[BUILD] New FET/RACK Official Help Thread - Please read first post!

[csavetman]

Figured it out. Bad Q1 FET. Changed out Q1 and Q11 with the ones that came with the kit. Re-calibrated.
Working now.

Carlos

Actually, looks like the 'bad" Q1 FET is ok after all. Decided to try and re seat it in socket and calibrate. Worked this time.

Carlos

 

[Echo North]

Actually, looks like the 'bad" Q1 FET is ok after all. Decided to try and re seat it in socket and calibrate. Worked this time.

Carlos

Ya that's the give and take with sockets.  They make switching the FETs out super easy, but they also create another point where you can have a bad connection.

That all makes sense based on what you were seeing.

Mike

 

[Echo North]

HI

Clarification on power Transformers for a  Mnat stereo D build and a Mnat stereo F build.

Will the Y236207 work for both builds?

thanks
fvf

Wrong thread. I assume you're talking about the old PCBs.  Yes it should work.

Mike

 

[landispearce]

Hello,

New to this so bare with me here. Built a few of these in the past and now with one  i've built (blue stripe) I am running into an issue on the last step of calibration whilst setting the meter. I attempted to contact and they sent me here to ask. The FAQ says to go to Ed's post, which I did but I was told I would not need to change out any components by someone at hairball via their support line. My input won't go to the desired +10 dbu while metering from the output XLR, and I have taken it apart multiple times and checked everything and cannot seem to figure out what to do. Did not run into this in the past and just purchased 3 more, if anyone has any help please let me know!

thanks,

 

[Echo North]

Hello,

New to this so bare with me here. Built a few of these in the past and now with one  i've built (blue stripe) I am running into an issue on the last step of calibration whilst setting the meter. I attempted to contact and they sent me here to ask. The FAQ says to go to Ed's post, which I did but I was told I would not need to change out any components by someone at hairball via their support line. My input won't go to the desired +10 dbu while metering from the output XLR, and I have taken it apart multiple times and checked everything and cannot seem to figure out what to do. Did not run into this in the past and just purchased 3 more, if anyone has any help please let me know!

thanks,

1. Make sure all 3 L brackets are secured to the PCB and enclosure. They are not just there for stability, they are part of the grounding system.

2. You were able to set the Q-Bias?

3.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

1. Using chassis as your ground reference, what is your AC V at TP22 for all 4 ratio settings.
2. Using chassis as your ground reference, what is your DC V at TP21 for all 4 ratio settings.

Mike

 

[ffarrell]

Wrong thread. I assume you're talking about the old PCBs.  Yes it should work.

Mike

thanks Mike,

I started these in 2012,    how is that for procrastination. 
 

 

[landispearce]

1. Make sure all 3 L brackets are secured to the PCB and enclosure. They are not just there for stability, they are part of the grounding system.

2. You were able to set the Q-Bias?

3.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

1. Using chassis as your ground reference, what is your AC V at TP22 for all 4 ratio settings.
2. Using chassis as your ground reference, what is your DC V at TP21 for all 4 ratio settings.

Mike

Call me stupid but I can't seem to find TP 21 and 22. I can only find 10 and 11.

but yes I can set Q Bias

 

[Echo North]

Call me stupid but I can't seem to find TP 21 and 22. I can only find 10 and 11.

but yes I can set Q Bias

Are you not working on one of the large new PCBs? Is this an older build?

 

[landispearce]

I just bought these 3 less than 2 weeks ago. I don't think these are old builds. I ordered them from you directly.  can attach photos if need be.

 

[Echo North]

I just bought these 3 less than 2 weeks ago. I don't think these are old builds. I ordered them from you directly.  can attach photos if need be.

They should have those TP points then. 22 should be near 10 (might be hidden by an orange drop, and 21 is by C21.

 

[landispearce]

AH got it okay.

For AC at 22. all of them are 0.000
For DC at 21.
20:1 =5.91
12:1 = 3.304
8:1 = keeps declining and doesn't stop. changes .001 every second or so.
4:1 = -1.659

 

[Echo North]

AH got it okay.

For AC at 22. all of them are 0.000
For DC at 21.
20:1 =5.91
12:1 = 3.304
8:1 = keeps declining and doesn't stop. changes .001 every second or so.
4:1 = -1.659

All the DC readings at TP21 should be negative DC values.

You get no AC voltage at TP22 with GR on?  Again:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR ON (Full CW)
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

Mike

 

[landispearce]

Apologies, all the values are negative for the DC but the number are correct.  new meter. not used to where the negative is. and no. I have no reading at Test Point 22, GR on, 20:1 and input and input both at 12 o'clock (24)

landis

 

[Echo North]

Apologies, all the values are negative for the DC but the number are correct.  new meter. not used to where the negative is. and no. I have no reading at Test Point 22, GR on, 20:1 and input and input both at 12 o'clock (24)

landis

What is your AC at TP15 with the same settings (ratio 20:1 only).

 

[landispearce]

4.56

 

[Echo North]

4.56

You've got some disconnect between your TP15 and TP22.  Have a look at the schematic:

http://mnats.net/files/fetrack/fet_rack_d_doc_v1.11.pdf

This is the D but this part is the same for the A other than a few resistor values. Or you can go to MNATS.NET and download the A if that's what you're working on.

http://mnats.net/files/fetrack/fet_rack_d_doc_v1.11.pdf

Find TP15...it's right before the output pot along the top in the middle. Look how the AC travels down through the relay then to the ratio PCB, exists the ratio PCB at the bottom depending on what switch is enabled then through the attack switch to PAD 22.

See if you can trace that AC to pad 22...it's dying somewhere along that short linear path.

Probably a bad joint or lifted pad somewhere.

Mike

 

[Pfgdad]

Hi everyone I'm currently building my second rev D and have an issue with the power supply.

When testing for 30 volts I'm getting a reading of 32.07 volts. In the build guide it is stated that +- 5% is ok but this is a little higher. On the second test point I'm getting a reading of -9.87 volts which seems to be right on.

Is this cause for alarm?  If so any advice or info that could assist the resolution would be greatly appreciated.

Thank you

 

[Echo North]

Hi everyone I'm currently building my second rev D and have an issue with the power supply.

When testing for 30 volts I'm getting a reading of 32.07 volts. In the build guide it is stated that +- 5% is ok but this is a little higher. On the second test point I'm getting a reading of -9.87 volts which seems to be right on.

Is this cause for alarm?  If so any advice or info that could assist the resolution would be greatly appreciated.

Thank you

Hard to say, that should be fine though. The stud diode should be regulating to 30V +/- 5%. That is assuming you have the 1N2989B we ship with the kits. The 1N2989A regulates +/- 10%.

Keep in mind your meter also has a tolerance, could be pretty high if it's cheaper.

I think you're fine. Particularly if it ready high in the other unit which you mentioned in your email.

Mike

 

[Pfgdad]

Hard to say, that should be fine though. The stud diode should be regulating to 30V +/- 5%. That is assuming you have the 1N2989B we ship with the kits. The 1N2989A regulates +/- 10%.

Keep in mind your meter also has a tolerance, could be pretty high if it's cheaper.

I think you're fine. Particularly if it ready high in the other unit which you mentioned in your email.

Mike

Thanks Mike for the quick response.  The first build to further explain did measure 30.3 volts so it was a little lower than this one.  Also I'm using only components included in the kit. Good to know the slightly higher voltage isn't cause for concern. 

Thank you

 

[Echo North]

Thanks Mike for the quick response.  The first build to further explain did measure 30.3 volts so it was a little lower than this one.  Also I'm using only components included in the kit. Good to know the slightly higher voltage isn't cause for concern. 

Thank you

It would be nice if you were within the tolerance of the diode. However, you're barely out of the tolerance and I suspect there may be some weird measurement anomaly going on I can't sort out without checking out the unit myself. With it only being a 1% or so out of normal tolerance, I would not worry.

Mike