[BUILD] 1176 Rev F/G - new board, new transformer!

[beaversaber]

gr control section

 

[beaversaber]

more gr control section

 

[beaversaber]

back

 

[beaversaber]

Anyone around?  :

 

[Echo North]

-Q bias set right?
-Tried replacing Q1?

Mike

 

[beaversaber]

-Q bias set right?
-Tried replacing Q1?

Mike

The unit isn't compressing, Qbias has no effect on the signal.  I have replaced Q1.  I've posted everything that I've done to troubleshoot over in the main 1176 help thread within the last few pages.

Also, I just tried replacing all the transistors in the GR control section.  Still no luck =(

 

[Echo North]

Have you confirmed with a continuity tester that pad 22 is NOT shorted to ground somehow with GR ON?

Mike

 

[beaversaber]

Have you confirmed with a continuity tester that pad 22 is NOT shorted to ground somehow with GR ON?

Mike

Yup.  With GR turned on pad 22 is not shorted to ground.  When GR is disabled, it shorts to ground

 

[beaversaber]

Have you confirmed with a continuity tester that pad 22 is NOT shorted to ground somehow with GR ON?

Mike

Yup.  With GR turned on pad 22 is not shorted to ground.  When GR is disabled, it shorts to ground

Anyone around?  ???

 

[armand1234]

Hello!!

Sorry, my English is not very good. My question is: which are the calibrations that have to be realized in the rev F?

Thanks!!

 

[armand1234]

Up! Please!!!

 

[Echo North]

Q Bias, Tracking, Distortion Trim.

CMRR Trim if you do the iC input.

Mike

 

[armand1234]

That has to be to adjust the CMR? I do not find information!! 
I locate the potentiometer R2 but I do not know like to adjust.

Thank you!!

 

[envelope]

That has to be to adjust the CMR? I do not find information!! 
I locate the potentiometer R2 but I do not know like to adjust.
Thank you!!

Post #43 in this thread has a link to a calibration procedure that may be useful.....http://www.axtsystems.com/index.php?option=com_content&view=article&id=56:1176lncalibration&catid=34:1176ln&Itemid=62

 

[armand1234]

Thanks!
But there is no reference to the CMRR!. In board rev F is a R2 to calibrate the CMRR. I have my first rev F, and for calibrate the Q Bias i don't have any problem, but I have to up very much the level of the input, because the 1176 does not start compress. I suppose that it is for the adjustment of the CMRR.

I don't find any document for it.

Best regards

 

[armand1234]

And other question, in the schematic of the review, the R5 it does not appear but in the PCB yes. This can be caused it of the low gain of the input?

Thanks!

 

[armand1234]

up!, sorry any idea???

Thanks!

 

[envelope]

Thanks!
But there is no reference to the CMRR!.
Best regards

I haven't got to the calibration, so I did not notice the lack of a CMR procedure, oops. Hopefully it is still useful for you....
for CMR adjust, something like...inject a common reference signal to pin 2 and pin 3, adjust R2 to maximize your Rejection Ratio, by trimming to minimize the output.......

 

[envelope]

And other question, in the schematic of the review, the R5 it does not appear but in the PCB yes. This can be caused it of the low gain of the input?
Thanks!

--R5 should not be populated on the main PCB if you are using an IC input with a potentiometer.
--If using the IC input option 'R5' is the potentiometer  
--If using the Transformer input option, 'R5' is the component on the main PCB
--R5 is in the schematic, study the input section of both the Transformer Input option and the IC Input, {upper let of the schematic}, it is [[attached]] here in PDF

 

[armand1234]

Thanks envelope, your information is very useful.

Another factor that me does not work is to put the switch of attack in off. I put the pin 22 to ground, but the VU meter not decibels decreased (gain reduction to put calibration). I have checked the unit...

Thanks!