Gator debug

[MmmPedals]

Ibuilt a Gator from here: http://gaussmarkov.net/wordpress/circuits/gator-clone/
I subbed tl071 for the lm308 (and jumped pins 5 and 8 together)
Subbed a ca3080 for lm3080
The effect works but the output is very low. I need to crank my amp to hear it.
Could the substitutions be the problem or should look elsewhere?

[Mark Hammer]

Um, an LM308 requires a compensation cap between pins 1 and 8, whereas a TL071 is already compensated and does not require anything between pins 1 and 8.  Don't know where pin 5 comes into play.  Is that a typo?

Substitution of an LM3080 for a CA3080 simply means that a different company makes a nickel on the part, and nothing more.

[Marcvv]

Ibuilt a Gator from here: http://gaussmarkov.net/wordpress/circuits/gator-clone/
I subbed tl071 for the lm308 (and jumped pins 5 and 8 together)
Subbed a ca3080 for lm3080
The effect works but the output is very low. I need to crank my amp to hear it.
Could the substitutions be the problem or should look elsewhere?

Hi,

I have build the gator from the PAIA kit a few years back and ran into some  problems. I remember posting about the remarks made by Scott Lee from PAIA to solve this.
For me that worked.   http://www.diystompboxes.com/smfforum/index.php?topic=72027.0


Marc

[Mark Hammer]

Interesting. I built mine using the PAiA layout, and had no problems getting it running.  Of course, the PAiA layout calls for a 4136 (the Anderton "chip of choice"), rather than a pair of tL072s.

[MmmPedals]

Um, an LM308 requires a compensation cap between pins 1 and 8, whereas a TL071 is already compensated and does not require anything between pins 1 and 8.  Don't know where pin 5 comes into play.  Is that a typo?

Substitution of an LM3080 for a CA3080 simply means that a different company makes a nickel on the part, and nothing more.

Wasnt a typo. I thought  the pins were reverse. my mistake. I did remove the cap though. I'll save it for another project. 

Interesting. I built mine using the PAiA layout, and had no problems getting it running.  Of course, the PAiA layout calls for a 4136 (the Anderton "chip of choice"), rather than a pair of tL072s.

I did have this issue. i needed to add a resistor between the junction of r12 and r13 to v+.
I still have volume and tone suck from it. I will continue debuging tom.

[MmmPedals]

Here are the voltages using a 9.33V battery
IC1-(tl072 subbed for a lm308 and left c2 off the layout)
1- .15
2- 4.68
3- 1.01
4-0
5- .15
6- 4.67
7- 9.37
8- 0

IC2 (ca3080 subbed for lm3080)
1- 0
2- 4.65
3- 4.66
4- 5.1
5- 4.62
6- 4.63
7- 9.35
8-0

IC4
1- 4.65
2- 4.65
3- 4.65
4- 0
5- 4.65
6- 4.57
7- 5.8
8- 9.33

IC-5
1- 4.9
2- 4.65
3- 4.63
4- 0
5- 4.63
6- 4.65
7- 4.22
8- 9.32

[MmmPedals]

Do those voltages look right? I am getting Very low volume and tone suck with the "level" cranked.

[Scruffie]

Here are the voltages using a 9.33V battery
IC1-(tl072 subbed for a lm308 and left c2 off the layout)
1- .15
2- 4.68
3- 1.01
4-0
5- .15
6- 4.67
7- 9.37
8- 0

TL072? Is that a typo?

And why do you have voltage on Pin 5... shouldn't be connected, I think your problem lies here.

[MmmPedals]

Yeah thats a typo. should be tl071
I will check out why there is voltage there.

[MmmPedals]

I get that .15 volts on pin 5 of the tl071 only when the IC is in the socket. There are no solder bridges. I tried 2 other tl071's.
Anything else look off?

[PRR]

R13 must return to GND; yet your voltages "make sense" if R13 is going to Vref.

Did you buy the board or do it your own way?

why do you have voltage on Pin 5

TL071 has offset trims on those pins. I ferget the internal details but a small voltage is probably correct and insignificant.

[MmmPedals]

I etched the board myself from the file at the above site.
Do you mean to say the voltages are wrong since r13 does go to ground? Which voltages?

[PRR]

Apologies. I misread what R13, R14, and D1 do to IC5a. IC5 pin 1 4.9V is probably correct.

I've stared at that plan for a long time, and don't expect to understand it soon. Especially flipping from plan to your voltage notes.... there's just too much stuff here to cross-check.

Since it works for others, I would assume a builder mistake. Bad solder joint. Wrong part. Even an etching-flaw (whisker-short or crack-open). A bright light and a magnifier may be more productive than working numbers to deduce the problem.