PT80 debugging help needed.

[tehfunk]

Well, i plugged in the PT80 and i smelled some smoke, so i took off the back, and the max1044 was heating up.. So, I looked at the back for solder bridges (throughout the whole board, i looked very carefully), and I found one between two of the pins of the max1044. So i tried again, no more heating up, but the pedal just makes a ticking sound. I opened it up again, and when i put my finger to the max1044 the ticking stops? but then starts again when i release. So, I assume it's something wrong with the charge pump, plus in many places, it seems that my voltages are around half what they should be. Is it possible that this short could have destroyed my max1044, or do you think it's fine and that something else is wrong with the pedal? Thanks, I'd really appreciate any help. Here are my voltages:

supply 7.81

1044
1: 7.81
2: 6.18
3: 0
4: .3
5: .3
6: 5.82
7: 6.9
8: 7.81

571
1- .653
2- 1.481
3- 1.482
4- 0
5- 1.074
6- 3.939
7- 3.937
8- 1.480
9- 1.479
10- 3.974
11- 1.191
12- 1.192
13- 4.71
14- 1.477
15- 1.477
16- .62  (cant get a steady reading)

2399
1- 4.66
2- 2.324
3- 0
4- 0
5- 2.017
6- 2.156
7- .82
8- .82
9- 2.324
10- 2.324
11- 2.324
12- 2.324
13- 2.324
14- 2.324
15- 2.324
16- 2.324

TL072
1- 2.322
2- 2.322
3- 2.345
4- 0
5- 2.151
6- 2.329
7- 2.329
8- 4.71

78L05
1- 6.16
2- 0
3-  4.64

78L12
1- 6.16
2- 0
3- 4.68

supply's a bit low, so take that into account.. but yeah. most everything to me looks okay except for regulators, some max voltages, and a couple voltages here and there which are about half what they are supposed to be. Please help! Thanks!
-Sam

[anchovie]

If you smelt smoke then something burned! If you suspect the 1044 then the obvious thing to do is to try another one. It's not multiplying the voltage like it should be.

[tehfunk]

ok, yeah, that's what i was going to do. but, before i ordered i wanted to make sure that it was the most likely problem. i mean, is it really possible to break the 1044 by simply shorting one of the leads to another? i was a little skeptical of that, and again, don't want to waste the money, while not getting something that i actually need. also, there was no smoke, but you know that smell? right, well yeah i smelled it and the leads were getting very hot.. i'll go ahead and order it soon, i just want a response to the above. thanks!
-Sam

[frequencycentral]

In my experience MAX1044 are quite sensitive to shorts, I've killed a few on my breadboard. Suspect it. And when they go, they melt the fkg breadboard under them!

[tehfunk]

In my experience MAX1044 are quite sensitive to shorts, I've killed a few on my breadboard. Suspect it. And when they go, they melt the fkg breadboard under them!

okay, i guess that's good news. the way you put it was pretty funny.. i wanted to check whether mine was still working so i tried to breadboard mine with the circuit outlined in the datasheet, and it began to heat up, i think i did something wrong.
But, more importantly, what i was wondering is that if it was able to heat up does that mean it is still working properly? or can they still heat up, and give voltages, but not work "properly", as in double the voltage? because if it's working properly then it would be a waste to order another one and i've got more difficult debugging to do... thanks!

if that's a bit confusing, my question simplified is, if my max1044 is broken will it still give voltages of some sort, just not double them, or will it just give 0v everywhere?

-Sam

[frequencycentral]

Can a chicken that's been deep fried still run around the farm?

[tehfunk]

Can a chicken that's been deep fried still run around the farm?

crap, are you saying that the reason that i'm not getting doubled voltages in the circuit is not the result of a fried max1044?

i can hear ticking in the circuit, and i'm pretty sure it is coming from the max1044 because it started after i repaired the short on it and whenever i touch it in a certain way the tick either stops or goes faster... i'm sure there is something wrong in the power section. so what could it be?

[frequencycentral]

I think your MAX is fried. If you run the test circuits on the data sheet and it won't play nice then it's fried. If it heats up it's fried. You can order some free samples from Maxim if you hit their site though!

[aziltz]

if the 1044 is so sensitive, it might be wise to order a few spares anyway.  money well spent as i see it.

[WLS]

Breadboard the charge pump to a couple of stages and check the voltage. This is how it's should be http://www.geofex.com/circuits/+9_to_33.htm


Bill

[tehfunk]

Breadboard the charge pump to a couple of stages and check the voltage. This is how it's should be http://www.geofex.com/circuits/+9_to_33.htm


Bill

Will do, thanks!

[tehfunk]

Breadboard the charge pump to a couple of stages and check the voltage. This is how it's should be http://www.geofex.com/circuits/+9_to_33.htm


Bill

Will do, thanks!

OK, i don't know what this means... but using the circuit outlined on that page which is supposed to generate around 17v... I was able to get voltages around 10-14v using a battery supply of 8.26v. The 14v was only after i let it sit for about 30 seconds to a minute, which brings me to my confusion. When taking measurements, I found that as soon as i started the output voltage would decrease. the higher it started, say 14v the faster it'd decrease. So, basically, the circuit was not supplying a steady increase in voltage. Now, is this normal, and means it's working or is this evidence of a broken max1044?

[WLS]

I believe that the chip is unfortunately crippled, and it will not hold up under load. Two stages should be 17+ volts as you say and my guess would be that the boost is shot. 

Just a guess though!

Try some TC-1044

It might just be my preference, but I think it is just a little more durable than the MAX.


Bill

[Stomp]

Mine was working working fine until I mounted it into an enclosure, stopped working.  Took it apart, & chip was warm to the touch, & voltages were cut in half.  My dc input jack ground was making a connection to the 9v pole by a spec of metal, fried the 1044. I bypassed it & hooked it up direct with 15 volts worked fine, waiting on another chip.

[ShortScaleMike]

An ICL7660 is another more hardy example.

[tehfunk]

Well, i guess that's pretty conclusive.. i mean i was worried. i was checking voltages in the circuit, at the place where i would get boosted voltages on the breadboard, and was getting 7 something volts when in the circuit, so the inability to stand up to the load makes sense... if that's not the case, then that narrows the problem down to only about 4 parts, the diodes and caps, and i checked them again, and they were fine. So, i'll order a new chip.