[BUILD] 1176LN Rev D DIY

[TijuanaKez]

It's actually correct.

As the ratio gets higher on 1176 (moving from 4:1 to 20:1), the threshhold gets higher.  So you "see" less GR.

To see the ratio, you compare the input to output over a couple different points.  Keeping in mind your ratio decreases toward the "knee" and FET saturation.

Mike

Edit:  Link about measuring ratios:
http://www.axtsystems.com/index.php?option=com_content&view=article&id=54:1176lnratios&catid=34:1176ln&Itemid=62

Ahh I do remember the threshold being ration dependant now. I followed that link though and it still doesn't seem right (see attachment) One thing I noticed that could have something to do with it.... when I set the input to 'straight up' (-24) I only have to set the input to -48 to get 0 on the meter. When I tested it next to a friend's real 1176 he said mine was 'super hot' in comparison to his. Is this normal for the mnats rev d board?

I'm not exactly sure how to determine my ratios from the readings I took but it doesn't look right compared to the graph in the link. It seems I have to turn the input down a lot to get below the threshold


Other notes: I used logic test oscillator and metering to do this test to get precise values. With my Duet 2, I set up logic's test oscillator to 1Kz -12db and logic's channel fader to +1.6db to get exactly 0.775VAC at the input XLR on the 1176.
I setup an input channel (set to XLR -10 in Maestro) and a gain plugin set to +3.3db to get exactly 0db on the logic input meter when the 1176 meter read's 0db with GR off the meter set to +4. I dropped the test oscillator level by -3 each time and took a reading off the logic input channel meter. The Input channel meter on logic was pretty spot on with the 1176 +4 meter reading.

 

[tandri79]

Hi fellow DIYers i´m building my first big project and i´m puzzled over the rotation on the trim resistors. Does it matter wich way I solder them in? On R59 the screw is facing towards the terminal block is that ok

 

[gemini86]

Which ever way is easiest to access, for you. they are linear, so there's no taper toward one end, therefor no specific orientation.

 

[tandri79]

Great  ;D  thanks for the quick reply.

 

[college101]

HEY GUYS! I am back... with Good News and the Bad News!  AND I need some advice on what to do next

I have cleaned up some solder joints around R44 and checked continuity around the area...
GOOD NEWS...I think it works! BUT BAD NEWS...

with R44 in the socket, it does not work, the needle drops to -20 just like before...So I decided to hook up some short pieces of wire, and breadboard out R44...After looking at MNATS trace layout...The middle terminal of R44 is tied to the trim knob side of R44...I connected these two point to one side of R44..then the other side to the far side of R44 dip socket...

WITH my 1k test tone going in to the 1176, with compression OFF, I adjust R71 to zero! AWESOME
Then I turn ON compression via the attack knob and the needle falls to -12..WOW thats close...BUT..If I actually GRAB R44 with my hand, THEN the needle adjust's to -10!! if I remove my hand, then the needle falls back to -12 again....

I think I am getting some conductance which is throwing the needle adjustment off? Does this sound right guys?

PLEASE help..I really am close now!!!

 

[erjos]

Then I turn ON compression via the attack knob and the needle falls to -12..WOW thats close...BUT..If I actually GRAB R44 with my hand, THEN the needle adjust's to -10!! if I remove my hand, then the needle falls back to -12 again....

You mean to -12 or -20 after touching?
Maybe a broken pot?you can try whatever pots available,not necessary multitrims. I build 2-nd piece with mixed transistor models (like Bc549 and some bc 107) and the trimpots are kind of normal ones adjustable with a Alen key, with a very rough resolution per turn,available at the local shop. Except a wrong resistor(should be very careful with them) everything was fine and the calibration pretty easy.
If -20 I think maybe you have a broken pot. If - 12 maybe wrong pot value.
What calibration procedure are you following, the +1 to 0 for q biasing  or +11 to +10 (which I think gives better results)?
Regards
Erjos

 

[college101]

erjos

If I breadboard out R44...then the needle sits at -20 when I am not physically touching R44( which is my orignal problem)...


AFTER I adjust r44- I can move the needle to the correct -10 position..
I am physically touching R44, after I have adjust the needle to show the -10 GR adjustment, once I take my hand OFF of R44, it drops down to -12 or -15 area...it does not stay at -10 after I remove my hand...



Seems like I am getting some issues right there r44

 

[college101]

BUMP anybody? 

ED  Anderson???

 

[edanderson]

whatever kind of pot you're using for r44, you can't be touching it directly with your hand while adjusting it.  this is usually not an issue with the type of trim pots used on the mnats PCB, since you have to use a screw driver and that will usually have an insulated handle.

if you've substituted in a pot with a shaft, secure it to the chassis, then put a knob on it, or better yet use a screwdriver, etc to adjust it.

ed

 

[college101]

Thanks ED for the quick response...

SO after reading your post... I have two options...

Connect R44 to the chassis and adjust it from there...(how would you recommend I go about this?)
or
Remove the dip socket, and try again in the circuit board...

I am using the blue 2K trim pots from Mouser...( I thought, since the case to the trim pot is plastic, it was insulating it enough?)

 

[Stagefright13]

I am away on a SLOW laptop. What kinda pot are you using? Touching a multiturn pot specified in the BOM will make no difference.

 

[edanderson]

if r44 is sitting in a dip socket on the PCB, can you secure it somehow, perhaps with a rubber band or cable tie, so that you don't have to touch it with your hand?  if you have it connected with wires, just find a way to tape it to something so that you don't have to touch it with your hand while you turn the screw with a screwdriver.

ed

 

[college101]

Hey Ed

The problem with it being in the dip socket, is that it does not adjust the needle movement while in GR mode...Does not adjust...meaning it has no action on the needle movement..

If I have it connected via the Dip Socket, the needle is pegged to -20...and no amount of adjustment to R44 makes the needle move...

This is why when I did it breadboard style it out of the dip socket, I found it work if I did not connect it the middle terminal slot of the dip socket...

I think you guys keep missing out on what I am trying to explain

In the circuit board, it does not work-no adjustment to needle
in the dip socket, it does not work-Just sits at -20 and no adjustment to needle
breadboarded out of the board, it works when not connected to middle of dip socket

The trim pot does show movement from my hand touching it...when I let go, the needle moves to the left, when I hold it, it adjust right to -10

Ed, I have adjusted it so I dont have to touch it with my hand to make the adjustment...I just think its funny how I got to this point!

 

[edanderson]

i know you are trying to be clear, but without actually SEEING what you are talking about, it is very hard to follow exactly what you are doing.  of course it makes sense to you, because you did it.

what i said in my last post still applies, whether the pot is in a socket, soldered to the PCB, connected via wires, etc -- when you are adjusting the pot, you cannot be touching it directly with your fingers.  as you've seen, touching the pot can affect the value that you see.

ed

 

[Stagefright13]

Obviously your fingers have resistance across them so will effect the meter... If you can't adjust R44 then more than likely the other pot has put it out of range of R44. As long as the board looks good and is properly assembled it seems your other trimmer is too far out. I had that problem myself on my first 1176. Try backing up in the calibration procedure to make sure.

And check the schematic to make sure the wiper and resistance are in the correct positions. It is possible to make the pot a resistor with NO wiper.

John

 

[Stagefright13]

tandri79 It IS possible to solder the trimmers in wrong. It HAS been done! They are reversible. But if soldered in sideways they will not work. Look at some pics of the board to be sure.

 

[gemini86]

College, please post a pic of what you're doing and a close-up of the r44 pads on your board. A picture speaks a thousand words! I still suspect your board may have a ground short around r44 somehow. I would cut r44s traces and jumper to a brand spanking new trim and glue that sucker to the board. 

 

[college101]

I took some pics with my phone, wife had my camera, but I think my pictures suck and they are too blurry...

so far, If I am touching the pot, the 1176 will meter correctly, otherwise, no amount of adjustment to R44 will move the needle(to the RIGHT) back twoards -10

I am going to buy another 2k trimpot and switch it out... any suggestion anybody..

New pictures on here soon...

 

[Biasrocks]

Pull the pot, measure the pads on the board to make sure they are going where they should and nothings shorted or grounded when it shouldn't be. IIRC, the Test Point 1 jumper should be shorted when doing the meter calibration, make sure it is. Look at the schematic, buzz out all the points around R44 to make sure they are going where they're supposed to.

Regards,
Mark

 

[college101]

Thanks Biasrocks...will go another round...

in the mean time, here is some crappy cell phone pics...

** realize ahead of time, by holding R44 a little tighter, the needle will adjust closer twoards 0 ***

This pic  is just to show, me with the breadboarded( out of the circuit board R44)