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

[Beauchamp]

Hi, I'm putting together a Rev D right now and the CR8 30V zener diode comes with a star lock washer that isn't mentioned in the build guide, where does it go in relation to the other parts? Between the normal washer and the pcb or between the normal washer and the nut? And which piece should the spikes on it be pointing towards?

 

[calleask]

Hi! Bought a 1176rev a and it sounds a bit broken?
Does it sound like its bad calibration or is it worse?

Heres an audio recording of how it sounds
https://pitchbend.se/1176.mp3
https://pitchbend.se/no_1176.mp3

Also on the mp3 with the 1176, after half of it, i turned the output know back and forth and almost nothing happened.
https://pitchbend.se/IMG_4592.MOV

My chain was a stam sa-800g -> adesign pacifica -> 1176
and i tried different outputs from the preamp and different inputs on the 1176.
Do you recognize the sound of it on? Maybe its typical of a broken "something"?

Best, Carl

 

[fallout]

i turned the output know back and forth and almost nothing happened.

Check your grounds.

Check the rest of your voltages against the schematic.

Output pot issue aside, how does the unit sound when GR is turned off?

 

[calleask]

Ok will check the voltages! Got the schematic for that! Thank you!
How do you mean check grounds, for this unit or the others in my rack? And how would you do that?

The unit sounds the same with GR off. Tried everything i can think of, very weird!

 

[fallout]

How do you mean check grounds

Unplug the unit. Look at the schematic, find DC ground on the power supply section and test for continuity at various points of the circuit that should be connected to ground. For instance, one of the outer legs of the output pot should be connected to DC ground according to the schematic. You can also measure continuity to ground @ test point 17 with the output pot fully CCW.

Since it doesnt sound right with GR turned off, I'd troubleshoot the signal preamp and output sections first. With the unit powered on, carefully checking voltages against the schematic in these sections would be my first step in trying to find where things aren't right. It'd be a good idea to check the voltages from the power supply first and work your way back through the input and output sections. You should get approx 30V @ the cathode of CR8 and -10V at the anode of CR9 (power supply).

Did you buy this 1176 as a 'non working'? Depending on your experience level with troubleshooting circuits, you might be better off returning the unit and getting your money back before going down the path of repairing it.

FWIW, the troubleshooting guide on Hairball's website is concise.

https://help.hairballaudio.com/hc/en-us/articles/360045942974-FET-RACK-Troubleshooting-Guide

 

[calleask]

Thanks fallout! Very appriciated!

I found ground in the output, but test point 17 didn't show/beep on my meter.
cr8 and cr9 was the correct voltage

i will try and probe around according to the schematics, alltough a few legs to the components is hard to reach (mounted flush to the pcb). But maybe i can find some other points to measure thats available, can do it a bit more serious later i hope.

I bought it as working, so i guess i'll have to think this through. It would've been nice with an easy fix, but im not sure it will be as easy as i imagined!

thanks again!

 

[fallout]

Thanks fallout! Very appriciated!

I found ground in the output, but test point 17 didn't show/beep on my meter.
cr8 and cr9 was the correct voltage

Remember when measuring to ground at test point 17, your output pot needs to be fully CCW otherwise you'll measure resistance.

i will try and probe around according to the schematics, alltough a few legs to the components is hard to reach (mounted flush to the pcb). But maybe i can find some other points to measure thats available, can do it a bit more serious later i hope.

I'm assuming you're referring to the transistors.. If you follow the schematics, you can take the measurements from the components connected to the transistors terminals (usually a resistor)

I bought it as working, so i guess i'll have to think this through.

I guess it depends on what you paid for the unit and how much time you're willing to invest in troubleshooting it. If you don't have much electronics experience or the desire to troubleshoot, it might be worth getting a refund. The kits aren't very expensive and if you paid more than the kit price, I'd expect a working unit. That said, it's a fairly easy circuit and with some patience you should be able to get it working but might take some effort (disassembling, removing parts, ordering parts.. .etc)

It would've been nice with an easy fix, but im not sure it will be as easy as i imagined!

The fix 'could' be easy but hard to tell without some troubleshooting. It's been a while since I built my 1176 and it looks like the Hairball version eliminates a lot of the off pcb wiring that could be more prone to mistakes.

thanks again!

 

[calleask]

Remember when measuring to ground at test point 17, your output pot needs to be fully CCW otherwise you'll measure resistance.

Yeah it was fully ccw! Does that error indicate something you think?

I'm assuming you're referring to the transistors.. If you follow the schematics, you can take the measurements from the components connected to the transistors terminals (usually a resistor)

I guess it depends on what you paid for the unit and how much time you're willing to invest in troubleshooting it. If you don't have much electronics experience or the desire to troubleshoot, it might be worth getting a refund. The kits aren't very expensive and if you paid more than the kit price, I'd expect a working unit. That said, it's a fairly easy circuit and with some patience you should be able to get it working but might take some effort (disassembling, removing parts, ordering parts.. .etc)

The fix 'could' be easy but hard to tell without some troubleshooting. It's been a while since I built my 1176 and it looks like the Hairball version eliminates a lot of the off pcb wiring that could be more prone to mistakes.

Thanks for the help! I'm gonna speak with the seller and see, i've also had some fun the last hour poking around, maybe its a fun project. Albeit i could build something else instead of repairing!

 

[fallout]

Yeah it was fully ccw! Does that error indicate something you think?

It explains why adjusting the output pot doesnt work but hard it's to say where the error is. Could be something as easy as a bad solder joint from the output pot to ground. You can check to see if the leg of the pot that is supposed to be connected to ground, is in fact connected to ground. I'm not familiar with the current Hairball enclosures but you'll likely have to access the pads for the output pot from the bottom since it's pcb mounted. I'm not sure if it explains why your unit sounds bad as there could be multiple issues. You'd have to troubleshoot a section/issue at a time.

Thanks for the help! I'm gonna speak with the seller and see, i've also had some fun the last hour poking around, maybe it's a fun project. Albeit i could build something else instead of repairing!

That was my point. If you didn't get a deal on the unit, the kits aren't that expensive and might be a fun project to put together yourself. If you overpaid for a unit that is in need of repair, it's probably better to send it back or at least get some money back.

edit * after watching your video in the other thread you posted, it looks like you may have some other issues to solve as well. When you pressed the +8 and +4 buttons (output metering), the meter didn't deflect whatsoever.

Now I'm curious to see what the bottom of the PCB looks like. It'll give you an idea of how well the unit was assembled.