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

[Jettison]

Hope I didn't make it sound like I was out of the woods. 
Searched the other threads but kinda got lost.
I could still use some help with the Q bias trim pot problem.
Anybody out there?

 

[Jettison]

OK. Negative DC voltage is getting all the way to R7, which has a small drop across it, but not to the gate of Q1/R6.
Pulling Q1 and looking for ground...

 

[Echo North]

Then this is the correct thread.

Does the meter work in +4 or +8? 

Get a good signal going through it...like at least 0dbu (0.775VAC) on the output.  Does the meter react in +8 or +4?

Nope, not at all. Just fed it a signal and the meter won't budge at all regardless of how loud of a signal is passed through or what the meter is set to display.

Hmmmm. Sounds like a damaged meter maybe. You have the signal wire harness on there? (Metal Spades).

If those are the terminals underneath the meter then yep.

Send us an email.

 

[Echo North]

OK. Negative DC voltage is getting all the way to R7, which has a small drop across it, but not to the gate of Q1/R6.
Pulling Q1 and looking for ground...

Does this one have output with Q1 in, but no output with Q1 out?

If so, you have a bad Q1.

 

[Jettison]

Q1 is good and I got the Q bias set. Just had to fix a couple solder pads/traces.
I set the null too after a pad fix as well.

Now I'm stuck on the tracking adjust procedure-
On step 4 turning up the input only gets me 1vac  at the output (attack off)
Also turning the compression on and of yields no change in output voltage. There is no compression  happening.

 

[Echo North]

Q1 is good and I got the Q bias set. Just had to fix a couple solder pads/traces.
I set the null too after a pad fix as well.

Now I'm stuck on the tracking adjust procedure-
On step 4 turning up the input only gets me 1vac  at the output (attack off)
Also turning the compression on and of yields no change in output voltage. There is no compression  happening.

With the new wiring, really the only issue can be solder, component mix up, or killing a semi on installation.  I'd go through the side chain (GR amp) and ratio board touching up anything that looks weird.  There is some PAD21/22 measurement stuff in these threads. If you still have issues after touching up the PCB or can't find the pad 22/21 stuff, let me know.

Mike

 

[Echo North]

Revision A question via email:

I calibrated one last night and everything went great. When I started the second one, the q bias didn't seem to change the voltage at the output xlr. However I noticed when I adjusted the q bias the meter would change. Also the output control changed the voltage at the output xlr. Any suggestions on where I should begin searching? I checked all solder points and components.

Seems like the qbias is probably working but the Q1 FET isn't responding to it. You might want to check solder joints on Q1. Possible it's dead too.

If you can, without damaging the pads, try swapping Q1 and Q11. If you can set the qbias and the meter stops reacting...the Q11 (currently your Q1) is dead.

Mike

 

[seb121314]

Hi,
i have a pair of these in revision D and i have the active stereo link in it. I have a problem to make them work in stereo, the one who receive the signal from the link have more gain reduction then the one who send. i try changing the cable and re calibrate the two but nothing changed.it's pretty problematic when i do parallel compression the stereo image change due to the difference of GR.
bye the way these are really cool product and fun to build !

 

[Echo North]

Hi,
i have a pair of these in revision D and i have the active stereo link in it. I have a problem to make them work in stereo, the one who receive the signal from the link have more gain reduction then the one who send. i try changing the cable and re calibrate the two but nothing changed.it's pretty problematic when i do parallel compression the stereo image change due to the difference of GR.
bye the way these are really cool product and fun to build !

Hi,

This is addressed in the link build guide.

The linking happens before the side chain, so all of the tolerance difference in the attack pots and release pots change things.

Read the bottom of this page:
http://www.hairballaudio.com/blog/resources/build-guides/fetrack-newbractive-link

You need to tweak the four controls slightly for perfect imaging.

Mike

 

[seb121314]

oh okay sorry i didin't read that part i will try this thanks !

 

[Jettison]

Got it.
The trace from C17 to the junction of R36, R37, and Q7 was open so the GR amp wasn't getting signal from the output of the preamp.
Fixed that and all is well. Both my units are cal'ed and ready to go. 
T'was fun except for the few pads that needed help.

Thanks man

 

[Hxcplayer]

I know this isn't really an issue to post about and I know I am going to sound like a mega noob but, I was curious as to what the roles of capacitors C1, C7, C8, and C10 are?

If anybody can give a brief explanation as to how each of them affects the rest of the audio circuit would be great.

I can't find anything on the web that gives an explanation of what a capacitor does in an audio unit (aside from the caps in the power supply acting as reservoir caps to maintain current *correct me if im wrong*)

I will be trying out the orange drops soon for my rev. D so I figured it would be nice if I could understand what each capacitors is doing to the signal.

But just curious about the those specific ones i named earlier.

Thanks!

 

[Echo North]

I know this isn't really an issue to post about and I know I am going to sound like a mega noob but, I was curious as to what the roles of capacitors C1, C7, C8, and C10 are?

If anybody can give a brief explanation as to how each of them affects the rest of the audio circuit would be great.

I can't find anything on the web that gives an explanation of what a capacitor does in an audio unit (aside from the caps in the power supply acting as reservoir caps to maintain current *correct me if im wrong*)

I will be trying out the orange drops soon for my rev. D so I figured it would be nice if I could understand what each capacitors is doing to the signal.

But just curious about the those specific ones i named earlier.

Thanks!

They are coupling caps. The connect two sections of the circuit together and block unwanted DC from one section from moving to the next. Since they are in series with the signal and the audio passes through them they have noticeable impact on the sound.

Deeper:
http://diy.ecpaudio.com/p/some-notes-on-coupling-capacitors.html

Mike

 

[Hxcplayer]

I know this isn't really an issue to post about and I know I am going to sound like a mega noob but, I was curious as to what the roles of capacitors C1, C7, C8, and C10 are?

If anybody can give a brief explanation as to how each of them affects the rest of the audio circuit would be great.

I can't find anything on the web that gives an explanation of what a capacitor does in an audio unit (aside from the caps in the power supply acting as reservoir caps to maintain current *correct me if im wrong*)

I will be trying out the orange drops soon for my rev. D so I figured it would be nice if I could understand what each capacitors is doing to the signal.

But just curious about the those specific ones i named earlier.

Thanks!

They are coupling caps. The connect two sections of the circuit together and block unwanted DC from one section from moving to the next. Since they are in series with the signal and the audio passes through them they have noticeable impact on the sound.

Deeper:
http://diy.ecpaudio.com/p/some-notes-on-coupling-capacitors.html

Mike

Cheers Mike!

Btw I got the T-pad, haven't installed it yet though.

Thanks for the awesome service!

 

[Diamondj421]

Hey guys,
Finished my 1176 Rev D build and am having trouble with the q bias calibration. I have everything set as recommended but turning R59 from max (CW) to its minimum only results in a -.5 Db change. Has anyone had/dealt with this problem before?

 

[Echo North]

Hey guys,
Finished my 1176 Rev D build and am having trouble with the q bias calibration. I have everything set as recommended but turning R59 from max (CW) to its minimum only results in a -.5 Db change. Has anyone had/dealt with this problem before?

What is the DC V range at pad 18 and then pad 7 (using chasis as common) as you rotate the Qbias?

Mike

 

[Diamondj421]

Hey guys,
Finished my 1176 Rev D build and am having trouble with the q bias calibration. I have everything set as recommended but turning R59 from max (CW) to its minimum only results in a -.5 Db change. Has anyone had/dealt with this problem before?

What is the DC V range at pad 18 and then pad 7 (using chasis as common) as you rotate the Qbias?

Mike

At pad 18 it reads 0 to -73.4 VDC and at pad 7 it's reading -1 to -71.8 VDC. 

 

[Echo North]

What is the DC V range at pad 18 and then pad 7 (using chasis as common) as you rotate the Qbias?

Mike


At pad 18 it reads 0 to -73.4 VDC and at pad 7 it's reading -1 to -71.8 VDC.

That'a not really possible.  Try gain and check your meter. Should be 0 to a couple volts negative.

You have -10VDC at that power supply test point right?

 

[Diamondj421]

That'a not really possible.  Try gain and check your meter. Should be 0 to a couple volts negative.

You have -10VDC at that power supply test point right?

So I have the DMM set to the 2V setting and pad 18 is reading 0 to -.092 and pad 7 is reading 0 to -.089.  Am I still far off?  Where is the power supply test point? This is all new to me. My Lola build was assemble and record.

 

[Hxcplayer]

So I have the DMM set to the 2V setting and pad 18 is reading 0 to -.092 and pad 7 is reading 0 to -.089.  Am I still far off?  Where is the power supply test point? This is all new to me. My Lola build was assemble and record.

I think he's talking about the Diode CR9, turn your unit on and measure it in DC and see if you get -10VDC./

Check the build guide and scroll down to the bottom to see how to test it

Link: http://www.hairballaudio.com/blog/resources/build-guides/fetrack-v2-build-and-calibration-guide

Wait for Mikes response though, that might not be it. Just tryin to help!

Good Luck