Re: [BUILD] 1176LN Rev D DIY
« Reply #5480 on: October 12, 2018, 04:05:57 PM »
Hi-

So I'm working on an older dual rev D with the mnats power supply.  I had the PSU working and trimmed to +30 and -10.  I finished one channel and applied power to test it, but forgot to disconnect the unfinished second channel from the psu and there must have been a short somewhere.  LEDs on the PSU went on briefly, heard a pop, lights out, I killed power after about two seconds.  Nothing smoked or looks fried.

Now the power trafo is acting funny.  Before, I was getting 25v between secondary ends and center tap.  Now I measure 0V between secondary ends and center tap, but I measure 75V between secondary ends and chassis.  Could I have fried the power transformer?  I should be able to read the correct transformer output voltage without the psu connected right? 

Thanks for any help.


weiss

Re: [BUILD] 1176LN Rev D DIY
« Reply #5481 on: November 08, 2018, 05:00:47 AM »
hey guys, can you answer a quick question for me?
if the rotary meter switch is set to GR off, should pad 22 show continuity to ground?

thanks

Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5482 on: November 09, 2018, 01:30:07 PM »
hey guys, can you answer a quick question for me?
if the rotary meter switch is set to GR off, should pad 22 show continuity to ground?

thanks

Yes.
Hairball Audio, LLC
DIY Parts and Kits
https://hairballaudio.com

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Re: [BUILD] 1176LN Rev D DIY
« Reply #5483 on: August 09, 2019, 12:40:45 PM »
Hello!

Weird thing happening to my RevD 1176: without any input signal the output self oscillates bring the output volume towards fully clockwise.

Things I found out:
-Disconnecting the output XLR or using a short 1 metre XLR of stops the oscillation.
-Different XLR produce different frequencies that vary 25Khz - 150Khz  about 4Vpp.
-Grounding output + doesn't do anything while grounding the output - produces the same high freq oscillation.
-Lifting the PCB and moving it around I could vary the frequency and amplitude.

Checked transformer wiring multiple times..

For the rest the 1176 works well, calibration was fairly straightforward. Tested earth points with multimeter and all earthing was good.

I'm desperate as I'm not sure what else to check!

Any help will be greatly appreciated!
Cheers!

ps. if anyone fancies the challenge there's another paranormal situation needing debunk:  if I disconnect the wire going to pin 17 -basically disconnecting the return signal from the output volume pot- the signal still passes through the line amp section, lower in volume and in low end but I can't understand how that's possible as that circuit is not connected to the other sections in any way but for that wire?

Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5484 on: August 11, 2019, 01:34:50 PM »
Hello!

Weird thing happening to my RevD 1176: without any input signal the output self oscillates bring the output volume towards fully clockwise.

Things I found out:
-Disconnecting the output XLR or using a short 1 metre XLR of stops the oscillation.
-Different XLR produce different frequencies that vary 25Khz - 150Khz  about 4Vpp.
-Grounding output + doesn't do anything while grounding the output - produces the same high freq oscillation.
-Lifting the PCB and moving it around I could vary the frequency and amplitude.

Checked transformer wiring multiple times..

For the rest the 1176 works well, calibration was fairly straightforward. Tested earth points with multimeter and all earthing was good.

I'm desperate as I'm not sure what else to check!

Any help will be greatly appreciated!
Cheers!

ps. if anyone fancies the challenge there's another paranormal situation needing debunk:  if I disconnect the wire going to pin 17 -basically disconnecting the return signal from the output volume pot- the signal still passes through the line amp section, lower in volume and in low end but I can't understand how that's possible as that circuit is not connected to the other sections in any way but for that wire?

That's usual caused by the wires from the meter PCB to the XLR output.  Keep them away from the PCB and/or shield them.
Hairball Audio, LLC
DIY Parts and Kits
https://hairballaudio.com

Top secret stuff and upcoming releases:
http://instagram.com/Hairballaudio
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Re: [BUILD] 1176LN Rev D DIY
« Reply #5485 on: August 11, 2019, 01:42:01 PM »
I see! Though I get that issue also when the meter is on GR? I’ll try anyway!

Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5486 on: August 11, 2019, 01:43:06 PM »
I see! Though I get that issue also when the meter is on GR? I’ll try anyway!

Yup you will. 
Hairball Audio, LLC
DIY Parts and Kits
https://hairballaudio.com

Top secret stuff and upcoming releases:
http://instagram.com/Hairballaudio
http://facebook.com/hairballaudio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5487 on: August 14, 2019, 06:53:42 AM »
Hello Hairball Audio,

I've tried removing the wire from the XLR to the meter but it didn't help.
Though what resolved the issue was rewiring both of the XLRs ground to the main PCB  star ground instead of using the wire coming out of the output transformer chassis. It seems so strange how that could be affecting the circuit, as the transformer chassis is physically connected to the case as well as the star ground just a few cm away!

Cheers

Re: [BUILD] 1176LN Rev D DIY
« Reply #5488 on: August 16, 2019, 11:09:15 AM »
Happened to fit the top panel finally!
There are still minor noise issues to fix but I’m quite happy!

The extra features are just a switch to reverse the order of compression and eq, and another rotary to send the sidechain through a high pass or to send it to the eq circuit.

Frontpanel made from frontpanels.de from a inkscape design I’ve drawn.

Cheers!
« Last Edit: August 16, 2019, 11:16:32 AM by Alexwfm »

Hairball Audio

Re: [BUILD] 1176LN Rev D DIY
« Reply #5489 on: August 19, 2019, 08:30:44 PM »
Happened to fit the top panel finally!
There are still minor noise issues to fix but I’m quite happy!

The extra features are just a switch to reverse the order of compression and eq, and another rotary to send the sidechain through a high pass or to send it to the eq circuit.

Frontpanel made from frontpanels.de from a inkscape design I’ve drawn.

Cheers!

Nice!
Hairball Audio, LLC
DIY Parts and Kits
https://hairballaudio.com

Top secret stuff and upcoming releases:
http://instagram.com/Hairballaudio
http://facebook.com/hairballaudio


 

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