[BUILD] 1176LN Rev D DIY

[MikeFFG]

Hi everybody. I'm building this based on the hairball kit and pretty much with the exact specifications between hairball and the mnats pages. I have it all built but now am having some problems. I've tried troubleshooting as much as I think and double checking connections, but alas, I am stumped. I am a relative beginner, so if I miss something stupid or sound dumb, please forgive me.

Here's where I'm at:

Everything's built, the unit passes audio fine (tested with both a sine and with a vocal). The vu meter changes with level perfectly fine. BUT no matter what I get NO gain reduction and the Q bias adjustment does not move the meter AT ALL. So, as you can probably guess, I've narrowed it down to the Gain reduction section...as all the voltage readings are fine in the power supply, preamp and line amp sections and the signal comes back out clean.

I know the Q bias trimmer isn't broken, because I can test voltages next to it and see them changing as I turn the trimmer. I've also been able to follow the voltage to the release pot and that is the same as the wiper of the Q bias resistor, as expected.

And it's not just that the meter isn't working, as I also have just used my ears and can tell there is obviously no GR...

But that's about as far as I'm sure of what to look for. Obviously, without seeing it you guys can't work miracles...but does anything obvious come to mind that would cause the Q bias adjust not to do anything and no gain reduction to happen under any circumstances? Besides of course, I hooked it up wrong? I've tried quadruple checking connections and following the schematic....

Even a hint or an idea would be HUGELY appreciated.

Thanks guys!!

 

[Echo North]

Hi everybody. I'm building this based on the hairball kit and pretty much with the exact specifications between hairball and the mnats pages. I have it all built but now am having some problems. I've tried troubleshooting as much as I think and double checking connections, but alas, I am stumped. I am a relative beginner, so if I miss something stupid or sound dumb, please forgive me.

Here's where I'm at:

Everything's built, the unit passes audio fine (tested with both a sine and with a vocal). The vu meter changes with level perfectly fine. BUT no matter what I get NO gain reduction and the Q bias adjustment does not move the meter AT ALL. So, as you can probably guess, I've narrowed it down to the Gain reduction section...as all the voltage readings are fine in the power supply, preamp and line amp sections and the signal comes back out clean.

I know the Q bias trimmer isn't broken, because I can test voltages next to it and see them changing as I turn the trimmer. I've also been able to follow the voltage to the release pot and that is the same as the wiper of the Q bias resistor, as expected.

And it's not just that the meter isn't working, as I also have just used my ears and can tell there is obviously no GR...

But that's about as far as I'm sure of what to look for. Obviously, without seeing it you guys can't work miracles...but does anything obvious come to mind that would cause the Q bias adjust not to do anything and no gain reduction to happen under any circumstances? Besides of course, I hooked it up wrong? I've tried quadruple checking connections and following the schematic....

Even a hint or an idea would be HUGELY appreciated.

Thanks guys!!

Read the 2-3 pages of this Steve_H exchange. Check the pad 22/21(or is it 20?) stuff.

http://www.groupdiy.com/index.php?topic=29981.msg614820#msg614820

 

[MikeFFG]

Thanks...well I think I discovered something. Per your advice to Steve, I checked for DC at the anodes of CR2 and CR3 where you said I should expect negative voltage, which should be the same for both, but change with ratio. Heres what I got.

CR2-
20    neg 6.46
12    neg  3.61
8      neg 2.61
4      neg 1.79

CR3-
20    pos  10.35
12    pos 10.52
8      pos 10.58
4      pos 10.63


So CR3 is positive...and I can verify it is inserted in the correct direction...would that mean a bad diode or something before the diode? On the cathode of CR3, I am getting similar readings but just down a half volt...so I'm going to keep poking around that area for now and continue to read your conversation with Steve.

Thanks

 

[MikeFFG]

I think C20 might be in backwards...I'll have to wait until tomorrow to check...but I know when putting those caps in I did not realize they were polarized!  d'oh!

 

[andydiy]

Hi!

Will the R59, R71, R44 by Multiturn the purpose and usage of R86 Distortion Trim someone can explain it?

 

[MikeFFG]

Hi everybody. I'm building this based on the hairball kit and pretty much with the exact specifications between hairball and the mnats pages. I have it all built but now am having some problems. I've tried troubleshooting as much as I think and double checking connections, but alas, I am stumped. I am a relative beginner, so if I miss something stupid or sound dumb, please forgive me.

Here's where I'm at:

Everything's built, the unit passes audio fine (tested with both a sine and with a vocal). The vu meter changes with level perfectly fine. BUT no matter what I get NO gain reduction and the Q bias adjustment does not move the meter AT ALL. So, as you can probably guess, I've narrowed it down to the Gain reduction section...as all the voltage readings are fine in the power supply, preamp and line amp sections and the signal comes back out clean.

I know the Q bias trimmer isn't broken, because I can test voltages next to it and see them changing as I turn the trimmer. I've also been able to follow the voltage to the release pot and that is the same as the wiper of the Q bias resistor, as expected.

And it's not just that the meter isn't working, as I also have just used my ears and can tell there is obviously no GR...

But that's about as far as I'm sure of what to look for. Obviously, without seeing it you guys can't work miracles...but does anything obvious come to mind that would cause the Q bias adjust not to do anything and no gain reduction to happen under any circumstances? Besides of course, I hooked it up wrong? I've tried quadruple checking connections and following the schematic....

Even a hint or an idea would be HUGELY appreciated.

Thanks guys!!

Read the 2-3 pages of this Steve_H exchange. Check the pad 22/21(or is it 20?) stuff.

http://www.groupdiy.com/index.php?topic=29981.msg614820#msg614820

So this definitely helped some...I switched the cap and that helped a lot (I had no clue that things that didn't look like standard electrolytics came polarized...) but I'm still having some problems. As far as I can tell, it's compressing 'a little'. If I test it at 20:1 with a .775v 1000khz sine wave, I can get about 3 db of compression for about a quarter second (with slow release, fast release is less compression and less time compressed). but it jumps right back up very quickly, and that is with the input absolutely CRANKED.  Also, I get the same amount of compression when I engage AND when I disengage the GR circuit via the attack knob.

I was able to complete the first two calibrations but when it came time to do the third, it became apparent that it was impossible for me to get 10db of compression for even an instant, let alone have it sustain there like in mnats video.  Could this be a threshold issue? some kind of wrong resistor somewhere?

My other question is about the shorting plug...which position is in and which is out? As far as I can tell mine is backwards to what mnats is in the video...when I have the shorting plug closer to the front side of the board where it says "GR Meter Driver", that is when my GR meter goes to zero and the tiny bit of compression I get happens...when it is further from that, the GR meter drops to -20 and doesn't do anything.

Any more ideas or places to look would be great! I'm going to have someone double check my resistor values visually (I'm colorblind, though I did test each one before putting them in circuit so they should be fine)

Thanks!

edit:

To add to this...the output seems really high...If I crank both in and out I can get an AC signal across the output pins of 15+ volts and can hear the oscillating without having it hooked up to a speaker...is that normal? Also, I just discovered, with GR engaged, if I turn up the output past about 6 the GR meter increases.... ugh... I'm going to keep at it. I will conquer this circuit lol. Sorry for all the stupid questions! Your patience is appreciated.

 

[jplebre]

I would check all connections and then like you said doublecheck resistors and caps (values and orientation for e-lytic cap).

Do you have a scope? that would make troubleshooting the GR section much easier, as there would be things you would be expected to see.

If you are uncertain of a resistor value, lift one leg up and test with a DMM

 

[MikeFFG]

Sorry to overpost here...but I just wanted to update that I figured out the problem...It was really dumb. I must have checked all connections including this one 30 times, but having the terminals on top of the pcb, I somehow mixed up the ground and the hot wire for the shielded wire coming from the attack pot... I was getting compression when GR was off and no compression when GR was on!

Anyways, thanks to everyone who tried to help and Mnats and Hairball for making this all possible. I now have a working 1176!!

 

[andydiy]

Hi!

The following fragment Release, Questions?


http://youtu.be/anRR_nhSfq8

 

[jplebre]

not sure what's causing it but mine are metering rock solid regarding the release

 

[Echo North]

Hi!

The following fragment Release, Questions?


http://youtu.be/anRR_nhSfq8

Check to make sure you meter wires the run from meter to the XLR are far away from the main PCB.  Keep them around the edge, not over the PCB.

Mike

 

[andydiy]

Hi Echo North!

Sorry my English is not good, I do not understand, it can be said more?

Thank you!

 

[allfreak]

Hi folks. Awesome read. Looking forward to building this iconic piece of music history.
Thanks for letting me read along... 

Markus

 

[jplebre]

run away whilst you can. Built my first project last summer and haven't stopped ever synce

Hi folks. Awesome read. Looking forward to building this iconic piece of music history.
Thanks for letting me read along... 

Markus

 

[allfreak]

;D

..., to late. I was drawn to the flame by some guitar effects pedals. There is no turning back.

Allready stuffed the power section - waiting for the EA-5002 to become avail. again for the hairball kit. Tomorrow?

I don't mind the grey hair.  :

 

[Echo North]

;D

..., to late. I was drawn to the flame by some guitar effects pedals. There is no turning back.

Allready stuffed the power section - waiting for the EA-5002 to become avail. again for the hairball kit. Tomorrow?

I don't mind the grey hair.  :

Won't be tomorrow.  But hopefully in the next 7-10 days.

I lied.  They're here!  They'll be up in a few minutes.

 

[allfreak]

Placed an order. Can't wait.

 

[allfreak]

Looking at various pictures, I noticed that the trimmers are not installed the same on every project.
Does the orientation matter? I mean weather the screw points up or down (or left/right for that matter).

 

[jplebre]

it depends on the trimmer type. Read mnats notes on his website.

3 pin inline go on top. the Y shape horizontal go sideways. For the inline, orientation doesn't matter as long as they are mounted in the correct holes

 

[allfreak]

Thanks.