Thermionic problem

[PKRPedals]

I need some help with my Thermionic OD. Just finished it and it has a crazy amount of noise and squealing. The D1 diode is getting really hot also. At first, the LED just below R34 would light up with 9 volt supply connected but now it doesn't. I've checked all caps and resistors, they are all good. Also checked for any solder bridges and there are none. Any ideas?

 

[Nostradoomus]

Pics?

 

[PKRPedals]

Hope this helps

 

[PKRPedals]

Here’s a larger one

 

[PKRPedals]

Could I have my LED's in backward? The board isn't marked A or K. I've got the Cathode in the square hole.

 

[Barry]

Cathode should be to round hole on this one, not so sure that would cause your problem though

 

[Nostradoomus]

Yep anode is square holes on these guys, but that wouldn’t do much to your protection diode. Can you take a pic of the bottom side as well? And your jack wiring as well would help. There’s gotta be a short somewhere or you’ve got a bad diode.

 

[Chuck D. Bones]

Two words: VISUAL INSPECTION.


Is the 1N5817 the only part getting hot?

 

[PKRPedals]

I have looked this thing over and over and can't see anything weird. I don't see any solder bridges or anything touching something else. The only thing I noticed getting hot is the 1N5817 in D1.

 

[Chuck D. Bones]

Take a real good look at R32 and R33. Are they 10K or 10R? I can't tell by looking at your pic, lighting is too dark.

As long as LED1 - LED4 are all backwards, the circuit will work they way it is supposed to work, no need to reverse them. LED5 needs to face the correct way or it won't light up. Read This.

 

[PKRPedals]

Led 5 lights up. I have the other led’s in correctly according to pedalpcb. They are reversed from the build doc on the board revision that I have. The resistors are also correct, I went back and measured each one to make sure I didn’t make a mistake there. I don’t know what is happening with this thing

 

[Chuck D. Bones]

Measure the voltage (w.r.t. ground) on each side of D1 with power on. If the cathode side is at or near 0V, then you have a hard short to ground. If it's between 0.5V and 3V, try pulling the ICs out of the sockets (with the power off), then power up and measure again.

 

[PKRPedals]

I'll try that this afternoon. Thanks

 

[PKRPedals]

Chuck
I have 9.13 on the anode side and 8.75 on the cathode side.

 

[Nostradoomus]

Your R33 and R32 are 10r...looks like R30 is a 1ohm too (though it could be the light, the band looks silver)

 

[PKRPedals]

Thank you. After going back and looking at it again, you're correct. Every 10K resistor is a 10R. I accidentally put 10R resistors in my 10K drawer and that's the ones I grabbed. R30 is correct though, it's a 10R. Man do I feel stupid. When I measured R32 and R33, I saw 10 and just automatically saw 10K instead of 10ohm. I ordered another board because I don't feel like trying to get all of these out and replaced. Thanks again for the help.

 

[Nostradoomus]

All props to Chuck for bringing it up, but my younger eyes for being able to see it haha

 

[PKRPedals]

Ah yes! Thanks to Chuck also! I read em but I saw 10 and in my mind, I saw 10K. That's what I get for just assuming. haha

 

[Nostradoomus]

It’d definitely be easier to swap those then make a new one

 

[PKRPedals]

It will be my reminder to make sure I have the correct parts. I got the pots off of it and the 5817's. No problem doing a new one.