[BUILD] 1176LN Rev D DIY

[JingleDjango]

Hi there. New to the boards. First complicated build and I'm following along with the Hairball Rev D complete kit. I have a couple questions about the caps.

First of all, the transistor at Q6 didn't come with a spacer, just a heatsink. Issue? Also, the heatsink supplied is a broad, round one and it's pusing C12 out of the way a bit so that it has to be mounted off-kilter. Doesn't seem like a huge issue, but I'm wondering if being in contact with this heatsink is going to affect the working life of the electrolytic cap.

Next question: C3 and C6, a little ceramic cap. The board and BOM call for  200pF. The closest I have in my kit in 220pF. Is this a problem? I'm just unsure.

(the captchas on this board are fucking impossible to make out

Last one: C7, C10. C17 calls or electrolytic or film. The kit supplied 3 elec. caps. The board does not indicate direction. How do I determine which way to orient them?

Thank you.

 

[Echo North]

First of all, the transistor at Q6 didn't come with a spacer, just a heatsink. Issue? Also, the heatsink supplied is a broad, round one and it's pusing C12 out of the way a bit so that it has to be mounted off-kilter. Doesn't seem like a huge issue, but I'm wondering if being in contact with this heatsink is going to affect the working life of the electrolytic cap.

Spacer isn't a huge deal, but the heatsink was an error on our side.  We can send you the correct one if you like.  Just email us.

Next question: C3 and C6, a little ceramic cap. The board and BOM call for  200pF. The closest I have in my kit in 220pF. Is this a problem? I'm just unsure.

(the captchas on this board are f**king impossible to make out

Yep 220pF is the more modern value.  Use those.

Last one: C7, C10. C17 calls or electrolytic or film. The kit supplied 3 elec. caps. The board does not indicate direction. How do I determine which way to orient them?

Thank you.

The board should have + for the positive lead.  If you're having trouble because of a weird silkscreen refer to the build doc silken layer here:

http://mnats.net/files/1176LN_REVD_V2.2_DOC.pdf

Mike

 

[lukeadams]

Mike-
Had my friend here helping me this morning. Here's what we found.

Measuring VDC at Pad 18= -2.416
Measuring VDC at Brown wire connection at release pot= -2.42
Measuring VDC at Red wire connection on release pot= + 6.57
Measuring VDC at Pad 7= +6.52

So- the reading goes from negative to positive.

In addition-

Checked and rechecked, and rechecked again ALL wiring. All seems to be good.
Checked power supply- and got proper readings according to build guide.

Lastly- when I connect the test tone- and monitor back into my DAW- we are hearing a pretty loud hum- which I can only assume is a grounding problem. However, holding black probe on CT and testing all ground connections- all seems good.

I'm stumped at this point. Any ideas?

Thanks,
L

 

[dbonin]

Lastly- when I connect the test tone- and monitor back into my DAW- we are hearing a pretty loud hum- which I can only assume is a grounding problem. However, holding black probe on CT and testing all ground connections- all seems good.

Put your black probe on the main ground lug on the rear of the unit and test for continuity by putting the other probe:
- on the side panels (anywhere there is no black finish)
- on the front panel: on the back side on the metal stand offs for the zero adjust
- on the metal can for the input transformer
- on both input and output xlr bodies (or pin one on both)
- on the output transformer (the metal band that attaches to the rear of the case)
- you have the green wire from the neg lead of the PS cap from under the board going to ground?

If you have all that proven then you have a  wiring issue that is causing the hum.

 

[Echo North]

Mike-
Had my friend here helping me this morning. Here's what we found.

Measuring VDC at Pad 18= -2.416
Measuring VDC at Brown wire connection at release pot= -2.42
Measuring VDC at Red wire connection on release pot= + 6.57
Measuring VDC at Pad 7= +6.52

So- the reading goes from negative to positive.

In addition-

Checked and rechecked, and rechecked again ALL wiring. All seems to be good.
Checked power supply- and got proper readings according to build guide.

Lastly- when I connect the test tone- and monitor back into my DAW- we are hearing a pretty loud hum- which I can only assume is a grounding problem. However, holding black probe on CT and testing all ground connections- all seems good.

I'm stumped at this point. Any ideas?

Thanks,
L

I thought earlier you said you have no VDC at pad 7?

If you disconnect pad 7 and measure the VDC at the end of that wire that was connected to pad 7 (now unconnected) what is your DC?

Mike

 

[lukeadams]

Mike-

Black probe on CT and red probe touching loose red conductor removed out of header on pad  7  yields= + 1.41 VDC
Reading with red conductor plugged into Pad 7 is +6.54 VDC .

Sorry for the "0" reading I gave earlier. It's entirely possible I was measuring the ground next to Pad 7 and not Pad 7. As I said. Newb.

Regardless- the measures above were done just now and that's where I'm at.

 

[lukeadams]

Don Bonin-

thanks for chiming in. I'm assuming you are describing similar process as when I tested continuity after building PS - Black probe on main ground lug, touching red to the points you mentioned- MEASURING OHMS. ??

Here's what I get:

Right side panel (looking at front of unit)=.5ohms
Left side panel= .5 ohms
Metal standoff of zero adjust= .5 and .6 ohms
Output XLR Pin 1 (Ground)= 6.7ohms
Input XLR Pin 1 (Ground)= .4 ohms
Output transformer (metal band)= .2ohms
Green wire soldered to bottom of PCB at negative side of PSupply Cap..(C25) and connected with a "toothy thing" between nut and screw that hold output tranny to case. Tons of coating scraped away at both tranny mounting holes. yes, it's going under PCB.

May the 6.7ohm reading at pin 1 of output XLR not right????

Thanks don,
L

 

[Echo North]

Mike-

Black probe on CT and red probe touching loose red conductor removed out of header on pad  7  yields= + 1.41 VDC
Reading with red conductor plugged into Pad 7 is +6.54 VDC .

Sorry for the "0" reading I gave earlier. It's entirely possible I was measuring the ground next to Pad 7 and not Pad 7. As I said. Newb.

Regardless- the measures above were done just now and that's where I'm at.

You've got to have an attack/release wiring error.  Or a measurement error.  Impossible to know since your experience is limited.  You should have someone look at it if you been through the wiring and it looks right.

Mike

 

[JingleDjango]

Hi again. Just finally got around to finishing wiring this thing up. I did test the power supply section when it was finished and everything checked out then. The device turns on and lights up. No smoke or odd smells but I will add that the big resistor between the power transformer gets rather hot. I know it's expected to get hot, but I was still a little surprised.

I wanted to do the Q-Bias calibration. I'm sending a 1khz sine from Ableton Live using the Operator synth. I was able to adjust the output to read a steady .775VAC at the input jack. However, I see no activity on the VU meter and I get no reading from the output XLR. I've started poking around a bit but I'm just not sure where to begin troubleshooting. Any guidance would be appreciated.

Thanks.

 

[JingleDjango]

I'm posting some images to help with this. 1 image per post so I'm sorry if I'm crowding the thread a bit.

 

[JingleDjango]

Internal Overview. This is my first significant build after doing some super hand-holdy passive stuff from DIYRE. I'm aware that some of the wiring is a bit sloppy. I bought two of these kits and I'm hoping to refine my skills with the next build. Still, I need both of these to function. I'm doing some recording this coming Monday and hoping I can get up and running by then.

 

[JingleDjango]

Output transformer. Notice I clipped the red lead accidentally. I soldered it back together and covered with heat shrink.

 

[JingleDjango]

The PCB I tested each resistor individually and matched the transistors as instructed. I believe the caps are all oriented properly, but I will begin to comb them over later. I would like to stress that I took my time stuffing the PCB, tried to be as meticulous and methodical as I could. Again, the power supply section worked as expected before I stuffed the rest of the board.

 

[JingleDjango]

Attack pot. I ran out of the shielded cable provided with the kit (due to a mistake a made early in the wiring) so I swapped in some quality braided mic cable. I wasn't 100% sure this was the best course, but it seemed like a good substitute.

 

[Echo North]

Hi again. Just finally got around to finishing wiring this thing up. I did test the power supply section when it was finished and everything checked out then. The device turns on and lights up. No smoke or odd smells but I will add that the big resistor between the power transformer gets rather hot. I know it's expected to get hot, but I was still a little surprised.

I wanted to do the Q-Bias calibration. I'm sending a 1khz sine from Ableton Live using the Operator synth. I was able to adjust the output to read a steady .775VAC at the input jack. However, I see no activity on the VU meter and I get no reading from the output XLR. I've started poking around a bit but I'm just not sure where to begin troubleshooting. Any guidance would be appreciated.

Thanks.

The current limiting resistor will get pretty hot.

If you have no output you could start by doing a basic signal check through the unit with a DMM.  You're looking for the presence of some AC signal where there should be from XLR in to XLR out.

Place your DMM common lead on the power CT and set your meter to read AC V.

1. Check your AC at + of the Tpad in and the + of the Tpad out. (AC V will get smaller each time)
2. Check at the + of the input tx and then the + of TX out. (again getting smaller)
3. Check at the + of the PCB input. Should be pretty small now. Around 0.08 V DC if you had 0.775 between input 2 and 3.
4. Check either of the pads at C7.  You should see a larger signal now.  Like 2V I think.
5. Check out your output XLR pin 2.

What are you seeing?

 

[JingleDjango]

I'm having a hard time now honing in on .775VCA though somehow I managed it last night. Is there an acceptable tolerance around that figure?

 

[JingleDjango]

Also, not sure what you mean by power CT. Do you mean the lead from the transformer secondary to the PCB? Either of the red wires?

Edit: I found the CT terminal on the schematic, although I still don't know what 'CT' is an abbreviation of.

 

[JingleDjango]

0.770VAC at input XLR jack between pins 2 and 3

0.381VAC between CT and tpad input +

0.251VAC between CT and tpad output +

0.75VAC between CT and the PCB input.

0.008VAC between CT and C7’s + lead
0.002VAC between CT and C7’s - lead

.006VAC between CT and output pin 2

 

[Echo North]

0.770VAC at input XLR jack between pins 2 and 3

0.381VAC between CT and tpad input +

0.251VAC between CT and tpad output +

0.75VAC between CT and the PCB input.

0.008VAC between CT and C7’s + lead
0.002VAC between CT and C7’s - lead

.006VAC between CT and output pin 2

I believe the PCB + input should be 0.075V AC?  Misprint?

You're losing your signal super early (in the first amp stage labeled "Signal Preamp" on the PCB).  Look for shorts around the FET or mis placed components in that first amp stage.

Check for cold joints.  Make sure your output pot and connections are wired correctly.

Mike

 

[Echo North]

Do you have AC signal on the leg of R14 that attaches to Q3?