Re: [BUILD] 1176LN Rev D DIY
« Reply #5400 on: March 06, 2018, 08:22:35 PM »
additional info: just checking the DC values and all the transistor works fine except Q12 and Q13 whose values are quite high (-4.4 G, 19.6 S, -2.4 D)


Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5401 on: March 08, 2018, 01:02:08 PM »
additional info: just checking the DC values and all the transistor works fine except Q12 and Q13 whose values are quite high (-4.4 G, 19.6 S, -2.4 D)

Those need proper calibration to read correctly.

You have a ton of extra DC in your bias rail. If you remove CR2/3 what does Pad 18 read?

Mike
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Re: [BUILD] 1176LN Rev D DIY
« Reply #5402 on: March 10, 2018, 07:02:37 AM »
Without Cr2 and 3 still having same value:
 -5,43 with qbias adj CCW and -6,30 qbias adj CW. 

:-\  :'(

Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5403 on: March 12, 2018, 10:03:49 PM »
Without Cr2 and 3 still having same value:
 -5,43 with qbias adj CCW and -6,30 qbias adj CW. 

:-\  :'(

Check the value of R58, R61, R62, R63, R64.

Mike
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jefepeters

Re: [BUILD] 1176LN Rev D DIY
« Reply #5404 on: March 13, 2018, 02:56:50 AM »
Hello,

I'm attempting the calibrate the Q bias (using this procedure: http://www.hairballaudio.com/blog/resources/build-guides/calibration)

The input and output voltages are correct (0.775 and 2.75 VAC, respectively), but adjusting  R59 as no effect on either the VU reading or the output voltage.  Any suggestion on where I should start troubleshooting?

Thanks,
Justin

Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5405 on: March 13, 2018, 12:56:13 PM »
Hello,

I'm attempting the calibrate the Q bias (using this procedure: http://www.hairballaudio.com/blog/resources/build-guides/calibration)

The input and output voltages are correct (0.775 and 2.75 VAC, respectively), but adjusting  R59 as no effect on either the VU reading or the output voltage.  Any suggestion on where I should start troubleshooting?

Thanks,
Justin

Most of this applies:
http://www.hairballaudio.com/blog/resources/post/fetrack-troubleshooting-guide

What are your QBias voltages?
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jefepeters

Re: [BUILD] 1176LN Rev D DIY
« Reply #5406 on: March 13, 2018, 01:51:26 PM »
Most of this applies:
http://www.hairballaudio.com/blog/resources/post/fetrack-troubleshooting-guide

What are your QBias voltages?

The initial voltage was -1.1 and I could twist it CCW to -2.4 VDC. What is considered the "extreme of the pot"? When I turn it, there is no obvious point where I feel it stiffen up.  I turned it  until I heard a click, but nothing was stopping me from turning it further.

The range of travel is 25 turns (per https://www.mouser.com/ds/2/54/299-776927.pdf), correct?
« Last Edit: March 13, 2018, 01:56:45 PM by jefepeters »

Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5407 on: March 13, 2018, 02:48:08 PM »
The initial voltage was -1.1 and I could twist it CCW to -2.4 VDC. What is considered the "extreme of the pot"? When I turn it, there is no obvious point where I feel it stiffen up.  I turned it  until I heard a click, but nothing was stopping me from turning it further.

The range of travel is 25 turns (per https://www.mouser.com/ds/2/54/299-776927.pdf), correct?

20 or 25, I can't remember. The click is the end.

It should go down to 0 VDC, that is your issue. Until you can get it below -1 VDC you are not going to see much compression.  CR2/CR3 in the right orientation?  What are you Pad 21 voltages per the guide?

Mike
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jefepeters

Re: [BUILD] 1176LN Rev D DIY
« Reply #5408 on: March 14, 2018, 12:03:29 AM »
20 or 25, I can't remember. The click is the end.

It should go down to 0 VDC, that is your issue. Until you can get it below -1 VDC you are not going to see much compression.  CR2/CR3 in the right orientation?  What are you Pad 21 voltages per the guide?

Mike

Yes, CR2/CR3 are correct.

For test point 21, the voltages are all lower than the specified values:


20:1   -6.22 VDC
12:1   -2.74 VDC   
 8:1   -1.43 VDC
 4:1   -0.35 VDC

Re: [BUILD] 1176LN Rev D DIY
« Reply #5409 on: March 14, 2018, 08:27:31 PM »
Hi Mike

Check the value of R58, R61, R62, R63, R64.

Mike

After checking, pulling away and soldering back lots of resistors, diodes, and caps, my 1176 is behaving better.
In the meanwhile i'm getting a lot more knowledge and curiosity in electronics, thank you for that!

I changed the 2k q-bias trimmer with a new one, and soldered back some "faulty/not perfect" connections.
Now what i have is -1.18 DCV- 0.00 DCV at TP18 (lower than expected).
Now that i have the opposite issue, what you suggest?

Thanks again for your help


Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5410 on: March 15, 2018, 03:51:50 PM »
Hi Mike

After checking, pulling away and soldering back lots of resistors, diodes, and caps, my 1176 is behaving better.
In the meanwhile i'm getting a lot more knowledge and curiosity in electronics, thank you for that!

I changed the 2k q-bias trimmer with a new one, and soldered back some "faulty/not perfect" connections.
Now what i have is -1.18 DCV- 0.00 DCV at TP18 (lower than expected).
Now that i have the opposite issue, what you suggest?

Thanks again for your help

Hmmmmm make sure your R35/R60 are soldered well and the correct value.

What is your V DC on either side of R35?
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Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5411 on: March 15, 2018, 03:56:07 PM »
Yes, CR2/CR3 are correct.

For test point 21, the voltages are all lower than the specified values:


20:1   -6.22 VDC
12:1   -2.74 VDC   
 8:1   -1.43 VDC
 4:1   -0.35 VDC


Check R58 and R61 to 63.

Are those right?
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jefepeters

Re: [BUILD] 1176LN Rev D DIY
« Reply #5412 on: March 15, 2018, 05:36:29 PM »
Check R58 and R61 to 63.

Are those right?

Here's what I get:


R1   (R58) = 146Ω (150Ω)
R2   (R61) = 434Ω (470Ω)
R3   (R62) = 509Ω (560Ω)
R4   (R63) = 1.1KΩ (1.5KΩ)

Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5413 on: March 15, 2018, 05:56:31 PM »
Here's what I get:


R1   (R58) = 146Ω (150Ω)
R2   (R61) = 434Ω (470Ω)
R3   (R62) = 509Ω (560Ω)
R4   (R63) = 1.1KΩ (1.5KΩ)


I assume that's with them still in circuit?

Does one of the outside legs on your bias trimmer have continuity to ground?

Mike
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jefepeters

Re: [BUILD] 1176LN Rev D DIY
« Reply #5414 on: March 15, 2018, 06:07:56 PM »
I assume that's with them still in circuit?

Does one of the outside legs on your bias trimmer have continuity to ground?

Mike

Yes to both questions. (Outside leg closest to edge of pcb).

Thanks,
Justin

Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5415 on: March 15, 2018, 06:09:46 PM »
Yes to both questions. (Outside leg closest to edge of pcb).

Thanks,
Justin

And you can't get PAD 18 down to 0 VDC?
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jefepeters

Re: [BUILD] 1176LN Rev D DIY
« Reply #5416 on: March 15, 2018, 06:11:06 PM »
And you can't get PAD 18 down to 0 VDC?

Correct, the lowest I can get it is -1.11 VDC. I assume there is no point in turning it beyond the click.

Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5417 on: March 15, 2018, 06:12:29 PM »
Correct, the lowest I can get it is -1.11 VDC. I assume there is no point in turning it beyond the click.

Weird.  What are you using for your common/ground probe test point? Screw hole in the enclosure?
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jefepeters

Re: [BUILD] 1176LN Rev D DIY
« Reply #5418 on: March 15, 2018, 06:14:17 PM »
Weird.  What are you using for your common/ground probe test point? Screw hole in the enclosure?

The IEC ground.

Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5419 on: March 15, 2018, 06:15:22 PM »
Is there continuity between that and the ground plane on the PCB?
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