Ch.1 on ART Pro VLA 2 is not working

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Mikeyrad

New member
Joined
Mar 27, 2013
Messages
4
Hey guys, been a lurker for some time and finally wanna post!

Anyway, i got a vla 2 for pretty cheap and so i decided to start modding it to see how great i can make this comp sound. So i open her up and get to work. Well the first 2 opamps i remove dont come off to easy for some reason and i end up breaking off a few pads!(ive never had so much trouble before removing these before!) So anyway, i read the datasheets for the opamps and see how and where i need to fix this so it will still work. Then i socket them and put in new ones. I did both channels at once, and really only struggled with the first 2. Forgot to mention they were NE5532 and i replaced them with OP275. So i turned this thing on today to see if anything would blow, ch.2 works and ch.1 will not pass audio! While it was powered on i started feelings around and noticed one of the resistors (27ohm 1w) was hot! I looked at the VLA1 schemo and determined the resistor is part of the power supply. Btw ch.2 resistor was not hot. 

So im trying to locate a schemo for the VLA2 and cant find it anywhere, does anybody have it? Can anybody shed some light on why that resistor is getting hot? Sorry for the rambling and thanks for the help!
 
Cant help with schemo, but check and see if any of the opamps get hot...if they do they might be backwards

also look for any solder joints that are shorting out (A bright light helps with this.)
 
I did check that and none of the opamps are hot or backwards. I could have possibly not repaired a pad good enough or maybe a pin got bent when I put them in the sockets? I know the positive and negative voltage on the pins are good, none of those pads had issues.
 
I'd look for solder bridges, as abechap024 said. Especially when doing repairs like lifted pads. Pull the opamp out of that channel and see if the resistor stops heating up.
 
You can refer to the Art Pro VLA (1) schematic. It's almost the same and worked well enough when I modded mine. Some opamp numbering might be slightly different IIRC and a few elco caps are definitely numbered differently. But that's about it. The basic circuit is the same. You do have to trace the board a bit though.

Schematics of the VLA (1) are in this thread.
http://www.groupdiy.com/index.php?topic=47664.0
The PSU is a bit further down.
The 27R 1W should be for the tube filament.

There are traces on both sides of the PCB. I'd also check whether there is enough solder connecting the Opamp socket pins to the traces on the upper side of the board.
 

Latest posts

Back
Top