War Scythe not working after possible short.

[Danny13]

Hello,

Pretty new to pedal building but have some experience with electronics although basic. My project currently powers on all leds and the dry signal bypasses but that's it.

I did have the input and output both wired wrong. I suspect that something fried. After hooking up the input and output correct the Reaper side worked great for a few minutes, the octave was working but scratchy then died also. So now I have dry signal and the leds do work. I've poked around testing the voltage around the board but I don't understand the circuit enough to know what I'm looking for. I've looked hard for any visible short, cold solder joint, loose wire etc.

If anyone has an idea what may be fried please let me hear your opinion. Thanks!


https://photos.app.goo.gl/5rVHW4jyqpPvzoty6

 

[Robert]

Those sockets need transistors.

On a more serious note, wiring up the input / output jacks wrong shouldn't have damaged anything.

Do any of the three effects work, or are they all dead?

 

[Chuck D. Bones]

Let's see a pic of the other side of the board. From the top side, it looks like you were pretty generous with the solder. If it was working then stopped working, that tells me you have an intermittent connection, either a short or open. Those disk ceramic caps are fragile and can crack where the leads attach, so inspect them carefully. Hard to tell from this angle, but the solder joints on the pots might need to be reflowed.

 

[Danny13]

Those sockets need transistors.

On a more serious note, wiring up the input / output jacks wrong shouldn't have damaged anything.

Do any of the three effects work, or are they all dead?

Yes all dead just dry signal passes through.

 

[Danny13]

Let's see a pic of the other side of the board. From the top side, it looks like you were pretty generous with the solder. If it was working then stopped working, that tells me you have an intermittent connection, either a short or open. Those disk ceramic caps are fragile and can crack where the leads attach, so inspect them carefully. Hard to tell from this angle, but the solder joints on the pots might need to be reflowed.

Ive looked very close at the ceramics, nothing jumps out. I reflowed the pots and any suspicious connection. The wires from the switches some look very close to each other but I rang them out nothing is shorting.

Ya too generous with the solder, I will be buying a proper fine tip iron for the next project.

Here is the other side https://photos.app.goo.gl/rj8YuDnJymHLJG5D6

 

[Danny13]

I think I have a dead component. The question is what would make the entire board go dead, I do have voltage at various point on the board. Also I tested each component before soldering. I found one bad ceramic before installing, I see that those cheapo ceramics aren't the best way to go and will upgrade on the next build.

 

[Nostradoomus]

Those little ceramics short closed when they fail. I use them here and there but I generally try to avoid them. It’s worthwhile to spend the money on better quality caps. Not saying thats your issue, just something to keep in mind.

Also I would recommend cleaning your board with isopropyl alcohol and a toothbrush. With open scrapes like you’ve got near your output jack, you’ll do well to take care and scrub it! If you have solder wick try to get excess solder off your switch wiring as well.

After you have cleaned it, maybe post some voltages from your 9v in and transistors...they can often be the key!

 

[Chuck D. Bones]

If you had one bad cap, then the entire lot becomes suspect. Might as well change them all out now, before cleaning up the solder. These are good boards, but can take only so many soldering cycles before the pads and traces start lifting.

Like Nostradoomus said, ceramic caps fail shorted. On the cheap ones, the ceramic layers are too thin and metal whiskers can grow thru tiny cracks and voids, creating shorts. I have seen cross-sections of failed ceramic caps. They can be good one day and fail the next.

 

[Danny13]

Those little ceramics short closed when they fail. I use them here and there but I generally try to avoid them. It’s worthwhile to spend the money on better quality caps. Not saying thats your issue, just something to keep in mind.

Also I would recommend cleaning your board with isopropyl alcohol and a toothbrush. With open scrapes like you’ve got near your output jack, you’ll do well to take care and scrub it! If you have solder wick try to get excess solder off your switch wiring as well.

After you have cleaned it, maybe post some voltages from your 9v in and transistors...they can often be the key!

I found 2 ceramics that had continuity but after removing them from the board they tested fine. Here are the transistor voltages-

 

[Chuck D. Bones]

I found 2 ceramics that had continuity but after removing them from the board they tested fine. Here are the transistor voltages-

View attachment 2680

Which 2 ceramics measured continuity on the board?

Q1 you have the readings for E & C swapped - otherwise looks ok
Q2 looks ok
Q3 you have the readings for E & C swapped - otherwise looks ok
Q4 looks ok
Q5 collector voltage is too high, should be similar to Q4
Q6 you have the readings for E & C swapped - even taking that into account, the collector voltage is too high, Vbe is too low. Could be a short or Q6 is blown.
Q7 you have the readings for E & C swapped - even taking that into account, all of the voltages are too low
Q8 is either saturated or you measured it wrong because E & C should be at different voltages.
Q9 you have the readings for E & C swapped - otherwise looks ok

The Tone Reaper part of the circuit (Q1 & Q2) has correct voltages on the transistors and should be passing signal.
The last two stages of the Big Muff part of the circuit have problems. Could be caused by shorted capacitors, or something else.
The first two stages of the Octave part of the circuit have a problem. If we correct Q7's voltages, then Q8 will probably good too.

Please recheck all of the measurements and correct the table above.

R37 looks like 6R2, should be 6K2. You need to recheck all of the resistors.

 

[Danny13]

I've found 4 resistors wrong, 2 my fault and 2 from a mislabeled bag from Tayda. Waiting on new parts for now.

Thank you to everyone who has helped me out so far! Much appreciated!