Re: [BUILD] FET/500 Official Support Thread
« Reply #420 on: January 11, 2019, 07:16:20 PM »
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?


Re: [BUILD] FET/500 Official Support Thread
« Reply #421 on: January 11, 2019, 09:23:11 PM »
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

Re: [BUILD] FET/500 Official Support Thread
« Reply #422 on: January 11, 2019, 10:01:12 PM »
I am having the same issue as warmtape on my rev F, weird pulsing. Was there a fix for this?

Re: [BUILD] FET/500 Official Support Thread
« Reply #423 on: January 12, 2019, 10:17:14 AM »
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

Hairball Audio

Re: [BUILD] FET/500 Official Support Thread
« Reply #424 on: January 13, 2019, 12:28:03 PM »
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
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Re: [BUILD] FET/500 Official Support Thread
« Reply #425 on: January 13, 2019, 12:29:29 PM »
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!
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Re: [BUILD] FET/500 Official Support Thread
« Reply #426 on: January 13, 2019, 12:32:51 PM »
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
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Re: [BUILD] FET/500 Official Support Thread
« Reply #427 on: January 13, 2019, 12:37:02 PM »
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).
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cah9858

Re: [BUILD] FET/500 Official Support Thread
« Reply #428 on: January 13, 2019, 08:47:42 PM »
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!

Re: [BUILD] FET/500 Official Support Thread
« Reply #429 on: January 13, 2019, 11:22:52 PM »
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.
« Last Edit: January 14, 2019, 12:53:46 AM by adam.schw »


Hairball Audio

Re: [BUILD] FET/500 Official Support Thread
« Reply #430 on: January 14, 2019, 01:23:42 PM »
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
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Re: [BUILD] FET/500 Official Support Thread
« Reply #431 on: January 14, 2019, 01:24:20 PM »
here is that peak circuit
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Re: [BUILD] FET/500 Official Support Thread
« Reply #432 on: January 15, 2019, 01:35:45 AM »
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?