[BUILD] 1176LN Rev D DIY

[dbonin]

Did you complete the Q-Bias step and subsequently verify, using your DMM, that there is no gain reduction?

Hey guys,

So I'm working on a rev d that currently passes an audio signal but has no sign of compression. When checking voltages at the gr control amp, Q7-Q10 all have high voltages(around28-29vdc) at each the C,E,B.

Has anyone run into a similar case who can point me in some direction?

Thanks!

 

[Commander Fluffypants]

I've been slowly making progress on my Rev D. I bought this thing off of someone who had started to build it. I've redone a lot of his wiring. I'm getting to the end of the audio wiring and I've noticed a couple of things.

First, everything was mounted in the case already except the output knob. The nut for the output knob is too big. Where do I go to get that? There's a star washer with the one I have. I'm assuming that those don't get used? Or do they?

Second, I have no “0″ set potentiometer. Also no screws to mount it. I do have the platform that it mounts on. The instructions say to use some extra nut as a spacer. Is that the nut that I have that doesn't fit the other knob?

I was looking for a BOM to see if I could find the part. I could not. I suspect that this was a Hairball supplied part and not a Mouser one.

Any help would be appreciated. So close to finishing...

Thanks

 

[Commander Fluffypants]

I found the mouser cart. Is this the "0" set pot?

https://www.mouser.com/QuickViewProdDetail.aspx?PartNum=785-53C22K&KeepThis=true&TB_iframe=true&height=375&width=530&QuickView=true

 

[Commander Fluffypants]

Pretty please?

 

[Echo North]

Pretty please?

That would work.  Pretty spend for what it does.  Something like this is fine:

RV16AF-10-15S1-C2K

 

[Commander Fluffypants]

Pretty please?

That would work.  Pretty spend for what it does.  Something like this is fine:

RV16AF-10-15S1-C2K

Awesome. Thank you! I also need the screws to mount the platform and I'm curious about the instructions that mention using the "extra nut" as a spacer. Where can I get a couple of those screws and what should I do about the spacer... oh, and I need a nut for the output pot as well.

 

[Commander Fluffypants]

OK. I finally solved all my little problems with nuts and screws. On to calibration. I plugged the sucker in and started sending a 1k signal into it. Meter lit up. No smoke. Looked good as far as I could tell. I did notice that the meter was pegged when set to GR, but all the way down when set to 4 or 8. I had to leave the room for a few minutes so I shut the thing off. Upon returning, it would not power up as far as I could tell. Meter was dark and did not move when I set it to GR. fuse is fine. Tried another power cable and outlet. I'm thinking the problem is at the meter board switch, but what do I know?  I figure I can test the switch, but I don't know enough to know where I should stick the multimeter to do that. Any ideas? As always, thank you.

 

[dbonin]

Test for continuity thru the fuse - visually they can appear fine when in fact they are open/blown.

How do the test points in the power section look?    Start there.

 

[Commander Fluffypants]

It was the fuse! It didn't LOOK blown, but it was. Did some searching here and found that others had problems with the fast blow fuses that shipped with these a while back. Replaced it with a Slow Blow 1/2 amp 250 volt fuse and it turned back on... and off and on again.

Thank you, thank you, thank you!

 

[Commander Fluffypants]

So close!!

I noticed other people have had the same issue that I'm having right now, but I can't find how they'd resolved it.

I'm trying to calibrate the meter. R44 doesn't seem to do anything when attack is on. I have found an area in it's sweep where it will affect the meter when the attack is off.

I've double checked everything and double again. When the attack control is off, the meter is all the way down. There is nothing I can do to bring it up to show a 10db decrease in signal.

When attack control is CW, meter reads 0.

I'm getting as close as possible to .775 on the way in (I think .777 was as close as I could get it) and I've got .775 on the way out when the attack pot is on and .244 when it's off.

Changes in R44 have no effect on the meter when attack is off. There is an area in R44 where I can bring the meter down from 0 when the attack is on, but when the attack is off, R44 does nothing. Also, I can never use R44 to get the meter higher than 0 when the attack is on.

Perhaps it is some silly oversight? I think I got the other calibrations done correctly.

Thanks again.

 

[Commander Fluffypants]

YES!!!

I did some more searching of the thread and someone mentioned dbonin's youtube videos.

I have no idea why this method would work and the other method not work... but from what I can figure, the range of my zero adjust was too far out to see the effect that R44 was having.

For anyone else having trouble with meter calibration, go here: http://youtu.be/pgSWfsEzU40

Thanks again to all of you and double thanks, Mr. Bonin!!

I'm ready to hear this thing!!!!

 

[Commander Fluffypants]

OK... it works!

Couple of questions, though.

First, there is a noticeable amount of hiss. How much hiss is normal? You have to crank the output for it to get loud, but I can see how it could add up if this device was used on a bunch of tracks.

Second, once I racked the thing, leaving one space between it and my Aurora's below it, I think it got warmer than when I had it on the bench. Now the meter is reading a little higher (1/2-3/4 db.) Should I just redo the meter calibration? Or just pull the meter down from the front and not worry about it? Or redo other calibrations?

Sorry for bumping the crap out of this thread so much tonight...

 

[dbonin]

http://groupdiy.com/index.php?topic=20058.msg648150;topicseen#msg648150
http://groupdiy.com/index.php?topic=20058.msg645971;topicseen#msg645971


it is 100% necessary to make sure you have a  good electrical connection between all panels of the case (I do that before adding a single wire).  You should have continuity from the ground screw in the back to both sides and the front of the case.  If you have that, this is very likely a wiring issue.  No wires over the PCB?  Ground wire from the PCB (from neg leg power supply cap) to chassis ground?  Grind the paint off where the cases connects to ground wires or where the case connects together. 

There should be no hiss.

OK... it works!

Couple of questions, though.

First, there is a noticeable amount of hiss. How much hiss is normal? You have to crank the output for it to get loud, but I can see how it could add up if this device was used on a bunch of tracks.

Second, once I racked the thing, leaving one space between it and my Aurora's below it, I think it got warmer than when I had it on the bench. Now the meter is reading a little higher (1/2-3/4 db.) Should I just redo the meter calibration? Or just pull the meter down from the front and not worry about it? Or redo other calibrations?

Sorry for bumping the crap out of this thread so much tonight...

 

[dbonin]

If you calibrated with the unit warmed up for about 30 minutes or so you will not need to repeat the calibration.

Let the unit warm up in it's new home in the rack then adjust using the front panel zero adjust when in GR mode and attack knob clicked into the off position.

Second, once I racked the thing, leaving one space between it and my Aurora's below it, I think it got warmer than when I had it on the bench. Now the meter is reading a little higher (1/2-3/4 db.) Should I just redo the meter calibration? Or just pull the meter down from the front and not worry about it? Or redo other calibrations?

 

[Commander Fluffypants]

Thank you so much, dbonin. Your videos were especially helpful as well.  I think you nailed the problem.  One of my twisted pairs is probably too close to the main pcb.  I was very thorough about checking the continuity of the case and also very thorough about sanding off the paint in all the right places, but that one set of wires ended up a bit short and is running the length of the pcb very close by, even touching one of the standoffs. I'll redo those and report back. You, Hairball, and this forum are all awesome!

 

[Commander Fluffypants]

I replaced those wires with some longer ones. There is still hiss if I crank the output past 12. I also just noticed that my volume pot is noisy. Sort of like wind blowing over a microphone.  Perhaps this and the hiss are related?

The compressor actually works and when I tried it on a bass track, I found the level of the  bass signal obliterated the hiss.

Thanks again

 

[Commander Fluffypants]

Just did some more tests. The Input pot also adds hiss, again getting loudest over 12. Then I tried to record the hiss and something strange happened. When I arm the track, and when I record, an additional 60 cycle hum gets added to the noise.  It's very faint, but it's there. I guess the hum might be related to the hiss and that would probably mean a ground issue. I can turn the hum up and down with the 1176, just like the hiss... but the hum doesn't exist, while the hiss does, when just monitoring the 1176 without being in record mode at all. But I also wonder if maybe it's not the 1176 causing the hum, as it only happens when Protools in is record. Perhaps it's an issue at my Aurora? Or a result of all the different heaters turning on in this building right now?

 

[dbonin]

If you can, post a few pictures of the inside of the case.
Do you have ground continuity between the metal case of the input transformer to the ground screw on the rear of the chassis ?
Check the orientation of C7.
Somewhere you have a ground issue.  If possible, check using another signal source.

Search through this and the rev A forum for things like "noise"  "hiss" and "hum" and see what you come up with.

Good luck and keep searching you will find the issue.

Don

Just did some more tests. The Input pot also adds hiss, again getting loudest over 12. Then I tried to record the hiss and something strange happened. When I arm the track, and when I record, an additional 60 cycle hum gets added to the noise.  It's very faint, but it's there. I guess the hum might be related to the hiss and that would probably mean a ground issue. I can turn the hum up and down with the 1176, just like the hiss... but the hum doesn't exist, while the hiss does, when just monitoring the 1176 without being in record mode at all. But I also wonder if maybe it's not the 1176 causing the hum, as it only happens when Protools in is record. Perhaps it's an issue at my Aurora? Or a result of all the different heaters turning on in this building right now?

 

[dbonin]

Happy Thanksgiving !

Thanks MNATS.
Thanks Mike & Hairball.
Thanks all to all the Group DIY's that continue to make this an educational and enjoyable place  on the web!

Don

 

[Commander Fluffypants]

OK. Back to work on this thing. I still have the hum and the hiss. I did recheck continuity between all panels and the faceplate. I also took the unit out of the rack to see if the rack or other items in the rack were causing the hum. No change. There's a hum. I'm going to try to upload some photos. Perhaps someone will notice something. In particular, I'm curious about the uninsulated wires that are dangling off of the output transformer.