[BUILD] 1176LN Rev D DIY

[andyfromdenver]

Hi Matt!  I'll try and pitch in, having just completed mine.
I initially did not have qbias success per the Hairball doc.
But I followed the video to a t and it worked.
Mike and mnats recommend turning the qbias trim pot all the way ccw.
Make sure u don't over crank it.
Put your meter on the underside so you can confirm when you've reached the start.
Then, you should have success!
Good luck

 

[babaorum]

Hello

I try to finish the first channel of my stéréo 1176 rev D (Hairball's stereo bundle + mnat's pcbs).
I make a rotary version (ratio and meter), could you tell me where are wired the X and Y pads of the meter pcb's for a rotary version ?
because on the mnats v2.2 25/02/2013 pcb's version there is no X and Y ... ?
I suppose on the output transformer but which colors wires ?

Thanks

Regards
Baba

 

[mattvon]

Hi Andy, thanks for your reply...unfortunately, I haven't had any luck with the mnats method either...no matter how high I turn the input and output pots, I cannot get the needle past -2, let alone +1.  Also, the output pot reflects the odd behavior with either method--it's as if either full CW or CCW are essentially zero, and midway through the travel of the pot is maxed out--but never high enough to use either Q bias method...

Any other thoughts?  I appreciate the help!

 

[andyfromdenver]

Hi Matt.
I dread giving bad info here, but will gladly run the risk to help or solicit better help, as I'm still digesting the circuit etc.
anyway.
Just to clarify how I thiiink I had success (two days ago is like an eternity with poor short term memory).
Input all the way down.  Jumper (lil molex connector thing) in circuit.
Output 3/4 up.  Attack set to off (switched off) release fast. Comp 20:1.  Meter on +4 (which I think Hairball said on GR?  I'm pretty sure mnats said +4. Foggy)
1k tone (used one on YouTube) meter on pins two and three of input, turn up daw output til you achieve your 0.775 vac
Then increase output so meter shows +1, then dial in qbias pot for the 1db drop which you confirm with the meter and the voltage reading on the output.

Does that sound like what you are doing?

If I made a mistake in my recounting I apologize.

Are all your grounds rock solid and did you do the power supply test and do you feel 100% about your wiring and pcb?  Gotta be 100% there or consider a fine tooth comb scrutiny.

I hope you have success!

 

[dbonin]

Hi Andy, thanks for your reply...unfortunately, I haven't had any luck with the mnats method either...no matter how high I turn the input and output pots, I cannot get the needle past -2, let alone +1.  Also, the output pot reflects the odd behavior with either method--it's as if either full CW or CCW are essentially zero, and midway through the travel of the pot is maxed out--but never high enough to use either Q bias method...

Any other thoughts?  I appreciate the help!

Set the front panel controls to get to needle to -2 (as you say, this is as far as you can get) then start turning R59 - can you get the needle to move up any further?

 

[mnats]

...if I set the input pot at "24" and slowly increase the output pot from full CCW, turning CW, I get a peak of just barely over 1.0 VAC and then it diminishes back to near 0 VAC at full CW.

That isn't normal, and you'll have to correct the problem before you can proceed with any of the calibration procedures.

What have you tried so far of the troubleshooting tips from my FAQ?

 

[mnats]

I make a rotary version (ratio and meter), could you tell me where are wired the X and Y pads of the meter pcb's for a rotary version ?
because on the mnats v2.2 25/02/2013 pcb's version there is no X and Y ... ?
I suppose on the output transformer but which colors wires ?

Unlike the G1176-style boards the output transformer isn't mounted on the main board for my A, D and F/G PCBs. Therefore it is impractical to put X Y pads on them.

Have a look at the schematic - the colors are shown there. Remember that you're measuring the output of the unit with the VU meter so the polarity isn't important.

 

[mattvon]

...if I set the input pot at "24" and slowly increase the output pot from full CCW, turning CW, I get a peak of just barely over 1.0 VAC and then it diminishes back to near 0 VAC at full CW.

That isn't normal, and you'll have to correct the problem before you can proceed with any of the calibration procedures.

What have you tried so far of the troubleshooting tips from my FAQ?

Thanks very much for your reply.  Following the Hairball guide, I built the power supply first and it tests good, all voltages appear correct.  I tested each resistor as I stuffed the PCB and feel confident the values are correct.  I've visually inspected my solder joints, I reflowed a couple which looked questionable, so I'm thinking it's either a wiring issue or something I'm not thinking of (faulty component?)

I have also built a version of Mark Burnley's signal tracer.  Since I'm not passing very much voltage, would you recommend I begin by checking voltages or testing the signal path?  I'm still mostly a newbie, but I'm committed to getting this working and I'll be grateful for any advice you might have.

 

[dbonin]

...if I set the input pot at "24" and slowly increase the output pot from full CCW, turning CW, I get a peak of just barely over 1.0 VAC and then it diminishes back to near 0 VAC at full CW.

That isn't normal, and you'll have to correct the problem before you can proceed with any of the calibration procedures.

What have you tried so far of the troubleshooting tips from my FAQ?

Thanks very much for your reply.  Following the Hairball guide, I built the power supply first and it tests good, all voltages appear correct.  I tested each resistor as I stuffed the PCB and feel confident the values are correct.  I've visually inspected my solder joints, I reflowed a couple which looked questionable, so I'm thinking it's either a wiring issue or something I'm not thinking of (faulty component?)

I have also built a version of Mark Burnley's signal tracer.  Since I'm not passing very much voltage, would you recommend I begin by checking voltages or testing the signal path?  I'm still mostly a newbie, but I'm committed to getting this working and I'll be grateful for any advice you might have.

Check for the simple things first when it comes to wiring - it's easy to get turned around and swap wires and leads and put similar looking pots in the wrong spots.  A quick glance can sometimes fool the eye into thinking something is correct when it's reversed.  But lets assume you have beat that horse to death! 

Start at the point where the input transformer enters the PCB - apply your .775V / 1khz test signal and measure the voltage as you increase the input pot from full ccw to full cw  - (if you used terminals for the wiring, disconnect them) -  let us know what you find.

 

[mattvon]

...if I set the input pot at "24" and slowly increase the output pot from full CCW, turning CW, I get a peak of just barely over 1.0 VAC and then it diminishes back to near 0 VAC at full CW.

That isn't normal, and you'll have to correct the problem before you can proceed with any of the calibration procedures.

What have you tried so far of the troubleshooting tips from my FAQ?

Thanks very much for your reply.  Following the Hairball guide, I built the power supply first and it tests good, all voltages appear correct.  I tested each resistor as I stuffed the PCB and feel confident the values are correct.  I've visually inspected my solder joints, I reflowed a couple which looked questionable, so I'm thinking it's either a wiring issue or something I'm not thinking of (faulty component?)

I have also built a version of Mark Burnley's signal tracer.  Since I'm not passing very much voltage, would you recommend I begin by checking voltages or testing the signal path?  I'm still mostly a newbie, but I'm committed to getting this working and I'll be grateful for any advice you might have.

Check for the simple things first when it comes to wiring - it's easy to get turned around and swap wires and leads and put similar looking pots in the wrong spots.  A quick glance can sometimes fool the eye into thinking something is correct when it's reversed.  But lets assume you have beat that horse to death! 

Start at the point where the input transformer enters the PCB - apply your .775V / 1khz test signal and measure the voltage as you increase the input pot from full ccw to full cw  - (if you used terminals for the wiring, disconnect them) -  let us know what you find.

Thanks for the reply!  Here are my measurements (along with my signal path measurement points, to make sure I've not goofed something up):

Signal generator set to deliver a 1khz tone at .770, measured at pin 2 of the input XLR.
Measurement at the input "+" of the L-pad PCB = .770VAC
Measurement at the output "+" of the L-pad PCB, fully CCW = .770VAC
Measurement at the output "+" of the L-pad PCB, fully CW = .770VAC
Measurement at the input "+" of the input transformer PCB, L-pad fully CCW = .773VAC
Measurement at the input "+" of the input transformer PCB, L-pad fully CW = .774VAC
Measurement at the point where the "+" wire connects to the PCB (wire detached from terminal), L-pad fully CCW = .317VAC
Measurement at the point where the "+" wire connects to the PCB (wire detached from terminal), L-pad fully CW = .317VAC

I don't believe it makes a difference, but the unit was not powered up for the above measurements. 

The L-pad doesn't seem to be doing anything?  FWIW, I have continuity from the input transformer case to any ground point on the chassis.

Thoughts?  I double-checked the L-pad wiring, it's wired correctly, grounds tied together, etc.

 

[Harpo]

Signal generator set to deliver a 1khz tone at .770, measured at pin 2 of the input XLR.

... at pin 2 of the input XLR in respect to pin 3 of the input XLR.

Measurement at the input "+" of the L-pad PCB = .770VAC
Measurement at the output "+" of the L-pad PCB, fully CCW = .770VAC
Measurement at the output "+" of the L-pad PCB, fully CW = .770VAC
Measurement at the input "+" of the input transformer PCB, L-pad fully CCW = .773VAC
Measurement at the input "+" of the input transformer PCB, L-pad fully CW = .774VAC
Measurement at the point where the "+" wire connects to the PCB (wire detached from terminal), L-pad fully CCW = .317VAC
Measurement at the point where the "+" wire connects to the PCB (wire detached from terminal), L-pad fully CW = .317VAC

I don't believe it makes a difference, but the unit was not powered up for the above measurements. 

The L-pad doesn't seem to be doing anything?  FWIW, I have continuity from the input transformer case to any ground point on the chassis.

Thoughts?  I double-checked the L-pad wiring, it's wired correctly, grounds tied together, etc.

The 'grounds' are only a cable shield for the floating transformer balanced input and output. The level of signal is neither related to this shield potential nor to 0V reference voltage when measured across the primary side of the input transformer or measured across the secondary side of the output transformer.

 

[dbonin]

...if I set the input pot at "24" and slowly increase the output pot from full CCW, turning CW, I get a peak of just barely over 1.0 VAC and then it diminishes back to near 0 VAC at full CW.

That isn't normal, and you'll have to correct the problem before you can proceed with any of the calibration procedures.

What have you tried so far of the troubleshooting tips from my FAQ?

Thanks very much for your reply.  Following the Hairball guide, I built the power supply first and it tests good, all voltages appear correct.  I tested each resistor as I stuffed the PCB and feel confident the values are correct.  I've visually inspected my solder joints, I reflowed a couple which looked questionable, so I'm thinking it's either a wiring issue or something I'm not thinking of (faulty component?)

I have also built a version of Mark Burnley's signal tracer.  Since I'm not passing very much voltage, would you recommend I begin by checking voltages or testing the signal path?  I'm still mostly a newbie, but I'm committed to getting this working and I'll be grateful for any advice you might have.

Check for the simple things first when it comes to wiring - it's easy to get turned around and swap wires and leads and put similar looking pots in the wrong spots.  A quick glance can sometimes fool the eye into thinking something is correct when it's reversed.  But lets assume you have beat that horse to death! 

Start at the point where the input transformer enters the PCB - apply your .775V / 1khz test signal and measure the voltage as you increase the input pot from full ccw to full cw  - (if you used terminals for the wiring, disconnect them) -  let us know what you find.

Thanks for the reply!  Here are my measurements (along with my signal path measurement points, to make sure I've not goofed something up):

Signal generator set to deliver a 1khz tone at .770, measured at pin 2 of the input XLR.
Measurement at the input "+" of the L-pad PCB = .770VAC
Measurement at the output "+" of the L-pad PCB, fully CCW = .770VAC
Measurement at the output "+" of the L-pad PCB, fully CW = .770VAC
Measurement at the input "+" of the input transformer PCB, L-pad fully CCW = .773VAC
Measurement at the input "+" of the input transformer PCB, L-pad fully CW = .774VAC
Measurement at the point where the "+" wire connects to the PCB (wire detached from terminal), L-pad fully CCW = .317VAC
Measurement at the point where the "+" wire connects to the PCB (wire detached from terminal), L-pad fully CW = .317VAC

I don't believe it makes a difference, but the unit was not powered up for the above measurements. 

The L-pad doesn't seem to be doing anything?  FWIW, I have continuity from the input transformer case to any ground point on the chassis.

Thoughts?  I double-checked the L-pad wiring, it's wired correctly, grounds tied together, etc.

connect both leads coming out of the input transformer to the leads of your dmm - you should be seeing somewhere around .340 AC coming OUT of the input transformer, with output turned full cw with the leads disconnected from the pcb - this should fall to ZERO volts as you turn the input knob fully off.  Check it again, I think your .317 is normal, as long as it falls to zero when you back it off.

 

[babaorum]

I make a rotary version (ratio and meter), could you tell me where are wired the X and Y pads of the meter pcb's for a rotary version ?
because on the mnats v2.2 25/02/2013 pcb's version there is no X and Y ... ?
I suppose on the output transformer but which colors wires ?

Unlike the G1176-style boards the output transformer isn't mounted on the main board for my A, D and F/G PCBs. Therefore it is impractical to put X Y pads on them.

Have a look at the schematic - the colors are shown there. Remember that you're measuring the output of the unit with the VU meter so the polarity isn't important.

Thanks for your help. So I can't wire on the main board, Do I have to wire X and Y with the outputs of the output transformer ?

Another thing, for the 22 and 7 pads is it necessary for your pcb to group the two shields, because there is a ground close to the 7 and another ground close to the 22 ?

(sorry if the questions are stupid,  it's my first DIY and I 'm a little newbee  )

it would be great to update the doc 'rotary version' with the new pcbs 

 

[mattvon]

Okay, with .775VAC present at the input of the input transformer and both DMM leads attached to the output wires of the input transformer I get 0.00VAC.  The L-pad doesn't have any effect, both full CCW and CW are 0.00VAC.

I still get .316(.317)VAC with one DMM probe to ground.

Not sure what to make of this...

 

[dbonin]

Okay, with .775VAC present at the input of the input transformer and both DMM leads attached to the output wires of the input transformer I get 0.00VAC.  The L-pad doesn't have any effect, both full CCW and CW are 0.00VAC.

I still get .316(.317)VAC with one DMM probe to ground.

Not sure what to make of this...

You have a wiring issue - check for continuity along each of the sections of the input wiring, from the input XLR to the t-pad, to the altran transformer and finally to the wires that connect to the PCB.

 

[mattvon]

Thanks for the help.  Here is what I've found in checking continuity:

On the "+" wire, I have continuity from pin 2 on the XLR->"+" input on L-pad->"+" output on L-pad->"+" input on input transformer.
On the "-" wire, I have continuity from pin 3 on the XLR->"-" input on L-pad->"-" output on L-pad->"-" input on input transformer.
On the ground wire, I have continuity from pin 1 on the XLR->the point where the grounds join near the L-pad.

I do have continuity between both "+" and "-" throughout the circuit, including pins 2 and 3 of the XLR?  If I break the ground by the L-pad, I lose continuity.  This is likely the cause of my issues, no?

 

[Harpo]

Check .775VAC signal present at input-XLR (both DMM leads attached to XLR-pins 2/3). Hereafter with both DMM leads attached to the input wires of the input transformer, the voltage will vary between 0V and 0.775VAC when turning the L-pad from its CCW to its CW position.
XLR-pin1 connects to chassis in the shortest possible way and cable shield. This shield is one-side connected at the XLR. There is no ground by the L-pad, only signal between XLR-pins2/3 and the input transformers primary winding wires.

I still get .316(.317)VAC with one DMM probe to ground.

Getting .316VAC where and whatever your definition of 'ground' might be (chassis/shield, 0V reference voltage, safety ground, center tap connection of mains transformer secondaries,...)?

 

[mattvon]

Check .775VAC signal present at input-XLR (both DMM leads attached to XLR-pins 2/3). Hereafter with both DMM leads attached to the input wires of the input transformer, the voltage will vary between 0V and 0.775VAC when turning the L-pad from its CCW to its CW position.
XLR-pin1 connects to chassis in the shortest possible way and cable shield. This shield is one-side connected at the XLR. There is no ground by the L-pad, only signal between XLR-pins2/3 and the input transformers primary winding wires.

I still get .316(.317)VAC with one DMM probe to ground.

Getting .316VAC where and whatever your definition of 'ground' might be (chassis/shield, 0V reference voltage, safety ground, center tap connection of mains transformer secondaries,...)?

Ok, thanks for helping me to understand the ground relationship.  When I referred to the ground near the L-pad, I meant the bare wire from pin 1 of the XLR.

I've checked and verified that I have .775VAC at the XLR by using one DMM lead on pin 2 and one DMM lead on pin 3.

I then checked and verified that I have .775VAC between the wire from pin 2 and pin 3 of the XLR before I soldered these wires to the L-pad. 

As soon as I connect the wire from pin 2 of the XLR to the "+" pad on the L-pad input and the wire from pin 3 of the XLR to the "-" pad on the input side of the L-pad, I get 0.00VAC at pins 2 and 3 of the XLR (as well as the "+" and "-" input pads of the L-pad).

I also get 0.00VAC when measuring between the "+" and "-"at the output pads of the L-pad. 

Rotating the L-pad fully CCW or CW has no effect on this reading. 

I checked and verified once again that I have .775VAC coming out of my signal generator.

Thanks for everyone's help and patience with this.

 

[dbonin]

Ok, thanks for helping me to understand the ground relationship.  When I referred to the ground near the L-pad, I meant the bare wire from pin 1 of the XLR.

I've checked and verified that I have .775VAC at the XLR by using one DMM lead on pin 2 and one DMM lead on pin 3.

I then checked and verified that I have .775VAC between the wire from pin 2 and pin 3 of the XLR before I soldered these wires to the L-pad. 

As soon as I connect the wire from pin 2 of the XLR to the "+" pad on the L-pad input and the wire from pin 3 of the XLR to the "-" pad on the input side of the L-pad, I get 0.00VAC at pins 2 and 3 of the XLR (as well as the "+" and "-" input pads of the L-pad).

I also get 0.00VAC when measuring between the "+" and "-"at the output pads of the L-pad. 

Rotating the L-pad fully CCW or CW has no effect on this reading. 

I checked and verified once again that I have .775VAC coming out of my signal generator.

Thanks for everyone's help and patience with this.

Pull the t-pad out of the case  if it's bolted to the front  and check your soldering there - if you can post a pic, it may help.

 

[mattvon]

Ok, thanks for helping me to understand the ground relationship.  When I referred to the ground near the L-pad, I meant the bare wire from pin 1 of the XLR.

I've checked and verified that I have .775VAC at the XLR by using one DMM lead on pin 2 and one DMM lead on pin 3.

I then checked and verified that I have .775VAC between the wire from pin 2 and pin 3 of the XLR before I soldered these wires to the L-pad. 

As soon as I connect the wire from pin 2 of the XLR to the "+" pad on the L-pad input and the wire from pin 3 of the XLR to the "-" pad on the input side of the L-pad, I get 0.00VAC at pins 2 and 3 of the XLR (as well as the "+" and "-" input pads of the L-pad).

I also get 0.00VAC when measuring between the "+" and "-"at the output pads of the L-pad. 

Rotating the L-pad fully CCW or CW has no effect on this reading. 

I checked and verified once again that I have .775VAC coming out of my signal generator.

Thanks for everyone's help and patience with this.

Pull the t-pad out of the case  if it's bolted to the front  and check your soldering there - if you can post a pic, it may help.

Ok, here are two pictures of the soldering on the L-pad, top and bottom.

I've checked continuity on the L-pad, no connection between the input and output "+" pads (regardless of position of rotation, CCW to CW), connectivity between the input and output "-" pads.  I also checked between each "+" to "-" pad for continuity, found none.