EHX Good Vibes Help Please

[Elysiumfx]

Hi guys,

I took a risk on a second hand "broken" Good Vibes pedal with no PSU. My educated guess was the user was using the incorrect power supply as these things are a bit funny with power. I purchased the electro harmonic wall adapter that runs 9.6v at 200ma in the hope that I was an easy fix.

Nope.

So the pedal as soon as its plugged in to the wall makes a high pitched noise. Like a kettle boiling. It does this without any input/output jacks and continues to do so plugged into an amp. There is bypass signal but no effect. Flicking between chorus and vibrato setting there is an audible difference in tone.

So I opened it up to have a look.

Someone has already had a go at this... As there is a small iron burn on top of the power jack. Obviously this is all pcb mounted surface components. But on inspection with a magnifying glass here's what I have found:

1. C25 has been reinstalled and they have burnt out the pcb pad. (220uf 25v electro cap.)
2. U2 looks like it has also been played with as there are burn marks along the solder joints. (7680 I think)
3. R38 & R39 excessive solder and burn marks.

Apologies for the blurred photos but the iPhone can't get it in focus.

Any help with this or further knowledge would be gratefully received. I'm not really expecting to fix it now, but would like to further my knowledge if possible - this is a bit beyond my limited ability.

Thank you.

Dave

[Elysiumfx]

Hmmm... no one? Shall I pop this in the F'd pile?

[rustypinto]

I have a Good Vibes. Its a nice sounding, if not very throbby, Univibe clone.

You should start making measurements at various points. Here is what I measured on mine:



U2 is marked TC7660HE. Looks like its boosting the 9V input to a higher voltage. Various points around the pre-amp measure 19.64V, so thats what it appears to be operating at. I can take more measurements if you need me to.

I hope you can solder SMT parts, thats what it will take to repair this one!

[Elysiumfx]

Thank you Very Much!!!

Can I solder SMT....? In a word? No.

But I figure someone has done a YouTube video on it right? I have a feeling the previous owner couldn't either and that's why I'm in this mess. I'll take some measurements this afternoon and see if I can start to focus in on the issue.

Really appreciate it.

Dave

[Elysiumfx]

My highest reading on all of those is 9 volts (more or less) I'm getting no where near what it should be. Mostly 7.5 ish volts. So first port of call is the 7660HE? Looks like its not raising the voltage at all. Just taken readings off the pins:

1 - 0v
2 - 2.9v
3 - 0v
4 - 0v
5 - 0v (This should be the high reading right?)
6- 2.8v
7 - 4.6v
8 - 8.5v

Thanks again in advance.

Dave

[Elysiumfx]

PS. When I take the reading from pin 7 (osc) the whistling stops. On inspection pins 5-8 are the ones that look burnt out.

[rustypinto]

As an aside, I consider these items essential for SMT work:

1. Fine-tip, non-magnetic tweezers.
2. Soldering iron with fine tip (I use 0.5mm) capable of 400-450C to deal with higher-temp, lead-free solder (typical of most any modern SMT assembly).
3. Spool of lead-free solder, typically 0.5mm diameter, tin-silver-copper.
4. De-soldering braid like Tec-Wik 758SO008. This is critical for removing parts, removing old solder from pads, correcting mistakes, etc.
5. Q-tips and 90% alcohol.
6. A very good light source. I use an articulating light with magnifying glass.

Aside from the basic way soldering SMT part electrodes to the respective PCB pads, I recommend learning techniques for heating two or more pads at a time for part removal, which makes life much easier.

With your Good Vibes assembly, the "burn marks" are most likely rosin deposits from soldering. You can gently scrape it off with tweezers, then wipe the area down with a q-tip and alcohol. This is very important to do, especially around IC pins, in order to keep the components clean and visible so you know whats going on (eg. no solder bridges).

[rustypinto]

Here are the readings I get on TC7660H:

1. 0V
2. 4.77V
3. 0V
4. 0V
5. 0V
6. 4.45V
7. 5.29V
8. 9.46V

[PRR]

...

Elysiumfx        rustypinto
1 - 0v           1 - 0V     
2 - 2.9v         2 - 4.77V   
3 - 0v           3 - 0V     
4 - 0v           4 - 0V     
5 - 0v(..?)      5 - 0V     
6 - 2.8v          6 - 4.45V   
7 - 4.6v         7 - 5.29V   
8 - 8.5v         8 - 9.46V