[BUILD] 1176LN Rev D DIY

[TijuanaKez]

Hey there peoples.
So I got jack of the meter bulbs always blowing on my (old version) FET RACK and decided to fit some yellow LEDs and a 5W resistor to the 30VAC out of the transformer.
As I was testing adding more leds to even out the light, wire slipped and found itself falling precisely onto the only tiny piece of exposed terminal on the mains plug that wasn't completely covered by heat shrink.
Sparks flew, circuit breaker flipped, fuse in the mains plug on the unit blew.
As one might expect, now it's not happy. Meter reacts to turning the knobs with nothing plugged in and only faint signs of audio at the output.
All voltages seem within range as per the schematic (with voltages added)
What's my next best bet?
Shotgun replace all the transistors except the matched pair and hope for the best?
Or is there something else I should try first?

 

[sjdowo]

hi, does anyone have a full part number for the GR meter function switch? need a replacement. rotary 3-position switch.

 

[zzzzz]

hi, does anyone have a full part number for the GR meter function switch? need a replacement. rotary 3-position switch.

Alpha SR2612F-0304-18R0B-D8-N fits

 

[TijuanaKez]

...coming back to this and reaching out to anyone with a bit of intuition here...
1176 RevD mnats 2.2:
- Passes clean audio with R23 (output) in the first %5 of travel, then cuts out into hissy distortion after that eventually nothing but DC offset.
Compression works as expected if R23 is within this %5
- Input knob can actually drive the level fairly high at the output still with compression off, so it's the position of R23 matters, not the level going into line amp.
- Looking for dry solders and warm components probing with my finger, I noticed there's a test point up above C10. Contacting this with a solid finger press and creating some good old body capacitance earthing fixes the problem entirely.
- It's not likely a dry solder because pushing around on the pcb with no electrical contact does nothing.

Can anyone care to have a stab at such a riddle? Should I just replace all the transistors in the lineamp and go from there?
thanks in advance!

 

[TijuanaKez]

...coming back to this and reaching out to anyone with a bit of intuition here...
1176 RevD mnats 2.2:
- Passes clean audio with R23 (output) in the first %5 of travel, then cuts out into hissy distortion after that eventually nothing but DC offset.
Compression works as expected if R23 is within this %5
- Input knob can actually drive the level fairly high at the output still with compression off, so it's the position of R23 matters, not the level going into line amp.
- Looking for dry solders and warm components probing with my finger, I noticed there's a test point up above C10. Contacting this with a solid finger press and creating some good old body capacitance earthing fixes the problem entirely.
- It's not likely a dry solder because pushing around on the pcb with no electrical contact does nothing.

Can anyone care to have a stab at such a riddle? Should I just replace all the transistors in the lineamp and go from there?
thanks in advance!

Okay well don't I feel silly now. Scraping away the paint at the points where the XLR connectors earth to the chassis turns out to be quite important!

 

[leo-666]

According to schematics Mnats Rev A has Chassis Ground and Second Ground.
Where second ground is connected to a chassis ground ?
Or they are completely isolated ?

 

[TijuanaKez]

According to schematics Mnats Rev A has Chassis Ground and Second Ground.
Where second ground is connected to a chassis ground ?
Or they are completely isolated ?

View attachment 140933

If it's same as REV D, it's a wire from the -ve leg of that cap to somewhere close by on the chassis.