EUC

Re: [BUILD] 1176LN Rev D DIY
« Reply #5460 on: April 18, 2018, 02:07:48 PM »
Yes I did check grounds but I'll give them another look over


weiss

Re: [BUILD] 1176LN Rev D DIY
« Reply #5461 on: April 20, 2018, 03:49:12 PM »
does anybody know how i have to wire this older H Pad?
i can't see +/- on the markings..

anyone?  ???
"We're gonna have a good time tonight - Let's calibrate, it's all right!"

scott2000

Re: [BUILD] 1176LN Rev D DIY
« Reply #5462 on: April 20, 2018, 04:15:35 PM »
I don't have one....found this though????

https://groupdiy.com/index.php?topic=20058.1340

If I see something , I'll post...I'm sure Mike will jump in after the bump.....

you have this board???

weiss

Re: [BUILD] 1176LN Rev D DIY
« Reply #5463 on: April 20, 2018, 08:24:34 PM »
I don't have one....found this though????

https://groupdiy.com/index.php?topic=20058.1340

If I see something , I'll post...I'm sure Mike will jump in after the bump.....

you have this board???


oh yes!! exactly what i have :) :) although i'm still not sure about the J2 connection on the right..  ???
"We're gonna have a good time tonight - Let's calibrate, it's all right!"

scott2000

Re: [BUILD] 1176LN Rev D DIY
« Reply #5464 on: April 20, 2018, 09:08:54 PM »
I hope you figure it out...

This one post said....

If you aren't using the Altran you will have to refer to your particular transformer datasheet. That is one reason why the polarity of these early boards is not marked, while the current ones supplied by Hairball - which are only designed for the Altran - are.

ilfungo

Re: [BUILD] 1176LN Rev D DIY
« Reply #5465 on: April 22, 2018, 07:52:14 AM »
Hi
C3 and C6 are 200pf mica.
I've 250pf mica caps, could work?
Thanks!

Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5466 on: April 22, 2018, 12:48:22 PM »
Hi
C3 and C6 are 200pf mica.
I've 250pf mica caps, could work?
Thanks!

I think that would fine.
Hairball Audio, LLC
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Re: [BUILD] 1176LN Rev D DIY
« Reply #5467 on: April 23, 2018, 09:34:38 PM »
I'm working on a build of the Rev D that I started from scratch using my own boards. I used mnats Rev D schematic as reference and copied his layout quite a bit minus the power supply as I'm building a dual unit and have a single supply for both channels. I initially had no trouble with it and recall being able to complete the first calibration step but I've since tidied up the wiring a bit and now my preamp section doesn't seem to be preamping.
If I input a .776VAC 1Khz sine I get about 100mV at the positive input of the board with the input attenuator up to max. I'm using a stepped attenuator that I made myself so that may be why it's not 129mV at midpoint as suggested by the Hairball troubleshooting guide.
My input transformer is a Lundahl 1540 in 2:1 step-down configuration. With the input attenuator at max I get 776mV at the + transformer input and ~100mV at + output of transformer. Not sure if this is too low and the cause of the problem.

Following the troubleshooting guide but with input and output controls at max my readings are:

TP1 = ~100mV AC
TP15 = ~110mV AC
TP17 = ~110mV AC
Output TX Brown = 2V AC

So it seems like the Line Amp is working. I checked DC voltages for the preamp transistors and they all seem to be within tolerance

Q2 - C=1.77V,  B=1.02V,  E=0.49V
Q3 - C=12.52V,  B=1.77V,  E=1.13V
Q14 - C=30.11V,  B=12.52V,  E=11.89V

My Q-bias voltage at Pad 18 is -3.1VDC fully CCW and goes to 0VDC fully CW and affects the voltage at Pad 15.
Q1 gate voltage is -2.6VDC.
I'm thinking there's a problem with Q1 or my input transformer/attenuator but before I take everything apart to test it I thought I'd see if anyone had a second opinion.

Also I may have an issue with my grounding. I have the main pcb ground wired to the chassis at the IEC ground point and with power off I'm getting 0ohms from ground to chassis everywhere, but when powered on it's almost an ohm on the main board and goes negative at 0V on the psu. Is that normal?
« Last Edit: April 25, 2018, 07:40:18 PM by trashcanman »

Matt C

Re: [BUILD] 1176LN Rev D DIY
« Reply #5468 on: June 08, 2018, 10:38:22 AM »
I have an 1176 that I built years ago that generally seems to be working well, but I recently measured the ratios and they are quite a bit higher than they should be.  4:1 was more like 7:1, 8:1 was 11:1, 20:1 was 33:1, etc. 

I checked the resistor ladders around the ratio switch and they all looked fine, which makes me think the issue is in the gain reduction control amp that is fed by the ratio switch.  But again no obvious issues there.  I did notice that the GR control amp loads down this resistor ladder quite a bit, so the signal levels at those switch nodes drop significantly compared to when GR is switched off, but maybe that's normal?  If not maybe the hfe of those GR amp transistors is too low?

Anyone run into this problem? I know I can just modify the ratio resistors to get the ratios I need, but when testing that out I had to change them so much that I'm suspicious there's a larger problem.

Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5469 on: June 11, 2018, 01:52:34 PM »
I have an 1176 that I built years ago that generally seems to be working well, but I recently measured the ratios and they are quite a bit higher than they should be.  4:1 was more like 7:1, 8:1 was 11:1, 20:1 was 33:1, etc. 

I checked the resistor ladders around the ratio switch and they all looked fine, which makes me think the issue is in the gain reduction control amp that is fed by the ratio switch.  But again no obvious issues there.  I did notice that the GR control amp loads down this resistor ladder quite a bit, so the signal levels at those switch nodes drop significantly compared to when GR is switched off, but maybe that's normal?  If not maybe the hfe of those GR amp transistors is too low?

Anyone run into this problem? I know I can just modify the ratio resistors to get the ratios I need, but when testing that out I had to change them so much that I'm suspicious there's a larger problem.

I've always found the ratios to have a small sweet spot (3-8db GR maybe).  Too close to zero and you're hitting the knee, in this case your ratios look too low.  Too much GR and your FET saturates making the GR way higher.

Mike
Hairball Audio, LLC
DIY Parts and Kits
http://hairballaudio.com/shop

Top secret stuff and upcoming releases:
http://facebook.com/hairballaudio
http://twitter.com/HairballAudio/


Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5470 on: June 11, 2018, 01:54:52 PM »
I'm working on a build of the Rev D that I started from scratch using my own boards. I used mnats Rev D schematic as reference and copied his layout quite a bit minus the power supply as I'm building a dual unit and have a single supply for both channels. I initially had no trouble with it and recall being able to complete the first calibration step but I've since tidied up the wiring a bit and now my preamp section doesn't seem to be preamping.
If I input a .776VAC 1Khz sine I get about 100mV at the positive input of the board with the input attenuator up to max. I'm using a stepped attenuator that I made myself so that may be why it's not 129mV at midpoint as suggested by the Hairball troubleshooting guide.
My input transformer is a Lundahl 1540 in 2:1 step-down configuration. With the input attenuator at max I get 776mV at the + transformer input and ~100mV at + output of transformer. Not sure if this is too low and the cause of the problem.

Following the troubleshooting guide but with input and output controls at max my readings are:

TP1 = ~100mV AC
TP15 = ~110mV AC
TP17 = ~110mV AC
Output TX Brown = 2V AC

So it seems like the Line Amp is working. I checked DC voltages for the preamp transistors and they all seem to be within tolerance

Q2 - C=1.77V,  B=1.02V,  E=0.49V
Q3 - C=12.52V,  B=1.77V,  E=1.13V
Q14 - C=30.11V,  B=12.52V,  E=11.89V

My Q-bias voltage at Pad 18 is -3.1VDC fully CCW and goes to 0VDC fully CW and affects the voltage at Pad 15.
Q1 gate voltage is -2.6VDC.
I'm thinking there's a problem with Q1 or my input transformer/attenuator but before I take everything apart to test it I thought I'd see if anyone had a second opinion.

Also I may have an issue with my grounding. I have the main pcb ground wired to the chassis at the IEC ground point and with power off I'm getting 0ohms from ground to chassis everywhere, but when powered on it's almost an ohm on the main board and goes negative at 0V on the psu. Is that normal?

Line amp seems broken. TP15 should be around 2VAC with GR off (0dB/1kHz input).  Pull Q1 see if that fixes TP15.

Mike
Hairball Audio, LLC
DIY Parts and Kits
http://hairballaudio.com/shop

Top secret stuff and upcoming releases:
http://facebook.com/hairballaudio
http://twitter.com/HairballAudio/

Mikolaj

Re: [BUILD] 1176LN Rev D DIY
« Reply #5471 on: June 13, 2018, 12:20:32 PM »
I'm building a dual 1176 rev d compressor rotary version using Hairball printed circuit boards.
On step three calibrating the meter I  short pad 22 to ground as per video and zero the meter. When i remove the ground i would expect a -10 db drop on the meter. The needle does not move.
Pad  22 has .22 volts ac. and pad 21 has -6.9 volts
Can any one help with a starting point to solve  this problem
Thanks
Mickey

Mikolaj

Re: [BUILD] 1176LN Rev D DIY
« Reply #5472 on: June 13, 2018, 07:31:15 PM »
Solve the problem. qbias was off

Shattersignal

Re: [BUILD] 1176LN Rev D DIY
« Reply #5473 on: June 25, 2018, 04:55:44 PM »
Start buy measuring the DC voltage at pad 18 as you rotate the qbias. It should go from 0VDC to some negative value like -2.2VDC.

Use the CT/0V of the power supply as your common.

Mike

Hi there!  I'm helping a buddy with a Rev A build.  We are having difficulty with calibration step 1.  We are seeing a bias voltage range of between -1.67v and past -3v with the sweep of the Q Bias pot--there seems to be no way to set this bias correctly, as we cannot achieve the correct voltage within the range provided by the pot.  No voltage reduction is observable on the output VU meter as the bias is adjusted.  Here's what we've tried, so far:

--We've installed a 5k pot in R59,
--We've installed new, and HFE matched transistors in Q12 and Q13,
--We've re-flowed all the solder joints in the Attack and Release signal path.

Are there other areas we ought to explore to get the GR circuit engaged and the bias point set correctly?

Thanks a ton!!
Producer, Engineer, Score Composer

Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5474 on: June 25, 2018, 10:23:33 PM »
Hi there!  I'm helping a buddy with a Rev A build.  We are having difficulty with calibration step 1.  We are seeing a bias voltage range of between -1.67v and past -3v with the sweep of the Q Bias pot--there seems to be no way to set this bias correctly, as we cannot achieve the correct voltage within the range provided by the pot.  No voltage reduction is observable on the output VU meter as the bias is adjusted.  Here's what we've tried, so far:

--We've installed a 5k pot in R59,
--We've installed new, and HFE matched transistors in Q12 and Q13,
--We've re-flowed all the solder joints in the Attack and Release signal path.

Are there other areas we ought to explore to get the GR circuit engaged and the bias point set correctly?

Thanks a ton!!

This is the Rev D thread.  What version is your Rev A PCB?

Mike
Hairball Audio, LLC
DIY Parts and Kits
http://hairballaudio.com/shop

Top secret stuff and upcoming releases:
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http://twitter.com/HairballAudio/

Shattersignal

Re: [BUILD] 1176LN Rev D DIY
« Reply #5475 on: June 27, 2018, 03:45:03 PM »
This is the Rev D thread.  What version is your Rev A PCB?

Mike

Thanks  ton, Mike.

Search took me here while looking for folks with the same issue as me.  Sorry if this isn't the correct thread--it seemed logical to me to inquire here. 

We have a FET Rack v. 1.12

Cheers from LA!
Producer, Engineer, Score Composer

Shattersignal

Re: [BUILD] 1176LN Rev D DIY
« Reply #5476 on: June 27, 2018, 04:02:11 PM »
This is the Rev D thread.  What version is your Rev A PCB?

Mike

I'll copy my last post to your FET RACK thread.  Thanks again, Mike.
Producer, Engineer, Score Composer

Zebra_PD

Re: [BUILD] 1176LN Rev D DIY
« Reply #5477 on: August 03, 2018, 07:30:19 AM »
Hi, I'm starting to collect parts for my rev D build. Came across some UTC H-8 input transformers that are 600ohm, respons 50 to 100k cps.

Do you guys think these would work as  substitute for the 0-12 transformer?
___________________________________________________
Semiprofessionell producer but newbie DIYer.
----------------------------------------------------------
www.zebrastudios.se

Re: [BUILD] 1176LN Rev D DIY
« Reply #5478 on: October 10, 2018, 07:48:06 AM »
Hello all, I completed the build of the 500 series FET/D, but when powered on the gain reduction LEDs are pulsing (with pulse rate controlled by the release potentiometer) and when passing audio through the device, the audio clicks at the rate of the LED pulsing. Last night I was able to investigate with a tech and we discovered that the negative supply pulses when the gain reduction knob is out. When pushed in, we do not see pulsing [which is the reverse of #4 of the FAQ for common issues with this device]. We are not sure why this may be happening and are wondering if anyone may have any advice on the issue?
Many thanks in advance

Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5479 on: October 10, 2018, 11:16:54 AM »
Hello all, I completed the build of the 500 series FET/D, but when powered on the gain reduction LEDs are pulsing (with pulse rate controlled by the release potentiometer) and when passing audio through the device, the audio clicks at the rate of the LED pulsing. Last night I was able to investigate with a tech and we discovered that the negative supply pulses when the gain reduction knob is out. When pushed in, we do not see pulsing [which is the reverse of #4 of the FAQ for common issues with this device]. We are not sure why this may be happening and are wondering if anyone may have any advice on the issue?
Many thanks in advance

Moved to FET/500 thread:

https://groupdiy.com/index.php?topic=57192.0
Hairball Audio, LLC
DIY Parts and Kits
http://hairballaudio.com/shop

Top secret stuff and upcoming releases:
http://facebook.com/hairballaudio
http://twitter.com/HairballAudio/


 

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