# repair question Boss CS-3



## pipelinepete (Jul 17, 2015)

I bought a bunch of pedals off a guy on Kijiji. They all work except the Compression Sustainer CS-3. He insisted they all worked fine last time he used them (and me, being the naïve trusting type, didn't insist on testing them prior to purchase). The pedal makes a continuous tick-tick sound when plugged in; spinning the dials does nothing. Doesn't matter if used straight into front of amp or in the loop. I'm using a new 9V battery and the red light energizes when turned on. I sprayed electrical cleaner into the jacks but no change. Any ideas? Thanks. Peter.


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## mhammer (Nov 30, 2007)

Ticking is generally a capacitor issue of some kind. The fact that it lights up is a good sign. The fact that it ticks and nothing else is not.

Does it at least pass clean signal in bypass mode?


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## pipelinepete (Jul 17, 2015)

mhammer said:


> Ticking is generally a capacitor issue of some kind. The fact that it lights up is a good sign. The fact that it ticks and nothing else is not.
> 
> Does it at least pass clean signal in bypass mode?


The tock-tock-tock sound is there continuously, whether the pedal is energized or off. Pics below. The previous owner says he never ran it off battery, always used an adapter, and he swears it worked fine. The fact that the Check light turns on when energized (to me) should indicate sufficient power,


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## cboutilier (Jan 12, 2016)

I'd say try it with an adaptor asap. If it works fine, that will greatly narrow down the location of the issue


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## mhammer (Nov 30, 2007)

Thanks for the pics. Doesn't look like anything has let out the magic blue smoke. But you still haven't answered my question: when you put it in bypass mode (LED off), do you hear clean signal, or is there nothing in either engage or bypass?


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## pipelinepete (Jul 17, 2015)

mhammer said:


> Thanks for the pics. Doesn't look like anything has let out the magic blue smoke. But you still haven't answered my question: when you put it in bypass mode (LED off), do you hear clean signal, or is there nothing in either engage or bypass?


With LED off, the pock-pock sound continues. This sound occurs whether LED is on or off.
BTW - I don't have a power adapter so cannot test that side of things....batteries only.


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## mhammer (Nov 30, 2007)

Yes, I understand the pock-pock, but is there ANY sound from the guitar coming through, or is ALL you can hear the pock-pock?


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## pipelinepete (Jul 17, 2015)

mhammer said:


> Yes, I understand the pock-pock, but is there ANY sound from the guitar coming through, or is ALL you can hear the pock-pock?


No sound from guitar - doesn't matter if pedal is on or off - just the ticking sound.


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## mhammer (Nov 30, 2007)

Now we're getting somewhere. Have you tried it with an adaptor?


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## pipelinepete (Jul 17, 2015)

mhammer said:


> Now we're getting somewhere. Have you tried it with an adaptor?


I don't have an adapter. If the red LED energizes with a new battery, doesn't that indicate power's getting through? I traced the internal wiring from the battery connection and adapter jack, and everything looks normal (no broken or loose fittings that I can see). I suppose I could next check for continuity....


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## mhammer (Nov 30, 2007)

Since it appears you have a meter, can you check the V+ pins on the various chips and confirm that power is reaching them as well as theLED.

This schematic shows a number of points where you can do that.


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## pipelinepete (Jul 17, 2015)

I got an adapter and tried it on the pedal....no change. It does not work.
Also checked several voltages, and all seems in order.
I think the fact that the pedal doesn't bypass is an important clue....the guitar signal doesn't get through, whether the pedal is energized or not.
Not sure what this means, but will keep searching. thx


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## mhammer (Nov 30, 2007)

One of the things to try is to "bridge" the switching FETs.

In the case of the CS-3, going from engage to bypass means turning Q4 "off" and Q5 "on". And going from bypass to engage means the reverse (Q5 off, Q4 on). Running a short piece of wire from one side of either of those transistors to the other side, should mimic what happens in either of those modes. I mention this because it CAN happen that, for some reason, either one or both of the FETs fry (and I still don't understand how it happens, but it does). In your case, you don't get either bypass or engage, which is low in probability of occurrence, but since it can be tested for easily, without having to remove or replace anything (just connect the appropriate pads on the copper side of the board), it's worth doing.

I will also note that IC1 is common to both the bypass AND the compressed signal paths. If IC1 were fried, that would still let the LED behave properly, but nothing would pass I either engage or bypass mode. You can test for its functionality by plugging your guitar in and measuring the AC voltage at pin 1. It should probably be in the range of 30-100mv, depending on your guitar. If you get nothing there, no matter how hard you strum, the chip is gone.

Many different chips are suitable replacements for a blown 5218, but it is in SIP (single in-line) form. This is easy enough to get, but generally has to be ordered in.


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## pipelinepete (Jul 17, 2015)

Thanks mhammer for taking time to help me with this. I realize I could just replace the pedal but I like troubleshooting electrical circuits and this has me intrigued.
Today I completely disassembled the unit, looking for signs of trouble....and I may have found something. In the pics below, I see two concerns:
1. The capacitor cluster between R1 and R3 is covered with yellow gunk. Is this normal?
2. Component "D1" (I assume a diode) appears cracked. See closeup.
Suggestions? thx. Peter


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## greco (Jul 15, 2007)

Poor old D1 certainly doesn't look healthy at all!
I'm betting the "goop" is normal/typical.
Bump to the top for for those of us interested in electronics.


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## mhammer (Nov 30, 2007)

Thanks again for the pic. Dave's right that the goop is normal. Normally that would be reserved for components that need to share the same temperature, but that would NOT likely be larger-value caps. Idon't know how it got there, but it isn't a sign of anything amiss. I'll bet you that if you google around for other gut shots, other CS-3s will have it too.

D1 is clearly one of the culprits. And I say *one* of the culprits with some discouragement. D1 is a protection diode that guards against inserting a power supply that is the opposite polarity from what is required; i.e., it it outside-ground/inside V+. If that diode were cracked accidentally by dropping something on it, or simply removed, the circuit/pedal should still function normally, but you'd want to be careful about only plugging in the right kind of supply, or simply using only a battery.

If, on the other hand, the diode blew up because of something that was plugged in, then there is also the possibility that, in the absence of "protection", some chips were destroyed. And unfortunately, what makes the CS-3 so good is also hard to get; specifically the THAT 2159 chip.

D1 is a very standard garden variety 1N4001 (or at least can be replaced with one). So score one of those first, and replace D1 before doing anything else. I'm not hopeful, but as shots in the dark go, at least it is cheap.


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## pipelinepete (Jul 17, 2015)

I will try to obtain and an 1N4001 diode.


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## pipelinepete (Jul 17, 2015)

I understand diodes can only be mounted in one direction. How will I know I am mounting it the right way?


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## mhammer (Nov 30, 2007)

1) Good on you for being cautious, and for at least being aware that orientation of the diode is important.

2) Look at your picture and you'll see that there is a silver/white stripe at one end. The new diode should be installed so that the stripe faces in the same diretion as that (i.e., towards the edge of the circuit board).


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## pipelinepete (Jul 17, 2015)

I installed a new 1N4001 diode. Upon reassembly the pedal check light comes on, but there's still no guitar signal getting through....there's no sound from guitar, whether pedal is on or off. The repetitive "tick tick" is gone. I'm next going to review post #13 to see if any of those tests reveal anything useful.


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## greco (Jul 15, 2007)

Congrats on being so determined and thanks for keeping us updated with your progress/findings and pics.


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## pipelinepete (Jul 17, 2015)

mhammer said:


> I will also note that IC1 is common to both the bypass AND the compressed signal paths. If IC1 were fried, that would still let the LED behave properly, but nothing would pass I either engage or bypass mode. You can test for its functionality by plugging your guitar in and measuring the AC voltage at pin 1. It should probably be in the range of 30-100mv, depending on your guitar. If you get nothing there, no matter how hard you strum, the chip is gone. Many different chips are suitable replacements for a blown 5218, but it is in SIP (single in-line) form. This is easy enough to get, but generally has to be ordered in.


I get various voltages at the pins of IC1 whether pedal is on or off....ranges from 8.3 to 9.4V. Strumming doesn't change readings. I have no idea what this means.


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## mhammer (Nov 30, 2007)

The key one will be pin 1. If you're not showing an AC voltage (and remember to set your meter for AC and not DC) that looks like a guitar signal should, chances are good the chip is fried. Be sure, though, that you are measuring on the right pins.


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## greco (Jul 15, 2007)

Non technical advice........take frequent breaks and keep well hydrated.


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## epis (Feb 25, 2012)

I would suggest to check out all solder points, especially at IC1, judging by the image where you're replacing D1, they don't look healthy.
Use magnifier glass, there shouldn't be any gap between IC's leg and solder point.


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## pipelinepete (Jul 17, 2015)

mhammer said:


> The key one will be pin 1. If you're not showing an AC voltage (and remember to set your meter for AC and not DC) that looks like a guitar signal should, chances are good the chip is fried. Be sure, though, that you are measuring on the right pins.


Ah yes, should've used AC. I'm assuming pin 1 is at one of the corners of IC1. With MM on AC and guitar plugged in, I see 18.5V to 20V on the four corners (I don't know which one is pin 1, they all have voltage though). No change in voltage when strumming guitar. No changes when pedal on or off.
Regarding the solder points, would it be recommended to touch each point with the tip of the solder pencil to reflow the solder?


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## greco (Jul 15, 2007)

*Please wait for mhammer, epis or others to confirm*, but I think pin #1 is nearest D2 & D3 ...it has a large white, circular orientation pad marking and there is a number "8" at the other end of the chip. 

Following this thread with interest and to learn.


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## mhammer (Nov 30, 2007)

Whenever a chip bamboozles you, searching for <chip number>+"pdf" (like this: http://www.bing.com/search?q=M5218L+pdf&src=IE-SearchBox&FORM=IENTTR&conversationid=&adlt=strict) leads you to a datasheet, which will always contain a pinout and physical diagram of the chip showing you where everything is.


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## pipelinepete (Jul 17, 2015)

greco said:


> Non technical advice........take frequent breaks and keep well hydrated.


Thanks for the reminder greco......my preferred re-hydrator these days is Corona Extra!


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## epis (Feb 25, 2012)

End pins (1 and 8) are marked on the board, also pin 1 is marked with big white dot.
To reflow solder point, add solder wire to the iron tip ( you want to create the drop of solder for better transfer of heat), heat up the point and add solder wire to the molten solder point (this way you will add more fresh rosin from the wire core which will help to create nice and strong joint) .


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## pipelinepete (Jul 17, 2015)

mhammer said:


> Whenever a chip bamboozles you, searching for <chip number>+"pdf" (like this: http://www.bing.com/search?q=M5218L+pdf&src=IE-SearchBox&FORM=IENTTR&conversationid=&adlt=strict) leads you to a datasheet, which will always contain a pinout and physical diagram of the chip showing you where everything is.


I got a drawing and located pin 1. With guitar plugged into pedal, I see 18.1 VAC at pin 1. Strumming guitar does not change the reading, neither does energizing or de-energizing the pedal. Note: My MM does not have AC milli-volt capability, only DC (its range is up to 750 VAC).


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## mhammer (Nov 30, 2007)

Well, you certainly shouldn't see 18 volts at that pin. Particularly with a 9 volt power supply! I'm guessing that you're reading the gauge wrong.

But, I'm sad to say that it is looking more and more like the pedal is a write-off. It's a pity we live so far apart, otherwise I would say bring it over and I'd have a look at it.


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## ed2000 (Feb 16, 2007)

1N4001 should be an easy replacement. I may have one to give/send if you're not able to source one in your area.
Perhaps a defective or wrong type of PS adapter was plugged in.

18VAC?? Using an (correct)adapter or battery for this test? Even though adapters look the same, polarity, voltage, ac or dc output and current capacity all differ.

I made a mistake of using the wrong adapter on a pedal and blew a diode...(and a 50 amp fuse!)


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## pipelinepete (Jul 17, 2015)

mhammer said:


> Well, you certainly shouldn't see 18 volts at that pin. Particularly with a 9 volt power supply! I'm guessing that you're reading the gauge wrong.
> 
> But, I'm sad to say that it is looking more and more like the pedal is a write-off. It's a pity we live so far apart, otherwise I would say bring it over and I'd have a look at it.


Here's a pic of my meter and the setting I'm using. When I connect this to the pedal at pin 1, the meter reads 18.1.
I'm beginning to lose hope that I can fix this thing....


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## pipelinepete (Jul 17, 2015)

ed2000 said:


> 1N4001 should be an easy replacement. I may have one to give/send if you're not able to source one in your area.
> Perhaps a defective or wrong type of PS adapter was plugged in.
> 
> 18VAC?? Using an (correct)adapter or battery for this test? Even though adapters look the same, polarity, voltage, ac or dc output and current capacity all differ.
> ...


Hi ed2000: Thanks for the offer, but I did replace 1N4001. See post #20.


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## mhammer (Nov 30, 2007)

pipelinepete said:


> Here's a pic of my meter and the setting I'm using. When I connect this to the pedal at pin 1, the meter reads 18.1.
> I'm beginning to lose hope that I can fix this thing....


I suspect that your meter does both AC and DC measurement at those settings between 9:00 and 12:00, and the 200/750 settings are for high voltage. Use 200m (200mv) or 2000m (2v) for measuring audio signal and the 20 settings for measuring things like supply voltage.


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## pipelinepete (Jul 17, 2015)

Using the 200m setting I get infinity on pin 1; using 2000m I see 8.62V. Strumming guitar does not change the reading.


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## pipelinepete (Jul 17, 2015)

pipelinepete said:


> Using the 200m setting I get infinity on pin 1; using 2000m I see 8.62V. Strumming guitar does not change the reading.


Meant to say 8.62/2000 = 4mV (I think).


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## mhammer (Nov 30, 2007)

Using the 2000mv range, 8.62 implies 8.62mv; no division required. The ranges simply tell you where the decimal place on the screen is going to sit. The display is such that the character to the far left can other be 0 or 1. Only the other characters to the right of it can go from 0-9.

So, in the 200mv range, you can measure up to 199.9mv. In the 2000mv range, you can measure up to 1999mv (=1.999V). And so on.


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## epis (Feb 25, 2012)

I just wanted to share (with guys who don't know) a few details how protection diode work in this circuit and why is not good enough.
Diode is supposed to work together with the fuse in power supply.
If power supply polarity is reversed, diode would conduct so all the available current from PS will flow through diode toward ground.
That means, if PS is strong enough, and current exceed max diode current and fuse doesn't break,diode will fail.
There is two way how to fail, fail short or open. If diode fails short (most likely), it will prevent reversed voltages at ICs and other semiconductors.
But, if it fail open, or if somebody keep power supply connected for long time ( so diode fails short and after a while breaks completely - open), PS will supply reversed voltage to electronic components and damage them permanently.
My personal opinion, Boss was supposed to add the fuse to pedal circuit, maybe it wasn't in their interest, pedals are cheap enough, just buy a new one instead fixing broken one.
So most likely, this happened with OP's pedal.
In my effect builds, I choose other way for reversed polarity protection, in series Schottky diode (low voltage drop 0.1 to 0.2V) so 9V supply isn't affected significantly.


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