oh dear, whammy, what did i do?

[kepeb]

so,
i was messing around with my whammy 4 pedal.
i put in the true bypass mod and all went well.

however, when i went to put the LED in too, i tapped the power from under on of the regulators(?) but managed to short it when i turned it on

i touched two of the pins together and there was a spark

so... my question is... have i ruined my pedal now or do i just need a new regulator?

how can i check?

any help would be greatly received, i feel like a right idiot now.

[Jazz P Bass]

new regulator

Can you identify the part number of the part in question?
More specifics would be a big help.

[Steve Conner]

Have you tested the pedal to see if it still works (after removing the short of course)

Voltage regulator ICs have all sorts of protection and can typically survive a short just fine.

However, if you shorted the input pin to the output, the following circuitry may well not survive having 9V applied to it when it was designed for 5.

[kepeb]

i will try it now.
there is definitley still power in the circuit board but the regulator just gets hotter and hotter while its powered.

if you are familiar with the whammy, all the controls and led's are on the right.
this section used to flash then settle on the last selected harmony. now it flashes but just goes straight of and doesnt light up again.

[kepeb]

yea.
the true bypass works
the signal is louder when the pedal is on but the controls dont light up and i cant change the sound

[kepeb]

also,
the common/ground is the centre right?
i think... hope, i bridged one side to ground thats all

[Steve Conner]

Oh well, time to:

Identify the part number of the offending chip

Order a replacement

Fit it

Hope it works


The centre pin is common on 78xx positive regulators. On the 79xx negative ones, it's something else.

Shorting the output to ground won't blow the regulator, but shorting the input to ground sometimes will, if there's lots of capacitance on the output.

[kepeb]

ok
well there are two regulators in big heatsinks. i replaced one (7805 ct) with a 7805 i had.
the other one is bigger. i guess i should just get it out
is there a way to check wether or not its definitely broken?
or is the excessive heat enough of a telltale sign?

[Steve Conner]

I assumed you'd have checked to see which of the two regulators was overheating, and replaced that one.

But then you don't really know. Regulators often run hot when they're working. Maybe the one that's getting hot is the good one, and the busted one has gone cold. So might as well replace them both.

You could probably test a 7805 with a 9V battery and a voltmeter, just apply 9v and see if it produces 5v. Though you really should connect an electrolytic cap between Out and Common, and another between In and Common, to make it a fair test.

[kepeb]

http://i109.photobucket.com/albums/n76/kepeb/gk112.jpg

is this this?

RoboSavvy UK - Store

[kepeb]

volts hrts?

i did some probing.

the 7805 i believe is reading ok. theres quite a bit of info bout that one on the net.

the other one however has a different pinout.
the ground isn't pin two so i shorted the in to the out.... :-0

now, presuming the now broken regulator isnt pulling the voltage down at the input somehow(?) its getting 9v... its only putting out 0.5

my question is.. how likely is it that i have damaged the following circuitry?
i am assuming the next components were meant to be fed between 3 and 6 volts? would they they survive a jolt of 9??

[Jazz P Bass]

Part Numbers

Can you please supply us with some part numbers?
The "other one" may be a 7905 which is a negative voltage regulator.
Pin #1, on the left, is 0 volts, or ground if you will.
The center tab is input, the right pin is output.
Then again, if the part is like you pictured above, LD33V, that is a 3.3 volt regulator.
The left pin, #1, is ground. The center pin is Vout, the right pin is Vin.

[kepeb]

hey jazz
the other one, as i called it. is the one in my first link above. i took a pic because i didnt know which bit was the part number.

i have searched seperatley for all the combinations of letters on there and had most luck with 'LD33v' as the search criteria, at least that brings back results.
so thats fine, yes that is the part.

but, presuming what i did when i shorted it was jumper the input voltage directly to the output, and that i fit a replacement.

i was just asking... what is the likelyhood the following circuitry will be ok after an unregulated 9v passed through them? is there an average volt limit or threshold for ic's and chips?

i understand the answer wont fix my pedal...
it will further my understanding tho

thanks

[kepeb]

also,
i'm looking for the part (my picture) of a '-3.3v' or a '+3.3v' version?


i looked at the chip info and searched for a 'LM7905' but they all say its a '-5v' output.

[Jazz P Bass]

LD33V

Forget the 7905 if it is not on the board.
The picture of LD33V is what I said. A 3.3Volt regulator.
Left pin is ground. Center is Vout. Right is Vin.
Presumably the 7805 5 volt regulator feeds it 5 volts to Vin.
Remove the IC & check (on the board) between the Vout & ground.
What is the resistance?
If it is high, like 2K, you "may" be o/k.
If it is low, like a few 10's of ohms or zero, you shorted something else out.
You have to understand without a schematic we are all shooting in the dark.