Sound Skulptor forums

Build help and troubleshooting => LA502 Optical Compressor => Topic started by: Dan on February 05, 2023, 02:24:24 AM

Title: All LEDs on - RESOLVED
Post by: Dan on February 05, 2023, 02:24:24 AM

2nd LA502 build.  First was flawless.

LEDs all turn on at startup and ALL stay on.
V+ and V- read +/- 16V
With 1KHz 1VAC input - signal is sent in Bypass
But no signal when switched to IN, no response with gain pot

R2 = 0.7 VAC with 1VAC Input
R5 = 0.0 V  -  that's not good, right?? - is it possible OC1 is backwards?? Can i tell without pulling it?  Step 11 is confusing - "direction is given by the beveled side on the left." but there's 2 beveled sides - Should the lettering be facing the front??  Or do i look elsewhere for issues?  I can't see any other problems.

TP1 = 0 VDC
TP2 = 15.24 VDC
TP3 = 13.48 VDC

R36 = 2.5V and 16V (right)
R37 = 2.48V and 0.4V



thanks for any help !!

Title: Re: All LEDs on - help
Post by: JPK on February 06, 2023, 10:58:33 AM

TP2 = 15.24 VDC
TP3 = 13.48 VDC
This is the issue. TP2 should be 0VDC.
Check around U5, look for bad solder joints, forgotten joints, ...

Title: Re: All LEDs on - help
Post by: Dan on February 06, 2023, 07:35:18 PM

Sure enough !!  I found a bad solder joint on U5.  Not sure how i missed that.

Re-flowed a bunch of the solder joints, and it came to life.  Calibrated fine. 
I believe all is working now.  Woohoo !!! 


disregard the rest .... except the THANK YOU !!!

Now...
TP2 = 0 VDC
TP1 = 0 VDC
TP3 = 0 VDC  :-\

V+ -  still 16V

In case it helps.  No gain, but looks like compression is working. 

THANK YOU for the help !!