Carlsbad Reverb Help!

[seagurt]

I have posted this @ Madbean as well.

I bought a kit from Mammoth, the Carlsbad reverb, a unit that uses the Belton Brick BTDR2.

I completed the build 2 days ago, but the pedal isn't working.

I have built a few pedals, but I am far from complete in my knowledge of electricity. I am still learning, and hope this will be another good learning opportunity.

Here is the parts list, and build document I worked from.
https://moodysounds.com/wp-content/uploads/2014/09/carlsbad-reverb-assembly-instructions.pdf

Here are the symptoms;

The pedal has been tried in and out of the enclosure
The LED lights up, and I am getting power to the board (more on that later)
I am getting signal through on bypass, but nothing when engaged.
The switch appears to be fine, as do my Jacks and battery snap/Dc jack

Voltages read as follows;

J4- J201
G- -0.00v
S- .28v
D- 1.05v

J5- LM78L05acz
1-VOUT- 5v
2-GND- 0v
3-VIN- 9.58v

Q1-MPSA18
C- .52v
B- 0.01v
E- .34v

U2 (IC) TL072CP
1- 7.96v
2- 8.64v
3- 8.65v
4- 9.58v
5- 8.66v
6- 8.66v
7- 7.09v
8- 0v

Belton Brick BTDR-2H
1- 5v
2- 0v
3- .26v
4- 0v
5- .04
6- .04

I understand some of these numbers, and from my limited knowledge, it seems that maybe something is off with my J201, and/or MPSA18.

I do have an audio probe, and plan on throwing that at this problem later on if I can find the time. I thought I would try my luck, and post here, as I have always found it helpful to do so.

Here is a link to a few pictures of the PCB, with off board components, unboxed.
http://imgur.com/gallery/5ISB0

Feel free to offer any suggestions.

I appreciate the time and capabilities of all who chime in.

[samhay]

Unfortunately, Mammoth do not include a schematic in the build document, which is going to make this much more difficult. I suggest you email them and ask for one.

J4 and Q1 look odd. What voltages do you get on the socket pins if you remove J4 and Q1?

All pins except 4 and 8 of the op-amp (U2) should be at about half supply voltage - 4.5-ish V.  As there is no schematic, I can't tell you which resistors set the bias, but you could try re-flowing your solder joints (do this with the sockets empty and leave the BTDR joints alone). Also, check for solder bridges/shorts, ideally with a magnifying glass.

[seagurt]

So I emailed about a schematic, I will post one when I get it.

On J4, just the socket pins, with J201 removed I am getting;
G- 0.0v
S- 0.0v
D- 1.24v

On Q1, just the socket, MPSA18 removed, I am getting;
C- .87v
B- .01v
E- .00v

I have reflowed my solder joints, and inspected with a magnifying glass.

The fact that I should be getting half voltage on my IC is clearly a problem, as pin 4 is reading 9.58v, and pin 8 is reading 0v ( I am counting from the top left corner, counter clockwise, back up to the right corner, as the datasheet indicates the pins this way.)

I will keep looking over the board, and my joints, and if I do get any additional info, I will post it.

Thanks again.

[duck_arse]

do you have a spare TL072? if so, take out the one fitted to your board, throw it away, and put the new know good one in so the pin 1 pip on the IC faces downwards, to match the silk screen. then try the effect again, report back.

[seagurt]

do you have a spare TL072? if so, take out the one fitted to your board, throw it away, and put the new know good one in so the pin 1 pip on the IC faces downwards, to match the silk screen. then try the effect again, report back.

That was indeed the issue. Confirmed by Mammoth as well. I replaced the TL072 CP with a TL072 CN I had lying around (appropriate substitute.).

Thanks for all the help, and to all those who replied!

[spacejail]

Hey, I just ordered one in the mail and was wondering if mammoth ever sent you anything about the schematics, and if so are you able to post it? Thanks!

[seagurt]

Hey, I just ordered one in the mail and was wondering if mammoth ever sent you anything about the schematics, and if so are you able to post it? Thanks!

I did ask for a schematic, but wasn't provided one. You may have better luck asking. Since I resolved my issue quickly, there was no real need to send me the schematic.

[spacejail]

Much Thanks, ill try and contact them.