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

[Che_Guitarra]

Hi guys - I finally received the last Wima cap to finish off my Rev A today, and it works!  Woop woop!

Signal is coming in and going out, input and output controls are working just fine.

I'm having trouble with calibration.  I've got 0.775VAC @ 1kHz going in, I can adjust to +1 on the meter with my input and output controls, but I can't get the Q-bias to trim +1 back to zero.  Watching Mnats calibration videos, he says to trim the Q-bias so the wiper is fully grounded.  I've tried both clockwise and anti-clockwise, but my trim pot just keep going and going and going and going - it doesn't seem to have a starting point nor an end.  Is this typical of these Bournes trimmers?  OR is my problem that i'm using a Rev D calibration guide to fine tune a Rev A?

I do have a correct replacement trimmer in my kit somewhere, but before I do anything i'm seeking the wisdom of those on this forum first 

 

[Echo North]

Hi guys - I finally received the last Wima cap to finish off my Rev A today, and it works!  Woop woop!

Signal is coming in and going out, input and output controls are working just fine.

I'm having trouble with calibration.  I've got 0.775VAC @ 1kHz going in, I can adjust to +1 on the meter with my input and output controls, but I can't get the Q-bias to trim +1 back to zero.  Watching Mnats calibration videos, he says to trim the Q-bias so the wiper is fully grounded.  I've tried both clockwise and anti-clockwise, but my trim pot just keep going and going and going and going - it doesn't seem to have a starting point nor an end.  Is this typical of these Bournes trimmers?  OR is my problem that i'm using a Rev D calibration guide to fine tune a Rev A?

I do have a correct replacement trimmer in my kit somewhere, but before I do anything i'm seeking the wisdom of those on this forum first 

They don't have start stop.  They only have 20 rotations however, and if you over rotate them you can break it.  You may want to pull it and test it.

 

[Danny1107]

Hi guys,

I've a strange problem with my Blue Strip.

If I switch on the unit all is ok, all Voltages are fine. But when I turn the Output Pot CW the unit gives a loud 50Hz hum and no audible tones.
The 30V test point BRN at output Trafo and after R17 drops to 20V when the hum is there.

Then I have to turn back the output Pot CCW, switch off the Unit and then on and all is normal.
Any ideas what that can be?
Thanks!

Cheers Danny

 

[Danny1107]

Hi,

ok I tested a little bit.
I found out, that when there is no input signal, Input pot to position 12, output position 12 there is a loud peak in the meter and on output around 40db when I push the ratio switch bank vom 20:1 to 4:1.
After that the unit overdrives and give me the loud 50hz hum. The hum is constant, don't react with input or output pot.

Is it possible to modify the ratio switch bank that the signal don't drop and don't peak when I change the ratio?
Ok here is a sample how the unit works, input and output at 12 o'clock. ratio 20:1 then switch to 4:1...  https://www.dropbox.com/s/bp3257ih2j9q540/1176%20Test.mp3

Danny

 

[Echo North]

Hi,

ok I tested a little bit.
I found out, that when there is no input signal, Input pot to position 12, output position 12 there is a loud peak in the meter and on output around 40db when I push the ratio switch bank vom 20:1 to 4:1.
After that the unit overdrives and give me the loud 50hz hum. The hum is constant, don't react with input or output pot.

Is it possible to modify the ratio switch bank that the signal don't drop and don't peak when I change the ratio?
Ok here is a sample how the unit works, input and output at 12 o'clock. ratio 20:1 then switch to 4:1...  https://www.dropbox.com/s/bp3257ih2j9q540/1176%20Test.mp3

Danny

That's wacky and not right at all.

I wish I had something to point you too.  Been around a while and never had heard/scene that. 

Does it happen whenever you switch ratio's or just 20 - 4?

 

[Danny1107]

That's wacky and not right at all.

I wish I had something to point you too.  Been around a while and never had heard/scene that. 

Does it happen whenever you switch ratio's or just 20 - 4?

Yes I'm very confused about that.

I measured the voltage at Q4, it should be 6,6V, I've 4,4V on this point, the other voltages are fine.
If the 50Hz hum is there, I measured on output trunny WHI/BLK and WHI/RED to ground 9V, when the unit is working correct it's 2,2V.

If the ratio changes from 20 to 12 I've a peak too, or from 12 to 8, and the needle dance to the right of the scale and then back to 0 in GR. The hum is coming if the unit overdrive when change the ratio in this moment.
If I change ratio from 4 to 8 the needle dance down to -12 and then back to 0, then there's no hum.
Ratio changes in low levels the unit works correct and there's no hum...

If I touch point 17 with my finger the hum is coming and don't get away. Same thing is if the unit is overdrived.
Q4 and Q5 has been changed, but the same. Next I will change Q6 and will see what happened.

 

[Echo North]

Wacky.

Open the schematic.

Check your C8, C9, C10, and C13 cap values and orientation if they are polarized.

Check the value of R24,25, 26, 35, 27, 28, 31,32.

Check out that loop from Q6 with R33, C15 then R34 and C16.

Make sure you don't have wires hanging all over the PCB in that section.

Mike

 

[Danny1107]

Ok,

the unit works 

Q6 was damaged, I have change Q6 and it works, no hum anymore after overdrive!!!

My voltage on Q4 isn't 6,6V, it's only 4,3V. And after C9 I measure 0.18V.
And the peaks when I changed the ratios. Biggest peak is if I change from 20 to 4.
Is this correct?



Danny

 

[lowend]

hi !

I just finished my new rev A SOund's good, calibration is OK

But when I change compression ratio, sometimes the needle of the view meter stay stuck on the right...
That's strange.... my solders looks good etc...

I posted a little video on Youtube : http://youtu.be/9cCYkNiVpb0

If someone can help me with that ! or have an idea ??

 

[lowend]

this is strange...
Take a look...

http://youtu.be/tC_qI1Qq-MQ

maybe the view meter is broken ?

 

[Danny1107]

this is strange...
Take a look...

http://youtu.be/tC_qI1Qq-MQ

maybe the view meter is broken ?

Hi lowend,

take out the meter from the front panel and then do the test again.
Maybe the screw is too fixed attracted, I had that once, so the needle hung on the scale from the meter.

Danny

 

[lowend]

HI Danny and thanks for your answer

I did it, but nothing change... that's strange
Do you think I can move the black screw on the front of the view meter ? I dont know what that screw for...
http://youtu.be/acBSFAeTzxQ

thanks for your help

 

[Echo North]

HI Danny and thanks for your answer

I did it, but nothing change... that's strange
Do you think I can move the black screw on the front of the view meter ? I dont know what that screw for...
http://youtu.be/acBSFAeTzxQ

thanks for your help

It looks more like a circuit level error than a mechanical error.  Does it look like it's mechanical "stuck" or just there because of an error in the circuit.  Is there oscillation or something happening?

 

[lowend]

HI Danny and thanks for your answer

I did it, but nothing change... that's strange
Do you think I can move the black screw on the front of the view meter ? I dont know what that screw for...
http://youtu.be/acBSFAeTzxQ

thanks for your help

It looks more like a circuit level error than a mechanical error.  Does it look like it's mechanical "stuck" or just there because of an error in the circuit.  Is there oscillation or something happening?

I can use the compressor.... working perfectly... I can see Gain reduction etc.... but only this problem... If it's not mechanical I dont know where to search. When the needle is stuck I can hear a "tik" in the view meter...

 

[Echo North]

Is the "tick" from it slamming hard right?  Does it appear to be physically stuck on something?

Mike

 

[lowend]

Is the "tick" from it slamming hard right?  Does it appear to be physically stuck on something?

Mike

Hi

"Is the "tick" from it slamming hard right?" Yes

no it's not physically stuck on something... I just have to do a little help with my finger and come back to normal position... as you can see on my  video... => http://youtu.be/tC_qI1Qq-MQ

 

[Echo North]

Is the "tick" from it slamming hard right?  Does it appear to be physically stuck on something?

Mike

Hi

"Is the "tick" from it slamming hard right?" Yes

no it's not physically stuck on something... I just have to do a little help with my finger and come back to normal position... as you can see on my  video... => http://youtu.be/tC_qI1Qq-MQ

I think it would be worth trying a new meter.

Send me an email (info at hairballaudio dot com) confirming your address and I'll get a replacement out to you.

 

[vanrivers]

First post 

Got mine running and calibrated correctly with voltages matching the ones provided on the schematics. Thanks to mnats and hairball for the documentation and parts, just amazing and so much fun, i didn't even own a soldering iron before starting... couldn't believe my eyes when the unit powered up.

Have a few issues that i would love to get some help with if someone might have a clue about what it might be.

- Even though the input knob is turned off (fully CCW) i'm still getting a low signal passing through.

- When i put my finger on C3 i'm getting fm/am radio interference. i'm also getting weird noise when touching C1 and C2.

thanks
Henrik

 

[Curran]

Super excited!!! My recording studio is starting to get on the upswing here in Ohio and I have just ordered a Rev A 1176 from hairball full kit! sooooooooooo physicked about this compressor!!! with this and the CLX clone on the way I am going to have a good time building compression for my studio!!!

 

[Chrome Heart]

Im not sure this is a "problem" because the compressor sounds great. But I have noticed a lot of drift on the zero adjust. It doesnt seem to be related to anything specific either, If I leave the unit on for two days it still drifts around anywhere from -3 to +2. My rev J units are really stable after they've been on for a while. When I performed the null adjust I was able to get it down to 0.00V so Im not sure why it fluctuates so much. But, like I said, it sounds terrific. With a Rode NTV and 1290 pre it sounds great on vocals.