Hi
I've a 1176 to fix in my bench... It's a long story, somebody built it, my customer bought it, some years later he brings to a "technician" to fix something (I don't know what, the customer says he doesn't remember), and then the "tech" brings it back to customer with much less gain and some kind of hiss (white noise?) going up with the output pot.
The board looks like home etched, not so bad, it has varnish or something (Flux? there are some yellow drops near the solder points...) that makes it so sticky in the solder side, it says Rev G near the holes for the input transformer, and it was using 5532 for the input. Looking further in the mnats site, it looks like a Rev H board, I'm not sure because the holes for Q8 & Q9, but the rest of the board looks like the same.
About the working state, It passes audio, it compress, but the customer says he used to work with the input and output pots pointing to 10 O`clock or so, and after the "tech" he has to raise them all the way up. I didn't make so serious measurements, but with both pots up and feeding it about 0dbus it gives me something like +24dbus or so (read in my mackie 24/8 meter) So I'm not really worried about that, I think there's level enough to work.
The hiss is what really cares me, tracing the signal I found it starts somewhere between Q2 & Q3, both of them BC107B, I replaced them and Q4, but the noise is still there. Voltage looks fine according to gyraf site's schematic, resistor values looks fine too, grounding looks ok, the only point from the board going to ground is through the input xlr (Actually I ran a wire from GND point to the mains earth and it made some kind of ground loop or something that made the unit Hum). I tried an OEP for the input and it's the same...
Any ideas? Maybe replace all the transistors? Thanks in advance
