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

[Echo North]

In the wiring guide it says "On the Rev F USA boards, use the pads for R55 - the "ZERO ADJ" trimmer footprint". But doesn't say where each wire goes on that footprint. Any help would be much appreciated.

Also, where do the grey, purple, green and blue output transformer wires go? The main pcb only has pads for the other four.

The middle pot lug, the "wiper" goes to the middle pad.  The out side ones go to each of the outside pads probably left facing the front of the pot to the top pad.  If your pot works in reverse when you fire it up, just switch the two out side pads.

For the out TX it's real simple.  Look at the schematic below.  Violet and Green get connected and attached to "X" which is XLR out pin 2.  Gray and Blue get tied together and go to Y which is XLR 3.  You also have and X and Y on your meter board that go to those XLR pins.

 

[Finlaywatt]

Thanks, got that all done now. Im reading the pcb info document and I'm stuck figuring out what to do with the BLK and GRN pads on the ratio board?

 

[Echo North]

Thanks, got that all done now. Im reading the pcb info document and I'm stuck figuring out what to do with the BLK and GRN pads on the ratio board?

http://mnats.net/1176_reva-d_hairball_wiring_attack_release.html

 

[Finlaywatt]

Gotcha! The only thing is the Rev G board has no earth pad next to pad 7, where does it go instead?

 

[Echo North]

Gotcha! The only thing is the Rev G board has no earth pad next to pad 7, where does it go instead?

Look at the schematic in the first post.  Pad 23 = ground.

 

[Finlaywatt]

I have it connected as main board pad 23 is connected to pad B on the back of the attack pot (shield of the cable). The main conductor of the cable is connected to pad C and main board pad 22 as it says in the build guide. My main board pad 7 is connected to the CW lug of the attack pot. Is this right?

Also what connects to pin one of the output xlr? Aside from the wire going to the ground lug on the xlr.

Apologies for all the newbie questions.

 

[Echo North]

Pin one just gets grounded .

For the switchI have no idea.  Whatever the wiring guide says.  22 get's connected to pad 4 in the GR on mode, and when the switch is off 22 should be connected to ground.  A simple continuity test will confirm this.

Mike

 

[Finlaywatt]

Thanks a lot, got it all wired up and ready to calibrate. I have looked at the calibration videos. Which do I follow for rev G? Just the 1st and 3rd?

Cheers, Finlay.

 

[Echo North]

Thanks a lot, got it all wired up and ready to calibrate. I have looked at the calibration videos. Which do I follow for rev G? Just the 1st and 3rd?

Cheers, Finlay.

You need to do Qbias and tracking at the very least.  You probably don't have the tools to do the distortion trim, but it most people don't and it's really not audible.  Same for CMRR.

 

[Finlaywatt]

Okay cool. Tried doing the qbias feeding it 1k from the desk oscillator I've established the input pot is wired back to front. When I fed it the signal with it at 20:1 and +4 the meter never went higher than about -17 or so. Although if I flip the input pot wiring I would have way more input to play with. Qbias pot didn't seem to do anything though. Tried feeding it a kick drum with it on the same settings
And the meter was reacting fine.

 

[Echo North]

For setting the qbias try this:

If you have a version with the "off" switch on the attack pot, you can just switch that.  That will ground pad 22.  Feed a 1khz signal into the input at about 0dBu.  You can put your DMM across input xlr pin 2 and 3 and look for 0.775VAC which is about 0dbu.  Your DAW might say it's sending out a -16dBu FS signal or something.  Just do what ever you need to do to get 0.775 VAC across 2 and 3 at the input.

Now put your DMM across pin 2 and 3 on the output xlr and turn the qbias (in and out knob mid way).  You should see the output moving up or down.  Turn the bias until it gets to the max and doesn't get any higher. 

Then adjust the output knob so you see +11dbu (2.75VAC) at the output.  Now pull the qbias back until you get a 1dbu drop 10dbu (2.45VAC).  That will set your bias.

 

[Finlaywatt]

Feeding 1khz from PT. it's at -20 on PT meter. Flipped the input pot so that it's the right way round but I have to have the input and output nearly fully up to get it on 0. When I flick to GR it pins hard right?

Also, with test meter probes on input pins 2&3 the meter doesn't register any voltage but the vu responds..

 

[Finlaywatt]

I can hear a 1khz ring from the circuit as well.. :/

 

[Echo North]

Feeding 1khz from PT. it's at -20 on PT meter. Flipped the input pot so that it's the right way round but I have to have the input and output nearly fully up to get it on 0. When I flick to GR it pins hard right?

Also, with test meter probes on input pins 2&3 the meter doesn't register any voltage but the vu responds..

Are you testing for AC?

 

[Finlaywatt]

Yeah, I was but the scale was very small. Gonna hunt down another meter today and try again.

 

[Finlaywatt]

Okay. Got hold of a decent meter. Got 0.775 vac at the input and cranked up the q bias to its max. my output was already pretty much full so i had to max the input so that i had the range on the output to get 2.75 vac. Tried dropping to 2.45 vac but i run out of qbias?

 

[frazzman]

Hey all, finally got my rev F full assembled. Happy that its passing audio and VU metering working straight off the cuff.

Unfortunately i've got the dreaded 'no compression'. I've been scouring the threads but at a bit of a loss (maybe i've spent too long on this thing tonight?)

I've completed what I can of the calibration, namely the q bias, dist trim & cmr adj adjustments.

All of the trimmers have an impact on the vu meter so I know they are doing something.

In bypass I get audio, in GR I get audio but no compression, meter sits at 0dB but moves with tracking & zero adj adjustments, I get VU metering and audio in VU mode.

My build is as follows:
- IC input
- Rotary switches for meter and ratios ala original  style
- Omitted 270r resistor in input section as per schematic

Areas that might be contributing to issue:: Any advice appreciated:
- I used hairball 25k attack pot with built in SPDT switch - since i'm not using push buttons i've ignored the SPDT part of the POT as I don't need it - could that be an issue? Better of using normal 25k pot without SPDT switch for rotary build?
- I've got nothing connected to point 23 on PCB (just another ground point right? or is it expecting something more specific here)

I'm pretty confident most of the wiring is right, it was self explanitory for most part and the fact its passing is a good sign.

Any obvious oversights? I'll keep going through the threads and apologies in advance if this is a no brainer

 

[Finlaywatt]

I'm getting very little compression. Meter shows compression but the audio coming out isn't as the meter would suggest. I have now realised that one of the power supply caps has domed out so ill replace that and try again.

 

[Echo North]

I'm getting very little compression. Meter shows compression but the audio coming out isn't as the meter would suggest. I have now realised that one of the power supply caps has domed out so ill replace that and try again.

Yes the polarity is probably wrong.

As noted above, you need to remove  R5 and leave it empty for the Reg G IC version.

 

[Finlaywatt]

The polarity is right which is why I'm confused :S ahh I didn't know to leave out R5. The one next to the input? Just get rid of it completely?