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

[dbonin]

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

 

[BobCurtin]

Thanks for the reply!

Im assuming the WIMA orange caps  in the line amp / pre amp would be the culprit?

Those WIMA caps were a little hard to interpret does anyone have a guide on how to read the codes on them?


Thanks!!
-Bob

 

[Echo North]

Thanks for the reply!

Im assuming the WIMA orange caps  in the line amp / pre amp would be the culprit?

Those WIMA caps were a little hard to interpret does anyone have a guide on how to read the codes on them?


Thanks!!
-Bob

If all else fails your meter should have a capacitance tester that you can use (out of circuit).

WIMA is kind of random and requires a little common sense.  The first thing you should know is that they are typically .0001uF - 1uF of film caps that size.

So ideally: some of the WIMA caps have a u or n after the number.  .22u = 0.22uF or 100n = 0.1uF

Not so ideally they just have the number and it'll either be in uF or pF.  Since 1uF - 0.000001 pF...

if you see .22 that has to be uF because we'd never use a cap as small as 0.00000022.  Alternatively if you 3300 if has to be 3300 pF (or 0.0033uF) because film caps don't really come as large as 3300uF.

Mike

 

[keevhren]

Hey there Mike and everyone in here!

I'm currently calibrating my first 1176 rev A build and am slightly confused about one of the steps... I'm following the guide on the hairball calibration page.

I've completed the first calibration for the Q bias adjustment and I'm onto the Discrete Meter Circuit/Null Adjust

Here's what's listed to do:

Disconnect your signal generator.  No signal is required for this step.

Take R44 out of circuit by placing the shorting pin in the “short position” .  This means the two pins furthest from Q13 are connected.  Set your DMM to measure DC volts and set it to measure the DC volts across R74.

    Zero the compressors “GR” meter with the R71 zero adjust pot on the front panel
    Adjust pot R75 (null adjust)  for 0.0 Volts across TP10 and TP11.
    Repeat 1 & 2 until both conditions are met.

1. I've disconnected the signal generator.
2. I've taken R44 out of the circuit.
3. Measuring the DC volts across R74... this is what is confusing me... what's the purpose of this?  I'm taking my DMM and measuring at R74 but then after the next step I'm attaching my clips to TP10 and TP11 so that I can measure for 0.0 volts on R75.

Measuring across TP10 and TP11 and adjusting the GR Meter with R71 makes complete sense to me.  It's the 'why' of my measuring R74 that I'm not understanding.  Can you clear it up for me please?

Much thanks in advance!

 

[dbonin]

Ignore R74 on the Rev A and just use the test points.  Mike will edit that out soon once he sees he left it in there from the rev D cal step!

Cheers!
-Don

Hey there Mike and everyone in here!

I'm currently calibrating my first 1176 rev A build and am slightly confused about one of the steps... I'm following the guide on the hairball calibration page.

I've completed the first calibration for the Q bias adjustment and I'm onto the Discrete Meter Circuit/Null Adjust

Here's what's listed to do:

Disconnect your signal generator.  No signal is required for this step.

Take R44 out of circuit by placing the shorting pin in the “short position” .  This means the two pins furthest from Q13 are connected.  Set your DMM to measure DC volts and set it to measure the DC volts across R74.

    Zero the compressors “GR” meter with the R71 zero adjust pot on the front panel
    Adjust pot R75 (null adjust)  for 0.0 Volts across TP10 and TP11.
    Repeat 1 & 2 until both conditions are met.

1. I've disconnected the signal generator.
2. I've taken R44 out of the circuit.
3. Measuring the DC volts across R74... this is what is confusing me... what's the purpose of this?  I'm taking my DMM and measuring at R74 but then after the next step I'm attaching my clips to TP10 and TP11 so that I can measure for 0.0 volts on R75.

Measuring across TP10 and TP11 and adjusting the GR Meter with R71 makes complete sense to me.  It's the 'why' of my measuring R74 that I'm not understanding.  Can you clear it up for me please?

Much thanks in advance!

 

[MountCyanide]

I haven't heard anyone mention the Cinemag CMOQ-2S as an output tranny in this build. Yes, in the Rev J but not in these Class A ones. Well it's working just swell in mine. I blew the UA-5002 output transformer in my Rev D that I'm currently building (hyperactively and pre-coffee morningly mis-wired and then a whizzing noise started up. Now it's distorted and choppy like a blown speaker). But that has caused me to get creative in testing to find out what was busted. Through the tests I wound up with a Cinemag CMOQ-2S in my Rev A. So far I'm really digging it. Seems a bit more aggressive than the 5002. Who knows, I might stick with it. I'll leave it in for now and if it bugs as I'm recording/mixing I'll grab another 5002. But main point here is that IT WORKS.

 

[mnats]

I haven't heard anyone mention the Cinemag CMOQ-2S as an output tranny in this build. Yes, in the Rev J but not in these Class A ones. Well it's working just swell in mine. I blew the UA-5002 output transformer in my Rev D that I'm currently building (hyperactively and pre-coffee morningly mis-wired and then a whizzing noise started up. Now it's distorted and choppy like a blown speaker). But that has caused me to get creative in testing to find out what was busted. Through the tests I wound up with a Cinemag CMOQ-2S in my Rev A. So far I'm really digging it. Seems a bit more aggressive than the 5002. Who knows, I might stick with it. I'll leave it in for now and if it bugs as I'm recording/mixing I'll grab another 5002. But main point here is that IT WORKS.

I too tried a simple output transformer while waiting for the correct one to show up from Purple in the original prototype. But you have to block the significant DC from the primary winding and you lose the feedback winding. 'Aggressive' is one word but technically 'distortion' is probably more accurate.

 

[MountCyanide]

But you have to block the significant DC from the primary winding and you lose the feedback winding.

D'oh! Okay.
Edit: the other transformer is fine. I jumped the gun. Putting everyone back where they belong.

 

[HomeSlice]

Hey everyone.  The power supply tested out fine and the lamp is lit.  However, I cannot pass step 1 of calibration as needle does not respond to signal.  The first few times when I powered up into GR mode, the needle flew all the way to the right.  Now it does not move when powering up into GR.
All resistors were checked on meter prior to insertion.  However I guess it’s always possible that I inserted a checked resistor into the wrong place. Did a check for cold joints and reflowed a few, and also looked for obvious shorts.  Found a number of discrepancies from the MNATS voltage guide. 
Q10 to R47 is 13.7V instead of 14.96V
TP10 is -0.5V instead of 9.5V
TP11 is 1.25V instead of 9.76V
Q12 to R68 is -0.5V instead of -1.41V
Q11 ti R79 is 1.23V instead of 10.52V
Q4 to R27 is 4.2V instead of 6.6V
Q4 to C10 is 12.82V instead of 13.72V
Q5, Q10, Q12 are 708s per the sticker in the Hairball kit versus 707 on the PCB.  Q11 is as marked on the PCB. Q4 cannot verify since it is blocked by a cap but it should be stuffed correctly.
Post #2116 covered some of the Q4 issues and mentioned resistors.  All resistors mentioned there check out.  Thanks for any assistance.

 

[MountCyanide]

You can't check your resistor values in circuit. Use this instead-
http://www.digikey.com/web%20export/mkt/general/mkt/resistor-color-chart.jpg

 

[HomeSlice]

Thanks.  I checked every resistor on the main PCB using their color codes and they all check out as correctly stuffed.  I was wondering if someone could take a look at the WIP and see if there is anything obviously wrong.  Much obliged.
PS - I am thinking that having the wrong polarity at TP 10 must be a clue.  I just don't know how to take it farther than that.

 

[HomeSlice]

I am still looking at this but don't know what to look for.  I am concentrating on the GR Meter Driver section of the board since this seems to have the most unusual voltages.  I re-verified Q11, Q12, and Q13 and the trimmers.  Everything has been placed in this section as required.  Orientation of Q11, Q12, and Q13 is correct.  30V arrives at R79 as indicated.  However, after R79 the voltage drops dramatically as mentioned (to 1.23V).

 

[dmnieto]

If you input some signal directly to the meter disconnecting everything else... does it react?

Q12 seems to be strongly into saturation... can you measure the voltages in the base, emiter and collector both in Q12 and Q13?

 

[HomeSlice]

The collector for Q13 goes through TP11 which is 1.3V.  The base is -0.9V.  The emitter is -1.0.  The collector for Q12 goes through TP10 which is -0.5V.  The collector is also -0.5V.  The base is 0.2V.  About sending input directly to the meter, do you mean sending signal to the usual input.  If so, signal input does not do anything in GR mode.  In +4 and +8 mode, applying signal and turning up the Input knob makes the meter needle move upwards as expected.

In addition to all resistors being rechecked via color codes, all diodes have been checked for orientation and caps have been rechecked.

 

[mnats]

The collector for Q13 goes through TP11 which is 1.3V.  The base is -0.9V.  The emitter is -1.0.  The collector for Q12 goes through TP10 which is -0.5V.  The collector is also -0.5V.  The base is 0.2V.  About sending input directly to the meter, do you mean sending signal to the usual input.  If so, signal input does not do anything in GR mode.  In +4 and +8 mode, applying signal and turning up the Input knob makes the meter needle move upwards as expected.

In addition to all resistors being rechecked via color codes, all diodes have been checked for orientation and caps have been rechecked.

I suspect either a wiring error or faulty soldering in your meter driver circuit (both of which are mentioned in the troubleshooting FAQ). In spite of what gets parroted often it is possible to measure resistors in circuit - you just have to account for any parallel resistance. Half the resistors in the meter circuit can be measured with accuracy and no calculations; a greater percentage in the rest of the limiter circuit. Remove the jumper and you have two more resistors that can be measured accurately!

Your earlier comment about the wrong polarity at TP10 is spot on. Measure the resistance from that point to ground, then to the negative rail at the junction of R66 and R72. What do you read?

 

[HomeSlice]

Thanks Mnats, much appreciated. TP10 to ground is 10.75K. TP10 to R66/R72 junction is 10.3K. 
I have been looking this over for another hour.  Still not finding anything.  I would not doubt that it is a wiring error as I found that more challenging than stuffing the PCB. 

I did notice that the positioning of the purple wire to the Ratio board in the Hairball photos seems to involve two seemingly different locations.  In the first one http://www.hairballaudio.com/blog/wp-content/uploads/2013/09/IMG_0307.jpg  , the purple wire is between the green and black ones.  But it goes to the back of the PCB in this photo http://www.hairballaudio.com/blog/wp-content/uploads/2013/09/Resistorconn.jpg  Mine is wired like the first photo if it helps anything.

Also, if anyone would like to use my debugger Excel spreadsheet, have at it.  What I did to make this was to divide the PCB by eyeball into an approximate 8 x 4 grid. The coordinates of all resistors and caps are referenced to the 32 sections.  This makes locating a particular resistor or cap very quick if you are new to the PCB.

It looks like the forum does not support Excel files so here is a download link.
http://www.sendspace.com/file/zx68pw  If Sendspace prompts you to download an executable, you have clicked on an ad.  I have no idea what is in the executable so don't download that.  The file name is Rev A Debugger.xlsx

 

[dbonin]

In the first photo, that wire goes to pad 20 on the main PCB.  Ignore the second photo - that was a workaround likely due to flakey pad on the meter pcb.

I did notice that the positioning of the purple wire to the Ratio board in the Hairball photos seems to involve two seemingly different locations.  In the first one http://www.hairballaudio.com/blog/wp-content/uploads/2013/09/IMG_0307.jpg  , the purple wire is between the green and black ones.  But it goes to the back of the PCB in this photo http://www.hairballaudio.com/blog/wp-content/uploads/2013/09/Resistorconn.jpg  Mine is wired like the first photo if it helps anything.

 

[Echo North]

Ignore R74 on the Rev A and just use the test points.  Mike will edit that out soon once he sees he left it in there from the rev D cal step!

Cheers!
-Don

Hey there Mike and everyone in here!

I'm currently calibrating my first 1176 rev A build and am slightly confused about one of the steps... I'm following the guide on the hairball calibration page.

I've completed the first calibration for the Q bias adjustment and I'm onto the Discrete Meter Circuit/Null Adjust

Here's what's listed to do:

Disconnect your signal generator.  No signal is required for this step.

Take R44 out of circuit by placing the shorting pin in the “short position” .  This means the two pins furthest from Q13 are connected.  Set your DMM to measure DC volts and set it to measure the DC volts across R74.

    Zero the compressors “GR” meter with the R71 zero adjust pot on the front panel
    Adjust pot R75 (null adjust)  for 0.0 Volts across TP10 and TP11.
    Repeat 1 & 2 until both conditions are met.

1. I've disconnected the signal generator.
2. I've taken R44 out of the circuit.
3. Measuring the DC volts across R74... this is what is confusing me... what's the purpose of this?  I'm taking my DMM and measuring at R74 but then after the next step I'm attaching my clips to TP10 and TP11 so that I can measure for 0.0 volts on R75.

Measuring across TP10 and TP11 and adjusting the GR Meter with R71 makes complete sense to me.  It's the 'why' of my measuring R74 that I'm not understanding.  Can you clear it up for me please?

Much thanks in advance!

Whoops.

Fixed, thanks guys.

 

[Dr_J]

Hi,

just finished a 1176A and the last calibration step, no problems  ;D

I build a Hairball kit, i must say very, very nice kit!!
All you need in a box 

Really great is the mounting system for the push buttons!
I build all ready a 1176 some time ago, it took me nights to build a mounting system (without screws on the front)!!

Unbelievable job Mike!! 

Maybe tomorrow going into the studio... 

ROCK-ON!

 

[Dr_J]

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!