Valvecaster at 12 Volts?

[jaki54321]

I tried running my Valvecaster pedal that I built, on a 12 Volt Wall wart. It is 12 volts with 500mA current. When I plug it in, the tube lights up, but the LED does not when I turn it on, and I even changed the resistor value. When I turn on the Pedal, it doesn't work at all. The LED indicator stays off, and there is no sound coming through my amp, but when i turn it off, my guitar plays through(With no effect of course...), but when it runs on my 9 Volt Wall wart, tube lights, LED lights, and the effect works, but I want to run it at 12 volts to get the best sound.

Can somebody help? I have built this thing PCB-less with a 3PDT switch. I have tried putting a 100uF Electrolytic Cap across the power jack for filtering and it still did not work. There is no voltage regulator installed or anything, no mods, no changes, just normally built. Is there something I must do/change/Put in to have this pedal able to run on 12 Volts?

[PRR]

Voltages at all tube pins.

[frequencycentral]

Polarity or hookup of DC socket?

[GibsonGM]

+1 Freq. Central

[MikeH]

+2

[jaki54321]

Ok you were all right! The polarity was reversed... I would have checked it earlier before i asked this question but my multi meter's ground peg was broken off so i couldnt use it, but i got it working now so i checked and the polarity of the 12 volt wall wart, it is opposite of the 9 volt wall wart.

is there a possible easy way to open the 12 volt wall wart and change the polarity around? I changed the cables inside my pedal and now it works with the 12 volt but not the 9 volt because of polarity. Can I change the polarity on the 12 volt wall wart? Or is it easier to jus get a new one?

[anchovie]

is there a possible easy way to open the 12 volt wall wart and change the polarity around?

I'm guessing the wall wart is sealed, so I'd say the easier option is to cut off the plug and solder it back on the other way round, using heatshrink for insulation as required.

[jaki54321]

is there a possible easy way to open the 12 volt wall wart and change the polarity around?

I'm guessing the wall wart is sealed, so I'd say the easier option is to cut off the plug and solder it back on the other way round, using heatshrink for insulation as required.

Actually I think I am going to buy myself a pedal power supply. I checked the polarity of the dunlop power brick and It will work just fine. I am going to use the 18V plug and use a volt regulator and filter cap to lower it to 12 volts to kill buzzing and to have an effective power supply.

[GibsonGM]

Always good to have a reliable power supply!  One thing you might try is putting a cap across the power supply first, where it enters the pedal (470uF, 1000uF, whatever) and see if it affects the buzz.  That would give you an idea of if this will help.
But anyway, you will use the power supply for other projects, so no harm if the problem is something else - at least you'll have eliminated that as a cause!!

[jaki54321]

Always good to have a reliable power supply!  One thing you might try is putting a cap across the power supply first, where it enters the pedal (470uF, 1000uF, whatever) and see if it affects the buzz.  That would give you an idea of if this will help.
But anyway, you will use the power supply for other projects, so no harm if the problem is something else - at least you'll have eliminated that as a cause!!

All i have is a 100 uF and tat didnt seem to help the buzz. Im guna buy a 1000uF electrolytic and a 7812 Regulator. I do have one question however. How much current should the 7812 put out? My power supply is running at 500mA of current and i was about to buy a 7812 that output one whole amp of current. So I was a lil worried to buy it. I think I am going to buy my voltage regulator and electrolytic from Mouser Electronics. I just don't know if its safe to have 1 amp of current or not. Im still sort of a newbie at this kina stuff lol. i learn somethin new everyday.

So is it safe to have the 7812 regulator with 1 amp of current?

http://www.mouser.com/ProductDetail/STMicroelectronics/L7812ABV/?qs=sGAEpiMZZMtUqDgmOWBjgBuyVw5VvOi7zjTVGKNeumc%3d

[GibsonGM]

The 7812 is perfect )

It can DELIVER up to 1A of current...but current isn't something that's forced into a circuit - the circuit DRAWS the current.  If enough current isn't available, the voltage of the power supply falls....

So, if your valvecaster wants 150mA for the heaters, and maybe 10-20mA for the actual tube work, you're only looking at a conservative maximum of up to 200mA, or .2A.  No problem current-wise.   Try it, and monitor it to see if it gets really hot.  If so, unplug (it has thermal protection built in, so will auto shutoff if things go too far, but why chance it?).
   
What you'll probably need to do in that case is to mount the 7812 on your enclosure or on its own heat sink, so that it doesn't get too hot.  As it delivers current, heat is generated.  Now, some power transistors/FETs have the collector connected to the outside of the case.  The 78XX series regulators have the GROUND going to the case (shiny back side of the IC), so you are ok to connect it to a heatsink/grounded enclosure using thermal compound.  This will 'wick away' the excess heat and protect the IC.  I do it anyway because it is stable.
 

[jaki54321]

The 7812 is perfect )

It can DELIVER up to 1A of current...but current isn't something that's forced into a circuit - the circuit DRAWS the current.  If enough current isn't available, the voltage of the power supply falls....

So, if your valvecaster wants 150mA for the heaters, and maybe 10-20mA for the actual tube work, you're only looking at a conservative maximum of up to 200mA, or .2A.  No problem current-wise.   Try it, and monitor it to see if it gets really hot.  If so, unplug (it has thermal protection built in, so will auto shutoff if things go too far, but why chance it?).
   
What you'll probably need to do in that case is to mount the 7812 on your enclosure or on its own heat sink, so that it doesn't get too hot.  As it delivers current, heat is generated.  Now, some power transistors/FETs have the collector connected to the outside of the case.  The 78XX series regulators have the GROUND going to the case (shiny back side of the IC), so you are ok to connect it to a heatsink/grounded enclosure using thermal compound.  This will 'wick away' the excess heat and protect the IC.  I do it anyway because it is stable.
 

Where could I get a heat sink for that thing? an should i put it on using like silver thermal compound? I have some left over from my Xbox 360's Red ring of death fix xD

[GibsonGM]

It's really easier (IMO) to mount the '12 right to your enclosure.  A lot of metal there keeps it very cool!  You can leave it at the edge of a strip of perf board and lightly bend the legs so it fits flat against it.  Mark and drill a mounting hole, apply compound, all done.

If you need a real heat sink, Mouser has them....just guess on the size (say 1"x1").  But why pay the $ if you can use the enclosure?   Ya can't do that with every power IC (some are 'hot' on the back = collector!!), but you can with the regulator.

Yes, basically any thermal compound will do. You're not pulling huge Amps out of the thing, so you just need to let it cool off a little.   The heatsink might even be overkill, but I'd do it 'just in case'... 

[jaki54321]

It's really easier (IMO) to mount the '12 right to your enclosure.  A lot of metal there keeps it very cool!  You can leave it at the edge of a strip of perf board and lightly bend the legs so it fits flat against it.  Mark and drill a mounting hole, apply compound, all done.

If you need a real heat sink, Mouser has them....just guess on the size (say 1"x1").  But why pay the $ if you can use the enclosure?   Ya can't do that with every power IC (some are 'hot' on the back = collector!!), but you can with the regulator.

Yes, basically any thermal compound will do. You're not pulling huge Amps out of the thing, so you just need to let it cool off a little.   The heatsink might even be overkill, but I'd do it 'just in case'... 

ok man im guna see if i can mount it on the side of the enclosure, i think i got the perfect spot. An ill put some thermal compound on it.

Thank you SOO much for all your help! you have really helped me! And thank you everybody else for all your kind help and patience 

[GibsonGM]

No problem, jaki, that is what we're here for!!  Let us know if it works out, or if there's still noise or anything.  I am curious if this will cure it for you. 

[pleiades]

I've used 7812/7912/7805 regulators successfully without heatsinks.  YMMV based on load and how noisy the supply voltage is, but especially for temporary testing purposes you are absolutely fine to run without them.

[thedefog]

Jaki,

I'd be interested in knowing whether or not the 7812 generates any excess noise in the circuit.

[anchovie]

The whole point of using a voltage regulator is to get rid of PSU noise. It won't add extra.

[jaki54321]

Jaki,

I'd be interested in knowing whether or not the 7812 generates any excess noise in the circuit.

I always hear it doesnt... I always hear it kills the noise, 18V through a 7812 and a 1000uF filtering Capacitor kills all the noise. im eager to find out.

[jaki54321]

No problem, jaki, that is what we're here for!!  Let us know if it works out, or if there's still noise or anything.  I am curious if this will cure it for you. 

I do have a question tho. I can get the parts but I cant get the power supply jus yet. If I installed the parts in the pedal, that includes the Cap and the Regulator, can I still run the pedal at 12 volts even with the 7812 volt regulator?