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???
"Give me a 25-stack of 9V batts, I'll monitor my truck's spark or fuel injection on the magic eye." PRR

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.
"Give me a 25-stack of 9V batts, I'll monitor my truck's spark or fuel injection on the magic eye." PRR

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
DIY Parts and Kits
http://hairballaudio.com/shop

Top secret stuff and upcoming releases:
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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


 

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