[Hairball Audio]

Hi chaps,
I building a my first Rev D and my output transistor is very hot.
How hot do they generally get?
I have a small heatsink in mine but it's too hot to holda  finger on.
Is that normal??
thanks

Yes.

https://help.hairballaudio.com/hc/en-us/articles/360049490733-FET-RACK-Operational-FAQ

[Alistair]

Thanks for the quick reply Mike.

I've followed that guide through and am only getting 0VD to -1.2VDC at TP18, so I am assuming the issue is within the q-bias circuit as I can't get it to the approx  -3VDC suggested.
The -10VDC supply is looking fine, as are R35, R59 and R60 (I've pulled all of them from the circuit and tested resistance).

My other voltages are massively off from those AC voltages listed in your troubleshooting guide, however the DC voltages on all transistors are within 15% of those listed by mnats here: http://mnats.net/files/1176REVD_VOLTS.pdf

Looking at the schem I'm still wondering if Q1 and Q11 might be the issue, but very happy to hear if anyone has any other suggestions.

Thanks all

This will still apply to older boards:
https://help.hairballaudio.com/hc/en-us/articles/360045942974-FET-RACK-Troubleshooting-Guide

And will help you find exactly where the error is.

Mike

[Hairball Audio]

Thanks for the quick reply Mike.

I've followed that guide through and am only getting 0VD to -1.2VDC at TP18, so I am assuming the issue is within the q-bias circuit as I can't get it to the approx  -3VDC suggested.
The -10VDC supply is looking fine, as are R35, R59 and R60 (I've pulled all of them from the circuit and tested resistance).

My other voltages are massively off from those AC voltages listed in your troubleshooting guide, however the DC voltages on all transistors are within 15% of those listed by mnats here: http://mnats.net/files/1176REVD_VOLTS.pdf

Looking at the schem I'm still wondering if Q1 and Q11 might be the issue, but very happy to hear if anyone has any other suggestions.

Thanks all

That Qbias voltage is bumped lower by the - DC resistors on the ratio PCB.  I would check all of those values.

[mrclunk]

Yes.

https://help.hairballaudio.com/hc/en-us/articles/360049490733-FET-RACK-Operational-FAQ

thankyou 

Also kids, check you resistors before populating ya boards. All my 10k's turned out to be 1K's... 

[Alistair]

That Qbias voltage is bumped lower by the - DC resistors on the ratio PCB.  I would check all of those values.

Thanks Mike- there was a burnt trace on one leg of a resistor on the ratio board (that I received already completed). Fixed and calibrated and the unit is working as it should. Thanks for the assistance, would have taken me forever to find that by myself.

[patxiplg]

Hello everyone,

My 1176LN Rev D DIY compressor (old version) is not working properly. I tried everything, calibrated the unit 4 or 5 times (apparently "successfully") but I don't know how to solve this issue or see where it comes from. My voltages are way off in general and I don't know why. It's the old 1176 version but it's been unused, just assembled.

I followed rigorously all the steps described here: https://help.hairballaudio.com/hc/en-us/articles/360045942974-FET-RACK-Troubleshooting-Guide

To make things easier for Mike from Hairball or anyone here to help me I decided to write all the measurements I made from that troubleshooting guide down to an Excel (see attachment). Any hints will be welcome...

Thank you A LOT in advance.




PD: There are no Test Points in the old version but I just checked the schematic and measured at the equivalent points. The measurements have been made after calibration.

[egav2]

Hi all, a little help please! I just "built" my first rev D, and by built I mean I ran into a problem.

I finished the whole thing and got to the calibration steps. Q Bias was fine, discrete meter circuit I also guess was fine, but the GR tracking was not working. It seems my unit is not compressing and/or the VU meter isn't responding to the attack being engaged. I followed all the troubleshooting steps after hearing back from Mike and figured I would post here to not just bother him, haha.

Anyways, here are all my voltage readings: https://docs.google.com/document/d/13zXCI9Jio-xdexQ3Kz8hQPpoDCK2VHI_Ln7QtSpz0bE/edit?usp=sharing

I noticed some voltages weren't low, but in fact high. The brown wire reading, for example is supposed to be 3.07vac but I was coming in at over double that.

In the GR Control Amp Input you will notice two numbers, I was consistently getting one or the other which was strange, so I put them both. Q8 is where the readings really start to dip and everything after that is low so I'm assuming my problem is in the GR Control Amp.

I'm currently out of town but want to tackle this when I get back as I have another rev D I need to put together so I can clean out my workspace but want to set this one up properly before moving on. I'm assuming the first thing to try is check my joint at Q8 and possibly just redo that, but is there anything else I need to check as well, or is there anything else I should try in case that doesn't work?

Sorry if this is a bit of a general question, I'm a little bit of a noob when it comes to following schematics (I can read simpler ones fine) although I've put together a decent amount of DIY projects before, so I'm not sure where to start with something much larger like this.

Thanks in advance!

[patxiplg]

Hello everyone,

My 1176LN Rev D DIY compressor (old version) is not working properly. I tried everything, calibrated the unit 4 or 5 times (apparently "successfully") but I don't know how to solve this issue or see where it comes from. My voltages are way off in general and I don't know why. It's the old 1176 version but it's been unused, just assembled.

I followed rigorously all the steps described here: https://help.hairballaudio.com/hc/en-us/articles/360045942974-FET-RACK-Troubleshooting-Guide

To make things easier for Mike from Hairball or anyone here to help me I decided to write all the measurements I made from that troubleshooting guide down to an Excel (see attachment). Any hints will be welcome...

Thank you A LOT in advance.




PD: There are no Test Points in the old version but I just checked the schematic and measured at the equivalent points. The measurements have been made after calibration.

Hi again,

Does anyone know how to reach Mike or anyone from Hairball audio? I tried contacting them by e-mail as they wrote out on their website website but haven't received a reply... Thank you in advance!

[radiance]

Did anyone over here ever tried a low cut filter in the side chain of a 1176?
I seem to remember this but could not find any info...

[andow]

Is there a reason the capacitors in the power supply are axial?

[andia]

Hi, i am having 3 hairball 1176 (2x revD, 1x revA) on the bench. I cleaned them, found some errors, rewired and now they calibrate fine, everything seems to work.
Now, I am looking for noise numbers. And i cant seem to find real numbers anywhere.

The units seem to be rather noisy and i don‘t know if thats how it is supposed to be: with in and out controls at 12 o‘clock i measure -64dBu at the output.
Its roughly the same on all units. Even if i do it like i *think* UA measured it. (pots set for unity gain at the brink of compression for a 0dBu signal) i only reach about -72dBu. Far away from the -81 that is to find in the UA datasheet
Does anyone have numbers to to this question? What should the noise level (in numbers, please) be in a healthy 1176(hairball or other)?
As always, thank you very much!

[grid_stopper]

currently trying to calibrate a rotary version of the Rev D.

It passes signal ok, and I got through the first 2 calibration steps seemingly ok. when I get to step 3, and it comes time to remove the jumper from pad 22 to ground, the meter doesnt go down at all like its supposed to. Ive gone back to check voltages, and at pad 18, i only get a range of a couple milivolts to about 350mVDC, which seems well under what it should be. Hoping someone here can point me in the right direction!

[grid_stopper]

currently trying to calibrate a rotary version of the Rev D.

It passes signal ok, and I got through the first 2 calibration steps seemingly ok. when I get to step 3, and it comes time to remove the jumper from pad 22 to ground, the meter doesnt go down at all like its supposed to. Ive gone back to check voltages, and at pad 18, i only get a range of a couple milivolts to about 350mVDC, which seems well under what it should be. Hoping someone here can point me in the right direction!

ok-solved that problem and the q bias voltage is now good, however there is trouble with the GR control amp input.  When i check the voltages at TP 22, i dont get anything at any of the different ratios. According to the hairball site, that would seem to indicate an issue with the ratio board, however everything there looks to be wired correct, so im at a bit of a loss. I reflowed the solder joints on the board just in case, and still nothing. can anyone provide some insight on getting this sorted?

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