[BUILD] 1176LN Rev D DIY

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I can't see a lifted trace there, but it's hard to tell. You can check for continuity using your multimeter, in either continuity mode or ohms mode, with the unit unplugged and off of course. Just follow the trace to any two pads on either side of the damaged area and make sure you have very low DC resistance. If not then it's certainly lifted.

The easiest way to fix a lifted or blown trace is to simply jumper between the two closest pads which are directly connected to the damage part using a short piece of wire. I have about 100 feet of nice tinned 28 gauge that I keep around just for this kind of thing. Once repaired, double check everything for continuity in the surrounding area that should have continuity using your multimeter.

I believe the next closest pad would be right next to it, R10 on the PCB (R58 on the schematic, 56k according to this document http://www.hairballaudio.com/docs/FET%20Compressor%20PCB%20Board%20Info%20V3.pdf )

If that pad is completely screwed, you could just send that wire straight into the leg of R10 if there's room, ignoring pad "6-15" altogether. Easiest way might be, if that resistor is already too short, would be to desolder it and replace it with another 56k ohm resistor, leaving the leg long enough there to attach the wire directly to it where it pokes through the PCB. Or lift just one side of it and solder the red wire right to it where the short trace would normally go.

Sorry if this is confusing, it's just hard to explain. The point is simply to follow the trace and connect what should be connected.

Yes, it's possible that a lifted pad would give you problems. I think that wire, if it's the one I'm thinking of, it brings the output of the preamp section into the resistor ladder that feeds the gain reduction amp. That would cause there to be no gain reduction at any setting

Also, there appears to be a stay wire hanging from the green wire over to the purple one? That's not touching anything is it?
 
Thanks for the detailed response, hymtoptera. Your explanation is totally understandable.

Apparently I do have continuity between R10 on the ratio board and  the red conductor of that shielded cable.

I'm looking for the stray wire you mention, 'from the green wire over the purple one'. I'm really not sure what you mean here. I don't think these are shorting in any way that's obvious to me.

I have a question for the next build I plan on doing if I ever get this working: Is there any reason I shouldn't use wire headers for the ratio board like we're given for the main PCB? It seems it would make this part of the process much less finicky, as well as any troubleshooting connected to the ratio board. Do headers exist for connections this tight together?
 
Hmmmm.  I would start by checking your DC voltages as described here:
http://mnats.net/files/1176REVD_VOLTS.pdf

These voltages are for a fully calibrated unit so some in the meter section might be a little off, but compare and see what you find then report back.

Mike

Thanks Mike,

Only just got round to checking this I've been out the country for a few weeks. Will report back in the next few hours with the results.

Milo
 
Hmmmm.  I would start by checking your DC voltages as described here:
http://mnats.net/files/1176REVD_VOLTS.pdf

These voltages are for a fully calibrated unit so some in the meter section might be a little off, but compare and see what you find then report back.

Mike

Ok so the voltage values are as Follows:

Power supply -

CR6 = 9.72v
R87 = 30.12v

GR Control amp -

R49 and Q10 = 16.45v

Q9 Left pin = 2.88v
        middle pin = 17.03v
        right pin = 3.44v

Q7 Left pin = 3.94v
        middle pin = 14.95v
        right pin = 4.49v

GR meter Driver

this is where its starts to get interesting...

Q11 - 5.5v

Q12 L= 0.52v
        M= -3.27v
          R= 0.09v

Q13  L = 1.34v
            M= 1.33v
            R = -1.03v


 
milomofo said:
...

GR meter Driver

this is where its starts to get interesting...

Q11 - 5.5v

Q12 L= 0.52v
        M= -3.27v
          R= 0.09v

Q13  L = 1.34v
            M= 1.33v
            R = -1.03v

Did you happen to socket any of those transistors? If so, pull them one at a time and swap in a fresh part.. I'm thinking one of them might be fried.

Also, make sure the shorting jumper is back where it belongs. I'm not sure if this will affect anything, but it might?
 
Hey,

I tested all the transistors before soldering them inlace and they all seemed ok, Potentially I could have damaged them during soldiering.

would you recommend replacing all of them?.. or is there one in particular that looks like it may be the culprit? I started noticing problems between Q11 and Q13 so i'm guessing one of the 3 in the meter driver circuit.

I tested the voltage with the jumper in place and it was bypassing most of the GR circuits transistors I originally thought that all trannys were faulty.. it wasn't till I realised it was in the circuit and removed it that I was able to get some readings.
 
Well, it's hard to say.. You mentioned it seemed to be working, calibration was going okay, then suddenly the meter returned to the far left. Could be a componant failure. Also check all those solder joints  in the meter section and also at the meter switch PCB for any bad solder joints, faulty switch contacts, etc.

I don't think I've heard of this exact problem so I'm not sure where to start.
 
Hello

I'm on phase calibration of the Qbias.
I replaced the R59 trimmer 2k by a 5k because I couldn't do the calibration before.

Must I move the trimmer with the lowest or the highest tension before Qbias calibration ?
at the moment it's on the highest (I have 1687 V) . For the maximum signal pass where is the start position of the trimmer ?

thanks
 
babaorum said:
Hello

I'm on phase calibration of the Qbias.
I replaced the R59 trimmer 2k by a 5k because I couldn't do the calibration before.

Must I move the trimmer with the lowest or the highest tension before Qbias calibration ?
at the moment it's on the highest (I have 1687 V) . For the maximum signal pass where is the start position of the trimmer ?

thanks

You should not change the Qbias trimmer value. If 2K is not working you have an issue with your Qbias circuit.

Common probe on CT/0V:
1. What is your DC V on either side of R35.
2. What is your DC V on either side of R60.
3. What is your highest and lowest DC V at pad 18 when you rotate the Qbias trimmer.

Mike
 
1. What is your DC V on either side of R35.        3.7V      9.7V
2. What is your DC V on either side of R60.        3.7V      0V
3. What is your highest and lowest DC V at pad 18 when you rotate the Qbias trimmer.  4.2V      0V
 
babaorum said:
1. What is your DC V on either side of R35.        3.7V      9.7V
2. What is your DC V on either side of R60.        3.7V      0V
3. What is your highest and lowest DC V at pad 18 when you rotate the Qbias trimmer.  4.2V      0V

That all looks good.

What about at pad 7?  What is your highest and lowest DC V at pad 7 when you rotate the Qbias trimmer?
 
babaorum said:
What is your highest and lowest DC V at pad 7 when you rotate the Qbias trimmer?    3.30V    0V

Now what about the highest and lowest DC V at the GATE of Q1 when you rotate the Qbias trimmer?
 
What is your highest and lowest DC V at pad 7 when you rotate the Qbias trimmer?    3.34V    0V

Q1 : 1.19V (maybe more but I 'm afraid to broke the trimmer if I continue ! - so I revised the max of the pad 7 3.34 instead of 3.30)    0V
 
babaorum said:
What is your highest and lowest DC V at pad 7 when you rotate the Qbias trimmer?    3.34V    0V

Q1 : 1.19V (maybe more but I 'm afraid to broke the trimmer if I continue ! - so I revised the max of the pad 7 3.34 instead of 3.30)    0V

Wait these are negative values right (-)?  These values are correct but they need to be negative. COM on CT and measuring lead on the test points.
 
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