Boss CE-2 doesn't work with a PSU - I'm baffled

[DC9V]

I have a weird problem with my old Boss CE-2. It works fine with a battery, but it won't turn on if powered with a wallwart.
The pedal is an original Boss -- not a clone. It has never been modified.

I've drawn a small schematic of the part of the circuit where I think the problem comes from:

(The circles denote solder pads on the PCB and are numbered the same way.)
The diode is a small, unmarked glass case model. I did some research and if I remember correctly it's a Japanese equivalent of a 1N4148.

So with a battery connected the usual way (i.e. between points 3 and 9) and a cable plugged in the input, the pedal works fine. But when a wallwart or a battery with a 2.1mm adapter is plugged into the power jack, nothing happens.
I've checked continuity on the wires and all seems in order. I thought the DC jack might be oxidized (the pedal is 27 years old!), but it conducts fine.
I've tried to connect a battery in different ways and it boils down to this: the CE-2 doesn't work when the negative pole of the battery is connected to point 4.
So the problem must come from the resistor or the diode, right? But I've checked both with a DMM and they seem to behave correctly. I've also checked continuity with a small LED circuit and it works as it should (i.e. the diode conducts only one way). So in effect there is continuity from 3 to 4, but it still won't work when the battery is connected between 4 and 9. I'm baffled.

If you have any idea of what's going on, please tell me before I lose what's left of my sanity.

[anchovie]

I bet the underside of your pedal tells you to use a Boss ACA adaptor - which was 12 volts unregulated. If you use a 9V wall wart, the diode and resistor between points 3 & 4 drop the voltage too low for the pedal to work. Put a jumper between those two pads and all should be fine.

[zombiwoof]

Here's the info on the ACA adaptor:

http://www.bossarea.com/other/aca.asp

If you daisy chain the pedal with other 9v pedals, it will work.  The other option is to remove the two voltage-reduction components (a diode and a resistor), then it will work with a regulated 9 volt supply.

I have also found that my old ACA-powered pedals seem to work with the adaptors that come wtih BBE effects.  It seems that those adaptors are also unregulated 9 volt adaptors, which put out around 13 volts.  I believe you can also use a regulated 12 volt adaptor for the ACA-powered Boss pedals.

Al

[trjones1]

If it's not the power supply you are using, you might want to check for broken traces on the pcb.  I had a similar problem with an old Ibanez pedal.  Battery worked fine, but it wouldn't work with the power supply unless I put pressure on it in a specific way.  After close inspection it turned out to be a broken trace which was easily fixed with a jumper over the damaged area.

[jkokura]

I thought about this recently too. I have a traded CE-3 in the mail, wanna mod it to sound as good for a fraction of the price of a CE-2. The guy I'm getting it from said it doesn't work with a powersupply. I suspected he never tried 12V unregulated power...

Jacob

[zombiwoof]

I thought about this recently too. I have a traded CE-3 in the mail, wanna mod it to sound as good for a fraction of the price of a CE-2. The guy I'm getting it from said it doesn't work with a powersupply. I suspected he never tried 12V unregulated power...

Jacob

The ACA adaptor was actually an unregulated 9 volt adaptor (it said "9 volts" on it), which put out around 12-13 volts without a load on it.  If you try a 12 volt adaptor, make sure it's a regulated one.

Al

[jkokura]

I was thinking of throwing the switches on my SupaCharger which outputs 12V I think. I thought that was the point of those switches, to be able to power ACA pedals? Same as the PP2+

jacob

[ejbasses]

I bet the underside of your pedal tells you to use a Boss ACA adaptor - which was 12 volts unregulated. If you use a 9V wall wart, the diode and resistor between points 3 & 4 drop the voltage too low for the pedal to work. Put a jumper between those two pads and all should be fine.

What he said.

Worked on one a few weeks ago. It had the same issues. I just installed jumpers inplace of the diode and resistor.

[Processaurus]

You should keep the diode, for reverse polarity protection, but jumper/short out the two legs of the resistor, that's where the couple volts of drop is coming from.  The diode only only drops .7v, and is a good idea to leave in.

I did that with a CS-3 and it did the trick.

[DC9V]

Thanks for your answers.

If it's not the power supply you are using, you might want to check for broken traces on the pcb.  I had a similar problem with an old Ibanez pedal.  Battery worked fine, but it wouldn't work with the power supply unless I put pressure on it in a specific way.  After close inspection it turned out to be a broken trace which was easily fixed with a jumper over the damaged area.

I'm certain it's not a broken trace. I've checked and re-checked continuity, and even inspected the PCB with a powerful magnifier. Everything seems OK so I guess it's down to PSU voltage. I've never tried more than strictly 9V, I've first used a regulated wallwart and then I made all tests with a 9V battery. I'll try 12V tonight. I wouldn't worry about using more than 12V, though, since the other diode is a RD11EB Zener used for voltage regulation and its Zener voltage is about 11V.

You should keep the diode, for reverse polarity protection, but jumper/short out the two legs of the resistor, that's where the couple volts of drop is coming from.  The diode only only drops .7v, and is a good idea to leave in.

I did that with a CS-3 and it did the trick.

I was thinking of shorting the diode/resistor pair, but I'm not very familiar with Zeners and I don't know if the one in this circuit is providing polarity protection as well as voltage regulation. So you're right, it makes more sense keeping the diode. I will probably replace it with a power diode (1N4001) since there will not be a limiting resistor anymore, or perhaps a Schottky. So much for all-Japanese early-1980s components mojo, though.  

P.S. I've found this useful webpage about the original CE-2.

[zombiwoof]

Thanks for your answers.

If it's not the power supply you are using, you might want to check for broken traces on the pcb.  I had a similar problem with an old Ibanez pedal.  Battery worked fine, but it wouldn't work with the power supply unless I put pressure on it in a specific way.  After close inspection it turned out to be a broken trace which was easily fixed with a jumper over the damaged area.

I'm certain it's not a broken trace. I've checked and re-checked continuity, and even inspected the PCB with a powerful magnifier. Everything seems OK so I guess it's down to PSU voltage. I've never tried more than strictly 9V, I've first used a regulated wallwart and then I made all tests with a 9V battery. I'll try 12V tonight. I wouldn't worry about using more than 12V, though, since the other diode is a RD11EB Zener used for voltage regulation and its Zener voltage is about 11V.

You should keep the diode, for reverse polarity protection, but jumper/short out the two legs of the resistor, that's where the couple volts of drop is coming from.  The diode only only drops .7v, and is a good idea to leave in.

I did that with a CS-3 and it did the trick.

I was thinking of shorting the diode/resistor pair, but I'm not very familiar with Zeners and I don't know if the one in this circuit is providing polarity protection as well as voltage regulation. So you're right, it makes more sense keeping the diode. I will probably replace it with a power diode (1N4001) since there will not be a limiting resistor anymore, or perhaps a Schottky. So much for all-Japanese early-1980s components mojo, though.  

P.S. I've found this useful webpage about the original CE-2.

Well, the "experts" on the Bossarea Forum say to remove both the diode and resistor, and replace them with jumpers.  I think there might be another diode for reverse polarity protection (but I'm not sure about it).  And remember the pedal will work as is, if daisy-chained with other pedals using a regular 9 volt power supply, so if you daisy-chain your pedals try that.  Or if you are using a power supply with dedicated outs that has a 12 volt option, that should also work with the pedal as is.  I would go with the known fix, though, if you are going to remove components, and that means both the resistor and diode but you can experiment if you want to.

There's no "mojo" involved, they just used a different type of power supply on the early Boss pedals, as in those days there was no standard for that stuff (note that most US-made pedals used a 1/8" power supply plug/jack while the Japanese pedals used the barrel plug/jack).  Later on, companies decided to go with the Boss scheme, which has become the standard now.  Similarly, most pedals now have standardized to using regulated 9 volt power supplies.

Al

[Processaurus]

Well, the "experts" on the Bossarea Forum say to remove both the diode and resistor, and replace them with jumpers.  I think there might be another diode for reverse polarity protection (but I'm not sure about it). 

We build pedals, they just buy 'em.  There's a good article at Geofex on series and shunt diode power polarity protection, if you're interested.  The gist is if you get rid if the series diode (short it), and the pedal gets the wrong polarity power, and it is connected for more than an instant, it will sit there and cook the shunt zener diode (or a shunt 1N4001 power diode in the case of my old CS-3) until it fails and if it burns out in a way where it opens, then the reverse polarity power gets to go on to the rest of the pedal, probably destroying all of the IC's in a few seconds.  With the series diode we were originally talking about in place in the circuit, no current can flow into the pedal if the wrong PSU is connected.  The "experts" probably are at least expert enough to use the correct adapter, and never loaned it out to someone less versed, so they've never had a problem.  If their pedals got the wrong polarity power for a little while, they'd fry.

Boss PSA adapters are 9.6v, so that the .7v voltage drop of a series Si diode can be subtracted and have close to 9.0v getting through to the pedal's power rails.

[zombiwoof]

Well, the "experts" on the Bossarea Forum say to remove both the diode and resistor, and replace them with jumpers.  I think there might be another diode for reverse polarity protection (but I'm not sure about it). 

We build pedals, they just buy 'em.  There's a good article at Geofex on series and shunt diode power polarity protection, if you're interested.  The gist is if you get rid if the series diode (short it), and the pedal gets the wrong polarity power, and it is connected for more than an instant, it will sit there and cook the shunt zener diode (or a shunt 1N4001 power diode in the case of my old CS-3) until it fails and if it burns out in a way where it opens, then the reverse polarity power gets to go on to the rest of the pedal, probably destroying all of the IC's in a few seconds.  With the series diode we were originally talking about in place in the circuit, no current can flow into the pedal if the wrong PSU is connected.  The "experts" probably are at least expert enough to use the correct adapter, and never loaned it out to someone less versed, so they've never had a problem.  If their pedals got the wrong polarity power for a little while, they'd fry.

Boss PSA adapters are 9.6v, so that the .7v voltage drop of a series Si diode can be subtracted and have close to 9.0v getting through to the pedal's power rails.

There are knowledgeable people on the Boss Forum and there are noobs.  You are suggesting that all of them don't know anything about pedals and you're wrong.  I was referring to the people there that are knowledgeable about building and modding pedals, not the people who just "buy" them.   However, I don't know if the diode that is part of the voltage reduction on those pedals is the reverse polarity diode or something else, so if you say it IS the reverse polarity protection diode then obviously it should be left there.  I was just passing on the info that the common mod for those ACA-powered pedals is to remove both of the components (or to leave them alone and power the pedal in a daisy chain with other 9 volt pedals).

Here's the in-depth story about the ACA/PSA thing:

http://www.stinkfoot.se/andreas/diy/articles/bossadapt.htm

Al

[DC9V]

I tried shorting the resistor only and it works perfectly -- I tested it with a not-so-fresh 9V battery connected to the power jack, so even with a voltage a little under 9V keeping the diode works. I will replace it with a 1N5817 Schottky, though -- just to be on the safe side.

There's no "mojo" involved

You're wrong! I opened the pedal, and there it was:

[sevenisthenumber]

Can someone show me the parts on this pic to jumper? Im confused...

[jkokura]

I'm guessing the diode you need to look at will be the lowere diode (black with grey stripe) in the bottom of the pic.

The easiest way to find it is probably to trace the power supply to the board. start at the jack, then go to the board. See if that diode is connected to the power supply first by using your DMM to check for continuity. If that's the diode I wouldn't be supprised.

I'm not sure of what parts to jumper either, but I can tell you that's the power protection diode by my best guess. Double check it and try reading that stuff above.

Jacob

[Processaurus]

No, that is probably the shunt diode, and if that were to be shorted out it would short out the power supply.  The series diode that's been discussed is the smaller silicon diode up from there, by the yellow wire (Boss used smaller diodes for the series protection because analog pedals draw under the 100mA those 1n914 type diodes are rated for).  There should be a low value resistor connected to one end of it, that is the resistor to short out.  The other end of that resistor should go to circuit and chassis ground. The other end of that smaller diode should be connected to the tip connection on the DC jack, which it looks like it might be, through the blue wire.

[simondolanbass]

Worked for me. I removed the resistor between pads 3 and 4 and kept the diode in place. In the schematic the resistor is marked as 100ohm but it is a 390 ohm. Thanks to everybody!  Simon