All things G1176 - the new "repost" thread.

[beaversaber]

Here's my DC voltages for the transistors:
B          C          E
q2 1.038 1.727 0.556
q3 1.727 11.91 1.144
q4 11.91 29.71 11.32
q5 3.453 27.91 3.211
q6 16.28 27.91 28.46
q7 16.28 28.46 29.1
q8 29.71 16.29 15.69
q9 0.7         15         15.68
q10 13.66 12.9         12.9

q12 4.39         14.86 3.84
q13 14.86 29.72 14.24
q14 3.393 16.47 2.824
q15 16.46 29.72 15.9

I have not actually measured the output of each stage, but both input and output knobs seem to be working fine.  I will check this next.

When I try to calibrate, I send a tone out with the unit in bypass, output at about halfway, adjust the input knob so the tone is coming back at 0.
I then attempt to turn the qbias trimmer until I see a 1db drop in level, but nothing happens

You have a problem around Q5. The voltages from here to Q8/Q9 are not right. Check the resistors. Do not bother with calibrations until you have the circuit working correctly.

I checked all the resistors in this section, replaced the 100ohm resistor (r36), and this is what i came up with:
B C E
q2 1.038 1.727 0.556
q3 1.727 11.91 1.144
q4 11.91 29.71 11.32
q5 3.449 27.9         3.191
q6 16.19 27.9    28.46
q7 16.19 28.46 29.1
q8 29.72 16.19 15.58
q9 0.6         14.87 15.57
q10 13.66 12.9         12.9

q12 4.39         14.86 3.84
q13 14.86 29.72 14.24
q14 3.393 16.47 2.824
q15 16.46 29.72 15.9

not much different from before, and the unit is still not compressing.  passing audio just fine, input and output gain work fine, but qbias pot as no effect on the signal.  I guess I'll try replacing the transistors q5,6,7,8,9 next?

 

[gswan]

Until you've fixed the problem that upsets the bias around Q5, you do not have a working ciruit, so calibration and passing signal through it is pointless. Look for solder shorts, reversed components and incorrect resistor values around the Q5-Q9 section of the circuit.

 

[beaversaber]

Until you've fixed the problem that upsets the bias around Q5, you do not have a working ciruit, so calibration and passing signal through it is pointless. Look for solder shorts, reversed components and incorrect resistor values around the Q5-Q9 section of the circuit.

Just replaced all the caps in that section (checked all resistor values yesterday), checked for shorts with a magnifying glass, is there any chance the problem could be coming from somewhere else in the circuit? I'll keep looking

 

[beaversaber]

Blargh.  Just about out of ideas.  I've double and triple checked resistors/caps/solder points in the line amp (q5-q9) section of the circuit and cannot find anything wrong.  Also tried replacing the 2n2925 and removing the sockets that I had under the mpsw06 (not sure why this would make a difference, but I've been trying everything)

Here's a picture of the section....

 

[beaversaber]

Just double checked the transistor pinouts for Q5-Q9 as well.  Everything checks out okay

 

[gswan]

This is a different circuit from the one I am using, I'm referring to the Mnats Rev J. I don't have the circuit for the board you have shown in the photograph and since I can see component differences I can't comment further on it.

 

[beaversaber]

Ah I see. 

The board I'm doing is MNats rev f/g and the schematic can be found here:
http://mnats.net/files/1176REVFG_SCHEMATIC.pdf

I've also been doing some reading to try and figure out why the bias wouldn't be right on the transistors in this section, and I've found that each transistor needs a base-bias and load resistor to work correctly.  It looks to me like R29 is the base-bias resistor and R31 is the load resistor for Q5.  Is this correct? And if so, why would the bias be incorrect on this transistor even if both of those resistors are okay and there are no issues before Q5 in the circuit?

 

[mac]

Hey Beaver,
Maybe post this over in the Rev F thread as well - http://www.groupdiy.com/index.php?topic=33834.0

Might find others who can provide further assistance and comparison voltage readings in that part of the circuit for this board.

you will find it! Good luck...

Mac

 

[beaversaber]

Hey Beaver,
Maybe post this over in the Rev F thread as well - http://www.groupdiy.com/index.php?topic=33834.0

Might find others who can provide further assistance and comparison voltage readings in that part of the circuit for this board.

you will find it! Good luck...

Mac

Thanks, I checked it out over there but it looks like nobody's posted in a couple months  ??? I'll give it a shot anyways

 

[beaversaber]

Just replaced all the transistors q5-q9 in the line amp section to no avail.  This morning I probed around with my signal tracer thing and signal when i have GR disabled, no signal goes to the GR control section of the pcb, and when i engage it, signal is sent to the section, so it seems like that is working properly.

So at this point, the unit is passing audio, but the voltages are a bit odd in the Q5-Q9 (line amp) section of the circuit and it is not compressing.  I've replaced all caps, transistors, and double checked resistor values/looked for shorts in that section.

Not really sure where to go from here

 

[intercorni]

Hello.
I look a little confused on the schematic
My question is: if the Attack-Switch is off, which connects pin 22? Black or green?

Thx, Cornel

 

[mac]

Hi Intercorni,
when pad 22 is taken to ground then the compressor is in "bypass" or "GR off" as per the gyraf rotary version, or also can be wired as the attack switch "off" position as per the original which is the same thing.

Are you building on mnats Revision J boards, with the rotary meter switch?

Mac

 

[intercorni]

Hello,

thx for the answer. I build the Gyraf version.

 

[schrobbelbop]

Hi,

Since i've finished my G1176 REV J and dual 1176 REV-D i've been comparing these 2.
The rev-d has much more mid'lows and deep end. The REV J is much more transparant.

i've sweept them with smaart analyzer. the REV J seems starting to cut low freqs under 125
but only -1DB @ 50hz. But it is audible. Now it seems that if i turn the input all way up and
output down, the response becomes more like the rev-d.
The input on the board is flipped in phase i guess that would not be the issue?
Can i drive my input section harder on the REV J? so that i have a hotter input stage?
What would u guys suggest?
They both have EA in/out trannies.

 

[beaversaber]

Just replaced all the transistors q5-q9 in the line amp section to no avail.  This morning I probed around with my signal tracer thing and signal when i have GR disabled, no signal goes to the GR control section of the pcb, and when i engage it, signal is sent to the section, so it seems like that is working properly.

So at this point, the unit is passing audio, but the voltages are a bit odd in the Q5-Q9 (line amp) section of the circuit and it is not compressing.  I've replaced all caps, transistors, and double checked resistor values/looked for shorts in that section.

Not really sure where to go from here

Anyone around?  I also just replaced all the transistors in the gr control section

 

[beaversaber]

Just replaced all the transistors q5-q9 in the line amp section to no avail.  This morning I probed around with my signal tracer thing and signal when i have GR disabled, no signal goes to the GR control section of the pcb, and when i engage it, signal is sent to the section, so it seems like that is working properly.

So at this point, the unit is passing audio, but the voltages are a bit odd in the Q5-Q9 (line amp) section of the circuit and it is not compressing.  I've replaced all caps, transistors, and double checked resistor values/looked for shorts in that section.

Not really sure where to go from here

Anyone around?  I also just replaced all the transistors in the gr control section

...Hurro? ???

 

[Dr-Mbogo]

My dear Pro's!

I built 2 1176 with Mnats Boards rev. H and these devices sound just fine. (Thanks to Jakob, Mnats and everyone who is around)...
Unfortunately with both devices something is wrong. The release pot is affecting the vu-meter.
I conducted the following test: A bassdrum loop into the compressor. The gain reduction has been set to -5dB with the input control. With a fast release time the VU-Meter reads -5dB. Everything is fine. But: As soon as I put the release pot to slower release times the VU-Meter reads -20dB (and even more) if the scale would go further.


Thanks in advance for any idea and best regards.

Chris

 

[aclac]

My dear Pro's!

I built 2 1176 with Mnats Boards rev. H and these devices sound just fine. (Thanks to Jakob, Mnats and everyone who is around)...
Unfortunately with both devices something is wrong. The release pot is affecting the vu-meter.
I conducted the following test: A bassdrum loop into the compressor. The gain reduction has been set to -5dB with the input control. With a fast release time the VU-Meter reads -5dB. Everything is fine. But: As soon as I put the release pot to slower release times the VU-Meter reads -20dB (and even more) if the scale would go further.


Thanks in advance for any idea and best regards.

Chris

I had same problem Mnats rev. J even without signal. First... be sure, that You have calibrated right your comp. I had read all posts here, but there is no much information about this problem. But, my opinion was lastly, that FETs an audio circuit and VU meter circuit should be like 'matched'.  I changed Q10, and my problems was solved, as I wroted here (Reply #3104 ). Good luck!

- Aclac

 

[Dr-Mbogo]

Thanks for your reply aclac!

I just calibratet the unit again from scratch. FETts are matched. I even checked all voltages. These are ok. Q10 ist ok too. Otherwise I would have no movement of the meter in gain reduction mode. Right?

Because I have no symmetrical input signal, I shorted pin 1 and 3 of the input and the output connection during calibration. Is this ok? Because when I put the 0dB sine wave into the input, I get different signals on pin 2 and 3 at the output. Is this normal?

I am frustrated 

No one here with a similar problem?

Chris

 

[trapiche2]

Thanks for your reply aclac!

I just calibratet the unit again from scratch. FETts are matched. I even checked all voltages. These are ok. Q10 ist ok too. Otherwise I would have no movement of the meter in gain reduction mode. Right?

Because I have no symmetrical input signal, I shorted pin 1 and 3 of the input and the output connection during calibration. Is this ok? Because when I put the 0dB sine wave into the input, I get different signals on pin 2 and 3 at the output. Is this normal?

I am frustrated 

No one here with a similar problem?

Chris

Hello!
Can you try with a 1 kHz tone??
The drum has a quick attack and possibly the VU does not indicate....
good luck!!