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

[galloni21]

Sorry I meant I'm still getting these readings below with the replacement pcb and switch...

with the switch in 115V...

blk/wht resistance: not getting a reading
blu/red resistance: not getting a reading

with the switch in 230V...

blk/wht resistance: 97.6 ohms
blu/red resistance: 116.2 ohms

is the voltage selector switch bad in 115V (my region)?

 

[Echo North]

If you're in the USA it might be best for you to send in the Voltage SW, Power Tx, and Meter Switch.

I could try sending you a new TX but it seems fine in 230V mode and I hate to just keep sending you stuff when nothing really adds up.

Email me.

Mike

 

[Spaceyjb]

Hi,

I have strange issues regarding my REV A build (the new one).

First I have unfortunately missplaced CR 10. Repaired it and everything was pretty nice working. When compared to my other unit they were sonically as twin brothers.

After some time though the unit sounds quite unpleasantly distorted pretty soon and seems not compressing as it should.
Also the unit starts to distort pretty soon when adjusting input gain. under 36 marking already. And to get any compression I need to drive it quite hot (around 18). Funny though as soon as I turn off compression (with attack knob) sound is nice and clear as it should.

I have followed DC voltages and found out these problematic values:



Q3:  B:      7.04 VDC (should be 6.73 VDC)
          C:  16.02 VDC (13.74 VDC)
´        E:      6.44 VDC (6.13)

Q7  B:  4.6VDC (5.22)
        C: 
        E:  4.05VDC (4.71)

Q8  B: 15.28VDC (16.93)
        C:  30,5VDC
        E:  14.6 VDC (16.31)

Q9: B: 3.5 VDC (3.6)
        C: 17.3 VDC (14.96)
        E:  2.97 VDC (3.09)

Q10  B: 17.3 VDC (14.96)
            C: 30,5 VDC
            E:16.7 VDC (14.39)

Everything else seems more or less on the place (cca 0.1- 0.2 VDC variations)
My PSU gives 30.5VDC/-9,7VDC

I have checked visually all resistors in GR CONTROL AMP circuit, such as all of them around problematic transistors and did not find any false piece.

Unfortunately I do not have access to oscilloscope at the moment to see where and when is something wrong going on.

Calibration can be made correctly, but  audibly generates  unit when fed with  +10dBU  for step 3. quite lots of harmonics content.

Thanks for any suggestion where should i look at

Jan

 

[Echo North]

Hi,

I have strange issues regarding my REV A build (the new one).

First I have unfortunately missplaced CR 10. Repaired it and everything was pretty nice working. When compared to my other unit they were sonically as twin brothers.

After some time though the unit sounds quite unpleasantly distorted pretty soon and seems not compressing as it should.
Also the unit starts to distort pretty soon when adjusting input gain. under 36 marking already. And to get any compression I need to drive it quite hot (around 18). Funny though as soon as I turn off compression (with attack knob) sound is nice and clear as it should.

I have followed DC voltages and found out these problematic values:



Q3:  B:      7.04 VDC (should be 6.73 VDC)
          C:  16.02 VDC (13.74 VDC)
´        E:      6.44 VDC (6.13)

Q7  B:  4.6VDC (5.22)
        C: 
        E:  4.05VDC (4.71)

Q8  B: 15.28VDC (16.93)
        C:  30,5VDC
        E:  14.6 VDC (16.31)

Q9: B: 3.5 VDC (3.6)
        C: 17.3 VDC (14.96)
        E:  2.97 VDC (3.09)

Q10  B: 17.3 VDC (14.96)
            C: 30,5 VDC
            E:16.7 VDC (14.39)

Everything else seems more or less on the place (cca 0.1- 0.2 VDC variations)
My PSU gives 30.5VDC/-9,7VDC

I have checked visually all resistors in GR CONTROL AMP circuit, such as all of them around problematic transistors and did not find any false piece.

Unfortunately I do not have access to oscilloscope at the moment to see where and when is something wrong going on.

Calibration can be made correctly, but  audibly generates  unit when fed with  +10dBU  for step 3. quite lots of harmonics content.

Thanks for any suggestion where should i look at

Jan

Start by reading that. There are a few nuggets in there.

http://www.hairballaudio.com/blog/resources/post/fetrack-operational-faq

Also if you're input signal is +10dBu, that is way too high.

Mike

 

[Spaceyjb]

Start by reading that. There are a few nuggets in there.

http://www.hairballaudio.com/blog/resources/post/fetrack-operational-faq

Also if you're input signal is +10dBu, that is way too high.

Mike

Hi Mike,
Thanks for response.
I have read that already, such as whole forum. I have misled you by saying I fed the unit with 10 dB. What I meant was when I pushed input to gain 10dB for step 3 in calibration procedure I had these distorted harmonics audible at the output. I fed the unit with 0dBU from my Neutrik signal generator. Also my unit does not compress until I am with inout at way beyond "noon". First I thought I had the problem at preamp stage, but as I have said, when I bypass compression by using attack knob, signal is clear. So I think there is probably something in GR circuit. But I have found out these weird voltages around transistors as stated in my first post. Unfortunately I am not so expert in electronic to see where else should I look at. I think to swap Q1 and Q11 to see if it helps. I thought to ask you first about any other ideas or if these voltages is somewhat ok. Or I should look at transistors.

Thanks for suggestions
Jan

 

[Echo North]

Hi Mike,
Thanks for response.
I have read that already, such as whole forum. I have misled you by saying I fed the unit with 10 dB. What I meant was when I pushed input to gain 10dB for step 3 in calibration procedure I had these distorted harmonics audible at the output. I fed the unit with 0dBU from my Neutrik signal generator. Also my unit does not compress until I am with inout at way beyond "noon". First I thought I had the problem at preamp stage, but as I have said, when I bypass compression by using attack knob, signal is clear. So I think there is probably something in GR circuit. But I have found out these weird voltages around transistors as stated in my first post. Unfortunately I am not so expert in electronic to see where else should I look at. I think to swap Q1 and Q11 to see if it helps. I thought to ask you first about any other ideas or if these voltages is somewhat ok. Or I should look at transistors.

Thanks for suggestions
Jan

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

 

[Jacob123588]

Question.. so how much would replacing R70 with a 5% tolerance resistor instead of 1% effect the meter and the accuracy. Will it even work? Thanks!

 

[Echo North]

Question.. so how much would replacing R70 with a 5% tolerance resistor instead of 1% effect the meter and the accuracy. Will it even work? Thanks!

Doesn't mater. It's calibrated anyway.

The original units used 10% resistors.

 

[Spaceyjb]

Hi Mike

here are my voltages:

TP 21
20:1  -5.84  VDC
12:1  -3.177 VDC
  8:1    -2.341 VDC
  4:1    -1.505 VDC

TP 22
20:1  0.511 VAC
12:1  0.246 VAC
  8:1    0.160 VAC
  4:1    0.075 VAC

Thanks

Jan

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

 

[Jacob123588]

Question.. so how much would replacing R70 with a 5% tolerance resistor instead of 1% effect the meter and the accuracy. Will it even work? Thanks!

Ok so another question. With my signal generator set at 1khz and as loud is my system can physically output it, my DMM on the input gives me a reading of anywhere between 0.066-0.093 never does it give me a reading of the suggested 0.775. So what is wrong, also the needle on the meter stays and -20, and can be adjusted as high as -10 I can get it no where near 0.

This is after following all the calibration steps

Thanks.

 

[Echo North]

Ok so another question. With my signal generator set at 1khz and as loud is my system can physically output it, my DMM on the input gives me a reading of anywhere between 0.066-0.093 never does it give me a reading of the suggested 0.775. So what is wrong, also the needle on the meter stays and -20, and can be adjusted as high as -10 I can get it no where near 0.

This is after following all the calibration steps

Thanks.

If you can't get 0.775 VAC at your input, it's most likely an issue with your set up.  What is your signal generator termination? XLR? Try seeing what you have across pin 2 and pin 3 of the terminating connector when it's disconnected from the FET/RACK.

 

[Echo North]

Hi Mike

here are my voltages:

TP 21
20:1  -5.84  VDC
12:1  -3.177 VDC
  8:1    -2.341 VDC
  4:1    -1.505 VDC

TP 22
20:1  0.511 VAC
12:1  0.246 VAC
  8:1    0.160 VAC
  4:1    0.075 VAC

Thanks

Jan

Doesn't seem off.

What is your VAC in the same set up at + side of CR2?

Mike

 

[Spaceyjb]

Doesn't seem off.

What is your VAC in the same set up at + side of CR2?

Mike

CR2 Anode:
20:1  4.58VAC
12:1  2.21VAC
  8:1  1.446VAC
  4:1  0.698VAC

 

[Echo North]

CR2 Anode:
20:1  4.58VAC
12:1  2.21VAC
  8:1  1.446VAC
  4:1  0.698VAC

Seems good.

You sure you're calibrating the QBias and Meter correctly?

Mike

 

[Spaceyjb]

Seems good.

You sure you're calibrating the QBias and Meter correctly?

Mike

Pretty much. I did it several times already... This is second unit I have built. 
And the unit did sound ok. The nasty dostortions and funny behavior started a bit later. Like after couple days of using it. I mean distortion is really unpleasant.... and if i stay with input knob under the distortion level I cannot reach compression "threshold"
That is why I have started to look at possible issues.
So you mean these shifted DC voltages I have sent before around transistors are ok?

Jan

 

[Echo North]

Pretty much. I did it several times already... This is second unit I have built. 
And the unit did sound ok. The nasty dostortions and funny behavior started a bit later. Like after couple days of using it. I mean distortion is really unpleasant.... and if i stay with input knob under the distortion level I cannot reach compression "threshold"
That is why I have started to look at possible issues.
So you mean these shifted DC voltages I have sent before around transistors are ok?

Jan

Nothing these seems crazy.

And it sounds fine in GR off?

What if you increase the level going into the unit? Maybe you input is not high enough?

 

[Spaceyjb]

Nothing these seems crazy.

And it sounds fine in GR off?

What if you increase the level going into the unit? Maybe you input is not high enough?

Yes it does. It sounds wonderfull with GR off. I have tried with hotter signal with same effect. I mean the harmonics sounds like too much transistor O/L. All buttons in mode is unusable whil it was pretty great on drums before...  I will give it one more shot though... and see what happens.... maybe I will post audio so you can hear for yourselves...

Besides of this one problem I have I have to say you guys did absolutely amazing job. These beasts sound great and build quality is awesome. I must have ****** it up somewhere ...
Thanks again
Jan

 

[Echo North]

Yes it does. It sounds wonderfull with GR off. I have tried with hotter signal with same effect. I mean the harmonics sounds like too much transistor O/L. All buttons in mode is unusable whil it was pretty great on drums before...  I will give it one more shot though... and see what happens.... maybe I will post audio so you can hear for yourselves...

Besides of this one problem I have I have to say you guys did absolutely amazing job. These beasts sound great and build quality is awesome. I must have f**ked it up somewhere ...
Thanks again
Jan

We'll get it sorted. Even if you have to send one in.

Sounds like something is off in your GR amp.

Mike

 

[Spaceyjb]

We'll get it sorted. Even if you have to send one in.

Sounds like something is off in your GR amp.

Mike

So I have tried to recalibrate again using DMM and if I send from my neutrik 0dBu it reads 0.552 VAC at input testpoints

 

[Echo North]

So I have tried to recalibrate again using DMM and if I send from my neutrik 0dBu it reads 0.552 VAC at input testpoints

That's impedance loss.  Just boost your signal till you see 0dBu.