[BUILD] 1176 Rev A - Back to the beginning...

[King Sound Studio]

You should not be using the mA setting at all.  That is for something completely different and a completely different process.

Use VAC (V with sine) for EVERYTHING related to testing audio signal level.  You need to have it to this for setting the input and test the output level.

Start fresh in the AM, set your 0.775 with the VAC (V with sine) and check the output with the same.  If you have no output trace though like above. 

There might not even be anything wrong.  8)

Mike

Okay, new day. Ready to start fresh. Here's where I am.

I turned my qbias all the way to the left (CCW) until I got a reading of -2.830 VDC
In Pro Tools, I ended up having to set my 1khz signal at -8.8dbfs to get my .775 VAC on the input. This seems a little out of range when reading the guide. Cause for concern? 

Moving on, I put my leads on the XLR output and adjusted the output knob until we got our reading of 2.73 VAC (couldn't quite get it to stop on 2.75). Cool, great. Went to adjust the q-bias CW/RIGHT to get to the 2.44 VAC, but moving the qbias had no affect on the output.

So, in short, the qbias is adjusting my input, but seems to have no affect on the output. Does that make sense?

Hmmm not really.  That's a bit of a head scratcher.  Could be a bad FET but I'm still suspicious of the calibration set up.  Unfortunately I'm not sure where to look next.  Your Q1 gate has a negative voltage that changes w/ the bias rotation but you're not seeing an output drop?  If you turn the bias pot full CW what does the G show in DC? Still no drop at the output?

I'll just toss this out there so you know it's and option, we do repairs on these builds:
http://www.hairballaudio.com/shop/index.php?cPath=45

If it just need calibration and is built fine we'd probably just charge you $50.

Mike

Okay, we moved the qbias all the way to the right(CW) and 0-ed it out. We then checked the XLR outputs just to be sure, and saw that it had in fact changed from our reading with the Qbias all the way to the left(CCW). We then worked backward until we reached the 2.44 reading.

But going back to when the qbias was all the left(CCW) at 2.75, I swear I would turn the screw 8-10 times and get no difference at all.

So to recap how I got to where I'm at...

1khz signal going through.
Qbias all the way CCW
XLR INput - .775
THEN, moved to output xlr and adjusted output gain until we got 2.75
THEN, moved qbias all the way CW and noticed that the voltage had changed, so without changing the output gain knob, we moved the qbias back CCW until we reached 2.44.

I think (assume? ahhh!) we're good to move on from this step and everything is okay?

Also, thank you for sharing the link. If I'm just not getting this today, I will happily send this to you guys and have you work your magic for a fee. I'm confident things are hooked up correctly and it's just my inexperience with electronics affecting the calibration.

p.s. where do I send the free steak dinner once this is all finished?

 

[Echo North]

Ya man look good!

You're compressor is working (compressing) at this point.  The next calibration steps involve getting the meter to work.

Good luck!

Mike

 

[King Sound Studio]

Ya man look good!

You're compressor is working (compressing) at this point.  The next calibration steps involve getting the meter to work.

Good luck!

Mike

Okay, we were cruising right along and got to step 3, "Gain Reduction Meter Tracking Adjustment"

Now when we check our input with the original 1khz signal going through, we're getting a reading of 1.281 VAC on our input xlr. Before I do anything, I wanted to check for some clarification. I'm (ahem) assuming that since we've moved the qbias back in step one, it's going to affect our reading on the input of the XLR.

If that's true, then I should EXPECT after the calibrating we've done to get a reading other than the original .775 we got back during the setup process.

The first thing we're told to do on step 3, "Gain Reduction Meter Tracking Adjustment" is to "Apply a 1 KHz, 0dBu signal, confirmed with your DMM at pin 2 and 3 of the input XLR (0.775 VAC)."

Again, I'm assuming here....that I should NOT adjust the qbias at this point to get that .775, but instead ...adjust the gain level of my 1khz signal in my DAW to achieve the .775?

Or am I just wayyyy off? ha ha!

 

[King Sound Studio]

Or is that just saying, essentially, "Send the original 1khz signal" ?

 

[Echo North]

Position of the input knob will change the input signal level.  When it says send a 1K  0.775VAC signal you may have to re-dial in your signal source.  But honestly the level is not important.  You just need 1K signal in the say -5 to +5dBu range.  The output is more important.

Yes adjust your signal level.  DO NOT touch the Qbias.  You set it in the first step.  If you touch it you'll have to start over.

Mike

 

[King Sound Studio]

Position of the input knob will change the input signal level.  When it says send a 1K  0.775VAC signal you may have to re-dial in your signal source.  But honestly the level is not important.  You just need 1K signal in the say -5 to +5dBu range.  The output is more important.

Yes adjust your signal level.  DO NOT touch the Qbias.  You set it in the first step.  If you touch it you'll have to start over.

Mike

1. Apply a 1 KHz, 0dBu signal, confirmed with your DMM at pin 2 and 3 of the input XLR (0.775 VAC).

2. Move your DMM to pin 2 and 3 of the output XLR.

3. Set output control for 0dBu (0.775 VAC) at the output.

4. Set attack full CCW (off position). Set input control for +10dBu (2.44 VAC) at your output XLR.

5. Turn the attack control ON (Fully CW) and readjust the output level control for “0dBu” if necessary.

6. Now lets set the meter to display this 10dBu drop.  When the attack is “off” (full CCW) and you see +10dBu at the output, set the meter to 0 by using the front panel zero adjust trimmer.

7. When the attack control is “on” (full CW) and you see 0dBu at the output, use R44 to set the meter to -10.
Repeat 6 & 7 until the output drops 10dBu whenever the attack control is turned ON.  This can be a bit tricky.  You’ll want to anticipate how one control will change the other."

OKAY...So, new problem (we're so, so close!) I get down to step 6...I noticed that my attack knob is having no affect on my Voltage at the XLR output. Normal? Not normal?

 

[Echo North]

Where is your input knob?  If it's below the threshold, then you won't see a drop.  You need to get it above the threshold.

To get the 10dBu drop, the input is generally around 10 o'clock and the output around 12o'clock.  Very generally speaking.

Mike

 

[King Sound Studio]

Where is your input knob?  If it's below the threshold, then you won't see a drop.  You need to get it above the threshold.

To get the 10dBu drop, the input is generally around 10 o'clock and the output around 12o'clock.  Very generally speaking.

Mike

Set controls as follows.

Input = “24″ mid rotation
Output = “24″ mid rotation
Attack = full CW
Release = full CW
Compression ratio = 20:1
Meter mode = “GR”

DONE no problem.
=========================


1. Apply a 1 KHz, 0dBu signal, confirmed with your DMM at pin 2 and 3 of the input XLR (0.775 VAC).
  DONE

2. Move your DMM to pin 2 and 3 of the output XLR.
  DONE

3. Set output control for 0dBu (0.775 VAC) at the output.
  Had to move output just barely CW to get to .775VAC. Just barely before the first dot that is CW of 24
  DONE

4. Set attack full CCW (off position). Set input control for +10dBu (2.44 VAC) at your output XLR.
  Had to move input to the dot between 18 and 12, rigiht on the dot to get 2.44 VAC
  DONE

5. Turn the attack control ON (Fully CW) and readjust the output level control for “0dBu” if necessary.
    "0dBu" = .775 correct?  Moved output knob just barely CCW past 36. Got .775
    DONE

So far so good? Or is there a misstep in there?

 

[King Sound Studio]

BTW, I'm not seeing the needle on the VU meter drop at all during any of this. It's sticking right at 0 in GR mode. No matter what I do with the input/output/attack knobs.

This, of course, with our 1k signal going through.

 

[Echo North]

BTW, I'm not seeing the needle on the VU meter drop at all during any of this. It's sticking right at 0 in GR mode. No matter what I do with the input/output/attack knobs.

This, of course, with our 1k signal going through.

Sounds like you might be ok.  There are also these vids by Don Bonin which are super helpful for calibration.  I think you're on the last one.

https://youtu.be/0Uuk1Y7M2D8
https://youtu.be/lRStwXwmBUw
https://youtu.be/pgSWfsEzU40

 

[King Sound Studio]

BTW, I'm not seeing the needle on the VU meter drop at all during any of this. It's sticking right at 0 in GR mode. No matter what I do with the input/output/attack knobs.

This, of course, with our 1k signal going through.

Sounds like you might be ok.  There are also these vids by Don Bonin which are super helpful for calibration.  I think you're on the last one.

https://youtu.be/0Uuk1Y7M2D8
https://youtu.be/lRStwXwmBUw
https://youtu.be/pgSWfsEzU40

Going to watch right now.

When I get to step 7, "When the attack control is “on” (full CW) and you see 0dBu at the output, use R44 to set the meter to -10." I'm not seeing the 0dbu (.775) when moving the attack control to on. It's still at +10 (2.44). Moving the attack control on or off makes no change. My output XLR VAC stays at whatever it was on regardless of on or off..in this case 2.44

 

[King Sound Studio]

It seems like, even when following along with the video, that my attack knob is not working. It's having no affect on anything.

 

[Echo North]

It seems like, even when following along with the video, that my attack knob is not working. It's having no affect on anything.

Restart from the top using the videos. Reset all our trim pots to center.  Turn them one way till you hear a "clicking", that is the end.  Now turn them back the other way exactly 10 turns.  Now they are centered.

Go through the whole calibration again using his vids.

If still no luck you may just need to send it in :/

Mike

 

[King Sound Studio]

It seems like, even when following along with the video, that my attack knob is not working. It's having no affect on anything.

Restart from the top using the videos. Reset all our trim pots to center.  Turn them one way till you hear a "clicking", that is the end.  Now turn them back the other way exactly 10 turns.  Now they are centered.

Go through the whole calibration again using his vids.

If still no luck you may just need to send it in :/

Mike

I'm going to go ahead and box it up and send it in. If I don't, I may just launch the unit out the door and in to the trash and my wife wouldn't be happy  with me if I do that. After day 6 of wrapping my brain around this, I'm at wit's end.

Boxing it up right now. Will ship today.

 

[King Sound Studio]

Regardless of my failure, I appreciate the time and patience and assistance you've provided. It will be in better hands there in Seattle. Thank you Mike!

 

[Echo North]

Regardless of my failure, I appreciate the time and patience and assistance you've provided. It will be in better hands there in Seattle. Thank you Mike!

We'll get it all fixed up and sounding right for you!

 

[Djankies]

Hi all,

I thought I was smart. I thought buying a DIY 1176 clone kit from Hairball audio would save me a bit of cash.  Well come to find out it isn't as easy as it looks and, despite my highschool-level understanding of electronics and acute attention to details in the build guide posted on Hairball's site, I find I've made a error in my build. I'm not going to exaggerate my knowledge here: I need help. Now, I knew a few things from the get-go. I knew that the power supply was working correctly and the +30 and -10 V test points were reading as they should and I also know that an input signal was going into the input transformer and came out at a lower voltage than was put in. This signal was also getting to the board however no signal was coming out of the unit. The VU meter was tested and both the light and needle were working as they should.

I had thought to go through the circut board and try to identify faulty components, and going through every component, I had found capacitors C21 and C4 to be shorted, and after waiting a few days for another mouser order to be delivered, I replaced the caps and wired everything back up. Surprise. There's no movement from the meter. However now when a signal tone is fed into the unit and the input knob is brought up, the signal can be physically heard coming from the output transformer. There is also a signal (don't know if it's the correct signal) coming from the output terminal.

My next attempt at fixing the problem focused on the meter board, thinking that maybe there was a bad connection between the board and the pins of the pushbutton mechanism, so I soldered the mechanism to the board. At this point I measured the power circuit test points and the -10V test point was reading correctly and the 30V test point was reading 23 V.

The next thing to happen was the unit failed to turn on and no power was even getting to the VU lamp. I chased this down to a blown fuse, tried another fuse and it blew as well. That was confirmed with continuity tests. I have checked the wiring again and again forwards and backwards, sideways and upside down. I really believe this has something to do with the board. Because I'm not an electronics aficionado I don't know any other way to diagnose issues other than the brute force way of testing every component. But because parts are failing in front of my eyes now, I'm afraid any further steps I take without complete knowledge of what is happening may damage the circuit further that it already is.

I know a little bit about electronics and how components work within a circuit, but I feel this issue that I face is a little too complex for my "current" understanding of this circuit. I've been researching for days on how to solve this problem. I've found nothing that I don't already know. So before I move forward, my questions here to anyone who can help is:

Is there any insight that anyone can give me on diagnosing my issue? Is there a more methodical way to find out what's going on within the board? Any other test points that can be used?

I've invested around 600 dollars on this thing and I'm not going down without a fight. I'm willing to start back at square one if I have to. Id be so grateful to anyone who can help. I'm so in over my head here.

Thanks,
Daniel

 

[Echo North]

Hi,

Let's just take a step back and get you sorted.

I should start by saying we offer flat rate repair service on those. But you may have a supply issue which we would not address:

http://www.hairballaudio.com/shop/index.php?cPath=45

Let's start here:

1. What is the fuse you are using? You need a 350mA-400mA SLO BLOW fuse.  What are you using?

2. Try the unit with the proper fuse and all wires including the transformer, removed from the PCB.

Let's get it powering correctly first.

Mike

 

[Djankies]

Hi, Mike

Thanks for your reply. Im using the fuses that Hairball had in the Rev. A cart. The fuses are rated for 250 mA and 250 V (mouser pt # 693-0034.3111)

I disconnected everything from the board and hooked my multi's clips to the AC entry module terminals. I'm getting a good reading of 120 VAC.

Daniel

 

[Echo North]

Hi, Mike

Thanks for your reply. Im using the fuses that Hairball had in the Rev. A cart. The fuses are rated for 250 mA and 250 V (mouser pt # 693-0034.3111)

I disconnected everything from the board and hooked my multi's clips to the AC entry module terminals. I'm getting a good reading of 120 VAC.

Daniel

Ah I need to update that, those fuses are rated a little low. I can drop some in the mail for you if you like (email me).

Sorry I mean leave the power secondary connected. See if you can get +30 and -10 with the other wires disconnected. You may need to wait for the better fuses. (Mouser #576-0218.400MXP).

Mike