TijuanaKez
Well-known member
- Joined
- Jul 19, 2011
- Messages
- 51
Hey guys,
I built an 1176 revD with the hairball kit and mnats board and it passes audio and compresses but it doesn't sound right.
It has way more gain in the preamp stage when a/b'd with an origional and the g/r stage seems to react somewhat randomly to some signals. It also produces clicking and popping noises with heavy g/r. My UAD plugin version doesn't exibit any of these behaviours (haven't a/b'd the last 2 symptoms that with a real unit though).
Anyways I have double checked all the components with a DMM in circuit and %90 are reading correct. I started pulling the ones that didn't but they were all reading correct values when pulled out of circuit so i stopped as it was making things messy. Best get to the source of the problem.
The first thing I can see is that all voltages test points are reading correct except for the preamp stage which is way out compared to the schematic.
The first and most obvious is the C pin on Q3 is only reading 5V but it should be 12V according to the schematic. Same with Q14 pin E
Following the schematic: 30V -> R17(6.8k) -> R14(22k) -> Q3 pin C (12.58V)
I tested R17 and R14 and they are the correct values but testing each side of the resistors along the way I get this
30V -> 30V[R17]23.85V -> 23.85V[R14]5V -> 5V [Q3 pin C]
It would seem something is going wrong at R14 but it reads 22K exactly as it should.
Can someone help me solve this mystery? My electronics knowledge is fairly limited.
Here are some other Readings
SCHEMATIC MY UNIT
C B E C B E
Q2 1.75 1.05 0.54 1.5 0.71 0.21
Q3 12.58 -- 1.15 5.0 1.5 0.85
Q14 -- -- 12.0 30.0 5.0 4.39
And I'm getting exactly 30V and -10V at the test points in the power supply section.
I built an 1176 revD with the hairball kit and mnats board and it passes audio and compresses but it doesn't sound right.
It has way more gain in the preamp stage when a/b'd with an origional and the g/r stage seems to react somewhat randomly to some signals. It also produces clicking and popping noises with heavy g/r. My UAD plugin version doesn't exibit any of these behaviours (haven't a/b'd the last 2 symptoms that with a real unit though).
Anyways I have double checked all the components with a DMM in circuit and %90 are reading correct. I started pulling the ones that didn't but they were all reading correct values when pulled out of circuit so i stopped as it was making things messy. Best get to the source of the problem.
The first thing I can see is that all voltages test points are reading correct except for the preamp stage which is way out compared to the schematic.
The first and most obvious is the C pin on Q3 is only reading 5V but it should be 12V according to the schematic. Same with Q14 pin E
Following the schematic: 30V -> R17(6.8k) -> R14(22k) -> Q3 pin C (12.58V)
I tested R17 and R14 and they are the correct values but testing each side of the resistors along the way I get this
30V -> 30V[R17]23.85V -> 23.85V[R14]5V -> 5V [Q3 pin C]
It would seem something is going wrong at R14 but it reads 22K exactly as it should.
Can someone help me solve this mystery? My electronics knowledge is fairly limited.
Here are some other Readings
SCHEMATIC MY UNIT
C B E C B E
Q2 1.75 1.05 0.54 1.5 0.71 0.21
Q3 12.58 -- 1.15 5.0 1.5 0.85
Q14 -- -- 12.0 30.0 5.0 4.39
And I'm getting exactly 30V and -10V at the test points in the power supply section.
