Anyone know why my Sunking II board keeps blowin' up?

[upthepunxxx]

Hey Doodes,

Ok maybe not blown up but I needed to draw you in with a little yellow journalism. I was testing my build yesterday and as soon as I hooked up the board to power, R32 (the 10R 1/2 watt Resistor) would heat up and turn black, essentially burning from the inside out. I realized I didn't have a cap in c8 as I had added a socket in order to be able to dial in the FAT mod. I am not using the THICK mod just the FAT mod. I checked the schematic and realized that that shouldn't have anything to do with it right? I replaced r32, added a cap in c8, and checked out the tranny and that seemed fine as well. I was looking for some advice on how to trouble shoot this bad boy? Mainly cause I can't keep the power hooked up long enough to probe or take voltages without the resistor frying. I was checking out the schematic, could it be the voltage regulator? It was getting late so I didn't switch that out yet. Here are some pics of the board with the fried resistor. Let me know if anyone has any advice, if not I will keep plugging away and see what I come up with. Thanks homies!

[murdog47]

What are you using as a power supply?

[madbean]

For whatever reason, your board is pulling too much current and causing the resistor to overheat. Go ahead and jumper it instead. Make sure you get a good reading on your voltages afterward to make sure they are correct.

[upthepunxxx]

I am using there power breakouts from JMK's Testing rig. That is being powered by a standard boss power supply.
Same setup I used to test the previous 2 Sunking Boards I made. Only difference is I wanted to try one of the mods this time.

What are you using as a power supply?

[mgwhit]

You may have a solder bridge or a whisker of stranded wire shorting to ground somewhere.  I would recommend clipping one lead of your multimeter to a ground point (lug 1 of your volume pot?) and then testing every point on the board that should NOT have continuity to ground.  It's a good exercise and shouldn't really take more than about 10-15 minutes.

If you have to fire it up again before you've found your problem, I'd recommend doing it without the ICs in their sockets.  Test your charge pump (IC1) socket for approximately 9V on pin 1 and 0V on pin 3.  If that checks out okay, add your charge pump and then test all the relevant power and ground points on the IC2 and IC3 sockets for appropriate voltages.

Good luck!

[upthepunxxx]

thanks for responding my man. You mean just pull that resistor out and solder in a jumper wire?

For whatever reason, your board is pulling too much current and causing the resistor to overheat. Go ahead and jumper it instead. Make sure you get a good reading on your voltages afterward to make sure they are correct.

[upthepunxxx]

Thanks! This definitely seems like a good place to start.  I really appreciate it. I'm hoping you are right about a solder bridge. I was probably going a little faster than normal considering I had already made 2 with no problems. Got a little cocky 
When checking the IC2 & IC3 sockets last, am I looking for the same voltages as the regulator? 9V on pin 1 0V on pin 3? Or are they different voltages? If they are different I'd imagine someone has probably already posted them in a another thread. I'll keep searching.

You may have a solder bridge or a whisker of stranded wire shorting to ground somewhere.  I would recommend clipping one lead of your multimeter to a ground point (lug 1 of your volume pot?) and then testing every point on the board that should NOT have continuity to ground.  It's a good exercise and shouldn't really take more than about 10-15 minutes.

If you have to fire it up again before you've found your problem, I'd recommend doing it without the ICs in their sockets.  Test your charge pump (IC1) socket for approximately 9V on pin 1 and 0V on pin 3.  If that checks out okay, add your charge pump and then test all the relevant power and ground points on the IC2 and IC3 sockets for appropriate voltages.

Good luck!

[upthepunxxx]

Thanks so much for helping out guys! I really appreciate it!

[mgwhit]

Check out the power section of the schematic.  IC1 should have about 9V on pin 8 and 0V on pin 4.  IC2 should have not quite 18V on pin 8, and -9V on pin 4.  If those look good, insert IC1 and IC2.  The other pins on those ICs (1-3, 5-7) should have about half of what you see on pin 8 of IC1, which is your VB.   This VB voltage should also be found on the + leg of C21.  These are all approximate, of course.

When checking the IC2 & IC3 sockets last, am I looking for the same voltages as the regulator? 9V on pin 1 0V on pin 3? Or are they different voltages? If they are different I'd imagine someone has probably already posted them in a another thread. I'll keep searching.

[Scruffie]

Pull the zener (D3) out...

[upthepunxxx]

Replace it?

Pull the zener (D3) out...

[upthepunxxx]

At first I wasn't sure how you knew what pins 4 & 8 should be. I thought you got it from the data sheet or it was just one of those things everyone but me knows. I re-read your comment a couple times and finally realized why you said look at the power section. It took me a bit but I see pins 4 & 8 for both ics now, and what there corresponding voltages should be. Well this all gives me some good points to jump off from. I'm gonna start there and let you know how it goes. Thanks again brotha,
I really really appreciate it!

Check out the power section of the schematic.  IC1 should have about 9V on pin 8 and 0V on pin 4.  IC2 should have not quite 18V on pin 8, and -9V on pin 4.  If those look good, insert IC1 and IC2.  The other pins on those ICs (1-3, 5-7) should have about half of what you see on pin 8 of IC1, which is your VB.   This VB voltage should also be found on the + leg of C21.  These are all approximate, of course.

When checking the IC2 & IC3 sockets last, am I looking for the same voltages as the regulator? 9V on pin 1 0V on pin 3? Or are they different voltages? If they are different I'd imagine someone has probably already posted them in a another thread. I'll keep searching.

[Scruffie]

Replace it?

Pull the zener (D3) out...

Nope, just take it out, cut one of the leads, whatever.

Edit: Just saw you have it in a socket, even better, pull it out and try powering up.

[upthepunxxx]

Sorry man, one last question. In order to take voltages on the sockets I have to plug it in. Should I remove r32 and jumper it or replace it with a new one before I do that? Everytime I plug it in it just gets super hot and I unplug it before it burns out again. How would I go about checking voltages while avoiding burning up the board right there?

At first I wasn't sure how you knew what pins 4 & 8 should be. I thought you got it from the data sheet or it was just one of those things everyone but me knows. I re-read your comment a couple times and finally realized why you said look at the power section. It took me a bit but I see pins 4 & 8 for both ics now, and what there corresponding voltages should be. Well this all gives me some good points to jump off from. I'm gonna start there and let you know how it goes. Thanks again brotha,
I really really appreciate it!

Check out the power section of the schematic.  IC1 should have about 9V on pin 8 and 0V on pin 4.  IC2 should have not quite 18V on pin 8, and -9V on pin 4.  If those look good, insert IC1 and IC2.  The other pins on those ICs (1-3, 5-7) should have about half of what you see on pin 8 of IC1, which is your VB.   This VB voltage should also be found on the + leg of C21.  These are all approximate, of course.

When checking the IC2 & IC3 sockets last, am I looking for the same voltages as the regulator? 9V on pin 1 0V on pin 3? Or are they different voltages? If they are different I'd imagine someone has probably already posted them in a another thread. I'll keep searching.

[mgwhit]

I'd take Bean's suggestion and jumper it.