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

[dbonin]

Hi
I've finished my first rev a build
I was concerned that I recived 2 Wima film caps in stead of the 2 smaller Orange drops.
I've got it up and running and all is well and calibrated correctly.
My only concern is that it doesn't seem to to take much signal to make the unit distort.
the unit acts right and compresses . The vu meter doesn't move much before I get distortion.
Is this the charter of the rev a?
It sound fine ,just can't crank on it much.
Thanks for any help.
Wnlively

The wima caps are not causing the issue - I have use both wima and orange drops and neither cause what your are experiencing, AFAIK.

Thanks!
Don

 

[Bonsaimaster]

This is my second Mnats build. The first one went great. The second one the first calibration step went great. However, I cannot get the calibration step 2 to zero out the voltage. I can get the meter to go to zero but the voltage remains 0.63 volts no matter how much I turn the null adjust. Any thoughts?

 

[dbonin]

This is my second Mnats build. The first one went great. The second one the first calibration step went great. However, I cannot get the calibration step 2 to zero out the voltage. I can get the meter to go to zero but the voltage remains 0.63 volts no matter how much I turn the null adjust. Any thoughts?
[/quote

Are you saying turning the trim pot has no effect at all or that it changes the voltage but only goes down to 0.6 volts?

 

[Bonsaimaster]

It changes the voltage just fine but will not go below 0.63.

Thanks

 

[Echo North]

It changes the voltage just fine but will not go below 0.63.

Thanks

Are you measuring at TP10 and 11?  The Rev A is different than the D in where you measure the 0V.

 

[Bonsaimaster]

Yes measuring at TP10 and TP11

 

[aberant]

hello all,
I've been an incredibly happy user of my hairball audio 1176 compressor since july of 2013 until yesterday.  I woke up one morning and realized i left it on all night, so i turned it off without thinking much of it.  I went to use it later that night and it wouldn't turn on.  I checked and the fuse had blown. 

I opened it up and checked the board for any burnt parts, odd caps, and found nothing out of the ordinary.  i double checked the wiring from the transformer to the board.  i then disconnected power from the board and when it was only the transformer it still blew the fuse.

so, i'm out of fuses now.  i was reading another groupdiy thread and a person said that a spike could magnetize the core and blow small fuses until it was degaussed. 

I'm thinking of grabbing some ~1A slow blow fuses from a soon to be bankrupt electronics store in an attempt to fix this and then go back to the normal 250mA fuses.  Is this insane?

 

[dbonin]

so, i'm out of fuses now.  i was reading another groupdiy thread and a person said that a spike could magnetize the core and blow small fuses until it was degaussed. 

I'm thinking of grabbing some ~1A slow blow fuses from a soon to be bankrupt electronics store in an attempt to fix this and then go back to the normal 250mA fuses.  Is this insane?

Try a 500mA fuse - that should do the trick.  However, since you have been using the unit since 2013 I'm surprised  it's only now that you are seeing blown fuses....  That symptom usually decreases over time.

 

[aberant]

just tried some 500mA fuses and it works again.  thanks for your help dbonin!

 

[Bonsaimaster]

This is my second Mnats build. The first one went great. The second one the first calibration step went great. However, I cannot get the calibration step 2 to zero out the voltage. I can get the meter to go to zero but the voltage remains 0.63 volts no matter how much I turn the null adjust trim pot. It will go up in voltage but not below 0.63. Any thoughts?

Thanks

 

[dbonin]

This is my second Mnats build. The first one went great. The second one the first calibration step went great. However, I cannot get the calibration step 2 to zero out the voltage. I can get the meter to go to zero but the voltage remains 0.63 volts no matter how much I turn the null adjust trim pot. It will go up in voltage but not below 0.63. Any thoughts?

Thanks

Are you looking good from a voltages perspective?  I know some  test voltages will not match until calibration is complete, but after testing something may jump out at you.  May be worth a look.  No swapped/misplaced resistors?

http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

 

[onday]

Successfully built and calibrated one of these today! It took a while to get calibration done though... I couldn't get enough VAC on the input XLR pins - turned out it was a massive impedance loss from my DAW & interface. Nothing a preamp couldn't fix

One question though: None of the 2N3708's that came in the kit were above 250 hfe, the two that I matched came closest at 238 & 240; the rest hovering around 200-220.

Is this a problem? Just curious as to why the requirement for 250 hfe and what difference it would make if they're all under.
Other than that, great build - great kit.

Thanks!

 

[Echo North]

Successfully built and calibrated one of these today! It took a while to get calibration done though... I couldn't get enough VAC on the input XLR pins - turned out it was a massive impedance loss from my DAW & interface. Nothing a preamp couldn't fix

One question though: None of the 2N3708's that came in the kit were above 250 hfe, the two that I matched came closest at 238 & 240; the rest hovering around 200-220.

Is this a problem? Just curious as to why the requirement for 250 hfe and what difference it would make if they're all under.
Other than that, great build - great kit.

Thanks!

They are all above 250.  The 2N3708 have a higher hfe (averaging around 350) compared to the 2N3707's (avg 250) that's why I put them in the kit.  Likely if you're testing them in a meter, the meter isn't supplying the proper conditions to be in the fully active region.  Meter's are kind of a "ballpark thing" with hfe.  To really test it, you'd need a specific jig for the transistor.

Congrats on the build!

Mike

 

[onday]

Ah ok that's awesome! I wasn't sure if the 3708's were tested for ratings before being put into the kit..

Yeah I did some reading on hfe testing and that did cross my mind.. Yep 45-660 hfe range on the 3708's - I've got 100 on the way in my panic haha. Also ordered some sip sockets which I'll cut into 3's for transistors in future builds...

Note to self and others who are having transistor dilemmas, this may help you: MILL MAX  311-93-164-41-001000  SIP SOCKET, 64 POSITION . Mouser stocks them, just search the part # . Super useful for troubleshooting if you can just pull out and swap any transistor without damaging your neat soldering

thanks again!

Andre

 

[keevhren]

Hey there!

Just finished building two of the Rev A kits and I'm pretty excited to get them into use!  I was on the last step of the process (calibration!) and my first one went through all three steps as it should have.  However, my second 1176 is having a slight issue.  The Q-bias adjustment worked fine, as did the null adjust.  However, on calibration step 3 (Gain Reduction Meter Tracking Adjustment) I'm running into an issue.

I'm following the hairball blog post method ( http://www.hairballaudio.com/blog/d_assembly/reva/calibration/ ) and am getting caught up on step 4:  Set attack full CCW (off position). Set input control for +10dBu (2.44 VAC) at your output XLR.

When I'm measuring VAC at the output XLR for this step, I am topping out at 2.38 VAC with my input knob cranked all the way clock-wise.  In the previous step, my output knob goes down to about "46" on the knob reading in order to get to the required 0.775 VAC.  It's when I switch to the input knob that I can't get it to 2.44 VAC to move on to the adjustment of R44 and the meter adjust pot on the front panel.  Thoughts/suggestions?

I've double and triple checked that I'm following all the steps correctly (including moving the shorting pin back to normal position, etc... but still no luck.  Any help would be much appreciated!

 

[Echo North]

Hey there!

Just finished building two of the Rev A kits and I'm pretty excited to get them into use!  I was on the last step of the process (calibration!) and my first one went through all three steps as it should have.  However, my second 1176 is having a slight issue.  The Q-bias adjustment worked fine, as did the null adjust.  However, on calibration step 3 (Gain Reduction Meter Tracking Adjustment) I'm running into an issue.

I'm following the hairball blog post method ( http://www.hairballaudio.com/blog/d_assembly/reva/calibration/ ) and am getting caught up on step 4:  Set attack full CCW (off position). Set input control for +10dBu (2.44 VAC) at your output XLR.

When I'm measuring VAC at the output XLR for this step, I am topping out at 2.38 VAC with my input knob cranked all the way clock-wise.  In the previous step, my output knob goes down to about "46" on the knob reading in order to get to the required 0.775 VAC.  It's when I switch to the input knob that I can't get it to 2.44 VAC to move on to the adjustment of R44 and the meter adjust pot on the front panel.  Thoughts/suggestions?

I've double and triple checked that I'm following all the steps correctly (including moving the shorting pin back to normal position, etc... but still no luck.  Any help would be much appreciated!

You ever get this sorted?

 

[keevhren]

Hey there!

Just finished building two of the Rev A kits and I'm pretty excited to get them into use!  I was on the last step of the process (calibration!) and my first one went through all three steps as it should have.  However, my second 1176 is having a slight issue.  The Q-bias adjustment worked fine, as did the null adjust.  However, on calibration step 3 (Gain Reduction Meter Tracking Adjustment) I'm running into an issue.

I'm following the hairball blog post method ( http://www.hairballaudio.com/blog/d_assembly/reva/calibration/ ) and am getting caught up on step 4:  Set attack full CCW (off position). Set input control for +10dBu (2.44 VAC) at your output XLR.

When I'm measuring VAC at the output XLR for this step, I am topping out at 2.38 VAC with my input knob cranked all the way clock-wise.  In the previous step, my output knob goes down to about "46" on the knob reading in order to get to the required 0.775 VAC.  It's when I switch to the input knob that I can't get it to 2.44 VAC to move on to the adjustment of R44 and the meter adjust pot on the front panel.  Thoughts/suggestions?

I've double and triple checked that I'm following all the steps correctly (including moving the shorting pin back to normal position, etc... but still no luck.  Any help would be much appreciated!

You ever get this sorted?

Nope.  Read through a bunch of the pages in here to no avail, have pulled our the main PCB to check over my work and everything looks good as far as I can tell... still stumped.  Suggestions?  Thanks in advance!

 

[dbonin]

Nope.  Read through a bunch of the pages in here to no avail, have pulled our the main PCB to check over my work and everything looks good as far as I can tell... still stumped.  Suggestions?  Thanks in advance!

What are you using for an input test signal?  Measure the VAC going into the unit and let us know.

 

[keevhren]

Nope.  Read through a bunch of the pages in here to no avail, have pulled our the main PCB to check over my work and everything looks good as far as I can tell... still stumped.  Suggestions?  Thanks in advance!

What are you using for an input test signal?  Measure the VAC going into the unit and let us know.

Input signal was a 1k tone from a signal generator off of my macbook pro into a preamp to give it the extra gain it needed to reach the correct measurement of input pin 2 & 3 reading 0.775 VAC.  I didn't change the signal path/chain at all from calibrating my first 1176 to the 2nd one, so know for lack of a better term that the issue must be contained within the actual 2nd unit.

 

[mnats]

Nope.  Read through a bunch of the pages in here to no avail, have pulled our the main PCB to check over my work and everything looks good as far as I can tell... still stumped.  Suggestions?  Thanks in advance!

What are the transistor voltages compared to the ones on the Rev A schematic linked from the troubleshooting FAQ? If no issues there, try signal tracing using Mark Burnley's signal tracer also linked from the FAQ.