[BUILD] FET/500 Official Support Thread

[adam.schw]

Need some help on calibration...

I'm doing a rev A.

On the gain trim calibration, at 4.88V even when I have the trimpot fully rotated CC, the peak light doesn't light up. when I rotate the output to 7.2V it lights up.

on the next step with VU trim, at .388v the -10 led does not light, but when i adjust the output to .65v with the trimpot fully rotated CC the -10 led lights up.

Curiously, when I bypass the unit, my sine wave output appears to be reduced to half the voltage....any ideas for what I messed up?

 

[adam.schw]

Need some help on calibration...

I'm doing a rev A.

On the gain trim calibration, at 4.88V even when I have the trimpot fully rotated CC, the peak light doesn't light up. when I rotate the output to 7.2V it lights up.

on the next step with VU trim, at .388v the -10 led does not light, but when i adjust the output to .65v with the trimpot fully rotated CC the -10 led lights up.

Curiously, when I bypass the unit, my sine wave output appears to be reduced to half the voltage....any ideas for what I messed up?

Update/Side note, SLAM led is constantly lit. I threw it on a vocal track and I can the compression and whatnot, so maybe it's just an issue with the metering board? Still doesn't explain the output measuring half voltage with the module bypassed though.  I checked in my DAW as well, and whatever gets ran through it bypassed is definitely a lower output.

 

[cah9858]

I am having the same issue as warmtape on my rev F, weird pulsing. Was there a fix for this?

 

[emmanuel_szczygiel]

Hi Mike,
I finally achieve to calibrate my FET/500. By turning it, the q bias has finally reacted and I was able to go through the process.
Works great and sound great!
Thanks for your help,
Manu

I doubt you damaged the IC from the trimmers.  Maybe it's just bad from heat or static.  I would check every joint and trace.  If you're swapping our parts it's really easy to lose a pad.

Everything else works?

Mike

 

[Echo North]

I am having the same issue as warmtape on my rev F, weird pulsing. Was there a fix for this?

What's happening exactly?

I think we fixed that one, if it's the one I'm thinking about the 100Ω and 100KΩ trimmers on the main PCB were swapped.

Mike

 

[Echo North]

Hi Mike,
I finally achieve to calibrate my FET/500. By turning it, the q bias has finally reacted and I was able to go through the process.
Works great and sound great!
Thanks for your help,
Manu

Nice!

 

[Echo North]

Update/Side note, SLAM led is constantly lit. I threw it on a vocal track and I can the compression and whatnot, so maybe it's just an issue with the metering board? Still doesn't explain the output measuring half voltage with the module bypassed though.  I checked in my DAW as well, and whatever gets ran through it bypassed is definitely a lower output.

So with say a 0.775 VAC input in bypass mode you get 0.375 VAC ish on the output?

Probably on of the relays isn't working so you're getting an unbalanced signal. Check all of those solder joints.

Mike

 

[Echo North]

Need some help on calibration...

I'm doing a rev A.

On the gain trim calibration, at 4.88V even when I have the trimpot fully rotated CC, the peak light doesn't light up. when I rotate the output to 7.2V it lights up.

on the next step with VU trim, at .388v the -10 led does not light, but when i adjust the output to .65v with the trimpot fully rotated CC the -10 led lights up.

Curiously, when I bypass the unit, my sine wave output appears to be reduced to half the voltage....any ideas for what I messed up?

Not sure what you mean on the first two.  Not enough info for me to diagnose (where the GR ON/OFF and so on).

 

[cah9858]

What's happening exactly?

I think we fixed that one, if it's the one I'm thinking about the 100Ω and 100KΩ trimmers on the main PCB were swapped.

Mike

That was totally it. Calibrated, tested and is working/sounding great. Thanks!

 

[adam.schw]

Not sure what you mean on the first two.  Not enough info for me to diagnose (where the GR ON/OFF and so on).

Ok, first off for the half output on bypass thing...apparently I wasn't paying attention when I grabbed a cable, because I had a TS instead of TRS. So i've got that sorted out now.

As far as the other stuff...

Going through the calibration steps, 20:1, GR off, trying to do gain trim calibration, at 4.88VAC, the peak light does not come on, regardless of the position of the gain trimpot. Once I increase output to about 7.2VAC, I can get the peak light to come on.

In regards to VU trim, at .388VAC, the -10db LED will not come on regardless of the position of the trimpot. At about .7VAC, I can adjust the trimpot to bounce between the -10db and -20db LED.

Also, the SLAM LED is always on when unit bypass button is activated. I've checked (nearly anyway) all off my solder joints on both boards and re-flowed any that I thought might be suspect.

I have checked with actual audio, however, and can confirm that the unit is actually compressing. I know my calibration is a bit off (obviously). I'm not sure how the SLAM LED is supposed to work, but when the unit is "not doing" any GR the slam LED is lit up, but as audio hits the treshold, the GR meter seems to be working. It's confusing to explain, and could email a video if necessary.

Edit/update:
I dicked around with the 0 adjust, and got the slam light to come off and sit at 0 while there's no GR - so that's cool.

 

[Echo North]

Going through the calibration steps, 20:1, GR off, trying to do gain trim calibration, at 4.88VAC, the peak light does not come on, regardless of the position of the gain trimpot. Once I increase output to about 7.2VAC, I can get the peak light to come on.

That's a fairly simple/small circuit built around the 2N5088. It's posted below. You need to triple check all of those component values and solder points.

In regards to VU trim, at .388VAC, the -10db LED will not come on regardless of the position of the trimpot. At about .7VAC, I can adjust the trimpot to bounce between the -10db and -20db LED.

Also, the SLAM LED is always on when unit bypass button is activated. I've checked (nearly anyway) all off my solder joints on both boards and re-flowed any that I thought might be suspect.

I have checked with actual audio, however, and can confirm that the unit is actually compressing. I know my calibration is a bit off (obviously). I'm not sure how the SLAM LED is supposed to work, but when the unit is "not doing" any GR the slam LED is lit up, but as audio hits the treshold, the GR meter seems to be working. It's confusing to explain, and could email a video if necessary.

Edit/update:
I dicked around with the 0 adjust, and got the slam light to come off and sit at 0 while there's no GR - so that's cool.

The GR meter works like the traditional meter. Having the SLAM light lit, just means the meter is drifting right of zero.I would center both the zero adj and GR tracking trimmer before that calibration step.  They are 20 turn trimers, turn one direction until you here a quiet click then turn back the other direction 10 turns.

Mike

 

[Echo North]

here is that peak circuit

 

[adam.schw]

That's a fairly simple/small circuit built around the 2N5088. It's posted below. You need to triple check all of those component values and solder points.

The GR meter works like the traditional meter. Having the SLAM light lit, just means the meter is drifting right of zero.I would center both the zero adj and GR tracking trimmer before that calibration step.  They are 20 turn trimers, turn one direction until you here a quiet click then turn back the other direction 10 turns.

Mike

I went through and verified all the values on the meter board, everything seems to be correct. Went over all the joints that seemed could be possibly suspect, no avail. Is it possible I fried something to cause this? Maybe a problem somewhere on the main board? or would this for sure be a metering board thing?

 

[adam.schw]

I went through and verified all the values on the meter board, everything seems to be correct. Went over all the joints that seemed could be possibly suspect, no avail. Is it possible I fried something to cause this? Maybe a problem somewhere on the main board? or would this for sure be a metering board thing?

I've continued to attempt to troubleshoot with no avail. No matter what it seems the output meter is not lighting up correctly with what is going on with the actual output despite what the trim is set to.

At some point in the coming months I intend to build another one of these. Would it be possible to purchase a meter board? That way, if the problem still exists, we can at least narrow it down to the main PCB as the problem, and then i'd already have a meter board ready to go for my next build. Is there potentially a dead component or damaged component somewhere causing this? Any better ideas?

 

[ninopelo29]

Hi Mike,

I've got an issue with my FET 500 Rev D units...actually, the issue is probably with me.

They worked fine up to a week ago when I recalibrated then. Now I get a huge amount of hiss out of both as I increase the output past 8 o'clock. This happens in both regular and GR OFF modes.

The noise does not get louder when I increase the Input or any other pot. Only when I turn up the output. It completely disappears when I bypass the unit.

I calibrated it according to the Hairball Calibration Guide using a proper tone generator and oscilloscope.  I should also note that the Q6 and it's heatsink are blazing hot to the touch.

Is there something I got wrong when calibrating?  Any help would be super appreciated.

Thanks, Mike!

 

[ninopelo29]

Ok, I've done some more research and I'm thinking there might be a faulty component.

The unit's noise is measuring -44dB whether there is a preamp plugged into the input or not. The settings under test are:
- Input: 12 o'clock;
- Output: 10 o'clock
- Attack: 11 o'clock
- Release: 4 o'clock
- Ratio: 4:1

The noise remains at -44dB in both GR OFF mode and GR ON mode and is unaffected by any control other than the Output pot.

In bypass, noise drops to -70dB.

I had a friend bring by a WA76 and I could only get hers to make a similar hiss with the Input and Output cranked up all the way.

Q6 is running very hot - I would say the heatsink is upwards of 175 degrees Fahrenheit.

Any help in figuring out if there is something wrong with the unit would be great so I can replace the parts. If there's something wrong with me, well, there's no cure for stupid is there? 

Thanks!

 

[Echo North]

I stopped getting notifications on this thread, sorry guys.  As a reminder, if I don't respond in a couple of days, feel free to poke me by email.  Sometimes the notifications stop working and I have to unsubscribe then resubscribe.

Some of these seem familiar so maybe I spoke to you over email or phone, but feel free to post again if you are still having issues.

Mike

 

[electric_underground]

hey everybody!
i ran into some serious issues with my FET500 revA build and hope to get some ideas here how to proceed:

- audio passes the unit clean in BYP mode, but distorts heavily when ON, even in GR OFF mode
- the distorted signal is 25dB less than BYP
- the SLAM LED is lit all the time unless GR kicks in (in BAR mode the GR METER works reverse (is this normal? i didnt find any  videos with BAR MODE on. eg. -5dB GR -> LEDs -22 - -5 are lit))
- i am reading weird values at Q2 or Q3, rather around -8 to -12V, far away from the schematics

i noticed Q3 and Q5 were 2N3707s in the kit rather than 2N3708s on the BOM, but that shouldn't be a problem should it?
i triple checked all values, orientations, trimmers are centered, ROPT1 is bridged, solder joints look ok.

any ideas?
thanks a lot

 

[Echo North]

hey everybody!
i ran into some serious issues with my FET500 revA build and hope to get some ideas here how to proceed:

- audio passes the unit clean in BYP mode, but distorts heavily when ON, even in GR OFF mode
- the distorted signal is 25dB less than BYP
- the SLAM LED is lit all the time unless GR kicks in (in BAR mode the GR METER works reverse (is this normal? i didnt find any  videos with BAR MODE on. eg. -5dB GR -> LEDs -22 - -5 are lit))
- i am reading weird values at Q2 or Q3, rather around -8 to -12V, far away from the schematics

i noticed Q3 and Q5 were 2N3707s in the kit rather than 2N3708s on the BOM, but that shouldn't be a problem should it?
i triple checked all values, orientations, trimmers are centered, ROPT1 is bridged, solder joints look ok.

any ideas?
thanks a lot

Were you able to calibrate it at all?

Mike

 

[electric_underground]

Were you able to calibrate it at all?

Mike

well, since it drops audio significantly it doesnt make much sense i guess - if i apply 1k sine @ .775V (measured in BYP at the output), it drops to NOTHING even with the QBias fully CCW and input and output centered, and .110V with input and output fully CW.