RobertBraz

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1540 on: December 04, 2018, 07:29:12 AM »
Weird...I'll need to poke around a working unit tomorrow and get back to you.

Mike

Awesome. Thanks for all of your help, Mike!


Hairball Audio

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1541 on: December 04, 2018, 07:37:41 PM »
Ya wacky.

With the signal as described in the troubleshooting guide, your signal should be at the base of Q2.  You're saying you have signal at the drain (about 60mVAC) but nothing at the base of Q2?

Either:

-C1 is dead
-R8 is the wrong value or dead
-R9/C2 are dead
-A trace/pad between any of those is dead.

Mike
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RESOLVED. Re: ground hum after orange drop mod
« Reply #1542 on: December 04, 2018, 09:35:36 PM »
Looks like an older build.

Have you confirmed continuity in your cassis and to the IEC ground.

Resolved.  After swapping everything on the compressor, the problem was a nick in the signal wire coming out of the attenuation transformer that probably got jostled when adding the new caps and began touching shield foil around it.
The 60hz noise is from the stereo link jack being wired to the shield on the wire, creating a ground loop during the trouble shooting.  The 120hz was from the nick in the wire coming out of the attenuator

3dB

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1543 on: December 06, 2018, 06:16:16 AM »
I just finished two FET/RACK REV F's. The calibration procedure doesn't seem to apply to this version other than the Q-Bias setting and the Distortion Trim setting, but no Meter Tracking Adjustment that makes sense for this rev. For example, the Rev F has an R54 Tracking Adjustment and an R16 Linearity trim which are not addressed in the cal procedure. There are also no jumpers on these boards. Is there another doc somewhere which I missed?

Rob

3dB

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1544 on: December 07, 2018, 11:28:22 AM »
Thanks for the reply scott2000.

Hairball Audio

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1545 on: December 07, 2018, 12:25:20 PM »
I just finished two FET/RACK REV F's. The calibration procedure doesn't seem to apply to this version other than the Q-Bias setting and the Distortion Trim setting, but no Meter Tracking Adjustment that makes sense for this rev. For example, the Rev F has an R54 Tracking Adjustment and an R16 Linearity trim which are not addressed in the cal procedure. There are also no jumpers on these boards. Is there another doc somewhere which I missed?

Rob

I'll update it today.  Ignore the null adjust it's not needed. Then trim the tracking the same as the Rev A or D.
Hairball Audio, LLC
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Hairball Audio

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1546 on: December 07, 2018, 01:43:22 PM »
The FET/RACK calibration guide has been update to include the Rev F.  Please post here if there is any confusion and I'll update accordingly.

Mike
Hairball Audio, LLC
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cmac

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1547 on: December 07, 2018, 03:41:35 PM »
Hello,

On my REV A Rack build  I inadvertently left off the plastic standoff for Q6.  I had already soldered and trimmed the leads when I realized this mistake. After learning it runs hot I decided to desolder the joints to get the plastic standoff on there. I trimmed the plastic standoff down on one side as there were little ridges, in an attempt to get the leads further down into the holes.. After resoldering, it appears the pad in the middle of Q6 when looking from the bottom of the PCB,  has been removed. The other two seem fine but I sure did a number on the bottom side. I cannot get any further solder on this middle joint, as the pad has been removed.

I have read on the forum it is possible to use a "jumper wire" when a pad comes off.  Is it possible on Q6 with the additional heat? I may need to order another Q6 transistor to get the leads to fully reach out of the bottom, then having to desolder yet again? I have stopped the build at this point, as I don't want to continue adding additional components until I know this is repairable. Looking at the schematic I am a bit confused as to what it would "jump" to, if this is even possible.

In my power supply section of the REV A, I have triple checked all wiring, resistor values, and polarity on everything. I can't seem to figure out why my unit won't read the proper DC voltage. I have a Fluke 117 set to the proper setting, V with one solid line and dashed line above it, to read DC volts. It is properly grounded and reads less than 0.2 resistance. When testing the common probe on the top panel mounting hole, touching CR8 reads 1.549 volts DC. Touching CR9 reads .154 volts DC.. It may be worth noting this value is the same with the "OFF" button selected, as well as the "GR" button.

I have built four Hairball Pre's with no problem! I am a bit embarrassed at all of my issues. Love the products and thanks so much for the help. Really did a number on this one!
« Last Edit: December 07, 2018, 03:44:36 PM by cmac »

Hairball Audio

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1548 on: December 07, 2018, 03:57:38 PM »
Hello,

On my REV A Rack build  I inadvertently left off the plastic standoff for Q6.  I had already soldered and trimmed the leads when I realized this mistake. After learning it runs hot I decided to desolder the joints to get the plastic standoff on there. I trimmed the plastic standoff down on one side as there were little ridges, in an attempt to get the leads further down into the holes.. After resoldering, it appears the pad in the middle of Q6 when looking from the bottom of the PCB,  has been removed. The other two seem fine but I sure did a number on the bottom side. I cannot get any further solder on this middle joint, as the pad has been removed.

I have read on the forum it is possible to use a "jumper wire" when a pad comes off.  Is it possible on Q6 with the additional heat? I may need to order another Q6 transistor to get the leads to fully reach out of the bottom, then having to desolder yet again? I have stopped the build at this point, as I don't want to continue adding additional components until I know this is repairable. Looking at the schematic I am a bit confused as to what it would "jump" to, if this is even possible.

In my power supply section of the REV A, I have triple checked all wiring, resistor values, and polarity on everything. I can't seem to figure out why my unit won't read the proper DC voltage. I have a Fluke 117 set to the proper setting, V with one solid line and dashed line above it, to read DC volts. It is properly grounded and reads less than 0.2 resistance. When testing the common probe on the top panel mounting hole, touching CR8 reads 1.549 volts DC. Touching CR9 reads .154 volts DC.. It may be worth noting this value is the same with the "OFF" button selected, as well as the "GR" button.

I have built four Hairball Pre's with no problem! I am a bit embarrassed at all of my issues. Love the products and thanks so much for the help. Really did a number on this one!

There should be traces coming from the middle pad of Q6 (base). They may be on the top of the PCB. In this case, looking at the schematic there should be continuity from the base of Q6 to the emitter of Q5 and that's it.  Look for continuity there. If there is no continuity you need to connect them with something like a 22AWG solid core wire.

Are you sure your fuse is inserted? Does your fuse looks like it might be blown?

Mike
Hairball Audio, LLC
DIY Parts and Kits
http://hairballaudio.com/shop

Top secret stuff and upcoming releases:
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cmac

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1549 on: December 07, 2018, 06:12:02 PM »
There should be traces coming from the middle pad of Q6 (base). They may be on the top of the PCB. In this case, looking at the schematic there should be continuity from the base of Q6 to the emitter of Q5 and that's it.  Look for continuity there. If there is no continuity you need to connect them with something like a 22AWG solid core wire.

Are you sure your fuse is inserted? Does your fuse looks like it might be blown?

Mike

Thanks for the quick reply! Thanks for the help. To me the best news there is continuity! What a botched job but hey it appears to be working. Now with the power supply, I swapped out the fuse with the other 400 mw amp provided in the kit, still nothing. I also tried another power cable to just rule that out and nothing. At a loss, I have verified everything three times, going through my build.. Ill go through it all again tomorrow, any other suggestions are appreciated! Thanks again Mike, appreciate it.


Hairball Audio

Re: [BUILD] New FET/RACK Official Help Thread - Please read first post!
« Reply #1550 on: December 07, 2018, 06:30:53 PM »
We'll need  to measure the power supply section from start to finish to see where the issue is.  You'll want to be very careful while doing this, there is a dangerous level of V/I in this section.

To start, with the unit ON (GR Push switch IN). Measure your AC V between the Live and Neutral terminals at the IEC. You may have to pull back the connectors a little.

Mike
Hairball Audio, LLC
DIY Parts and Kits
http://hairballaudio.com/shop

Top secret stuff and upcoming releases:
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Hi Mike!

I built 2 units of 500/Rev D. So far so good... It's working properly, but for 2 things.

1st is the VU meter... I can't get to set -10 on the calibration process... The VR2 almost does nothing to the VU behavior...

The other thing is about the stereo link... when I plug the p2 cable in both units, one of the units reacts really weird. GR meter gets pinned to -9 varying a lil bit and it acts very weird, not properly. Any ideas?

Also, I kind of didn't understand how it works... It sums both sidechains? Or it's about the settings I do at one of the units that controls the other one?
Sorry for the newbie question... But it'd help me a lot to clarify this!

I'll come back with pics of the st link issue and maybe upload a video of the calibration thing...

Thanks very much!