mrclunk said: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??
Hairball Audio said:This will still apply to older boards:
And will help you find exactly where the error is.
Alistair said: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.
thankyou :-[Hairball Audio said:Yes.
Hairball Audio said:That Qbias voltage is bumped lower by the - DC resistors on the ratio PCB. I would check all of those values.
patxiplg said: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.
grid_stopper said: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!
dbonin said:Jumper should be in "normal operation" mode.
Perhaps it doesn't matter? I was just going by this page, which says nothing about taking it out of circuit for the q-bias step.andow said:In the build manual from Hairball it says about the 3-pin header with shunt:
In calibration, you'll start with it out of normal operation. You so can place it over the two pins on the right in the image above for now.
And since the first step of calibration is Q-bias adjustment I did it with R44 out of the circuit. It actually works and sounds fine, but I'm wondering if I should redo calibration...