Whammy WH-4 Won't Power Up

[Jamforthelamb]

Hello All,

I was working on my Whammy pedal that I had previously true bypassed and ran into a problem. I had figured out that the LED that I had installed was causing a noise, but while trying to fix that two of the contacts where bridged by my soldering iron. Ever since then the whammy won't power up. It will blink the LEDs once, and then go out, but the internal LED for the expression pedal stays on.
I believe the problem may be with one of the power regulators. I've already replaced the 1000uf power caps, and tested all the diodes. The part of the board by the diodes/regulators gets hot to the touch. I'm referencing this post for some of my info http://www.diystompboxes.com/smfforum/index.php?topic=82383.0

U1 = LD33V
I = 4.36
O = 1.71

U2 = 7805
I = 10.5
O = 5.02

U3 = 7905
I = -13.6
O = -4.9

Any help from those more knowledgable then I would be much apprecitated.

God bless,
jftl

[Jamforthelamb]

bump, hoping to get this fixed this weekend for church 

[ppatchmods]

i've had this problem with mine. i don't think it's the chip because it works most of the time. something you might try is covering the inside of the case with tape or something to shield it from anything grounding out. it has seemed to help mine.

[Jamforthelamb]

I'm testing this with the board completely removed from the case. Makes no difference unfortunatley.

-jftl

[thedefog]

All your voltages look fine on the regulators, and regulators do run hot normally, especially if they aren't heat-sinked.

A bridge/short on a digital board like this usually ends in the memory being flashed/corrupted. You probably shorted out the ROM chip, so it isn't booting up. Think of it like an Arduino board starting with no software loaded on it. It will still initialize all the inputs and outputs and whatnot on the DSP, but it just won't do anything.

[Jamforthelamb]

I shorted out the legs of one of the voltage regulators (that's where I was pulling the power for the LED from). Would that cause the board to get hot? The section where the power diodes are get hot to the touch, but none of the chips get hot.

-jftl

[R.G.]

I shorted out the legs of one of the voltage regulators (that's where I was pulling the power for the LED from). Would that cause the board to get hot? The section where the power diodes are get hot to the touch, but none of the chips get hot.

Are you familiar with the concept of the evil twin of the Light Emitting Diode (or LED)?

Sometimes a component that's otherwise good can be transformed by a combination of power and transients into a device that not only takes in power, but can actually receive and store light from the surrounding environment. The light actually disappears, gathered up by the device, and leading to its informal name, the Darkness Emitting Diode, or DED.

Shorting the legs of a voltage regulator feeding a low voltage CMOS logic circuit is a quick way to create a DED.

[Jamforthelamb]

I get that. The only thing that puzzles me is the heat coming from the area of the diodes (which I've heard are there to convert the power from AC to DC). I'm going to do some more checking in there in see if they are letting AC power through.

-jftl

[R.G.]

I get that. The only thing that puzzles me is the heat coming from the area of the diodes (which I've heard are there to convert the power from AC to DC). I'm going to do some more checking in there in see if they are letting AC power through.

If the load - that is, the voltage regulator, filter caps, and logic chips - was damaged by shorting the voltage regulator and is now pulling too much current, especially if it not approximates a short circuit, then yes, the power in the diodes will be high, and they'll heat up. It's part of the same syndrome.

[analogmike]

HI,

I find the Wh4 is VERY sensitive, the chips will blow out when you work on them or solder on them. So we don't work on those anymore after two died.

Also the true bypass method that someone posted is not true bypass at all, it's hard bypass like a big muff or old MXR. You need to cut a trace on the back of the board to isolate the input jack correctly.

Hope that helps but sorry for the bad news!