[BUILD] 1176LN Rev D DIY

[Bri]

Hey Josh.

It's hopefully just some confusion in the calibration procedure...seems that way since both meters act the same.

Meter needle drops to -10VU with no signal?
What happens when you inject the signal then?

From what you wrote, two things came to mind, however, ignore any incorrect assumptions.

During tracking adjust, it sounded as if you were using R44 to try and adjust to 0VU instead of using R71?
Still, -10 initially, with no signal, that may be a little far in regards to the needed trim ranges in the tracking procedure...but maybe not.

Secondly, were you implying that you were in GRmode during the Qbias procedure? Or did you just note the meter's position before and after?
If you're using the unit's meter to make the Qbias adjustment, make sure you short pad 22 to ground, so you're basically in "GR bypass" but still have the meter function...don't Qbias in GRmode, of course. That could be suspect.

In regards to tracking adjustments, I assume in lieu of "shorting pad 22 to ground," to keep the meter functioning whilst bypassing GRmode, you're just muting your source signal?
I did the "short pad 22 to ground" to be on the neurotic side, but you should be fine the other way.

So when you're sure about your Qbias, and have then done the Zero meter, 0volts across R74 step....
Here's an outline of my tracking adjust method...maybe it will help:


R44 in
GRmode(20:1)
Your controls set for the 10db swing(10db of GR)
Your source signal coming through...being compressed.

Now, adjust your meter needle to -10VU using the R44 "tracking adjust" trimmer(reflecting the 10db of reduction).

Now, mute your source signal(or short pad 22 to ground), and adjust the needle back up to 0VU using the "0 Set"(R71) trimmer.

Now un-mute your source signal again(or un-short pad 22), and readjust R44 trimmer so the meter needle again shows the 10db of gain reduction(-10VU).

Mute the source signal(or short the 22 pad), and again use the "0 Set"(R71) trimmer to adjust the meter needle back to 0VU.


You should see a slight bit of change(for the better) after each adjustment cycle.

So, repeat this back and forth adjustment procedure until the meter finally holds it's adjustments...
i.e., the meter needle will eventually hold at -10VU when you have the source signal present, and then go back to 0VU when you mute the source signal(or short pad 22 to ground).
Getting to this point usually requires many repetitions of that adjustment cycle.


Is any of this relevant to your troubles then? I'm getting tired of typing.

--Brian

 

[JdJ]

That seemed to do it Brian! Thanks! I guess my issue was that I didn't realize that the "null adjust" was used to bring the meter back to zero during the tracking adjust phase of the calibration. The JBL instructions mention the adjustment through the front panel on a 1176 (which I don't have), so I was assuming they meant the zero adjust. I was also assuming that the null adjust should stay put after doing the meter/null adjustment. You did mean Null adjust and not meter zero adjust, right? Where were you getting you calibration info from? I forgot to check the Gyraf site...

Thanks again-

I'll have to run it through some tests after work, but all seems well.

You guys rock!

:guinness: :guinness:

Josh

 

[Bri]

Whoa, my bad, I did mean the "0 Set" Trim.
I'll re-edit my post so as not to confuse anyone even further.
Thanks for pointing that out...It was 4am here when I wrote that.
Of course, now you may be back where you started.
But, I'm sure you'll figure it out soon.

--Brian

 

[kato]

Brian, I just wanted to say thanks / show my appreciation / send you some beers :guinness: :guinness: :guinness: :guinness: :guinness: :guinness: :guinness: for the step-by-step calibration procedures.

I have been wading through posts with conflicting information, apparent misinformation and posts specifically for non-clones with attack switches. While the info in the original manual is certainly sufficient for more experienced users, your detailed steps saved me from banging my head against the wall.

Once I figured everything out, I vowed to make a detailed calibration page but your instructions have pretty much rendered that need obsolete. Thank you for taking the time to share in newbie language what must have taken you many hours to figure out. :thumb: Kato

 

[Bri]

Hey thanks Kato.

If I can spare you the hours of frustration, well then I'm glad to be of help.
It's so simple too.....think of all the needless suffering.

Just think, mnats is probably rolling his eyes about now,
dumbfounded by how the calibration procedure could become the most difficult part of a first time build. LOL!

Cheers,
Brian

 

[Stagefright13]

I had trouble myself so don't feel bad. First time I didn't use discrete directions. Now I would like to build another but took alot of work to get the parts for this one!

Wish I coulda help a bit better but has been a while since I did the Calibration.

 

[Ilya]

I'm going to home-etch some Rev D pcbs 'cause they are not available... I found out that both meter and ratio boards differ from mnats g1176 (at least on the photos they are different, I'm talking about rotary version). I can't find any info about these small boards (except input trafo pcb). Can somebody point me in the right direction? Or at least tell me what for is the trimmer used on the ratio switch board? Thanks!

 

[mnats]

[quote author="Ilya"]I'm going to home-etch some Rev D pcbs 'cause they are not available... I found out that both meter and ratio boards differ from mnats g1176 (at least on the photos they are different, I'm talking about rotary version). I can't find any info about these small boards (except input trafo pcb). Can somebody point me in the right direction? Or at least tell me what for is the trimmer used on the ratio switch board? Thanks![/quote]
http://www.groupdiy.com/index.php?topic=258435#258435

It's kind of crazy referencing an earlier part of the same thread each time someone asks a question, so you might want to try a search next time. That's how I found it!

If you are going to try a home-etch, make sure you remove the extra base pads from the top layer of the GR Control Amp section.

 

[Ilya]

Thanks, mnats.
I was re-reading the thread once again and found that post. Probably I missed that 'cause there're only 2 posts about that trimmer and I skipped them.
Thanks for reminding about the base pad - there's plenty info here, so I won't miss that one

 

[Arrigotti]

I finished up my REV. D 1176, and have calibrated it, (at least I think it is calibrated correctly).

The problem I am having is that the output is really hot. I have to turn the output pot almost down to nothing to make sure that I don't clip my converters. The input is set so that I am just starting to get some compression.

The compressor is compressing, and the audio sounds fine (no nasty distortion).

Any thoughts? I know, check all the connections and component values and also check for solder blobs.

Beside that, any thoughts, or at least a starting point to check?

Thanks,

E. Arrigotti

 

[Arrigotti]

Well, here I go again answering my own question:

The output pot was wired backwards, but now I have another problem: It isn't compressing now. I am royaly stumped on this. It isn't just the meter either. I can't hear any compression.

I checked the voltage at point 7 and 19, and it is about -1.3v no matter where the input or output is set. (This is in GR mode)

Any thoughts?

 

[Stagefright13]

Been using mine ALOT but the vintage 1985 input pot is very scratchy now. Or if I can clean it? Sigh... Anyone know of a replacement? I would like to get A real one from Andrew at Purple. But would hate to bother him...

 

[Stagefright13]

Arrigotti Did you set the FET into conductance range? After that it is just a meter thing. And I will vouch it being a great compressor!

And pots may seem to work in reverse on 1176 Or Purple. Attack is faster clockwise and same as Release.

 

[Arrigotti]

Arrigotti Did you set the FET into conductance range? After that it is just a meter thing. And I will vouch it being a great compressor!

If you mean did I set the Q-BIAS, then yes I did, and I double checked it a few times also.

On a side note, I do like the sound of the signal chain. It seems to tighted up the low end, maybe taking out some of the low-mid muddiness?

I'm gonna poke around a bit more.....

 

[Siegfried Meier]

Hey guys,

I'm doing a pair of Rev D's and I have a couple of extra Lundahl 1540 input transformers laying around. I know that the transformer board will accept it, but I haven't seen anyone using it for a Rev D. Any reasons, other than it won't be original, why I shouldn't use them?

Also, I'm looking for a pair of T-pads. Anyone got any leads on some?

Thanks,
Sig

 

[Arrigotti]

Okay, so here is some further development in my troubleshooting woes:

I figured out that the compressor actually does compress, but only when I feed it a signal with peaks. If I feed it a test tone, it doesn't really show compress, or at least it doesn't show it.

The other strange thing, that is probably related, is that when I switch the to GR OFF mode, the output drops quickly, and then ramps back up, and usually past where it was before (I assume because it isn't compressing). When I switch the GR back in, it drops quickly and then slowly comes back up. The Attack and Release knobs have no effect how quickly it comes back.

I am stumped again.....

Maybe a problem with the 2N3708's? I just put them in as I didn't really know how to test them.

Maybe a wrong/bad electrolytic?

 

[kato]

[quote author="Arrigotti"]
I figured out that the compressor actually does compress, but only when I feed it a signal with peaks. If I feed it a test tone, it doesn't really show compress, or at least it doesn't show it.
[/quote]

It could be
that your compressor
is working just fine. :thumb:

 

[Arrigotti]

It could be
that your compressor
is working just fine.

I wish...... but I've built a few of the regular Rev. F ones and I had no trouble feeding the unit a test tone to calibrate the meter tracking. They have always resgistered the compression with a sine wave.

The way I have this unit now, I am unable to calibrate the tracking since it won't compress if I send it a sine wave (or at least the meter section doesn't show compression.

BTW, I like your Avatar. It reminds me of my childhood. Oh the hours I pissed away with the Atari 2600.

 

[kato]

[quote author="Arrigotti"]
I wish...... but I've built a few of the regular Rev. F ones and I had no trouble feeding the unit a test tone to calibrate the meter tracking. They have always resgistered the compression with a sine wave.
[/quote]

Oh I misunderstood. That sounds like how it would act under normal operation. But you're in calibration mode. Sorry. Something wired wrong with the bypass/GR switch? (I wish I knew more to help.)

[quote author="Arrigotti"]
BTW, I like your Avatar. It reminds me of my childhood. Oh the hours I pissed away with the Atari 2600.[/quote]

Defender was my first cartridge.
Sometimes it makes me sad that I wlll never enjoy a video game as much as Defender. 3D games make no sense to me.

 

[Arrigotti]

This has been the most perplexing troubleshooting I've ever done. I have always been able to troubleshoot my builds and they all work now (Four 1176's, Chimera, Bellerophon, LA2A, Four Channels API, Two SSL's, as well as several guitar amps).

So upon further investigation, probing, and re-soldering if wires that broke off, here is what it seems like the main issue is:

Compression is directly related to the level of the output. When I have the output low, there is no compression, but when I push it up, I can get much more compression.

By looking at the schematic, I can see that the top leg of the output pot it tied to the compression circuit, but I can't figure out how it is acting as a threshold as well as an output pot.

Any help would be appreciated, even if it is just a starting point.

Thanks...