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

[Echo North]

So, I went to calibrate my 1176A and when I put a .775 1K tone on the input the meter oscillates. Looks like Im sending a vibrato to the input but its a sine wave. Any clues?

Could be a million things.  See if you can get the qbias full negative. If it still oscillating, you need to go through everything.

 

[Echo North]

i thought that was cray.  so ya after dropping the output a bit they both max out around 2 vac before they jump into crazy land.

That's pretty normal. Usually it's that shielded wire to pin 7 or the wiring to the output. Cleaning that stuff up and getting it away from the PCB should eliminate it. I may also just be caused by having the lid off. Either way it's not your main issue (the oscillation at max output).

If you can't get a 10dB drop I would expect something off in the GR amp. Maybe try switching out the semi's?

Mike

 

[junkface]

Worth a shot. It just seems odd to me that I wouldn't be getting any off voltages in there if there were faulty 2n3708s.

 

[Echo North]

Worth a shot. It just seems odd to me that I wouldn't be getting any off voltages in there if there were faulty 2n3708s.

True.

I'm pretty stumped. I'd have to see it at this point I think. Maybe one of your FDH333 diodes is dead. Just a wild guess at this point.

 

[Chrome Heart]

So, I went to calibrate my 1176A and when I put a .775 1K tone on the input the meter oscillates. Looks like Im sending a vibrato to the input but its a sine wave. Any clues?

Could be a million things.  See if you can get the qbias full negative. If it still oscillating, you need to go through everything.

OK so, color me red, my sine wave WAS oscillating. Dont know why but it went away after a reboot of the mac. Strange.
At any rate Im having trouble with the null adjust, I cant seem to get the voltage to zero without running out of room on the trimpot. As I recall I matched the 3707's so I dont know what else it could be. I built it in 2013 but Ive been experiencing some problems lately.

 

[jonathanmorbin]

Hi, I'm having a few issues and I'm a bit stumped at the moment. Basically my first issue seems to be that i have a clipped sine wave at pad 15. Its fine one side of R16 but on the 2n3707 side it has a clipped top half of the sine wave. All my voltages in that area of the circuit are pretty much bang on. I was able to Q Bias adjust but i cant do the next step. Voltages in the GR Meter circuit are pretty much bang on or at least will be once i can do that part of the calibration.

2nd problem is that i don't have GR. My ratio boards are working correctly. however as soon as i connect Pad 22 i loose my AC signal going in to the GR Circuit. at least it drops to almost 0. This part of the circuit i have voltages that are off. some are as much as 10v higher than they should be. They are all fairly relative however for example at Q7 i have 15v, 14v and 22v. My 30v rail is correct however at 29.8v.

I built 3 boards at the same time and they all have the same faults. I feel like I've exhausted all the options in testing. Any one got any ideas?

 

[Spencerleehorton]

Hi,

Just wanted to check I've done the wiring to the meter switch and GR switches correctly, if anyone could have a look please?

Regards

Spence.

 

[Echo North]

So, I went to calibrate my 1176A and when I put a .775 1K tone on the input the meter oscillates. Looks like Im sending a vibrato to the input but its a sine wave. Any clues?

Could be a million things.  See if you can get the qbias full negative. If it still oscillating, you need to go through everything.

OK so, color me red, my sine wave WAS oscillating. Dont know why but it went away after a reboot of the mac. Strange.
At any rate Im having trouble with the null adjust, I cant seem to get the voltage to zero without running out of room on the trimpot. As I recall I matched the 3707's so I dont know what else it could be. I built it in 2013 but Ive been experiencing some problems lately.

Are the voltages in that section looking ok referring to the schematic with voltages?

 

[Echo North]

Hi, I'm having a few issues and I'm a bit stumped at the moment. Basically my first issue seems to be that i have a clipped sine wave at pad 15. Its fine one side of R16 but on the 2n3707 side it has a clipped top half of the sine wave. All my voltages in that area of the circuit are pretty much bang on. I was able to Q Bias adjust but i cant do the next step. Voltages in the GR Meter circuit are pretty much bang on or at least will be once i can do that part of the calibration.

2nd problem is that i don't have GR. My ratio boards are working correctly. however as soon as i connect Pad 22 i loose my AC signal going in to the GR Circuit. at least it drops to almost 0. This part of the circuit i have voltages that are off. some are as much as 10v higher than they should be. They are all fairly relative however for example at Q7 i have 15v, 14v and 22v. My 30v rail is correct however at 29.8v.

I built 3 boards at the same time and they all have the same faults. I feel like I've exhausted all the options in testing. Any one got any ideas?

You can always send them (or one) in for repair.

http://www.hairballaudio.com/build-support-services

If none of them work I'd suspect basic build error like cold solder or damaged components from static electricity exposure.  Just guessing.

 

[Chrome Heart]

So, I went to calibrate my 1176A and when I put a .775 1K tone on the input the meter oscillates. Looks like Im sending a vibrato to the input but its a sine wave. Any clues?

Could be a million things.  See if you can get the qbias full negative. If it still oscillating, you need to go through everything.

OK so, color me red, my sine wave WAS oscillating. Dont know why but it went away after a reboot of the mac. Strange.
At any rate Im having trouble with the null adjust, I cant seem to get the voltage to zero without running out of room on the trimpot. As I recall I matched the 3707's so I dont know what else it could be. I built it in 2013 but Ive been experiencing some problems lately.

Are the voltages in that section looking ok referring to the schematic with voltages?

Im gonna put it back on the bench tomorrow night and check it out, I double checked all the component values when I had it open to see if I made some simple mistake but everything is right.

 

[Spencerleehorton]

Hi All,

so did anyone take a look at the wiring for the 4 gang switches i posted in previous message, i think ive wired it right?

regards

Spence.

 

[Spencerleehorton]

My build so far, pcb all complete, power txf drilled and installed, still waiting on IEC.
Input and output transformers built,  faceplate waiting to be drilled, then I'll wire it all up.

Spence.

 

[Echo North]

Hi All,

so did anyone take a look at the wiring for the 4 gang switches i posted in previous message, i think ive wired it right?

regards

Spence.

Did you not use switch PCBs?

Checking that would take more time than I have, but you could always just give it a try. Nothing will blow up.

Mike

 

[blackartmixing]

Hi i'm just putting together my first 1176 rev A from hairball audio.  just a quick check before i proceed, i'm getting 29.5 on the 30V rail and -9.6 on the -10V rail.  does this look acceptable or should i go back and check what i've done?  if so, what do i need to look at?  my soldering skills are not the best at the moment  but i don't know if this could be a problem so far.  many thanks

 

[Chrome Heart]

Hi i'm just putting together my first 1176 rev A from hairball audio.  just a quick check before i proceed, i'm getting 29.5 on the 30V rail and -9.6 on the -10V rail.  does this look acceptable or should i go back and check what i've done?  if so, what do i need to look at?  my soldering skills are not the best at the moment  but i don't know if this could be a problem so far.  many thanks

i think your in good shape with that.

 

[Spencerleehorton]

Started sorting the case and managed to connect up a few more bits.

 

[Chrome Heart]

Ok. All of the voltage readings look good. I have a  1.2 circuit board and a 1.2.5 voltage chart but everything is certainly within 10%. The hfe is matched at  q12 and q13. The null adjust voltage gets to .067 when the trim pot is bottomed out. Is this a concern or should I switch the trim pot out to a 5 k?

 

[Chrome Heart]

A 21 turn 5k did the trick.

 

[Spencerleehorton]

Nearly finished!!

 

[Chrome Heart]

So how different sonically, is the Hairball Rev D from the Rev A? Has anyone build both?  It looks like they use the same Tx's in the kit.