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

[dbonin]

Hard to tell from the angle, but you may be right!

Hi HomeSlice,

just had a quick look at your photo. What found is, in my eyes, a wrong wiring of the output XLR.
Your shorted pin 2 to ground, couldn't it!?

ROCK-ON!

 

[HomeSlice]

I definitely thought that Pin 1 was the same on both XLRs.  It's very clear for the input XLR from the photo here
http://www.hairballaudio.com/blog/wp-content/uploads/2013/09/input.jpg

For the output, I can see the blob of solder on the tab but the wire is not distinct (to me) so I put it on the same left-hand side pin. 
http://www.hairballaudio.com/blog/wp-content/uploads/2013/09/OutXLR.jpg

So I guess Pin 1 is on the right hand side for the output XLR.  Thanks Dr. J, dbonin and mnats!  A bit late for desoldering but I will get on this soon. 

 

[HomeSlice]

I fixed the output XLR and confirmed Pin 1 is connected to ground on the meter.  So that's settled.  However, the transistors still have the incorrect voltages from before.  For example Q10 emitter is 13.84, base is 14.5.  These are both 0.5V below the normal values. TP10 is still -0.5V instead of 9.5V.  Guess I will keep looking around.

 

[HomeSlice]

Since quintuple-checking everything hasn't been turning anything up, I thought I would try running audio through again.  It passes audio.  When I put rhythmic material through it, the needle moves farther to the left in +4 mode than in +8 mode.  Is this expected behavior?  Also, in either +4 or +8 mode, the needle moves farther to the left as both the input and the output knobs are increased.  I am not familiar with this compressor so is the meter supposed to be linked to both input and output, or is this evidence of a short/connection issue?  Thanks.

 

[rainton]

Homeslice,


as far as I can tell from the picture it seems like your voltage regulator in the PS section is soldered in the wrong way around.
I can't really see it to be sure because the heatsink covers it, but from all the 1176s I've built the heat-sink was always pointing in the opposite direction.

I fixed the output XLR and confirmed Pin 1 is connected to ground on the meter.  So that's settled.  However, the transistors still have the incorrect voltages from before.  For example Q10 emitter is 13.84, base is 14.5.  These are both 0.5V below the normal values. TP10 is still -0.5V instead of 9.5V.  Guess I will keep looking around.

If you look at the XLRs closely - they have all pins labeled - 1 through 3 :

While you're "looking around" it might be worth focussing on the PS section if the -voltage is off. Why did you stuff the entire pcb when the voltages in the power supply are not correct in the first place??

Since quintuple-checking everything hasn't been turning anything up, I thought I would try running audio through again.  It passes audio.  When I put rhythmic material through it, the needle moves farther to the left in +4 mode than in +8 mode.  Is this expected behavior?  Also, in either +4 or +8 mode, the needle moves farther to the left as both the input and the output knobs are increased.  I am not familiar with this compressor so is the meter supposed to be linked to both input and output, or is this evidence of a short/connection issue?  Thanks.

replace every word "left" with the word "right" and you're spot on  ;D
HONESTLY.

The meter is supposed to show output in +4/+8 - since the increasing input level increases the signal level (except the output knob is turned ccw)
turning either of the pots cw will make the output signal increase.

 

[HomeSlice]

Thanks Rainton about the XLR pin labeling.  I was also PM'd (by someone else) about this.  This issue has been fixed and I appreciate the help.

I did interchange left and right as you mentioned - sorry about that.  Thanks for clarifying about the meter. 

The vreg is oriented as here: http://www.hairballaudio.com/blog/wp-content/uploads/2013/12/IMG_05181.jpg  The two rails check out at 29.7 and -9.7.  I did check all this out before proceeding with the PCB but it is worth mentioning that this part of the circuit seems fine.

 

[telegraphcables]

Hey everybody, new here. I'm building this kit and everything seems to be going fine, except I managed to misplace the input transformer PCB. Does it seem like a terrible idea to just wire it by hand, and leave it unmounted? Or should I order a new transformer + PCB from hairball? If I can do it point-to-point, can anybody help with figuring out which pins need to be wired where?

 

[beardedlurker]

Hey everybody!

I just finished building my Hairball Rev. A kit, and started the calibration process. I had the controls set as required for calibration, but when I plugged in the output XLR, the meter pegged and the controls are unresponsive. Needless to say I can't calibrate it in this state. When I unplug the output, the meter drops back down. When I put my 1kHz signal thru the unit with the output XLR unplugged, and turn the input up as indicated in the calibration video, I barely have it to the first mark (54?) and the meter is at +1. That doesn't seem right.

I am not by any means an experienced builder, but I have built some smaller kits previously, and am pretty good at the manufacturing aspect, but definitely not very skilled in the tech/troubleshooting area. I'm hoping someone has an idea what boneheaded mistake I made, and can point me in the right direction. I also might be willing to pay someone who is qualified to check this out and calibrate it if you're in the Chicago area.

Any help would be greatly appreciated. Thanks!!

Mark

 

[curranm]

HA ZAAAAAAAAAAAAAAAAAAAA!!!!!!!!!!!!!!!!!!!!!!!!!!!!

So I have two rev A's that I build from the hairball kits and one of them has always been lacking in headroom and bottom end. I have recently bought an oscilloscope to work on tube amps and general trouble shooting. So I bust out the semi funky 1176 and started checking voltages again and signal tracing with a 1k clean sign wave. While going through the schnematic and the voltages I notice that C22 is calling for a .22uf cap and I have a .022uf cap in there?!?!?!?!? double checking the 1st one i built that sounds good, I notice the same thing.............. a .022uf in there. Checking the BOM and the Schematic I see clearly that it is needing a .22uf!!!!!! So I am thinking mouser gooned my on accident. pop in a couple .22uf and WAH LAH!!!!!!!!!!!!!!!! big full fat head roomy compression squashtastic!!!! so damn happy!!!

 

[Echo North]

Hey everybody, new here. I'm building this kit and everything seems to be going fine, except I managed to misplace the input transformer PCB. Does it seem like a terrible idea to just wire it by hand, and leave it unmounted? Or should I order a new transformer + PCB from hairball? If I can do it point-to-point, can anybody help with figuring out which pins need to be wired where?

You can hand wire it.  http://hairballaudio.com/docs/3837/3837.pdf

4 and 8 are you + and 5 and 8 -.

Or if you email us we'll send you a PCB.

 

[Echo North]

Hey everybody!

I just finished building my Hairball Rev. A kit, and started the calibration process. I had the controls set as required for calibration, but when I plugged in the output XLR, the meter pegged and the controls are unresponsive. Needless to say I can't calibrate it in this state. When I unplug the output, the meter drops back down. When I put my 1kHz signal thru the unit with the output XLR unplugged, and turn the input up as indicated in the calibration video, I barely have it to the first mark (54?) and the meter is at +1. That doesn't seem right.

I am not by any means an experienced builder, but I have built some smaller kits previously, and am pretty good at the manufacturing aspect, but definitely not very skilled in the tech/troubleshooting area. I'm hoping someone has an idea what boneheaded mistake I made, and can point me in the right direction. I also might be willing to pay someone who is qualified to check this out and calibrate it if you're in the Chicago area.

Any help would be greatly appreciated. Thanks!!

Mark

Probably oscillation or some noise.

You need to go through and check your voltages:
http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

Then double check all of your wiring.  Then check all of your component orientation.

This will take a while, but errors are not easy to find.  Keep at it, report back.

Mike

 

[Mark Mckeon]

Hi there,

I have just finished building the revision A 1176 build.  I thought everything was going well until the first calibration "Q bias"

I have set a 1Khz signal from my DAW reading 0.775 VAC  at pins 2 and 3 of the input XLR, but I am not getting anything on pins 2 and 3 on the xlr out.

I have read a previous thread of this issue but it was solved by replacing Q12 and Q13 to match.  I triple checked this stage whilst arranging the transistors and matched Q12 as 327 and Q13 as 324.  It maybe

something I can look at?  I feel that I may have overturned the Q bias trimpot too far, as I thought I might of needed to dial in the the 2.75VAC required on the XLR out pins 2& 3.

Here is my test results:

from +input xlr to ground 0.387 VAC
ground to trimmer pad + input 0.387 VAC
ground to trimmer pad + output  0.101VAC
ground to input transformer +  0.101 VAC
ground to input transformer output +  0.157VAC
ground to PCB input +  0.157 VAC
ground to both sides of C7 is 0.001 VAC  :-\

Really unsure of where to go next?  If anyone can help that would be great.

Thanks in advance.

Mark

 

[Harpo]

I have set a 1Khz signal from my DAW reading 0.775 VAC  at pins 2 and 3 of the input XLR, but I am not getting anything on pins 2 and 3 on the xlr out.

You don't care for voltage 'at' pins 2 and 3. You want to know the AC voltage reading between xlr pins 2 and pin 3 with a 1kHz signal feed.

from +input xlr to ground 0.387 VAC

Circuit is transformer floating balanced input and output. There is No relation to 'ground'. You measure voltage between xlr pin 2 and pin 3.

 

[Mark Mckeon]

I apologise if I have worded it incorrectly for you.  But I am testing between xlr pin 2 and 3 with a 1khz signal feed?

On a previous thread, Mike from Hairball suggested to another forumite to test from earth to all the above points?

Have you got any other ideas I could try?

 

[Echo North]

on your output transformer make sure the the yellow/orange wires are joined (soldered) together.

Other than that, it is likely a cap misplaced...

Hey All!

I have just built a Hairball 1176 Rev A. Build/Calibration went smoothly.

My problem is when running signal through the unit the output is very thin. Spectral analysis shows a low end roll off from 200Hz at about 6dB per oct.
The output freq. is the only symptom. Compression works and sounds great (when I eq the low end back in).

I have checked the Mnats voltages and all except for Q4 are correct.

G: 1.91
S: 4.07
D: 13.32

Could this be a faulty J309? Could it be responsible for the bass roll off?

Thanks!
-Bob

I don't see the voltages being that far off?

You can confirm all of those resistors around that Transistor are correct.

What are you issues?  Just a bad roll off?  Are you passing signal fine?  Can you adjust the QBias?

 

[dbonin]

also make sure you have connected the yellow & orange wires on the output transformer.  Not doing so will cause severe bass roll off.

on your output transformer make sure the the yellow/orange wires are joined (soldered) together.

Other than that, it is likely a cap misplaced...

Hey All!

I have just built a Hairball 1176 Rev A. Build/Calibration went smoothly.

My problem is when running signal through the unit the output is very thin. Spectral analysis shows a low end roll off from 200Hz at about 6dB per oct.
The output freq. is the only symptom. Compression works and sounds great (when I eq the low end back in).

I have checked the Mnats voltages and all except for Q4 are correct.

G: 1.91
S: 4.07
D: 13.32

Could this be a faulty J309? Could it be responsible for the bass roll off?

Thanks!
-Bob

I don't see the voltages being that far off?

You can confirm all of those resistors around that Transistor are correct.

What are you issues?  Just a bad roll off?  Are you passing signal fine?  Can you adjust the QBias?

 

[Echo North]

Thanks Rainton about the XLR pin labeling.  I was also PM'd (by someone else) about this.  This issue has been fixed and I appreciate the help.

I did interchange left and right as you mentioned - sorry about that.  Thanks for clarifying about the meter. 

The vreg is oriented as here: http://www.hairballaudio.com/blog/wp-content/uploads/2013/12/IMG_05181.jpg  The two rails check out at 29.7 and -9.7.  I did check all this out before proceeding with the PCB but it is worth mentioning that this part of the circuit seems fine.

So where are you on this?

1. Are you able to adjust the Qbias?
2. Are you passing audio?

Mike

 

[HomeSlice]

It passes audio but I can't complete the Q Bias step.  The reason is that the output dBu is nowhere near the required +11 dBu value.  I can keep raising the input past 0 dBu, and the 1176 needle will go up.  However, at some point the needle just stops moving well short of the max value.

I am ordering some more 2N3708s to see if they might be the reason why the voltages are off.  Feeling really bummed as I had some high hopes for a stereo 1176 build.  Not looking good for this unit though.

 

[Echo North]

It passes audio but I can't complete the Q Bias step.  The reason is that the output dBu is nowhere near the required +11 dBu value.  I can keep raising the input past 0 dBu, and the 1176 needle will go up.  However, at some point the needle just stops moving well short of the max value.

I am ordering some more 2N3708s to see if they might be the reason why the voltages are off.  Feeling really bummed as I had some high hopes for a stereo 1176 build.  Not looking good for this unit though.

Are you measuring for 11dBu at the output with a DMM?

 

[HomeSlice]

Special thanks to dbonin for sending me a video about Q Bias calibration.  I tried his method and then I was able to use the Hairball method.  Thanks also to Hairball for the helpful comments.  It seems to be working now...much obliged all.  Apparently there were no problems with the unit after all, I just did not understand the process.  For the next person, do not necessarily be alarmed if your voltages are off prior to all of the calibrations.