[BUILD] 1176LN Rev D DIY

[sr1200]

Just out of curiosity... did you 0 the meter before trying to calibrate?

edit: after lookin at your pics, there should be NO reason your output level should be that high for calibration.  You sure your input transformer is wired correctly?

 

[number2]

don't know how to do image
http://imageshack.us/photo/my-images/594/dscn2047c.jpg/

OK this is the level of my inexperience I guess. I am to test the power rails after wiring the power supply. My guess is that I place the black test lead of my multimeter where the wires attach to the board (CT, black wire) and then my red lead at the places where I drew circles.

I do get -10 vdc at the green circle but not +30vdc at the red circle. I only get millivolts at the +30 vdc area(red circle)

did I interpret correctly?

 

[pittsburgh]

I've been trying to send the .775VAC 1K tone from my Pro Tools Generator from a +4 Apogee Rosetta converter system. Alternatively I've also tried sending the same signal from my -10 mbox 2 setup. The reading on my multimeter reads approximately .775 VAC for both setups, but the input level for the Rev D shows much lower when I use my Rosetta system v. my Mbox rig. What's going on here? Shouldn't I be getting the same results if my multimeter is reading the same values? Do I just need to bite the bullet here and buy an NTI MR2?

P

 

[Echo North]

don't know how to do image
http://imageshack.us/photo/my-images/594/dscn2047c.jpg/

OK this is the level of my inexperience I guess. I am to test the power rails after wiring the power supply. My guess is that I place the black test lead of my multimeter where the wires attach to the board (CT, black wire) and then my red lead at the places where I drew circles.

I do get -10 vdc at the green circle but not +30vdc at the red circle. I only get millivolts at the +30 vdc area(red circle)

did I interpret correctly?

That's right. 

Something is wrong with your + rail.  First off get rid of that yellow tantalum cap at C23.  You should have used the 6.8uF electrolytic there and the tantalum for C19/20.

Check that CR6 Diode. It looks damaged?  Maybe just the picture.

Good job on testing the powersupply first.  Get this solved before you do anything and you'll save headaches down the road.

 

[Echo North]

I've been trying to send the .775VAC 1K tone from my Pro Tools Generator from a +4 Apogee Rosetta converter system. Alternatively I've also tried sending the same signal from my -10 mbox 2 setup. The reading on my multimeter reads approximately .775 VAC for both setups, but the input level for the Rev D shows much lower when I use my Rosetta system v. my Mbox rig. What's going on here? Shouldn't I be getting the same results if my multimeter is reading the same values? Do I just need to bite the bullet here and buy an NTI MR2?

P

Hard to say.  The could be a differential/not differential thing or and impedance thing.

The protools generator is fine.  Just use your DMM to make sure you see .775AC at the 1176 input XLR.  You'll probably see something like -18 to -16db on your DAW.

 

[pittsburgh]

My Rev D works great. The dsub connecting my output lines was loose. Two turns of the screw heads and my compressor came to life. It's strange because I was getting an accurate VAC reading from my multimeter but still reading very low levels @ input on the 1176 VU. Thanks all who helped me build this, I can't wait to go test it out!

 

[number2]

thanks Echo North! I see that there is a lot for me to learn.

I took out the tantalum cap but I read the BOM and it says I need a 35v 6.8 uf cap there. I have only a 100 v 6.8 uF cap at the moment. Can I use that?
OK I read that you can substitute with higher wattage and higher voltage components if they fit physically.

However, I tried it and it didn't help me with the positive rail at all.

I also took out CR6 and it was giving me -10vdc like it should when connected. after i took it out it gave me -2 vdc.
I tried to swap it for a 10 volt, 1 watt instead of 1.3 watt zener diode. That didn't budge it from -2 vdc so I put the original back in but now get -2 vdc on that too.
I toasted both diodes somehow. How? I just took it out and put it back in.

I'm not getting a response to this which leads me to believe that there is a better place for beginner questions like these. Is this a correct assumption?

 

[bspro]

Hi Guys, I've worked through this beautiful build so far from simply reading and re-reading the build guides and this forum.  I've also had a little bit of help from dbonin (thanks!), but I've now come to a spot that I can't seem to figure out.

I thought that I'd be asking help for the final step of the calibration process, because I thought that is where my problem lies, but I realize after understanding the process a bit more, that my problem must be earlier in the build.  When it came time to adjust the tracking, I could get no meter movement when shorting pad 22 to ground.  If I understand correctly, I should see a significant drop immediately when I short pad 22.  I found some instructions here (approximately page 125?) about things to test if that was not actually disabling the gain reduction.  All of those tests seem to work, proper wiring, continuity from each wire to the main pcb and continuity to the middle tab on the ratio switches.

I didn't realize what should be occurring on the meter for the first 2 videos of calibration, and seemed to be able to get everything to work properly on those to stages...however, now I realize that if I really wasn't bypassing the gain reduction, then there is no way that the Q bias could be right in the first place.

So, where to I begin to trace my problem?

thanks for your help!

 

[MatthisD]

When sending a 0.775v 1k signal into the input I read 0.2v (-11.7dBu) at the input transformer secondary with the attenuator fully clockwise. That level drop seems too high as the transformer loss should be about 4dB, if anyone can comment on this please do.
The maximum compression I can achieve is -7dB with ratio 4:1 and therefore cannot calibrate for -10 with ratio set 20:1.


bspro if your problem is in any way similar to mine I have to set the input fully clockwise and raise the output so that the meter reads -10 and then turn off gain reduction to observe a level change from the meter. With a lower input level I didn't realise I was getting any compression at all until measuring the output xlr with the volts meter whilst turning on and off the gain reduction.

 

[number2]

I keep blowing the zener diode in the power supply. I just ordered 5 more.

I thought the capacitors would be discharged I haven't plugged it in for a few days.

Am I about to kill myself? Should I stop here and get an electrical engineering degree before proceeding?

 

[MatthisD]

Number2 did you carry out the very last step below? (grounding the power supply to the chassis).

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

Also don't use the power transformer centre tap for your meter probe, you can use the front panel side of CR6 for ground and the -10v or the +30v points as marked on the PCB to measure for those voltages.

 

[sr1200]

bspro it would help to know what type of build you are doing (hair ball?) and if you're using the pot with the switch for your attack.

 

[pittsburgh]

Is there a way to turn the level of input coming into the compressor down? I'm testing my unit and would like to operate this Hairball build like an 1176 with the knobs set to 10 and 2, input and output. Operating at these levels requires me to turn down my input to the compressor which is ok, but if possible I'd like to address the issue internally. Is there a way to calibrate the comp so that I can make better use of my input and output pots?

Is there another set of potentiometers available for the input and output pots that will allow me to use the entire range of indicators inscribed on the front faceplate? The ones that I got use up about 90% of the indicators before running out of room.

Thanks for the help,

-P

 

[bspro]

Thanks for the input so far guys... sr1200, yes, I am doing the Hairball build, most recent version, Revision D, but I am using an Attack Pot WITHOUT the switch.

 

[sr1200]

BS (i feel weird wrting that but... u picked the name lol) hit up page 116 on this thread and read thru a few pages there after, there was a LOT of discussion regarding that issue with possible solutions to the issue.

Pitts... Not tryin to be a d*ck but.. I know im not the only that read that and thought...  ??? "HUH?!" ??? Are you trying to match some magic preset you found on some unit or plugin you've used in the past, or did someone tell you thats some kind of a "sweet spot" for the compressor?  EVERY unit is different and 10 and 2 on yours isn't going to be the same on mine or anyone elses (hell, 10 and 2 isnt even close between my 2 units) And if you have the unit on for a couple hours, and it gets nice and toasty, settings you used when you first turned it on will be different once its warmed up.
The way that post reads can be translated into, "I dunno how this thing works, so, can I mod the circuit to achieve a result i deem suitable"  Where ever you got that 10 and 2 idea, go back and just find out HOW MUCH compression is being applied at WHAT ratio and make note of the most important settings on the compressor, the attack and release...  Then go to your comp and instead of trying to set the DIALS the same try and set the compression the same (the attack and release should be a lot closer between units than the i/o) and you should get similar results to what you're looking for. 

 

[number2]

Number2 did you carry out the very last step below? (grounding the power supply to the chassis).

I thought that was my first step.

Also don't use the power transformer centre tap for your meter probe, you can use the front panel side of CR6 for ground and the -10v or the +30v points as marked on the PCB to measure for those voltages.

thanks for that tip

My diode sparked when I went to put it in the PCB. Everything was unplugged and hadn't been touched for a few days. The PCB was connected to the power transformer. I guess I don't know all about discharging capacitors yet.  I peeled up a rail too and so I got an new PCB. Can you fix that or did I do the right thing in getting a new PCB?

I figure I will install the diode first this time and then the caps?

 

[MatthisD]

You said before that you read 0.9 of an Ohm from PSU ground to the chassis, as you suggested yourself the grounding nut/washer may not have good enough contact.

You can measure from the centre tap point but theres a higher chance of shorting the transformer windings when measuring from the solder pad.

With just the PSU section installed there is no load so the capacitors remain charged after powering off the supply. A resistor and some clips will solve the problem.

I thought that was my first step.

Also don't use the power transformer centre tap for your meter probe, you can use the front panel side of CR6 for ground and the -10v or the +30v points as marked on the PCB to measure for those voltages.

thanks for that tip

My diode sparked when I went to put it in the PCB. Everything was unplugged and hadn't been touched for a few days. The PCB was connected to the power transformer. I guess I don't know all about discharging capacitors yet.  I peeled up a rail too and so I got an new PCB. Can you fix that or did I do the right thing in getting a new PCB?

I figure I will install the diode first this time and then the caps?

 

[TheWolfman]

Hi,

After having to take a break from the final stages of my project for a little while,due to not only going a little mad but also actually recording some music rather than mucking around my multimeter I have found a curious anomaly with my build.

When the output control is rotated all the way counter clockwise the unit outputs a repetative beating tone that sounds like a kick drum and the meter bounces full scale to reflect this.

Any ideas anyone?

 

[number2]

You said before that you read 0.9 of an Ohm from PSU ground to the chassis, as you suggested yourself the grounding nut/washer may not have good enough contact.

You can measure from the centre tap point but theres a higher chance of shorting the transformer windings when measuring from the solder pad.

With just the PSU section installed there is no load so the capacitors remain charged after powering off the supply. A resistor and some clips will solve the problem.

thanks mathis. I re did my ground.

so I put black probe on cathode end of zener instead of at CT?

One thing I'm unsure of is: There are 2 caps in series with the zener right?
those 2 caps read 250 mV dc right now and the zener reads -250mV dc
I know this new zener works because it reads a really high resistance in one direction and negligible in the other on ohmmeter.
My multimeter only has 200uf range so I don't know if the caps are good.
I also don't know yet how to test rectifiers.

and now that I have tried to test the capacitors I have altered something and I now get 40mV dc on each.
The zener now reads -40mvdc and I get 0mv at the point where I should get +30

I put a resistor on the cap to discharge it somehow? can you explain?

 

[MatthisD]

If your ground wire is in place like in this photo then you should have continuity from the centre tap point to the chassis and from either of those points to one side of CR6.
http://mnats.net/images/main_pcb_ground_to_chassis_thumb.jpg


Heres a video which explains how to drain the capacitors after turning off the power;

thanks mathis. I re did my ground.

so I put black probe on cathode end of zener instead of at CT?

One thing I'm unsure of is: There are 2 caps in series with the zener right?
those 2 caps read 250 mV dc right now and the zener reads -250mV dc
I know this new zener works because it reads a really high resistance in one direction and negligible in the other on ohmmeter.
My multimeter only has 200uf range so I don't know if the caps are good.
I also don't know yet how to test rectifiers.

and now that I have tried to test the capacitors I have altered something and I now get 40mV dc on each.
The zener now reads -40mvdc and I get 0mv at the point where I should get +30

I put a resistor on the cap to discharge it somehow? can you explain?