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

[Echo North]

Hey Guys,

i can´t finish the Calibration for my 1176 Blue. Everything until here worked fine.

I´m stuck Reduction Meter Tracking Adjusment.

I got the 10 DB drop and could calibrate 20:1 but when i switched to 4:1, 8:1 or 12:1
the Meter went crazy.

I then adjusted the null and these Ratios seem to work fine but 20:1 not.

Thanks for your help

Something must be wrong on your ratio PCB.  Triple check the resistor values and reflow all solder including the connectors.

Mike

 

[bjohnsonaudio]

Nice!

Hey Mike. I have a quick question about some of the resistor that I received. I have all of my resistors stuffed on my main PCB except for R032, R009, R065. My resistor that I have that reads 39 ohms for RO32 is a blue resistor and I notice in the build guide when you show the completed board it is a beige resistor. Is this still correct?

Also for the R009 and R065 my resistors are reading 4.2 ohms. They are the same beige color but I noticed the color coding is different. I have left pictures for you to look at as well.

Thanks!

 

[bjohnsonaudio]

Hey Mike. I have a quick question about some of the resistor that I received. I have all of my resistors stuffed on my main PCB except for R032, R009, R065. My resistor that I have that reads 39 ohms for RO32 is a blue resistor and I notice in the build guide when you show the completed board it is a beige resistor. Is this still correct?

Also for the R009 and R065 my resistors are reading 4.2 ohms. They are the same beige color but I noticed the color coding is different. I have left pictures for you to look at as well.

Thanks!

 

[Echo North]

Beige/blue doesn't matter.  Just depends on what we can get in stock.

What are they 3.9Ω?  Any resistor that low will read higher.  You probes have resistance they are adding to the total.

Super high resistors will measure lower, they are in parallel with your meters input resistance.

Mike

 

[bjohnsonaudio]

Beige/blue doesn't matter.  Just depends on what we can get in stock.

What are they 3.9Ω?  Any resistor that low will read higher.  You probes have resistance they are adding to the total.

Super high resistors will measure lower, they are in parallel with your meters input resistance.

Mike

Yeah it is for the 3.9 M ... my leads are registering at around .4 when I put them together so a 4.2 would make sense right? I can go ahead and solder those on?

 

[Echo North]

Yeah it is for the 3.9 M ... my leads are registering at around .4 when I put them together so a 4.2 would make sense right? I can go ahead and solder those on?

No 3.9M Ω is very different than 3.9Ω.

One second, let me check the kits.

 

[Echo North]

They should be orange, white, green for 3.9M.  You have orange, white, gold?  In the >100K bag?

 

[bjohnsonaudio]

They should be orange, white, green for 3.9M.  You have orange, white, gold?  In the >100K bag?

Yes. They were taped together in the >100k bag

 

[Echo North]

Yes. They were taped together in the >100k bag

That's super weird.  That's a mistake. Sorry about that.

Fill out a missing parts form:
Hairballaudio.com/missing

Mike

 

[bjohnsonaudio]

Hey Mike! So I am on the calibration step of the build and everything has been normal up until the Reduction Meter Tracking adjustment. I get my output to read .775 VAC and then when I switch the attack to off I go to read my Output and I can't seem to get a reading of higher than .82 VAC with my Input. I have my shunt over the two pins that read Normal Operation and I have power and everything else.

Could you please help me figure out what is going on.

Thanks!

 

[Echo North]

Hey Mike! So I am on the calibration step of the build and everything has been normal up until the Reduction Meter Tracking adjustment. I get my output to read .775 VAC and then when I switch the attack to off I go to read my Output and I can't seem to get a reading of higher than .82 VAC with my Input. I have my shunt over the two pins that read Normal Operation and I have power and everything else.

Could you please help me figure out what is going on.

Thanks!

Go through the troubleshoot doc.  See where you are off, that will tell us roughly where the issue is.

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

 

[tele27]

So  I completed my build. But I have nothing coming in thru the audio input.
I did build the power supply first, and the voltages check out. I measured the drop voltages across the transistors base and emitters and they are 0.66  which is close enough to the 0.7 drop. The one exception is Q12. That is measuring 2.4 V
across the base and emitter. Im looking for some direction on troubleshooting.
The polarization of caps checks, the resistor values check.  But when I put a .775 1k tone on the input nothing measures across the input test points. The xlr input legs buzz out okay. So right now I’m kinda lost on the problem.
Thanks







[quote author=Hairball Audio link=topic=63600.msg805567#msg805567 date=1472132620

 

[Echo North]

So  I completed my build. But I have nothing coming in thru the audio input.
I did build the power supply first, and the voltages check out. I measured the drop voltages across the transistors base and emitters and they are 0.66  which is close enough to the 0.7 drop. The one exception is Q12. That is measuring 2.4 V
across the base and emitter. Im looking for some direction on troubleshooting.
The polarization of caps checks, the resistor values check.  But when I put a .775 1k tone on the input nothing measures across the input test points. The xlr input legs buzz out okay. So right now I’m kinda lost on the problem.
Thanks

Have you gone through the troubleshoot doc above?  What did you find?

See if that can confirm for you the trouble stage is where Q12 is.

Mike

 

[bjohnsonaudio]

Go through the troubleshoot doc.  See where you are off, that will tell us roughly where the issue is.

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

Hey Mike, I was going through the troubleshooting guide and everything checked out good until I measured my Amplification Stage.

When measuring AC with my common in the chassis I got the following measurements...

TP 1 = 212.8 mV
TP 2 = 5.77 V
TP 17 = .775 V
Output Transformer Brown = 16.82 V
Output = 16.8 (measuring between the (+) and (-)

I have a 1k sine wave coming from my DAW measuring at .772 VAC and my qbias and power all checked out good.

Let me know your thoughts and thanks for your help!

 

[bjohnsonaudio]

Hey Mike, I was going through the troubleshooting guide and everything checked out good until I measured my Amplification Stage.

When measuring AC with my common in the chassis I got the following measurements...

TP 1 = 212.8 mV
TP 2 = 5.77 V
TP 17 = .775 V
Output Transformer Brown = 16.82 V
Output = 16.8 (measuring between the (+) and (-)

I have a 1k sine wave coming from my DAW measuring at .772 VAC and my qbias and power all checked out good.

Let me know your thoughts and thanks for your help!

I remeasured after resoldering the Q6 transistor and I got some slightly different readings

Above when I said TP 2 ... I mean 15

My brown output transfomer is now 11.6 as well as my xlr output. Everything else was relatively the same. If I don't have my leads on anything my AC V reads around 50 mV

Thanks again

 

[bjohnsonaudio]

I remeasured after resoldering the Q6 transistor and I got some slightly different readings

Above when I said TP 2 ... I mean 15

My brown output transfomer is now 11.6 as well as my xlr output. Everything else was relatively the same. If I don't have my leads on anything my AC V reads around 50 mV

Thanks again

I did the same measurements with the unit biased and I got

TP 1 = 213 mV
TP 15 = 5.03 VAC
TP 17 = 647 mV
Output Transformer Brown = 10.1 V
XLR Output = 10.1 V

I thought that the measurement were a bit high compared to what you have on the troubleshooting document, but not crazy out of control so I measured the VAC for the GR control amp and got these measurements

4:1 = 122 mV
8:1 = 323 mV
12:1 = 900 mV
20:1 = 2.33 V

definitely something weird there right?

 

[JDport]

Greetings builders,

Just finished building a FET/Rack Rev A & D. When installing the "Input" & "Output" control knobs, where do you set them?

If they are set full CCW, and snugged down and 6 o'clock them the min value is at 6 o'clock ( and the max value is 6 (doesn't go to "0").  If set at min value of 8 then my max value is 3 (doesn't go to "0"). Please advise.

Thank you guys,
JD

 

[Echo North]

Greetings builders,

Just finished building a FET/Rack Rev A & D. When installing the "Input" & "Output" control knobs, where do you set them?

If they are set full CCW, and snugged down and 6 o'clock them the min value is at 6 o'clock ( and the max value is 6 (doesn't go to "0").  If set at min value of 8 then my max value is 3 (doesn't go to "0"). Please advise.

Thank you guys,
JD

We recommend lining them up at "0".  The original pots were 320 degrees, most pots are now 295.

Mike

 

[Echo North]

4:1 = 122 mV
8:1 = 323 mV
12:1 = 900 mV
20:1 = 2.33 V

definitely something weird there right?

This is Pad 22?

Seems like you have no compression. 

Hard to say because your measurements are jumping around so that is either a bad solder joint, bad ground connection, or measurement error.

Your last amp stage measurements looked ok. Does it pass clean signal?

Mike

 

[Maxwell.ravitz]

I've recently built your FET/RACK REV D build, and while it's almost working certain things seem funky. I went through the trouble shooting guide and took measurements for each step. I was wondering if you could take a look and start pointing me in the right directions towards getting everything squared away.  Thanks in advance for the help.
-QBias Voltage

TP 18: 0 <> -3.042 VDC

-Amp Stages

TP1: .103 VAC
TP15: 2.07 VAC
TP17: .363 VAC
Output Trans BRN: 6.71 VAC

Output XLR: 6.12 VAC

-GR Control Amp Input

20:1 - .455 VAC
12:1 - .263 VAC
8:1 - .175 VAC
4:1- .96 VAC

-GR Control Amp Output

20:1 - 4.11 VAC
12:1 - 2.39 VAC
8:1 - 1.59 VAC
4:1 - .892 VAC

-GR Control Amp Threshhold

20:1 - -7.33 VDC
12:1 - -4.95 VDC
8:1 - -4.04 VDC
4:1 - -3.28 VDC