Trem Lune No sound- Fixed (now working)

[theundeadelvis]

Just boxed up a Lune and I'm not getting any sound. The led blinks and reacts to the controls fine, but I get no sound output.

Here are my IC voltages. I noticed all the readings on the TL072 seem to half what they should be. I used the commonsound layout.
TL072
1-1.46v
2-1.43v
3-1.59v
4-0
5-1.58v
6-1.46v
7-1.46v
8-9.4

RC4558 (these jump all over the place)
1-4-7v
2-4-7v
3-0
4-0
5-4-7v
6-4-7v
7-0-13v?
8-9.3v

Any ideas? Thanks in advance!

[theundeadelvis]

Found a reversed 10uf cap and now voltages seem better on the TL072. Still no sound? When I use an audio probe on the RC4558 I get nothing at any pin?

[theundeadelvis]

I get plenty of sound at pin 1 of the TL072 but none at pin 6 after it goes through the VTL5C2. Does this indicate a bad VTL5C2?

[theundeadelvis]

Solved my problem! The opto-thingy was in backwards too. Sorry to take up thread space! Let this be a lesson, double check those polarities!!!

[robbiemcm]

You sound like you had better luck diagnosing the problem on yours than I have on mine ( http://www.diystompboxes.com/smfforum/index.php?topic=61559.msg483500#msg483500 ). All my signal is disappearing after the LDR (same point as pin 6) in mine (I used an LED and LDR instead of the VTL5C2), but it's definitely present when it goes in to the LDR (same point as pin 1).  Do you think you could try using your audio probe on pin 6 and telling me what you get, i expect you'd get the volume fluctuation due to the fact it's a tremolo.

[theundeadelvis]

Robbie,

I will definitely do this for you as soon as I can (this afternoon). That is the exact problem I had and it was the polarity of the LED side of the optocoupler, so double check your LED. I always have trouble remembering which side of an LED is which and have to go to GGG and check the tech pages  . I post my findings for you ASAP.

[robbiemcm]

The thing about using the LED/LDR rather than the optocoupler is that I can see the LED is functioning perfectly, so that one has already been ruled out. I'm going to try getting a new LDR, but the value I need is not very easy to get hold of here so I was just hoping I might be able to get a bit more of an idea about what's happening in the meantime.

[theundeadelvis]

Robbie,

I just checked it out and there is audio at pin 6. It is much quieter than pin 1 and it is pulsating. Where are you located?

[robbiemcm]

Thank you very much for checking that for me.

I live in Perth, Western Australia. I know of one shop that sells the one I need, I'm just a bit too busy to go in to the city and get it right now. Hopefully I'll be able to pick one up in the next week and see if that solves my problem.