Echo North
Well-known member
mixguy said:
You got all 3 L Brackets tight and secure? They are part of the grounding.
What is your DC on either of this 1/2W 1k ohm Rs?
Mike
[BUILD] New FET/RACK Official Help Thread - Please read first post!
- Thread starter mnats
- Start date
Help Support GroupDIY Audio Forum:
You got all 3 L Brackets tight and secure? They are part of the grounding.
What is your DC on either of this 1/2W 1k ohm Rs?
Mike
mixguy
Active member
Brackets are tight. Voltage at the resistors is .32v
Echo North
Well-known member
mixguy said:
30 VDC rail is still good?
Try testing CR9 in circuit with the diode tester function on your DMM.
POWER OFF.
Mike
mixguy
Active member
Reading is 1.12 reversed it is over scale.
Echo North
Well-known member
mixguy said:
What is your AC V at the each of the orange wires at the power tx secondary. Power On, use caution.
mixguy
Active member
No voltage
Echo North
Well-known member
mixguy said:
No AC on either lead w/ power on?
But you have 30V DC at that test point? Wacky.
Maybe try referencing them against the yellow lead.
mixguy
Active member
No the 30v rail is .015V and Cr9 is .56 V
Echo North
Well-known member
mixguy said:
Do you have 120 VAC across your L and N terminals on your IEC inlet? Be careful, and you might have to pull the terminals back a little to measure.
mixguy
Active member
Thanks Mike. The fuse was not properly seated. Now all voltages are correct. Unbelievable how it's the simplest things that trips you up sometimes. Thanks again.
Echo North
Well-known member
mixguy said:
Glad you found it! I'm taking the rest of the day off
Mike
Deejsirois
Well-known member
- Joined
- Jun 26, 2018
- Messages
- 50
Hairball Audio said:
Just wanted to give an update that all is well. I did the calibration over several times, and it turns out that I wasn't picky enough with the null adjust. Hopefully this helps someone...then there will be some sort of redemption for my sheepish posture.
mixguy
Active member
Echo North
Well-known member
Nice job guys!
Hello,
I have a bult Rev A Rack unit, properly calibrated and was running some tracks through. To me it sounds like a very high pitched DC noise of sorts when turning up the output. Also, the low end was completely out of the passed signal, like a high pass filter.
- Checked proper grounding of rack, its fine
- Power Supply section A ok.
- Q bias voltage checked out perfectly
When checking the Amplification stage, the AC readings were quite less than published on the troubleshooting guide
- TP1 - 0.071
- TP15 - 2.896
- TP17 - 0.356
- BRWN T - 5.54
- Output - 5.53
Since I did check the Qbias volts before doing the Amplification Stage check, I didn't know if referencing the Unbiased numbers listed in the Amplification stage check was correct?
It should also be noted I did a number on the PCB when soldering Q6. The middle pad fell off, I measured the continuity as listed in your previous reply, and it checked out.
"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."
If the low readings in the amplification stage could be related I am willing to try the 22AWG gauge if it seems necessary? As always, thanks for the help!
I have a bult Rev A Rack unit, properly calibrated and was running some tracks through. To me it sounds like a very high pitched DC noise of sorts when turning up the output. Also, the low end was completely out of the passed signal, like a high pass filter.
- Checked proper grounding of rack, its fine
- Power Supply section A ok.
- Q bias voltage checked out perfectly
When checking the Amplification stage, the AC readings were quite less than published on the troubleshooting guide
- TP1 - 0.071
- TP15 - 2.896
- TP17 - 0.356
- BRWN T - 5.54
- Output - 5.53
Since I did check the Qbias volts before doing the Amplification Stage check, I didn't know if referencing the Unbiased numbers listed in the Amplification stage check was correct?
It should also be noted I did a number on the PCB when soldering Q6. The middle pad fell off, I measured the continuity as listed in your previous reply, and it checked out.
"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."
If the low readings in the amplification stage could be related I am willing to try the 22AWG gauge if it seems necessary? As always, thanks for the help!
Echo North
Well-known member
cmac said:
Ya could be a lot of things. I would check continuity through the 2 amp stages and hard wire anything damaged.
Also run that same test above with like a 200Hz signal and 10KHz signal and see where they start to differ.
Mike
Hi guys,
I'm having an issue on a Rev. D build. I was able to do everything, from Q Bias setting to Null Adjust and - 10 vu meter reduction. Problem is that when I patch the compressor, with or without compression active, the sound is completely without bass. Sound is only on mid frequencies. Where could I start troubleshooting?
I'm having an issue on a Rev. D build. I was able to do everything, from Q Bias setting to Null Adjust and - 10 vu meter reduction. Problem is that when I patch the compressor, with or without compression active, the sound is completely without bass. Sound is only on mid frequencies. Where could I start troubleshooting?
Echo North
Well-known member
frenkonio said:
I would triple check all of your capacitors values, particularly the small blue ones in the amp sections.
Report back.
Mike
Echo North
Well-known member
frenkonio said:
Yes sir.
In general, check all of the components in the line and signal amp boxes. A mis-placed cap and/or resistor can make a high pass filter.
Mike
