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mk-ultra
Copper Member
USA
4 Posts |
 Posted - 07/17/2008 : 01:12:09
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Hi All. I recently bought a broken DS-1 off ebay for $9. It shows all the signs of having been modded. However, the switch did not work at all. I took it out, examined the board, and it sure enough it has an LED on D4 (mod).
I accidentally tapped some resistor on the board and it switched it on. I kept tapping various component until I noticed that the only part of the board where it would emulate the switch to a 'T' would be shorting R36 on and off. Short once to turn on, short again to turn on. All other caps/resistor on that same circuitry required only a tap (no shorting) to either turn on or off. Caps C16 through C18 exhibit single tap on/off behaviour, and so did R26/R27.
I don't think a bypass mod has been attempted on this pedal. I do think that perhaps it was driven by 9v+ psu? and it could've perhaps burned something on the switching circuitry?
Need guidance on this as I'm more of a hack than an electronic technician.
Thanks!
Mk |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 07/17/2008 : 01:30:37
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Hi mk-ultra! Welcome to the forum!
Sounds like the switch might be toast. Can you check it with a meter? |
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mk-ultra
Copper Member
USA
4 Posts |
Posted - 07/17/2008 : 01:36:31
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quote:
Originally posted by Laurie
Hi mk-ultra! Welcome to the forum!
Sounds like the switch might be toast. Can you check it with a meter?
Thanks!
I disconnected the switch altogether. Theoretically, shouldn't I be able to emulate the switch by just shorting the wires on/off? (which isn't doing anything either) |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 07/17/2008 : 02:47:16
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Ah ha. So it's not the switch 
Obviously something to do with the flip-flop. What is curious is that shorting R36 (the input to the flip-flop) makes the flip-flop change state, so the flip-flop is basically OK. That's why i thought the switch might be toast.
Soooo... if you short "terminal 16" on the board to ground does it change state?
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mk-ultra
Copper Member
USA
4 Posts |
Posted - 07/17/2008 : 04:01:08
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quote:
Originally posted by Laurie
Soooo... if you short "terminal 16" on the board to ground does it change state?
16 is connected straight to the + pole on the battery.
I found a schematic for it, and what I think is terminal 16 on it, it's 13 on my pcb.
When I connect the wire on 13 (black) to 18 (green wire going to the LED), the distortion kicks in and the LED turns on. When I connect the same wire to ground, it changes its state to off. However connecting the same wire to ground again does not turn it on.
If it's of any help, the pcb board has the serial # ASS'7056263401
and there's an exact pic of it here.
http://i76.photobucket.com/albums/j23/overdrivespider/step2_01.jpg
Thanks! |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 07/17/2008 : 07:03:00
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Ah! My schematic is for the older version.
Here is a dumb question ... is the battery in the pedal known good? Low voltage can upset the flip-flop.
The purple wire should be the wire going to the switch? Trace that back to the circuit board and it should go straight into a 100 ohm resistor. What happens if you short the other side of that resistor to ground briefly a couple of times?
Any chance of some hi-res close-up photos of both sides of the board around the flip-flop components?
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 07/17/2008 : 09:27:18
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Hi mk-ultra
Welcome to the forum from Australia.
Looks like you are in good hands with Laurie, already looking after you.
Like he says Pics would be helpful.
And don't forget to look for bad solder joints, if it looks like it's been modded, & cracked PCB tracks.
Is your DS-1 MIJ or MIT?
Regards Dr. Bob |
Edited by - Dr. Bob on 07/17/2008 09:27:57 |
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mk-ultra
Copper Member
USA
4 Posts |
Posted - 07/17/2008 : 10:19:58
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Nevermind peoples!
It was the switch after all.
Ironically enough, I pulled the switch off another broken pedal I bought off the same seller also at $9. (a broken CS-3 which looks like he tried to mod as well)
However, I hope the mods don't mind if I keep this post alive since I'm pretty sure the pedal (since it has been clearly modded) it's got something else wonky with it. Otherwise the seller wouldn't have sold it for that cheap. ($9)
The other pedal has a completely burned out diode. D1. Is it salvageable? (or even worth to do so) |
Edited by - mk-ultra on 07/17/2008 10:50:35 |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 07/17/2008 : 14:23:19
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quote:
Originally posted by mk-ultra
Nevermind peoples!
It was the switch after all.
Ironically enough, I pulled the switch off another broken pedal I bought off the same seller also at $9. (a broken CS-3 which looks like he tried to mod as well)
However, I hope the mods don't mind if I keep this post alive since I'm pretty sure the pedal (since it has been clearly modded) it's got something else wonky with it. Otherwise the seller wouldn't have sold it for that cheap. ($9)
The other pedal has a completely burned out diode. D1. Is it salvageable? (or even worth to do so)
Hi mk-ultra
D1 -- is the reverse protection diode.
If I remember correctly it's one of the 1N400x series of 1 amp rectifier diodes.
Check it with a Meter & see if it's shorted, Shorted is better than open circuit.
If it cent short, it really protected the rest of the circuit.
If it went open circuit, then it might have allowed the reversed voltage to get into other parts of the circuit.
Op-amps HATE Rev. Voltages.
But you might have been lucky.
You can remove it & then run the pedal on a battery,
Just don't put the battery on backwards accidentally, even for a second.
And check the polarity of your power adapter.
If it works without the diode, then just replace it, when you get a new one.
The Cs-3 Schematic, is available on the web.
This has been covered Many Many times.
We might have to put it into the Tech FAQ.
Note: Some Boss pedals use a 11V 1W zener, instead of the 1N400x diodes.
Good Luck ---- mk-ultra
Regards Dr. Bob
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Edited by - Dr. Bob on 07/17/2008 14:25:16 |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 07/17/2008 : 15:17:30
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quote:
Originally posted by mk-ultra
Nevermind peoples!
It was the switch after all.
Ironically enough, I pulled the switch off another broken pedal I bought off the same seller also at $9. (a broken CS-3 which looks like he tried to mod as well)
However, I hope the mods don't mind if I keep this post alive since I'm pretty sure the pedal (since it has been clearly modded) it's got something else wonky with it. Otherwise the seller wouldn't have sold it for that cheap. ($9)
The other pedal has a completely burned out diode. D1. Is it salvageable? (or even worth to do so)
Good to hear it was something simple... it usually is unless you are dead unlucky
Post some hi-res photos of the circuit boards (top and bottom) and we can let you know what (if anything) has been done to them. I have some super hi-res pics of my DS-1 pedals and my CS-3 in my archives from when I modded them (too big to post) that i can compare your pedals to.
Dr. Bob is right on the money with the diode. Hopefully you will be OK. I've had a couple of burned out diodes in pedals from Cash Convertors and the pedals have turned out to be OK.
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Topic |
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DS-1 Faulty Switching Circuitry
