As I recall you had action on the FS output?  So does the same voltage changes appear at pins 1,2?

nosaj

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Re: boss sd-2 effect won't turn off
« Reply #11 on: August 04, 2015, 08:54:30 PM »
It is a logic gate wired as an inverter.  If a logic hi sits on pins 1 and 2, then pin 3 will sit at zero.  Since R6 is 1 meg, I doubt anything further along will affect pin 3.  The problem is either at the IC itself of in the circuit driving pins 1,2.

With the selector switch in the center two positions, the toggle line from the foot switch flip flop is connected to pins 1,2 of the 4011.  As I recall you had action on the FS output?  So does the same voltage changes appear at pins 1,2?

pin1 and 2 5.04vdc hit switch drops to 2.60vdc


So I should start looking at Q6 since pin 10 has the voltage that looks off to me?  Just a quick question : Would a logic probe be able to be used in verifying the IC good or bad?(Not that I have one)
Thanks,
Jason
« Last Edit: August 04, 2015, 09:47:04 PM by nosaj »

Enzo

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Re: boss sd-2 effect won't turn off
« Reply #12 on: August 05, 2015, 12:14:57 AM »
I don't know that 2.6v is a valid logic low.  Several tests come to mind.  Monitor the output voltage at pin 3.  Zero volts.  Now briefly ground pins 1,2.  Does pin 3 go to a positive few volts?

Or turn the selector switch over to the end position where the two lines down to the 4011 are both not connected to anything.  Now, does that switching line from the flip flop still only go from 2.5 to 5?  Or does it now go closer to zero?

Also at the flip flop, the collectors of Q1 Q2 should look the same.  We know what Q2 is doing, does the collector of Q1 have the same voltage levels?  or does it go closer to zero?

I'd be thinking one of the gates in the 4011 is faulty.

nosaj

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Re: boss sd-2 effect won't turn off
« Reply #13 on: August 05, 2015, 09:18:41 PM »
I don't know that 2.6v is a valid logic low.  Several tests come to mind.  Monitor the output voltage at pin 3.  Zero volts.  Now briefly ground pins 1,2.  Does pin 3 go to a positive few volts?

Answer:
Yes 4.50vdc

QUOTE:Also at the flip flop, the collectors of Q1 Q2 should look the same.  We know what Q2 is doing, does the collector of Q1 have the same voltage levels?  or does it go closer to zero?

Answer:
Just to sure on this transistor it is ECB, if so the collector voltage does not change from 0 at all.  I'm having a hard time figuring out what transistor it is on the schematic  I see 2sc24500r  but not finding anything online about it.



Or turn the selector switch over to the end position where the two lines down to the 4011 are both not connected to anything.  Now, does that switching line from the flip flop still only go from 2.5 to 5?  Or does it now go closer to zero?


Answer:
Closer to Zero




Since IC passed the grounding test this must now point to Q1?  If so what could sub for it?


Thanks,
Jason

nosaj

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Re: boss sd-2 effect won't turn off
« Reply #14 on: August 06, 2015, 08:55:08 PM »
I don't know that 2.6v is a valid logic low.  Several tests come to mind.  Monitor the output voltage at pin 3.  Zero volts.  Now briefly ground pins 1,2.  Does pin 3 go to a positive few volts?

Answer:
Yes 4.50vdc

QUOTE:Also at the flip flop, the collectors of Q1 Q2 should look the same.  We know what Q2 is doing, does the collector of Q1 have the same voltage levels?  or does it go closer to zero?

Answer:
Just to sure on this transistor it is ECB, if so the collector voltage does not change from 0 at all.  I'm having a hard time figuring out what transistor it is on the schematic  I see 2sc24500r  but not finding anything online about it.



Or turn the selector switch over to the end position where the two lines down to the 4011 are both not connected to anything.  Now, does that switching line from the flip flop still only go from 2.5 to 5?  Or does it now go closer to zero?


Answer:
Closer to Zero

 

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