Trouble with my first 2-in-1 - (Updated)

[mshuptar]

Hello everybody,

I'm still fairly new at this and I'm working on my first 2-in-1. I've run into a few problems regarding the wiring. I'm combining a Fatpants and an Afterlife (the Fatpants is first in the chain) and, after looking at the 2-in-1 wiring diagram from GGG,  here are my two questions:

1) Since the Fatpants has an 18v output, how do I wire these two boards together?

2) Can I still run the Fatpants buffered while having the Afterlife as true-bypass (or do they both need to run true-bypass like the GGG diagram shows)? If so, how does this change the wiring on the GGG diagram?

(And here's the diagram I'm referencing: http://www.generalguitargadgets.com/pdf/two_in_one_wiring.pdf?phpMyAdmin=78482479fd7e7fc3768044a841b3e85a)

Update 2/18/14: I finished wiring everything according to the diagram below (except for the battery snap) but the LED for the Afterlife doesn't work.

It's weird because the LED did light up when I first tested the circuits. When I first tested the circuits, I was getting sound and everything sounded like it was working correctly. However, the output jack was scratchy so I did a little touchup with the soldering iron. After I did that touchup and tested it one more time, the LED for the Afterlife didn't light up. (I'm still getting sound from both effects when the 3DPT switches are engaged).

After checking all my connections related to the LED (I thought a weak soldering joint might have come loose), I popped the LED out and tested it to see if it worked (I put the LED on a 9V battery) The LED didn't light up at all. I found a new LED, tested it to see if it worked, and swapped it in to the Afterlife circuit. It didn't work at all. When I removed the new LED and tested it, it also didn't light up.

Am I burning out LEDs? Am I doing damage to the circuit? What's going on? Any help would be much appreciated.

[oldhousescott]

Even though the Fatpants runs at 18v, the output swing is about ground so it's fine to run the Fatpants into the Afterlife. As far as leaving the Fatpants as buffered output, that will work fine, too. Just substitute the wiring in the Fatpants doc for the footswitch for SW1 wiring in the GGG doc. The green wire leading to the output jack on the Fatpants diagram will take the place of the blue wire going between SW1 and SW2 on the GGG diagram.

[mshuptar]

Thanks for the reply. To clarify, do I connect the 18v output on the Fatpants to the 9v on the Afterlife, instead of connecting the Afterlife to the 9v jack?

[oldhousescott]

I think the attached diagram should do the trick.

[mshuptar]

Oh man, that is above and beyond. Thanks! If you are ever passing through Lansing, Michigan, I'll buy you a drink!

[oldhousescott]

That little box I drew in below the LED is a current-limiting resistor. If you don't have a resistor in-line with the LED, you'll burn it up when you connect it to the 9VDC. You'll also burn LEDs up testing them on a battery without a resistor. Try values between 1k to 10k to get the brightness you desire. Also, note that LEDs have a flat indicating the cathode/negative (-) terminal. If you install them in reverse, they won't light.

[Clayford]

Given multiple leds working before hitting the circuit and then not once you pull them, my thought on the issue is a missing/too small CLR.

And when you say you're checking them on the 9v battery.. you are using a CLR there as well right?

[mshuptar]

I it got working! I did have a resistor hooked up to the LED, but it turns out the resistor was bad. I put in a new resistor, and everything fired up perfectly. It took less than 5 minutes to fix (I just needed to wait until the weekend when I actually had some free time). Thanks for the help! I'll post pics in the "build report" section.

[mshuptar]

Another Update (3/15): It's been roughly three weeks since I finished this project. It was sounding good and I didn't have any problems....until today. I was playing through the effect and when I went to engage the Fatpants side, there was a loud hum, and then no signal. Now, nothing happens.

I opened up the enclosure and took a reading off the 9v jack and the numbers on the DMM were all over the place. There was also a faint "electrical" smell. I took the effects out of the enclosure and didn't notice any burnt components or anything like that, so I'm not really sure what's going on.

When a pedal has been working, but then suddenly quits, what's the usual cause?

[jkokura]

Blown diode, transistor, or IC usually. Check and make sure your semiconductors are working. I hope you socketed the transistor at least.

[mshuptar]

Update: 4/7/14

After working on other projects over the last three weekends, I came back to this one. I used my testing rig and found that the IC on the Fatpants side was blown (the Afterlife side is totally fine). I popped in a spare IC and attached the board to my testing rig. I was getting sound and the board was working.

When I went to dial in the trim pot, I touched the board and found that the spot with the IC on it was hot to the touch. The temp would change as I moved the trimmer and the "Fat" control. I couldn't get the trimmer dialed in so that the IC wasn't hot.

I assume this is how the first IC blew up - what's going on? What am I doing wrong?

[rullywowr]

Sounds like a solder bridge where it shouldn't be, or something shorting out on the enclosure or pots. I'd clean the flux off the solder joints first and check. Can you post pics?

[mshuptar]

I have to pick up some flux remover (I haven't used it until now), but here are a few pics. At first glance, I didn't seem to notice any solder bridges or anything that would cause the shorting.

Also, forgot that I subbed 1n5818 diodes for D2 & D3 instead of 1n5817. Is this the cause of the heat?

[mshuptar]

Okay, hopefully this will be the final post on this thread...

1) I cleaned the excess flux off the board. I also (think) I have T1 dialed in correctly. The final voltage on the testing point is 14.03.

2) The board isn't hot to the touch anymore, but it does get warm near IC1 when it's connected to a power source. (It feels about as warm as a laptop that's playing a DVD). Is this normal? Is there supposed to be a little heat? Or is this problem going to "blow up" again in three weeks?