[BUILD] New FET/RACK Official Help Thread - Please read first post!
- Thread starter mnats
- Start date
Help Support GroupDIY Audio Forum:
Echo North
Well-known member
DC Resistance, not voltage.
Echo North
Well-known member
Doesn't seem bad.
I'd remove Q1. If your signal is back, you have a bad Q1. If not it's something else.
The unit will not compress with Q1 removed, but it'll pass signal fine. Basically it's a mic pre.
Mike
I'd remove Q1. If your signal is back, you have a bad Q1. If not it's something else.
The unit will not compress with Q1 removed, but it'll pass signal fine. Basically it's a mic pre.
Mike
noiro
Active member
- Joined
- Oct 22, 2011
- Messages
- 37
oh I see I will try that in the meantime I'm testing the connector between the main pcb and the attack/release and ratio, those also were force out of their place, man those postal services can be very hard on packages, that one was return from Australia, refunded the person of course. So now I'm just keeping it for me here in my little humble studio. ;-)
- Joined
- May 7, 2017
- Messages
- 32
Hey! I just finished a 1176 Rev. A build and got some problems with the calibration.. The unit is passing audio and is compressing, but it seems that my QBIAS pot (R59) does not affect the Meter / Output voltage like in the 1st calibration step of the calibration guide so i started troubleshooting via the FET/RACK troubleshooting guide..
1) I measured -15.57VDC at CR9 ... Before populating the PCB the Voltage was fine at about -10VDC...
Could this be the first problem?
2) My resistance across S and D of Q1 is about 300Ω with the unit powered OFF.. I read that it should be around 27kΩ.. Is my Q1 faulty?
Further i measured the QBIAS voltage with the following settings:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: None
With your DMM measure DC at TP18 using the chassis as reference . Rotate the Qbias pot (Rev A/D:R59) and note the DCV at each extreme of the pot. Expected negative DC voltages are noted:
The guide recommends to contact the forum if the measurements are off.. So here I am
PS: I Measured Voltages between -1.24VDC and -2.18VDC at the Q1 GATE when turning the QBIAS pot (R59) fully CCW/CW!
Every kind of help is much appreciated! Kind regards,
Leo
1) I measured -15.57VDC at CR9 ... Before populating the PCB the Voltage was fine at about -10VDC...
Could this be the first problem?
2) My resistance across S and D of Q1 is about 300Ω with the unit powered OFF.. I read that it should be around 27kΩ.. Is my Q1 faulty?
Further i measured the QBIAS voltage with the following settings:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: None
With your DMM measure DC at TP18 using the chassis as reference . Rotate the Qbias pot (Rev A/D:R59) and note the DCV at each extreme of the pot. Expected negative DC voltages are noted:
| Test Point TP18 | Rev A |
| EXPECTED | -1 VDC to -1.78 VDC |
| MEASURED | -1.603VDC to -2.837VDC |
The guide recommends to contact the forum if the measurements are off.. So here I am
PS: I Measured Voltages between -1.24VDC and -2.18VDC at the Q1 GATE when turning the QBIAS pot (R59) fully CCW/CW!
Every kind of help is much appreciated! Kind regards,
Leo
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EarthTone
Well-known member
Just finished and calibrated mine last night! SO stoked! Sounds awesome!!! Destroys the UAD plugin.
I have some questions!!
First- I noticed when I touch the output knob I hear a little click sometimes. Not loud, not mechanical, like an electrical click. In operation after you find your setting and stop touching it it’s fine. Seems like a grounding issue? Thoughts?
Then! Very important- How is everyone setting their knobs’ pointers on the faceplate markers? The pointers do not have full travel from start to finish of any of the markings. I currently have my knob pointers installed as per Hairball’s guide. But I’m really confused about the attack and release markings especially. How do you use it like a classic unit from 1~7 if you don’t have full travel of the pots from “OFF” to 7 on each knob? Confused…
Also! I used the Orange Drop caps mod in my build. I installed the mod already and I didn’t listen to it with the original caps that were sent before installing them. Should I have used the Orange Drops? Right now I love how it sounds! So big and crispy. What would change if I installed the stock capacitors in the 4 audio coupling spots? Would the action of the compression change, or would it be more that the tonality would change? Do I have to recalibrate it if I wanted to try the stock caps?
One last thing! One of the #6 screws for the case was missing. What thread pitch should I order if I want to replace it? Also one of the holes for the IEC inlet was not drilled which was annoying but I was able to drill one out by hand without ruining anything.
Overall I LOVE this compressor and had a ball putting it together. The wiring being pre-done is such a great perk! Made it so much easier. The only thing I ever hate doing on builds is crimping connectors. It was a super fun build! I may do another pair around Thanksgiving when they go on sale again!
Thank you Hairball!
I have some questions!!
First- I noticed when I touch the output knob I hear a little click sometimes. Not loud, not mechanical, like an electrical click. In operation after you find your setting and stop touching it it’s fine. Seems like a grounding issue? Thoughts?
Then! Very important- How is everyone setting their knobs’ pointers on the faceplate markers? The pointers do not have full travel from start to finish of any of the markings. I currently have my knob pointers installed as per Hairball’s guide. But I’m really confused about the attack and release markings especially. How do you use it like a classic unit from 1~7 if you don’t have full travel of the pots from “OFF” to 7 on each knob? Confused…
Also! I used the Orange Drop caps mod in my build. I installed the mod already and I didn’t listen to it with the original caps that were sent before installing them. Should I have used the Orange Drops? Right now I love how it sounds! So big and crispy. What would change if I installed the stock capacitors in the 4 audio coupling spots? Would the action of the compression change, or would it be more that the tonality would change? Do I have to recalibrate it if I wanted to try the stock caps?
One last thing! One of the #6 screws for the case was missing. What thread pitch should I order if I want to replace it? Also one of the holes for the IEC inlet was not drilled which was annoying but I was able to drill one out by hand without ruining anything.
Overall I LOVE this compressor and had a ball putting it together. The wiring being pre-done is such a great perk! Made it so much easier. The only thing I ever hate doing on builds is crimping connectors. It was a super fun build! I may do another pair around Thanksgiving when they go on sale again!
Thank you Hairball!
Attachments
Echo North
Well-known member
Hi,
Make sure you start here...
https://help.hairballaudio.com/hc/en-us/articles/360049490733-FET-RACK-Operational-FAQ
Knobs:
All the modern clones (that I know) have the same issue. Back in the UREI days pots commonly rotated 320 degrees. That is not true anymore. 290-295 is more standard. You can set it how you like. Set to the max rotation to the beginning/end or line up the middle. It's up to you, I usually set max rotation to the high setting. For the smalls I set the attack to line up to 6 o'clock in the off pos. Withe the release you can do whatever.Again I generally set everything to the max...except the attack because of the off Switch.
Caps:
It's really subtle, nothing that is going to knock you socks off. If you like it stick with it.
IEC Hole,
That is super weird. Sorry about that! I've never seen that before.
Screws:
The are 6-32 and 1/4" long but can be longer. The head is undercut.
Mike
Make sure you start here...
https://help.hairballaudio.com/hc/en-us/articles/360049490733-FET-RACK-Operational-FAQ
Knobs:
All the modern clones (that I know) have the same issue. Back in the UREI days pots commonly rotated 320 degrees. That is not true anymore. 290-295 is more standard. You can set it how you like. Set to the max rotation to the beginning/end or line up the middle. It's up to you, I usually set max rotation to the high setting. For the smalls I set the attack to line up to 6 o'clock in the off pos. Withe the release you can do whatever.Again I generally set everything to the max...except the attack because of the off Switch.
Caps:
It's really subtle, nothing that is going to knock you socks off. If you like it stick with it.
IEC Hole,
That is super weird. Sorry about that! I've never seen that before.
Screws:
The are 6-32 and 1/4" long but can be longer. The head is undercut.
Mike
EarthTone
Well-known member
Hey @Echo North thank you so much for the personal attention Mike! Gotta hand it to you- The quality of everything from the build guide to the parts to the sound and packaging- Rockin'! So fun to build and now to use.
Thank you so much for the rundown about all this! Yes I did read the operational FAQ page and that was helpful.
Thanks for the knob placement guide. OK sounds good. I'll just set it up like you mentioned, that all seems to make good sense to me.
I think I'll stick with these caps! I love the sound as it is now with the Orange Drops. Maybe if I do another, will try the stock caps.
Thanks for the verification on the screw size and threading. Great- I will order some of those. There is a chance I dropped one when installing the case top and bottom but I haven't been able to locate it yet so wouldn't hurt to have a few spares anyway.
Cheers man looking forward to building the next one sometime down the line! Now that I have heard this one I think I'll end up with at least one more, if not two!
Cheers,
Matt
EarthTone
Well-known member
Guys I just gotta say... My RevD rack version with orange drop mod is just incredible. Sounds so f'ing sick I love it! Thank you Hairball!
Just took my unit out of the box a couple of days ago and finished the build yesterday.
All instructions were clear and easy, everything's packaged nicely - clearly a lot of thought and love was put into this and it shows!
Calibration went through as expected and it seems all values are correct.
But, when passing audio through the unit, there's severe tone degradation - that is, to my ears the unit compresses as it should but affects the signal's tone in a major way.
I've had a look through the components and couldn't locate a specific component out of place or value at a quick glance.
Wanted to ask if anyone has any leads on where to start looking for this.
I've recorded a sample through the unit with the compression off so you can hear what I'm talking about, files attached below.
https://we.tl/t-B0xGVsnbT3
Thanks!
Esh
All instructions were clear and easy, everything's packaged nicely - clearly a lot of thought and love was put into this and it shows!
Calibration went through as expected and it seems all values are correct.
But, when passing audio through the unit, there's severe tone degradation - that is, to my ears the unit compresses as it should but affects the signal's tone in a major way.
I've had a look through the components and couldn't locate a specific component out of place or value at a quick glance.
Wanted to ask if anyone has any leads on where to start looking for this.
I've recorded a sample through the unit with the compression off so you can hear what I'm talking about, files attached below.
https://we.tl/t-B0xGVsnbT3
Thanks!
Esh
Hi! Just finished my rev A fet/rack, mike has been very helpful getting 0dbu into the unit but now i have further issues.
SO i am reading 7.7vac on the input tp + -, My output was reading 1.8vac at the highest output which i believe isnt right, now its reading nothing..
All power supply readings are correct as per the HB website.
The Q bias in CW position is =1.67vdc, and in CCW its reading .96vdc, which is a little off from the -1 VDC to -1.78 VDC on the website.
i am also getting 0vac at TP1, TP15 and TP17.
460ohm across S and D of Q1
I double and triple checked all components whilst building, so am quite confident that they are in the right place. Nothing looks like its missing a soldier joint or any damage to pcbs.
Thanks!
Alex
SO i am reading 7.7vac on the input tp + -, My output was reading 1.8vac at the highest output which i believe isnt right, now its reading nothing..
All power supply readings are correct as per the HB website.
The Q bias in CW position is =1.67vdc, and in CCW its reading .96vdc, which is a little off from the -1 VDC to -1.78 VDC on the website.
i am also getting 0vac at TP1, TP15 and TP17.
460ohm across S and D of Q1
I double and triple checked all components whilst building, so am quite confident that they are in the right place. Nothing looks like its missing a soldier joint or any damage to pcbs.
Thanks!
Alex
Diamondj421
Well-known member
- Joined
- Sep 24, 2016
- Messages
- 164
Finished populating the PCBs for a Rev D last night and got caught in the calibration process. Step 1 & 2 went fine but I'm stuck on Step 3. My multimeter is showing -10db of GR when the attack knob is CW but even with R44 turned all the way, I can't get the meter to read any lower (or higher?) than about -12db. I feel like I had this issue with one of my two previous builds and the issue was Q1 and/or Q11. I could be wrong. I'm certain the 2N5457s were the pair packaged together though. I've checked the resistors and trim pots in the "GR control amp" and "GR meter driver amp" sections. Everything seems to be in place. I was wondering what else should I be looking for to resolve this. Thanks!
When you are at 0 dBu/.775vAC at the output with full CW attack and you turn it back to full CCW (comp off), is the multimeter reading 10 dBu/2.44vAC at the output? I go back and forth adjusting the input and output until those two things measure dead-on at the output before starting to adjust the trimmer.
As far as setting step 1/Q Bias goes, I prefer this same method over the one in the Hairball instructions:
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