Informant overdrive problems

[ElReverendoRyan]

Hey guys.

Had some trouble with the informant. First it worked out of box, then didn’t once in box, then it did, then I’d get oscillation from the voltage doubler, then ONLY that sound + IC2 is heating up. All of this out of box now mind you.

I’m kinda running out of ideas and getting tired of looking/proving, my eyes are shot to s*** (been at it for 3 hours now). Anyone wanna take a look at these pics see if I’m missing something?

 

[carlinb17]

Is the back of your pot covered by something? They are notorious for shorting the back of the board once boxes

 

[ElReverendoRyan]

Is the back of your pot covered by something? They are notorious for shorting the back of the board once boxes

It’s got a bumper, and while testing out of the box I made sure to have it bend away from the board

 

[carlinb17]

What do your connections look like

 

[ElReverendoRyan]

What do your connections look like

They’re fine, getting signal through true bypass, and when engaged the knobs do have an effect on the squeal, ie can turn it down, distort it, and change the tone of it

 

[Diynot]

Looks like you are using the tc1044scpa charge pump, did you follow these instructions?

 

[ElReverendoRyan]

View attachment 23319Looks like you are using the tc1044scpa charge pump, did you follow these instructions?

Yes, put a blob of solder over this

 

[Diynot]

I would need to look at the IC pinout, but you should be able to remove the charge pump ic and jumper the in/out pins of the socket so that the pedal only sees 9v, or remove the ic and jumper from the cathode of d100 and the positive leg of c104. try that and see if the squealing resolves.

 

[Diynot]

Have you checked voltages on the tl072 pin 8 with the charge pump in?

 

[ElReverendoRyan]

Have you checked voltages on the tl072 pin 8 with the charge pump?

17 and a bit

 

[Diynot]

I will pull out mine after awhile and do some probing. For now though, have you tried swapping out the charge pump and the IC2 (one at a time) to make sure it’s not the IC itself? Also trying running it at 9v to see if the current IC2 still heats up. If it does, that at least eliminates the charge pump as the offender (aside from the oscillation) and maybe you can focus on the solder joints around IC2 to make sure there is proper grounding/no solder bridges

 

[ElReverendoRyan]

I will pull out mine after awhile and do some probing. For now though, have you tried swapping out the charge pump and the IC2 (one at a time) to make sure it’s not the IC itself? Also trying running it at 9v to see if the current IC2 still heats up. If it does, that at least eliminates the charge pump as the offender (aside from the oscillation) and maybe you can focus on the solder joints around IC2 to make sure there is proper grounding/no solder bridges

I’ve tried swapping them around, same deal. I’ll try omitting the charge pump (tried two different ones) and bridging to see if at 9v it still heats. If that’s still going on I’ll try reflowing all my sockets

 

[Diynot]

One last thing, make sure you have continuity from pin 4 to the ground plane on IC2. Hope some of this helps

 

[ElReverendoRyan]

One last thing, make sure you have continuity from pin 4 to the ground plane on IC2. Hope some of this helps

Alright just had a go through everything, nothing conclusive to me. Here's the results:

-IC2's pin 4 definitely has ground connection.

-Reflowed everything, then check all pins on my IC sockets with a multimeter for continuity to make sure there wasn't a connection between adjacent pins

-Tried a jumper between D100 and C104 - no dice

-Went over all componenet values, everything is ok and in the right place.

I tried plugging power without the charge pump or the jumper, IC2 still heats up. I found this odd, so unsocketed it and took voltage values on the socket pins. This is without the charge pump. Might be a clue:

1 - 002 (this started off at 010 and slowly drained, i think if i kept on it it would have gone to 000)
2 - 002 (same deal as pin 1)
3 - 1.32
4 - 0
5 - 1.32
6 - 0
7 - 0
8 - 9

I find it weird that without a jumper or charge pump in place that voltage is getting to the IC's (checked IC1 and have similar results)

 

[Diynot]

So, I just measured mine with and without the lt1054 (This is with IC2 in the socket since I couldn’t remove it with my honking pf cap in place) and here is what I get with a 7.95v source
IC2 With:
1-7.2
2-7.2
3-5.9
4-0
5-6
6-7.1
7-7.2
8-14
IC2 Without:
1-3.6
2-3.6
3-3.0
4-0
5-3.0
6-3.6
7-3.6
8-7.25
Lt1054
1-1.4
2-4
3-0
4-1.5
5-160mv
6-2.5
7-1.5
8-7.4
So, yes, your voltages look a little screwy. Where to go from here I may have to leave it in more technical hands.

 

[ElReverendoRyan]

Just did a continuity run through between socket pins and where they should be connecting, all is good.

I’m really stumped here

 

[ElReverendoRyan]

Refreshing thread, I still haven't had a 'eureaka' moment!

 

[ElReverendoRyan]

Resolved, bad ic. Popped one in I knew to be good from another build and it came to life

 

[ElReverendoRyan]

Scratch that, worked for a hot minute and was the best distortion I’ve ever played, then totally crapped the bed, started doing the same thing again minus the overheating chip

 

[music6000]

Scratch that, worked for a hot minute and was the best distortion I’ve ever played, then totally crapped the bed, started doing the same thing again minus the overheating chip

As you say, all the values look good!
When you magnify the PCB there is quite a bit of flux & solder bits on the back of the Board.
Would be a good idea to Clean with Electronic Cleaner and under Cut pot, there may be a stray bit of crap or you might find a bad joint!
The other thing is we can't see your Footswitch or Jack connections on the PCB or Off the PCB???