[BUILD] 1176LN Rev D DIY

[canidoit]

hi guys! my 1176 is working great, never had a problem with the circuit.

i have a problem with the meter instead: i do all the steps of the calibration and the meter goes to zero (almost),
after a couple of weeks the meter is 1/2 db off, i mean it goes not to zero, just -1/2 db.

this thing makes me mad, is it normal?

For me as well. I didn't know it fluctuated this badly. Its a real pain in the ass to notice these things after you finished the build, otherwise I would have made preventative measures and bought a pot to mount at my little zero hole on the front of my case and moved my zero adjust there.

I finished the build, calibrated it, powered it up and I was really happy. Then the next day, turned my unit on and I was like WTF, my unit is already broken. Anyways, I couldn't be bothered unracking, desoldering, etc. and buying a little pot that cost an arm and a leg to buy and ship so I let it be.

On a good day it will creep back to zero, but mostly its 1/2-2 a db off here and there or more on the VU.

 

[craigg]

just finished (sort of) my 1176d, and it seems to be working well, except for a few things, which I would love help with.  I got the hairball kit, and I can't figure out how to wire up the VU (and what resisters to use...I already blew out one lamp...I was using 2X10w 100 ohm in series, on one of the wires, and connecting both vu terminals for the lamp the the ac pads on the board.  Is this correct?  Also, my r71, isn't doing any vu calibrating.  i wired up a pot so i could make adjustments after it's all put together, but I think i wired it incorrectly (hence why it's not working!).  Any help here would be much appreciated.  Thanks so much.

 

[Stagefright13]

For the lamp you need to measure the AC voltage source you are using. Such as the recommended ac input wires to the main board. You may have hooked the source wires to the wrong posts. You want the center post and one next to it. Not the outer 2 wich will be double the voltage. After you read what voltage you have there then go here:

http://www.groupdiy.com/index.php?topic=275.0

If you take a pic of your r71 wiring I'm sure it would be easy to fix.

John

 

[Stagefright13]

It's normal for the VU to drift as it warms up. Even says +-1 db right in the original Urei manual.

I lay the lid on then slide it back in the rack for a few hours. THEN adjust for 0 VU. Mine power up at -1 and slowly slide to 0 VU later. And are stable that way. It has to do with heat. If you adjust with the lid open and not in the rack spot the meter will be wrong. Or you could simple glue the 0 adjust trimmer right to the front panel. And adjust it thru the faceplate hole.

John

 

[Biasrocks]

this thing makes me mad, is it normal?

The meter circuit is unregulated and will drift with the wall voltage, totally normal.

Mark

 

[craigg]

Thanks for the info on the lamp.  I put in a couple of yellow leds and wired it up and it looks very nice.  On to a more serious problem with my unit...It passes audio, compresses a bit (i sang to check it out), but while i was calibrating (q bias was fine, null adj. was fine) i noticed in the gain tracking adj. that the vu would drop -4 when i'd switch the attack knob on, but when i would turn up the input to get more gain reduction so I could get a correct reading of -10, the vu swung to the positive side, and i think it's because the unit isn't compressing correctly.  sound is getting through.  when i was singing this was happening as well.  i have a UA reissue, so i know how this unit should correctly operate.  How is my signal not getting compressed correctly?  do i need to take photos of the pcb to post?  everything else (not that it matters if it ain't compressing well) seems to work fine.  Thanks guys.

 

[jyrki3101]

I'm confused with the Q bias adjustment. I watched mnats video many times and followed the first instructions carefully  .R44 in circuit,attack/release full CCW,meter switch in VU mode(GR bypassed with a shorting lead,input CCW,output full CW,ratio switch in 20:1.  1kHz sine wave at 0dB(0,775Vrms) to input(with protools signal generator) After I turned the input control up till the VU meter reads +1dB, I started to turn Q bias trimmer CW(from fully CCW position) the meter goes UP??? instead of going down to 0dB. I matched Q12-13 and also Q7-10(all 2N3708) and bought  matched Fets(Q1,Q11)from hairball. I have checked my wiring many many times and everything is connected like the schematic shows. I checked the main pcb board and ratio/meter boards(rotary version) and did a continuity test between every component, ...couldn't find any mistakes.
This compressor took 2 weeks to build but now I have been trying to calibrate this unit almost 3 days without any sleep!!! ....I'm exhausted and frustrated, but I wouldn't want to give up yet.
Any kind of help would be greatly appreciated!!!
                 
                jyrki3101

 

[phatmateo]

did you flip your q-bias trimmer? If it is opposite from mnat's video, then its normal that you'd have to turn it the other way to get set the bias correctly.  Check the schematic and study the board to see exactly which way is pointing to ground from the q-bias trimmer

 

[jyrki3101]

I measured with DMM that wiper(Q bias trimmer) IS closest to ground when in fully CCW position? It's orientated(positioned) just like in the mnats video?.......

 

[Futureman]

Woot!

Finished my Rev D last night.. Excellent!

It worked straight away, I was very impressed.. The only thing that threw me a curve ball was the wiring of the "OFF" switch on the attack pot.. but as always, the schematics got me through!

This might sound like an awards ceremony, but I want to thank..

Mnats! Thanks for making my favourite compressor accessible to me!
Hairball! Thanks for making all those important parts available in one tidy store! Your cases look brilliant and very professional.
All of you! Reading through this long and massive forum, I learnt a lot, had a few laughs, raised a few eyebrows. Give yourself a pat on the back all who contributed..

Kind regards
Mike

 

[pacemaker]

hi Guys,
i have finished building a 1176 Rev D with Mnats PCB,
Altran input transformer, cinemag CM-96731 output,
I ahve fired it up,
my voltages are +30v and -10v,
and it passes audio but........
i must have made a mistake,
cause when teying to calibrate,
I noticed that with no input,
cranking the output knobs generate more and more noises,cracklings
and when the pot is fully clockwise, i really have a random noise generator,
surely caused by the PSU.....
I have cheched my wirings but couldn't find any mistakes ( doesn't mean they're ok ;-)
i have read again and again the thread, urei manual, Mnats pages,Skylar wiring guides,
REV D ver2 PDF files, hairball audio pdf file,
and all the resources i found with the magic "search" button.
I have to say thanks to all the people mentionned for their great work,
i might have never been so close to finish the unit without their astonishing work,
But i am now stuck and would like a few help for locating the problem,
I only have a multimeter and  use my x0xb0x as wave generator ....
Any idea where to start troubleshooting ?

 

[trancedental]

Still got a 1176 D not working properly with problems as mentioned in an earlier post. ???

After being too busy to do a detailed check over the last few weeks I have now done some fresh testing with a sine wave signal generator.

I have clear signal coming out of the unit but my VU meter doesn't move from the left -20db side at all.

Using an external VU meter for refernece I  get compression reduction (around -10db )when the the ratio setting buttons are engaged,  I have managed to do the Q bias setup this way. Also when activating  the GR disable switch I get a slight wavering in level of 1-2db when sending a signal @ 0db indicated on the external meter.
                                   

I'm wondering about the problems with the VU meter not indicating any signal so was studying the schematic around the GR meter driver / GR control amp, the voltage supply on both seems to be OK, but I'm not sure about how the this part of the circuit takes the signal & controls the compression at all.

Has anyone any reference or voltage charts that I can check or an brief description on how this part of the schematic operates???

Cheers JK

 

[pacemaker]

bump,
help still needed for these unwnanted noise on the output pot ,
any ideas on how to find the problem ?
regards
Pacemaker

 

[bdubya]

Pacemaker, I've experienced some funky noises when boosting the output stage with the input down as you mentioned, and it was when the input or output was interfaced with a non-balanced connection, maybe double-check that the gear (and the cables) are fully balanced.  It seems like you've checked over the internal wiring pretty thoroughly, it would be easy to miss a bunk solder joint on the XLR or something similar(these are the boneheaded mistakes that plague me, personally, not the complicated ones, the silly ones)  Does it freak out if the Gain reduction is off also?  If not, you know that it's happening in the Gain reduction circuit.  Hope that touches on a solution, or a path to one.

transcendental, if you're getting good metering on both gain reduction and output settings with a different, external meter, but not on your preferred one, then clearly the preferred one is busted, unless I'm misunderstanding your predicament.  The "wavering" you speak of when metering externally. . . if the compressor is compressing 1-2dB and you remove the gain reduction circuit from the path, by enabling the GR off switch, you're gaining 1-2dB back since it's now uncompressed.  If it's more complex/erratic than that, I apologize for oversimplifying, but hopefully that stirs something up.

 

[DanH]

Hey all,

I'm new to this forum, so I apologize in advance for the up-front request for help. I've had basic training in circuitry, but this is the most difficult project I've done yet. Needless to say, I'm learning a lot. I'm using the hairball kit and mnats rev2 board.

I tested the components, stuffed the board, and finished the wiring. When I plugged the unit in, R32 burnt out right away. The only discrepancy I can find is the wiring of the output transformer.. I initially followed the version one schematic, and realized after the fact that the rev2 pdf shows different wiring. I don't have the knowledge to know whether that alone would burn out R32. Thankfully, nothing else seems to be wrong... or rather, nothing else burns when i plug the unit in.

Any help would be appreciated. I look forward to learning from you guys!

 

[Futureman]

I tested the components, stuffed the board, and finished the wiring. When I plugged the unit in, R32 burnt out right away. The only discrepancy I can find is the wiring of the output transformer.. I initially followed the version one schematic, and realized after the fact that the rev2 pdf shows different wiring. I don't have the knowledge to know whether that alone would burn out R32. Thankfully, nothing else seems to be wrong... or rather, nothing else burns when i plug the unit in.

The frying of R32 seems like a common fault.  do a search in this post, but from memory it has only to do with the wiring of the output transformer...

Seems like you are pretty close to finishing it.. Obvously, you'll need to replace R32 now that it's cooked.

Regards
Mike

 

[DanH]

The frying of R32 seems like a common fault.  do a search in this post, but from memory it has only to do with the wiring of the output transformer...

Seems like you are pretty close to finishing it.. Obvously, you'll need to replace R32 now that it's cooked.

Regards
Mike

Thanks Mike. I'll do a search a see whats out there. Appreciate the feedback!

 

[phatmateo]

Make sure you check what wiring guide you are using.  What output transformer are you using?

 

[ilfungo]

I just finished the utime REV D Orange Drop caps  and carbon compostion resistors everywhere ... Sounds fine for me much better than with Wima caps and metal film resistors

I would do another with OEP in and out
how can I connect them?
Thanks

 

[Futureman]

Hey all.

I wonder if the brains here can help me out with this one.

I've build and calibrated my 1176 Rev D, and it's awesome.

Most of my gear is Synths & drum machines etc.. so largely unbalanced equipment.

I was using my 1176, and had it plugged in via a patchbay to an unbalanced Jack, then to desk etc.
(Effectively shorting the cold output of the 1176 to ground)

When turning up the Output knob, and in +4 or +8 mode, the Meter would pin itself hard to the right, even though no signal was present.. also some very high freq oscillations.
The meter would also pin itself to the right when the output is turned all the way down.

The 1176 seems to work perfectly with balanced audio, I was just surprised by this behaviour.

Is this normal? Any ideas if not, where I should be looking? I did a search, but could not come up with any real leads etc.

Kind regards
Mike