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Thread: BOSS RC-2 Fried from wrong PSU

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    BOSS RC-2 Fried from wrong PSU

    I have been given a rc-2 which has had the wrong psu plugged in and no longer turns on, i'm hoping that it's just a fried regulator rather than the dsp or other major components.

    i've opened it up and can't see any burnt out components, so if someone has experience repairing this sort of thing, a schematic and where to buy component's your help would be greatly appreciated.

    Thanks in advance!
    Ash

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    Similar Problem with RV-3

    Hi, I have the same issue but with the Boss RV-3. There is a thread discussing fixing fried DD3s on here and it says that replacing or just removing the diode D6 can solve this. Schematics for RV-3 are here:

    http://www.mif.pg.gda.pl/homepages/t...es/bossRV3.jpg

    D6 is on the right below VR Board 2/2. Does D6 provide the same safety valve function in the RV-3 as the DD3? Would removing it bring the pedal back to life if it has been plugged into an 18V supply?

    Thanks for your help and sorry for hi-jacking the thread!!!

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    I am Italian
    I also look for me the scheme de boss rc2

    After various tests I have decided dissaldare IC15 that was warm during to give feeding fermandoni to 3/4 volts with a scary absorption around 2ampere the itegrato it is a BD9861 of which I don't succeed for now to find his/her datasheet but of a similar BD9882 and they are of the ROHM
    From the photo the integrated dissaldato is seen, unfortunately I have had to break him/it for dissaldarlo because it had under the houses a fin settled in turn on the card that acts from squanderer.
    If someone finds where to purchase him and his/her datasheet could return profit to all those that have used that is a wrong non appropriate feeder with the positive central.
    I forgot that once dissaldato IC15 and given back feeding up to the 9volt without any absorption and you/he/she has logically ignited normally the red led of the CHECK without any sound because the other circuits are fed not because IC15 is dissaldato from the circuit
    make to know me
    a regard

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    Old Timer J M Fahey's Avatar
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    Marketta, re-posta in Italiano, piú faccile a leggere
    Doppo noi facciammo la traduzzione.

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    Juan Manuel Fahey

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    ko friend

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    Ciao io ho un problema sul tuo stesso Boss rc-2 che fintanto non collego il jack in OUT che fa da interruttore è tutto normale, poi quando lo collego va in cortocircuito io lo vedo alimentandolo con un alimentatore da banco logicamente con polarità invertita come gli alimentatori Boss PSA che sono col negativo centrale.
    Dimmi sa hai risolto e se hai trovato schema elettrico

    Dopo varie prove ho deciso di dissaldare IC15 che era caldo al momento di dare alimentazione fermandoni a 3/4 volt con un assorbimento pauroso circa 2ampere l'itegrato è un BD9861 del quale non riesco per ora a trovare il suo datasheet ma di uno simile BD9882 e sono della ROHM
    Dalla foto si vede l'integrato dissaldato , purtroppo ho dovuto romperlo per dissaldarlo perchè aveva sotto il case una aletta saldata a sua volta sulla scheda che funge da dissipatore.
    Se qualcuno trova dove acquistarlo e il suo datasheet potrebbe tornare utile a tutti quelli che hanno usato un alimentatore non appropriato cioè sbagliato col positivo centrale.
    Dimenticavo che una volta dissaldato IC15 e ridata alimentazione fino ai 9volt senza nessun assorbimento e si è acceso normalmente il led rosso del CHECK logicamente senza alcun suono perchè gli altri circuiti sono non alimentati perchè IC15 è dissaldato dal circuito
    fatemi sapere dove posso trovare uno schema elettrico per boss rc.2 come il nostro amico per rv-3
    un saluto

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    Lifetime Member Enzo's Avatar
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    Io non parlo italiano, ma mi piace il cibo.

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    Education is what you're left with after you have forgotten what you have learned.

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    how can I put a photo?
    thanks

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    Old Timer J M Fahey's Avatar
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    Hello. I have a problem on the same Boss rc-2.
    As long as I do not connect the IN/OUT jack which also works as a switch (Is he referring to the External Power Jack which switches the internal 9V Battery OFF when used?) everything is normal, then when I plug the PS there it shorts.
    I am feeding it with a Bench PSU, of course with the polarity inverted as in BOSS PSA PSUs: center negative plug. (I'm not so sure about that, please check and confirm).
    Tell Me if you solved the problem and if you have found the schematic.
    After various tests I decided to unsolder IC15 that was hot at the time of giving power shutting down to 3 / 4 volts while absorbing a frightening 2 amperes.
    (I guess he connected the PSU plug the wrong way and some Voltage Regulator or Switcher is freaking out, the normal power consumption is 50mA)
    The IC is a "BD9861" whose datasheet I can't find, only found a similar BD9882, ROHM brand.
    In the picture you can see I unsoldered it.
    Had to break it because it has an extra "fin" soldered to the PCB which acts as a heatsink (obviously he should have used a hot air desoldering station or something equivalent, not a simple soldering iron).
    Please tell me where to buy a new one or at least where/how to get a datasheet.
    I forgot to tell that after pulling IC15, I fed it 9V , got the red Led to turn on, but no sound.
    Please help me to get a schematic.
    NOTE: I found the original posting in an Italian site, where he claims he sent it to BOSS official service in Milan, it stayed there for a year and came back unrepaired, although they offered him a new replacement board for 100 Euro, which he declined.

    PS: is this the picture/photo?

    http://www.diyitalia.eu/forum/downlo...7303&mode=view

    PS2: I very much doubt even Boss themselves repair this pedal; at most they'll replace the entire board, if available.
    Besides, even getting a new IC15 does not guarantee it will work.
    Sorry.

    PS3: my *BIG* doubt is this: does it work when 9V battery powered?

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    Juan Manuel Fahey

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    PS: is this the picture/photo?
    http://www.diyitalia.eu/forum/downlo...7303&mode=view
    YES

    PS3: my *BIG* doubt is this: does it work when 9V battery powered? NO si accende solo il led rosso del check

    IC15 L'HO ACQUISTATO IN CINA L'HO MONTATO MA NON SUCCEDE NULLA LED ROSSO SPENTO

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    Old Timer J M Fahey's Avatar
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    Dear Marketta, I am very sorry but I think your Boss pedal is beyond repair.
    Not even Boss will repair it.
    Your IC15 *seems* to be both some kind of regulator *and* switcher, the manual said that if the "wall" power supply fails it automatically connects the 9V battery so you can finish the show.
    I guess it *may* also be some kind of voltage converter, to get what's needed by other chips.
    Maybe your only option is to pay the 100 Euro demanded by the Milan Boss Importer.
    Good luck.

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    Juan Manuel Fahey

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    I thank you
    but this I already knew him
    I would like to mend the pedal and I would appreciate someone whom has you has already faced the reparation
    thanks

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    does nobody have an electric scheme of this blessed Boss rc-2?

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    Let me start by saying that I do NOT have the schemos and other information.

    What I have is some background on broken pedals and other equipment that has been brought to my attention over time.

    A lot of equipment with DSP digital stuff in side runs from 5Vdc or 3.3Vdc, and uses one-chip stepdown switching regulators to make this voltage from nominally 9Vdc from an external supply. Some of it uses 9Vac or dc and sends you a 9Vac wall wart with the same plug as 9Vdc pedals, but that is another and different disaster waiting to happen.

    The switching down-converters work OK, but many of the designs I've debugged had a design flaw. If the input is suddenly shorted, the output capacitors are still at the full operating voltage and can cause current to flow backwards through the switching elements in the converters to the now-grounded input. The current is high and can fry the insides of the chip. The cure is simple: put a diode in parallel with the down-converter so it's normally reverse biased by the higher input voltage, but conducts when the input is shorted and drains the output caps without killing the converter.

    Every music DSP unit I've looked at leaves this $0.02 diode out. I think that today's engineers were never taught that ALL power supplies should be considered as failing in all kinds of ways during the design. All normal 3-terminal linear regulators can fail the same way, and very few people read the manufacturers' application notes, which state this clearly.

    Alas, this is not easy to fix after the fact. When the converter is shorted by any means, the next power-on cycle you try, the now-unregulated supply voltage fries the low voltage logic chips one way or another. It would be a matter of sheer luck if replacing the input diodes and reglator/converters fixed the pedal/box.

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    Noodle of Reality Steve Conner's Avatar
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    Hmm. We left that diode off the DSP board we just designed.

    In our case the converter steps 3.3V down to 1.4V so hopefully there won't be enough voltage to fry things.

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    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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    I suggest you do the necessary test on at least one and perhaps a few "victims" and see what happens. You might have time to glom it on before volume production. A lot depends on how much energy is stored in the output filter caps and whether the peak currents can fry the elements in the converter in reverse. You might also want to call the supplier of the converter IC and see if they have some words of wisdom. If they're not familiar with this as a possible failure syndrome, it tells you their application engineers don't have the right level of experience.

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    Old Timer J M Fahey's Avatar
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    I wouldn't be surprised if they hadn't included such diode "on chip" *or* suggested using it in the datasheet.
    Old Stone Age 78xx regulators already suggested that.

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    Juan Manuel Fahey

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    You'd think so, wouldn't you? It surprised *me* to not see it, but it's uncommon to find one. It may well be mentioned in the datasheets or app notes, but not prominently.

    The stone age 78xx regulators did mention it in datasheets and app notes, but they are commonly used without a "shorted input" protection diode, too.

    Protection devices for odd situations is one situation where Muntzing is not going to make a better product. Protection against uncommon circumstances is utter wasted effort - until that situation happens. I've never actually used a fire extinguisher on a fire, but I don't think having them sitting around is a waste of money.

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    Hi
    Had a similar problem with my RC2. I just replaced the switching regulator BD9851, which restored the 3v3 & 1v5 supply. However, it's clear that the Flash memory also got fried when the wrong PSU was plugged in, as the Flash gets hot (even from a battery supply) so unlikely I can fix the unit.
    The Flash is in a BGA package, which will be next to impossible to replace. It would also need reprogramming :-(
    I'll stick to fixing vintage pedals in future.....
    Would appreciate schematics if anyone has them. I reverse engineered the board PSU.
    Martin

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