[BUILD] 1176 Rev A - Back to the beginning...

[dbonin]

I just finished 2 rev A's - calibration was a breeze (mnats and mike:  thanks!)
All voltages match mnats rev A page, all Q's looked good.
Basic compression tests pass with no problems.
Measuring AC on pad 22 and DC on pad 21 through all the ratio buttons looks spot on.
These things are perfect mirrors of each other at every test point.

I'm just a little concerned that they both don't show correct compression levels (measured at output) through the various ratios.
There is virtually no difference between the 12 and 8 ratio positions when i measure output AC.
Is there a simple test that can put my mind at ease?

 

[Echo North]

Are you doing two point measurements?  The ratio can only be measured by testing several points and it also depends how close to the knee and saturation you are.  Also note the A saturates quickly (part of the charm).

Since the threshold changes with ratio you won't see much change on the meter (analog front panel or DMM)

Read here:
http://www.axtsystems.com/index.php?option=com_content&view=article&id=54:1176lnratios&catid=34:1176ln&Itemid=62

Mike

 

[dbonin]

Are you doing two point measurements?  The ratio can only be measured by testing several points and it also depends how close to the knee and saturation you are.  Also note the A saturates quickly (part of the charm).

Since the threshold changes with ratio you won't see much change on the meter (analog front panel or DMM)

Read here:
http://www.axtsystems.com/index.php?option=com_content&view=article&id=54:1176lnratios&catid=34:1176ln&Itemid=62

Mike

Thanks Mike,  no I was not doing two point meaurements - I hooked my scope up to input on ch1 and output on ch2 and tried to measure voltage drop at the 4 ratio settings.  I was expecting to see some kind of linear drop in AC as I moved from ratio 20 to 4.  I was not considering that threshold changes with ratio, as you pointed out - thanks for reminding me.  I'll keep reading with this in mind. 
Thanks!

 

[rainton]

I don't recall this issue...try back here:

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Title: Re: [BUILD] 1176 Rev A - Back to the beginning...
Post by: dmp on March 06, 2012, 11:09:12 AM
Quote
Does anybody have problems with Rev A oscillating if the output pot is set close to maximum? Mine goes crazy and stops only when I touch the "7" point. Looks like a sidechain thing... Anybody?

I had this problem and it took me forever to figure out what was going on. I finally installed the ground wire from the pcb ground to the chassis start point, and the oscillations stopped immediately!
Also check the shielding for the wires to the output pot.
If you pull the FETs you will be able to tell if it is the sidechain.-
-------

Also make sure your wires from the meter to the XLR are far away from the PCB.

Mike

Another quick heads-up on the oscillating issue:
I had the wires from the meter to the XLR running along the rails - so they were very close to the pcb. I did as Mike suggested and
placed them further away from the pcb -> ISSUE SOLVED

Thanks Mike - no oscillating anymore.

I also built another Rev A this weekend - again with carbon comps - worked perfectly from the first power-on! And it sounds amazing!!

 

[hymentoptera]

Another quick heads-up on the oscillating issue:
I had the wires from the meter to the XLR running along the rails - so they were very close to the pcb. I did as Mike suggested and
placed them further away from the pcb -> ISSUE SOLVED

Thanks Mike - no oscillating anymore.

I also built another Rev A this weekend - again with carbon comps - worked perfectly from the first power-on! And it sounds amazing!!

That's GREAT news! Any chance we could see pics of your PCB? I'm curious how well the 1/2w resistors fit in there. I imagine they are longer than the 1% metal films the board is spec'ed for, and I wonder if you had any fitment issues. Thanks!

 

[obutcher]

Hi all

New to the game, so please be nice!

I've got a problem with my Rev A. I've stuffed the power supply and wired it up, but my voltages don't seem to be right.

I'm getting -9.75v on the legs of CR6, but when testing on the legs of R87 I'm only getting 5.55V, not the approx 30V as to be expected.

I'm running 240v if that helps.

Cheers

 

[Echo North]

Hi all

New to the game, so please be nice!

I've got a problem with my Rev A. I've stuffed the power supply and wired it up, but my voltages don't seem to be right.

I'm getting -9.75v on the legs of CR6, but when testing on the legs of R87 I'm only getting 5.55V, not the approx 30V as to be expected.

I'm running 240v if that helps.

Cheers

You don't want to test between the leads of R87.  You're testing between the lead of R87 marked +30V and the CT.

 

[rainton]

That's GREAT news! Any chance we could see pics of your PCB? I'm curious how well the 1/2w resistors fit in there. I imagine they are longer than the 1% metal films the board is spec'ed for, and I wonder if you had any fitment issues. Thanks!

Unfortunately I didn't take any pictures after the conversion - but it's true the 1/2W resistors are a little too big - so I had to bend the legs of each resistor inwards a little and then after 5mm bent them out a little again so both of the legs would point straight downwards - you know how I mean?

Like so:

  [_Res._]
      >  <
      |    |

haha

 

[obutcher]

Hi all

New to the game, so please be nice!

I've got a problem with my Rev A. I've stuffed the power supply and wired it up, but my voltages don't seem to be right.

I'm getting -9.75v on the legs of CR6, but when testing on the legs of R87 I'm only getting 5.55V, not the approx 30V as to be expected.

I'm running 240v if that helps.

Cheers

You don't want to test between the leads of R87.  You're testing between the lead of R87 marked +30V and the CT.

That's what I'm doing. Sorry, should have said that in the first place!

 

[hymentoptera]

Unfortunately I didn't take any pictures after the conversion - but it's true the 1/2W resistors are a little too big - so I had to bend the legs of each resistor inwards a little and then after 5mm bent them out a little again so both of the legs would point straight downwards - you know how I mean?

Like so:

  [_Res._]
      >  <
      |    |

haha

Yes, I know what you mean. I figured this was the solution. if everything worked for you, then I'm comfortable proceeding with my build using 1/2w carbon comps

 

[Echo North]

Hi all

New to the game, so please be nice!

I've got a problem with my Rev A. I've stuffed the power supply and wired it up, but my voltages don't seem to be right.

I'm getting -9.75v on the legs of CR6, but when testing on the legs of R87 I'm only getting 5.55V, not the approx 30V as to be expected.

I'm running 240v if that helps.

Cheers

You don't want to test between the leads of R87.  You're testing between the lead of R87 marked +30V and the CT.

That's what I'm doing. Sorry, should have said that in the first place!

Check all of your components in that power section. It's the only thing stuffed correct?  All values and orientations.

 

[obutcher]

Alright, found it. I've been trying to keep the solder really neat, but a joint didn't have enough solder on it. Fixed it right up. Serves me right for trying to do it late night while tired. 8 hours sleep and a fresh look goes a long way! Sorry for wasting your time!

 

[jakearon]

Can anyone post a picture of a finished rev a board version 1.2.5?

Thanks!

 

[obutcher]

Alright, made it to the attack/release potentiometer stage. The instructions say "Mechanically secure the correct value resistor and capacitor in parallel to the attack potentiometer as shown. Here we are using the Alpha RV24A02F-10-15S1-BF4 potentiometer with the SPDT switch."

My only question is: What ARE the correct values for each potentiometer?

I can't seem to work it out!

 

[hymentoptera]

Alright, made it to the attack/release potentiometer stage. The instructions say "Mechanically secure the correct value resistor and capacitor in parallel to the attack potentiometer as shown. Here we are using the Alpha RV24A02F-10-15S1-BF4 potentiometer with the SPDT switch."

My only question is: What ARE the correct values for each potentiometer?

I can't seem to work it out!

The cap and resistors are on the BOM and on the schematic. Look for R57 (the resistor across the release pot, which is itself R56), and R54 and C27 which are across the attack pot (which is itself R55). the values of R57, R54 and C27 have changed many times over the revisions, so check the BOM for rev A v1.2.5 for the correct values for your build. Note that in the original Rev A from the 1960's, C27 was a 10nF Sprague film cap, but the designers of this "kit" have gone with a 12nF WIMA film cap which will work just fine. Be sure to double check the values of your resistors (as with everything!) with you multimeter before mechanically securing and soldering.

 

[hymentoptera]

Can anyone post a picture of a finished rev a board version 1.2.5?

Thanks!

There are tons of pics in this thread alone. I've even got a folder going on this PC where i'm copying pics i find for later refference. Note that many of the posters uploading pics are experiencing technical problems, or may have used custom selected parts in their build, not to mention the mouser cart is constantly being updated, so yours may not be identical. For instance, C22 (220nF) used to be a kemet EVOX film type, but was recently updated to a WIMA instead. it's unlikely that anyone has built the kit using the new WIMA from the updated cart in that position yet.

 

[evilcat]

Can anyone post a picture of a finished rev a board version 1.2.5?

Thanks!

Something like that? Is it clear enough for you?

Ben

 

[evilcat]

and another one...

 

[jakearon]

what happened to the power supply section? just curious...

 

[evilcat]

As you can see on the 2nd picture I've made a combo with a 500 serie preamp and the 1176, so I took one PSU (JLM power station 5 rails) for the 2 PCBs. So I haven't populate the 1176 PSU section.