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

[Diamondj421]

Ya that doesn't really help if readings are inconsistent and bobbing around.

If you have a missed up unit it could be anything. Swapped resistor values or cap values can create low pass filters. Bad solder joints can alter feedback networks or how gain stages work.

These are tough ones.  If you don't want to send it in for repair, you'll just have to poke through the gain stages comparing it to your other unit. Again try lower and higher frequencies and see if you can pin point where it differs and look there.

Ya cheep DMM's are pretty worthless above 1kHz.

Mike

I really wanted to have the satisfaction of completing one of these but I think at this point I've tried everything I can on my end. Plus, I had the feeling of satisfaction when I thought I finished it before. haha. I have a big gig this Friday night so Monday, I'll send it in. I'll keep trying to figure it out until then but come Monday, she's all yours!

 

[clockworkonions]

I doubt it. Did you ruin a solder pad when you flipped C21?.

If you have no AC voltage at pad 22 in GR mode you have an issue with your ratio PCB probably.  Look at the schematic...there is a linear path from pad 15, where the AC V is, to pad 22.  Where does it die?

Mike

I found it! The GR switch on the attack knob is faulty. Both sides stay open whether the switch is on or off. It's grounding my GR input even when it's turned on.

 

[Echo North]

I found it! The GR switch on the attack knob is faulty. Both sides stay open whether the switch is on or off. It's grounding my GR input even when it's turned on.

Send us an email...we'll send you a new one.

 

[Einestad]

I'm not sure what you mean.  You have pads that are filled with solder?  Can you post an image here?

Solved the problem however i noticed that in the build guide the pcb for ratio is in some pictures mounted with the CN2 pin connecter towards the vu meter and in some towards the main PCB. Im in the final assemby stage so need to know in which direction the ratio PCB should be so i can connect the 6 pin between CN2 to CN3.

Thanks

 

[Echo North]

Solved the problem however i noticed that in the build guide the pcb for ratio is in some pictures mounted with the CN2 pin connecter towards the vu meter and in some towards the main PCB. Im in the final assemby stage so need to know in which direction the ratio PCB should be so i can connect the 6 pin between CN2 to CN3.

Thanks

This is correct.

http://library.hairballaudio.com/images/fetrack/assembly_pushbutton_switches_vu_meter_rear.jpg

 

[Einestad]

This is correct.

http://library.hairballaudio.com/images/fetrack/assembly_pushbutton_switches_vu_meter_rear.jpg

So should the pin connector face towards the vu meter or the main PCB?

 

[Echo North]

So should the pin connector face towards the vu meter or the main PCB?

Like the image I linked to.  Connector on the side with the silkscreen for the connector. Facing the main PCB. If it's on the other side the cable won't reach.

 

[mrbobbailey]

There are 2 10Ω and 2 10K resistors on the PCB.  Official BOM:

http://mnats.net/files/fetrack/fet_rack_link_doc_v1.2.pdf

Mike

Thanks Mike.  I had not soldered yet and found my "swap" mistake. 

 

[mrbobbailey]

Greetings.

Is it just me or is there some switch-a-roo going on in some of the photos regarding the install of the Ratio PCB? 

In "Part 3. Final Assembly" guide, the photo following install of the Plastite screws into the XLR connectors, there is a photo of the Ratio PCB in which the CN2 is facing the VU meter.  Later in the guide is shows that it is installed with CN2 facing the Main PCB as it should (i'm guessing) in order to all the wiring bridge between CN2 and CN3.

I made the same mistake on both builds.

 

[Echo North]

Greetings.

Is it just me or is there some switch-a-roo going on in some of the photos regarding the install of the Ratio PCB? 

In "Part 3. Final Assembly" guide, the photo following install of the Plastite screws into the XLR connectors, there is a photo of the Ratio PCB in which the CN2 is facing the VU meter.  Later in the guide is shows that it is installed with CN2 facing the Main PCB as it should (i'm guessing) in order to all the wiring bridge between CN2 and CN3.

I made the same mistake on both builds.

Ya look at the conversation right above ours.

I'll clarify it in the guide.

 

[fiddlefro]

Hi There,
Just walking through the calibration settings of the Fet Rack Rev A that I just built.
When adjusting meter settings, the little meter adjustment trim on the front panel is acting really odd.  The needle jumps around almost randomly when it's being adjusted, and comes to rest at what seems like a random location.  It's very heard to get it to end up anywhere in particular...
Any chance the trim is busted? 
thanks
Drew

 

[Echo North]

Hi There,
Just walking through the calibration settings of the Fet Rack Rev A that I just built.
When adjusting meter settings, the little meter adjustment trim on the front panel is acting really odd.  The needle jumps around almost randomly when it's being adjusted, and comes to rest at what seems like a random location.  It's very heard to get it to end up anywhere in particular...
Any chance the trim is busted? 
thanks
Drew

Could be. Could also be a poor solder joint or short.

You can pull it out and test it with the ohm setting on your DMM.

 

[csavetman]

Question about the calibration process. I completed the calibration on the FET rack and everything went well.
Then I started thinking. When taking DMM measurements at the output XLR, does it matter if there's a physical xlr cable plugged into the output, or if I just use the test points I soldered in on either side of the connector, without the cable plugged in?
Would it affect the readings or calibration at all?

thanks
Carlos

 

[Echo North]

Question about the calibration process. I completed the calibration on the FET rack and everything went well.
Then I started thinking. When taking DMM measurements at the output XLR, does it matter if there's a physical xlr cable plugged into the output, or if I just use the test points I soldered in on either side of the connector, without the cable plugged in?
Would it affect the readings or calibration at all?

thanks
Carlos

You should load the output with a load that is realistic to what it would usually be plugged in to.  The DMM loads it, but not the same as say your A/D converter input.

Mike

 

[csavetman]

I finished building 2 FET racks. Both calibrated -no problems.
One of them works fantastic. The other one, passes audio, but I'm getting no audible compression at all.
Unit powers on fine and VU meter shows compression happening, but switching the attack knob from off to on, I'm hearing no change. (No momentary change in audio level as compression is turned on, like on the working unit.)

VU meter responding to ratio button switching as well, again,  just no audible change.
The attack knob seemed to be working during calibration, as going between CCW off and full CW, was giving me alternate AC voltage values on the DMM. (.775v / 2.44v)

Visually, everything looks good (no missing solder points that I can see)

I'm at a loss. Could it be a bad FET. (Q1 or Q11)?
Would swapping either or both out require a re calibration? I have the GR and meter FET's that originally came with the units as extra since I ordered a stereo matched set afterwards.

thanks
Carlos

 

[Echo North]

I finished building 2 FET racks. Both calibrated -no problems.
One of them works fantastic. The other one, passes audio, but I'm getting no audible compression at all.
Unit powers on fine and VU meter shows compression happening, but switching the attack knob from off to on, I'm hearing no change. (No momentary change in audio level as compression is turned on, like on the working unit.)

VU meter responding to ratio button switching as well, again,  just no audible change.
The attack knob seemed to be working during calibration, as going between CCW off and full CW, was giving me alternate AC voltage values on the DMM. (.775v / 2.44v)

Visually, everything looks good (no missing solder points that I can see)

I'm at a loss. Could it be a bad FET. (Q1 or Q11)?
Would swapping either or both out require a re calibration? I have the GR and meter FET's that originally came with the units as extra since I ordered a stereo matched set afterwards.

thanks
Carlos

No idea.  If you're getting compression during the calibration where you set the 10dB drop, you're getting compression.  If Q1 was dead you'd never get the 10dB drop, that's the unit compressing and working correctly.

Something else is going on. Feed it a steady tone with GR OFF, then turn it on...if you see a drop on the output...that's compression.

Does the release work?

Mike

 

[csavetman]

No idea.  If you're getting compression during the calibration where you set the 10dB drop, you're getting compression.  If Q1 was dead you'd never get the 10dB drop, that's the unit compressing and working correctly.

Something else is going on. Feed it a steady tone with GR OFF, then turn it on...if you see a drop on the output...that's compression.

Does the release work?

Mike

Just fed it a steady 1k sine wave. Went from attack full CCW off to on, NO change at all in output volume. (Vu meters did respond)

Carlos

 

[csavetman]

Just fed it a steady 1k sine wave. Went from attack full CCW off to on, NO change at all in output volume. (Vu meters did respond)

Carlos

So I decided to recalibrate the unit to try to see what's up. I reset all the trimmer pots to their initial state, and now i can't get the Q bias  adjust to drop the AC voltage. It stays at 2.75VAC, after moving the adjust all the way from CW to CCW.

Carlos


Any thoughts?

Carlos

 

[csavetman]

So I decided to recalibrate the unit to try to see what's up. I reset all the trimmer pots to their initial state, and now i can't get the Q bias  adjust to drop the AC voltage. It stays at 2.75VAC, after moving the adjust all the way from CW to CCW.

Any thoughts?

Carlos

Figured it out. Bad Q1 FET. Changed out Q1 and Q11 with the ones that came with the kit. Re-calibrated.
Working now.

Carlos

 

[ffarrell]

Wrong Thread sorry.