[BUILD] FET/500 Official Support Thread

[thp]

I finished building the pair of revision A's
Both sound great but one is a little weird with the meters.

with gain reduction bypassed and all knobs in the middle,
if I turn release full clockwise, 0 & Slam light up
if I turn release full counter clockwise -1 lights up

if i engage gain reduction, it does one of the above -
turning release full counter clockwise -1 lights up

Is it just a calibration issue, what should I do?

 

[thp]

Any thoughts on what's going on?

 

[Echo North]

Any thoughts on what's going on?

It's normal for the release to to effect the meter a little.  This is true of the vintage units where under the same conditions you may see a little meter drift.

Are the leads on your output transformer very long? They should be a short s possible.

Mike

 

[Ragan]

I've just completed a FET 500 Rev A and am trying to get it calibrated correctly. 

Everything is working correctly except one thing. The gain trim (internal) has no effect on the output voltage. So in the step where you adjust that gain trim to calibrate the meter, I can't get anything to happen.

I've been emailing Mike at Hairball (who's been very helpful) but I haven't been able to get it sorted out after trying his suggestions (checking/reflowing any suspect joints on the meter board).

Anyone have any suggestions?

 

[mattjhuber]

Hey all!

I have a Rev D.

Audio works fine; I was able to calibrate q bias just fine.

But, when I get to calibrating the meters, it's basically a no-go. I can't get the peak LED calibrated, but at this step:

"Adjust the VR2 "VU Trim" until the -10 LED LED starts to illuminate."

VR2 does nothing to affect the meters. The 0 Adj also does nothing on the subsequent steps.

I have re-flowed all solder points on the meter board, and it appears that all resistors are the correct value.

Any ideas on how to get to the bottom of this?

 

[Echo North]

Hey all!

I have a Rev D.

Audio works fine; I was able to calibrate q bias just fine.

But, when I get to calibrating the meters, it's basically a no-go. I can't get the peak LED calibrated, but at this step:

"Adjust the VR2 "VU Trim" until the -10 LED LED starts to illuminate."

VR2 does nothing to affect the meters. The 0 Adj also does nothing on the subsequent steps.

I have re-flowed all solder points on the meter board, and it appears that all resistors are the correct value.

Any ideas on how to get to the bottom of this?

Some of that circuit is on the main PCB as well.  Around IC1.

Mike

 

[Musepro]

Hey gang,

So I am having the most odd problem with my pair of FET/500 RevAs.

Both of them calibrate properly: Q-bias, VU meter with VR2 for -10 and VR1 for Peak, GR meter using 0 adj. for 0 and tracking adj. for -9. All voltages comply with the calibrate guide sending an exact 0.775VAC from my generator. Both units SOUND good.

BUT, here's the problem: both GR meters work IN REVERSE, starting at -22 and moving toward 0 and I can HEAR compression before the meter shows anything.

Obviously, something has gone awry, but I cannot figure it out! I have gone over both PCBs over and over again using both the Hairball BOM and the MNATs BOM, verifying correct placements and polarities. The only thing I see odd is that both IC204s have a different manufacturer number and printing - even though they're the same part number - so that doesn't seem to be the issue. All of the solder joints are clean, shiny and isolated.

Is there something painfully obvious I have missed? Attached are photos of one of the builds. Thanks!

 

[Echo North]

Hey gang,

So I am having the most odd problem with my pair of FET/500 RevAs.

Both of them calibrate properly: Q-bias, VU meter with VR2 for -10 and VR1 for Peak, GR meter using 0 adj. for 0 and tracking adj. for -9. All voltages comply with the calibrate guide sending an exact 0.775VAC from my generator. Both units SOUND good.

BUT, here's the problem: both GR meters work IN REVERSE, starting at -22 and moving toward 0 and I can HEAR compression before the meter shows anything.

Obviously, something has gone awry, but I cannot figure it out! I have gone over both PCBs over and over again using both the Hairball BOM and the MNATs BOM, verifying correct placements and polarities. The only thing I see odd is that both IC204s have a different manufacturer number and printing - even though they're the same part number - so that doesn't seem to be the issue. All of the solder joints are clean, shiny and isolated.

Is there something painfully obvious I have missed? Attached are photos of one of the builds. Thanks!

1) Is it in dot or bar mode?
2) Were you able to calibrate the metere for a -9db drop?
3) Does it rest at 0?
4) Sure your not compressing heavy past -22 and just seeing the release coming back to 0? Hard compression will bounce past -22.

Mike

 

[Musepro]

1) Is it in dot or bar mode?
2) Were you able to calibrate the metere for a -9db drop?
3) Does it rest at 0?
4) Sure your not compressing heavy past -22 and just seeing the release coming back to 0? Hard compression will bounce past -22.

Mike

1) It is in bar mode.
2) Yes, meter calibrated to -9 using tracking adjust - everything went accordingly with the calibrate guide.
3) No, it does not rest at 0 - 0 never lights up at all.
4) Positive I'm not slamming it that hard. I bring input up, start hearing compression, then the GR starts lighting up from -22 going toward 0 as I apply more compression.

 

[Echo North]

1) It is in bar mode.
2) Yes, meter calibrated to -9 using tracking adjust - everything went accordingly with the calibrate guide.
3) No, it does not rest at 0 - 0 never lights up at all.
4) Positive I'm not slamming it that hard. I bring input up, start hearing compression, then the GR starts lighting up from -22 going toward 0 as I apply more compression.

I'm confused, it would have to rest at zero to complete that GR meter calibration step. Getting it to rest at 0 is part of that calibration step.

 

[Musepro]

I'm confused, it would have to rest at zero to complete that GR meter calibration step. Getting it to rest at 0 is part of that calibration step.

OK - see that's the issue, my GR meter is fully lit up when I adjust for the 0 LED to light. Following the guide and setting the output GR ON and input GR OFF  controls over and over again until both read 0dBu and +9dBu in their respective modes, I adjust the "0 adj" trimmer until 0 lights up - BUT, the entire GR meter is lit up when I do this. I didn't even think about the entire meter being lit up when I did this, I just got the correct voltage readings and turned "0 adj" until 0 lit up!

I've built/calibrated 4 CAPI FC526s that went without a hitch first time around and are happily sitting in my rack with a 0 light lit up. This doesn't answer my question - but I should have noticed the entire GR meter lighted!

 

[Echo North]

OK - see that's the issue, my GR meter is fully lit up when I adjust for the 0 LED to light. Following the guide and setting the output GR ON and input GR OFF  controls over and over again until both read 0dBu and +9dBu in their respective modes, I adjust the "0 adj" trimmer until 0 lights up - BUT, the entire GR meter is lit up when I do this. I didn't even think about the entire meter being lit up when I did this, I just got the correct voltage readings and turned "0 adj" until 0 lit up!

I've built/calibrated 4 CAPI FC526s that went without a hitch first time around and are happily sitting in my rack with a 0 light lit up. This doesn't answer my question - but I should have noticed the entire GR meter lighted!

I'm confused. 

So you have it in bar mode. It's like a meter on an 1176 sitting at zero. When operating properly the meter should sit at zero when in GR off or with no signal. If you have it in BAR it'll be all lit up.

Then when you apply compression it the meter lights move down like on the analog 1176 meter.

That's not what your seeing> Or you can't calibrate it?

Mike

 

[Musepro]

I'm confused. 

So you have it in bar mode. It's like a meter on an 1176 sitting at zero. When operating properly the meter should sit at zero when in GR off or with no signal. If you have it in BAR it'll be all lit up.

Then when you apply compression it the meter lights move down like on the analog 1176 meter.

That's not what your seeing> Or you can't calibrate it?

Mike

Yes, the meter should sit at zero, then dive down when compression starts, just like my FC526s do. My FET/500s show no LEDs lit on the GR meter, you hear compression, then -22 lights up and the meter moves towards 0 the deeper you push into compression - literally backwards - and unlike any real 1176 I have used (or any other compressors for that matter).

As for the calibration, I can follow every step in the guide and get all correct readings/voltages, however, my GR meter is lit fully up when I have it set to calibrate for 0. I just turned the trimmer until 0 lit up and didn't even think about the whole bar being lit.

Maybe my bar mode jumpers are causing some kind of an issue?

UPDATE: I went back and snipped the bar mode jumper on the GR meter. Now when I calibrate, 0 lights up, but as soon as I take it out of SLAM, the 0 LED goes out and the GR meter still moves from -22 toward 0, backwards, when compressing a signal. I can email you a video of this behavior if it helps.

 

[Echo North]

Yes, the meter should sit at zero, then dive down when compression starts, just like my FC526s do. My FET/500s show no LEDs lit on the GR meter, you hear compression, then -22 lights up and the meter moves towards 0 the deeper you push into compression - literally backwards - and unlike any real 1176 I have used (or any other compressors for that matter).

As for the calibration, I can follow every step in the guide and get all correct readings/voltages, however, my GR meter is lit fully up when I have it set to calibrate for 0. I just turned the trimmer until 0 lit up and didn't even think about the whole bar being lit.

Maybe my bar mode jumpers are causing some kind of an issue?

No, we have some in bar mode here working well.

What's confusing me (maybe I'm too tired) is in the first part of your statement it seems you say the meter is all unlit...and only lights as you increase the compression and it lights from the bottom up.

But in the second part is seems you're saying you can calibrate it for zero and it's all lit up.

So is it all lit up or off in GR OFF mode.
What happens when you turn GR on with no signal?

Mike

 

[Echo North]

Yes, the meter should sit at zero, then dive down when compression starts, just like my FC526s do. My FET/500s show no LEDs lit on the GR meter, you hear compression, then -22 lights up and the meter moves towards 0 the deeper you push into compression - literally backwards - and unlike any real 1176 I have used (or any other compressors for that matter).

As for the calibration, I can follow every step in the guide and get all correct readings/voltages, however, my GR meter is lit fully up when I have it set to calibrate for 0. I just turned the trimmer until 0 lit up and didn't even think about the whole bar being lit.

Maybe my bar mode jumpers are causing some kind of an issue?

UPDATE: I went back and snipped the bar mode jumper on the GR meter. Now when I calibrate, 0 lights up, but as soon as I take it out of SLAM, the 0 LED goes out and the GR meter still moves from -22 toward 0, backwards, when compressing a signal. I can email you a video of this behavior if it helps.

Are you calibrating in SLAM? You can't so that. You need to calibrate in 20:1.

Calibrating in SLAM will definitely mess up the meter. In SLAM your meter should be pegged in the highest RED LED.

Mike

 

[Musepro]

Are you calibrating in SLAM? You can't so that. You need to calibrate in 20:1.

Calibrating in SLAM will definitely mess up the meter. In SLAM your meter should be pegged in the highest RED LED.

Mike

Oh good heavens, I was calibrating with all the knobs off and had the ratio switch set to the wrong value! Such a ridiculous oversight on my behalf. Now they are behaving in all respects as I would expect.

So after recalibrating both units from the beginning, this time assured I was in 20:1, both units work perfectly with the GR meter in dot mode. However, when I bridge the pads for bar mode, the entire GR meter lights up, both in GR IN or OUT, and when compressing, GR is shown by LEDs going out from 0 down, not coming on. So my GR bar mode is still acting funny (my VU bar mode had always been fine). I have a video of this behavior if it would help to see.

So sorry I overlooked my ratio settings - I thought I had them in 20:1 the first time around. But I still have odd behavior in bar mode, so hopefully this can be worked out easily. Thank you for your patience and help!

 

[Echo North]

Oh good heavens, I was calibrating with all the knobs off and had the ratio switch set to the wrong value! Such a ridiculous oversight on my behalf. Now they are behaving in all respects as I would expect.

So after recalibrating both units from the beginning, this time assured I was in 20:1, both units work perfectly with the GR meter in dot mode. However, when I bridge the pads for bar mode, the entire GR meter lights up, both in GR IN or OUT, and when compressing, GR is shown by LEDs going out from 0 down, not coming on. So my GR bar mode is still acting funny (my VU bar mode had always been fine). I have a video of this behavior if it would help to see.

So sorry I overlooked my ratio settings - I thought I had them in 20:1 the first time around. But I still have odd behavior in bar mode, so hopefully this can be worked out easily. Thank you for your patience and help!

That sounds normal if I understand you correctly.

Think of it as an analog 1176 meter. With GR OFF, or GR on with no signal the needle sits at zero. So in bar mode, the LEDs would be all lit up to zero. Than as you compress on the analog meter the needle moves down or back to the left, so on the LED meter the lights turn off moving down as you compress.

We've done it different than most, thinking of the LED meter how an analog 1176 meter works.

Mike

 

[Musepro]

That sounds normal if I understand you correctly.

Think of it as an analog 1176 meter. With GR OFF, or GR on with no signal the needle sits at zero. So in bar mode, the LEDs would be all lit up to zero. Than as you compress on the analog meter the needle moves down or back to the left, so on the LED meter the lights turn off moving down as you compress.

We've done it different than most, thinking of the LED meter how an analog 1176 meter works.

Mike

Mike,

Ah! See, I was expecting the GR bar mode to work the same as my FC526s, or any other LED GR meter. I didn't realize you intentionally designed the GR bar meter to work that way - it's an interesting take - I'll have to see now whether I prefer dot or bar for GR (I prefer bar for VU, this much I know). My Western Dynamo 19-09s use dot metering and while they sound awesome, I prefer bar metering - it's just what my eyes are accustomed to seeing.

Glad it's all sorted out and the only problem was my lack of diligence in assuring my ratio switch was at 20:1 with the knobs off. When I went through the calibration steps and checked each setting, I thought they were 20:1. I only realized I had calibrated in SLAM once the units were assembled and the front panel and knobs were on, which I commented about, missed that detail, and you caught!

I owe you coffee or beer or something!

 

[DonnieDarko]

Hey guys,

I´m having some problems with a recent Rev D FET 500 i build.

Before that, I build a Rev F Fet 500 and several Rack Rev D and A. Never a problem beside a faulty output transformer on my first Rev A.

When feeding in a 1khz test tone, the audio (or voltage) doesn´t come tru. DMM reads about 0.003 on output. When turning QBias Adjustment, this varies between 0.001 and 0.003 at max.

The LEDs are set to Bar mode. The compression LEDs somehow decrease when turning the QBias adjust clockwise.

The Output LEDs don´t light up at all.

When pushing hardware Bypass, signal is audible or readable as unity gain when measuring with DMM.

Witougth hardware bypass, no signal can be heard, even when cranking Input and Output, and it measures 0.003 V at max.

I doublechecked all components.

Also resoldered everything on main pcb and meter pcb.

The only thing odd on my build is a smaller electrolytic replacement cap on C7 (They forgot that on in the kit). Smaller meaning: It is in a smaller form factor, of course it´s rated correctly  1µf @50v.  So this should work fine.

The unit makes odd noises when touching the output pot, it definitely reacts to touching this one - but it can´t be wiggled or held in a way that current/signal will pass trough, it just makes noise.

Any suggestions? Faulty output pot? Output Transformer?

Thanks guys!

 

[Echo North]

Hey guys,

I´m having some problems with a recent Rev D FET 500 i build.

Before that, I build a Rev F Fet 500 and several Rack Rev D and A. Never a problem beside a faulty output transformer on my first Rev A.

When feeding in a 1khz test tone, the audio (or voltage) doesn´t come tru. DMM reads about 0.003 on output. When turning QBias Adjustment, this varies between 0.001 and 0.003 at max.

The LEDs are set to Bar mode. The compression LEDs somehow decrease when turning the QBias adjust clockwise.

The Output LEDs don´t light up at all.

When pushing hardware Bypass, signal is audible or readable as unity gain when measuring with DMM.

Witougth hardware bypass, no signal can be heard, even when cranking Input and Output, and it measures 0.003 V at max.

I doublechecked all components.

Also resoldered everything on main pcb and meter pcb.

The only thing odd on my build is a smaller electrolytic replacement cap on C7 (They forgot that on in the kit). Smaller meaning: It is in a smaller form factor, of course it´s rated correctly  1µf @50v.  So this should work fine.

The unit makes odd noises when touching the output pot, it definitely reacts to touching this one - but it can´t be wiggled or held in a way that current/signal will pass trough, it just makes noise.

Any suggestions? Faulty output pot? Output Transformer?

Thanks guys!

Something is bad in your two main gain stages. It could be a transformer or pot, but that would be rare. More likely it's a bad joint, misplaced component, or damaged component.

You need to trace through and try to find the error.

If you can, clear some space in your rack (if you don't have a jig) and try the following:

IN/OUT: mid way
att/release: full CW
GR OFF: Selected so the LED is lit
BYPASS: Unselected so LED is NOT lit
Ratio:20

Feed a 1K 0dbu signal into the unit.

Clip the common lead of your dmm to anode (+) side of D4. Then with the unit on (careful, please use mini-grabber leads so you're not reaching in) and getting the signal, measure for AC V at:

C1:
C7:
C8:
Output tx BRN:

Post your AC results. For the capacitors it doesn't matter which lead. They should both be basically the same.

Mike