[BUILD] New FET/RACK Official Help Thread - Please read first post!

[Echo North]

When I try turning the screw when GR is off it will go to about half way between -3 and -1 GR and then pop back down the -20.

If I turn it all the way on it goes to -20 and no matter what I do to turn it it won't go anywhere.

I would guess you have an issue in the GR Section.  Check all of your values and soldering.  Make sure you see appropriate drops across BJT base emitter junctions (about half a volt) that'll tell you if you have any busted ones.

Mike

 

[bjohnsonaudio]

I would guess you have an issue in the GR Section.  Check all of your values and soldering.  Make sure you see appropriate drops across BJT base emitter junctions (about half a volt) that'll tell you if you have any busted ones.

Mike

When you say appropriate drop what do you mean?

 

[bjohnsonaudio]

When you say appropriate drop what do you mean?

Nevermind, I think I figured it out. When I turned the Tracking adj all the way counter clockwise I get the -10 when I have the attack fully clockwise and it is at 0 when I am turned off. I believe that is correct right? My output is .775 VAC and my input is 2.44 VAC ... I might just be a dummy ???

 

[Echo North]

Nevermind, I think I figured it out. When I turned the Tracking adj all the way counter clockwise I get the -10 when I have the attack fully clockwise and it is at 0 when I am turned off. I believe that is correct right? My output is .775 VAC and my input is 2.44 VAC ... I might just be a dummy ???

Your output w/ GR ON is 0dB (0.775) set by the output.
Your output w/ GR OFF is +10dB (2.44) set by the input.

Cal page should be correct.

 

[bjohnsonaudio]

Your output w/ GR ON is 0dB (0.775) set by the output.
Your output w/ GR OFF is +10dB (2.44) set by the input.

Cal page should be correct.

Yeah that is what i am reading.

 

[bjohnsonaudio]

Yeah that is what i am reading.

I may have had a end of the day brain fart and everything was fine. Would it make a difference the position of the Tracking Adj Resistor? Because it was fully CW and then I put it fully counter clockwise and it seemed to sort it out

 

[Echo North]

I may have had a end of the day brain fart and everything was fine. Would it make a difference the position of the Tracking Adj Resistor? Because it was fully CW and then I put it fully counter clockwise and it seemed to sort it out

If it's calibrated it's good.

 

[jgremlin]

Ok looking for some help again. I've completed a REV D partial kit w/orange drop caps mod. Powered up fine, Q Bias went fine, Null adjust also seemed to go fine. But when I get to reduction meter tracking I hit a dead end because it seems as though we're not compressing at all.

I went back over everything and low and found a mistake Seems I installed C17 backward. I replaced C17 with a new cap installed correctly but the results are still the same. No compression.

When I compare volts around the board to the typical values on MNATS RevDVolts pdf, all are normal until I get to the GR Control Amp section. Instead of seeing 4.54 on the + side of C17, I'm at 8.48. And of course most of the values downstream of that are also high.

Did I fry other things with the first C17 cap being in backward? If so what?

 

[scott2000]

When I compare volts around the board to the typical values on MNATS RevDVolts pdf, all are normal until I get to the GR Control Amp section.

Was it calibrated after the cap mishap??

 

[jgremlin]

Was it calibrated after the cap mishap??

Q Bias and Null adjust set fine but still unable to do reduction meter adjust because I can't get it to compress.

 

[scott2000]

Q Bias and Null adjust set fine but still unable to do reduction meter adjust because I can't get it to compress.

Not sure about your voltages being off.  As far as the compression goes....Have you read this ....???

https://groupdiy.com/index.php?topic=62551.0

 

[Echo North]

Ok looking for some help again. I've completed a REV D partial kit w/orange drop caps mod. Powered up fine, Q Bias went fine, Null adjust also seemed to go fine. But when I get to reduction meter tracking I hit a dead end because it seems as though we're not compressing at all.

I went back over everything and low and found a mistake Seems I installed C17 backward. I replaced C17 with a new cap installed correctly but the results are still the same. No compression.

When I compare volts around the board to the typical values on MNATS RevDVolts pdf, all are normal until I get to the GR Control Amp section. Instead of seeing 4.54 on the + side of C17, I'm at 8.48. And of course most of the values downstream of that are also high.

Did I fry other things with the first C17 cap being in backward? If so what?

Did you go through this:

http://www.hairballaudio.com/blog/resources/post/fetrack-troubleshooting-guide

You likely have an issue with your pad 21 voltages, Pad 22 voltage or CR2 voltages.  Figure out which is bad and we can proceed from there.

You definitely didn't fry anything with that cap.

Mike

 

[alex_dempsey]

Hello!

I'm building a Rev A 1176 and the build was great! Im up to the calibration process and having some troubles. I am up to setting the Q Bias step and got a little stuck. My readings in the first step with the input were normal but my readings on the output aren't. I was able to adjust the output nob and get the 2.75 VAC it asked for with all of the components in the correct positions. But as I adjust the Q Bias, it doesn't change my reading on the output test leads. Could this be a mistake I made somewhere in the build? Or is it something simpler that I am missing. Help please!!

Alex

 

[Echo North]

Hello!

I'm building a Rev A 1176 and the build was great! Im up to the calibration process and having some troubles. I am up to setting the Q Bias step and got a little stuck. My readings in the first step with the input were normal but my readings on the output aren't. I was able to adjust the output nob and get the 2.75 VAC it asked for with all of the components in the correct positions. But as I adjust the Q Bias, it doesn't change my reading on the output test leads. Could this be a mistake I made somewhere in the build? Or is it something simpler that I am missing. Help please!!

Alex

I wouldn't worry about the output too much, as long as you have similar readings. The output pot tolerence has a lot of effect on those readings, we're going to update that part.

What are you pad18 DC readings on either end of the Qbias trimmer?

Mike

 

[alex_dempsey]

I wouldn't worry about the output too much, as long as you have similar readings. The output pot tolerence has a lot of effect on those readings, we're going to update that part.

What are you pad18 DC readings on either end of the Qbias trimmer?

Mike

I am reading 2.75VDC from ground to Pad18.

From what I understand in the theory of operation section, without the Q Bias calibrated properly, nothing will work properly so I want to make sure its right. Adjusting the setting on the trim pad does not effect the reading across the + and - at the output like the instructions say it should.

 

[Echo North]

I am reading 2.75VDC from ground to Pad18.

From what I understand in the theory of operation section, without the Q Bias calibrated properly, nothing will work properly so I want to make sure its right. Adjusting the setting on the trim pad does not effect the reading across the + and - at the output like the instructions say it should.

Positive voltage? Sure that's not negative?

 

[alex_dempsey]

Positive voltage? Sure that's not negative?

Yes it is negative my bad!!

 

[Echo North]

Yes it is negative my bad!!

Ya that's way too much voltage. If you have a Rev A, you need something like -1.00 VDC at one side of the trimmer and -1.75VDC at the other side. You'll never get compression with what you're seeing.

Stuff to check:

C21 oriented correctly
CR2 and CR3 oriented correctly
C19 and C20 oriented correctly
All resistor values and soldering on the ratio pcb
Resistors and caps on the attack/release PCB
R60/R83 values/soldering and the QBias trimmer.

Mike

 

[jgremlin]

Did you go through this:

http://www.hairballaudio.com/blog/resources/post/fetrack-troubleshooting-guide

You likely have an issue with your pad 21 voltages, Pad 22 voltage or CR2 voltages.  Figure out which is bad and we can proceed from there.

You definitely didn't fry anything with that cap.

Mike

Here's my voits

TP22
4:1 - .311AC
8:1 - .628AC
12:1 - .957AC
20:1 - 1.48AC

TP21
4:1 - -1.83DC
8:1 - -2.74DC
12:1 - -3.82DC
20:1 - -6.73DC

CR2
4:1 - -1.82DC
8:1 - -2.72DC
12:1 - -3.80DC
20:1 - -6.69DC

Also I checked with headphones and I'm getting audio test tone to negative leg of C17,

 

[Echo North]

Here's my voits

TP22
4:1 - .311AC
8:1 - .628AC
12:1 - .957AC
20:1 - 1.48AC

TP21
4:1 - -1.83DC
8:1 - -2.74DC
12:1 - -3.82DC
20:1 - -6.73DC

CR2
4:1 - -1.82DC
8:1 - -2.72DC
12:1 - -3.80DC
20:1 - -6.69DC

Also I checked with headphones and I'm getting audio test tone to negative leg of C17,

Anode of CR2 is AC.  Are you measuring DC there?