[BUILD] FET/500 Official Support Thread

[ericyoshino]

Those fuses in the picture are the same.  Looks like you got two instead of one.

The labeling on them is just build date and location info.  Use either one.

Thanks a lot! Appreciate it

 

[rockprocess]

Hi,

I'm having trouble calibrating my Rev A unit.  When trying to set the Q bias, the maximum output I get with the output knob maxed is .237 volts, far away from the 2.18v needed.  Also, I can clearly hear my test tone coming out of the unit.  I'm thinking this is not normal.

At the Q bias settings specified (noon on input/output, max attack release and 20:1, etc.) I have a .073v reading, where my Q bias adjustment stops increasing.  This seems low. 

I've confirmed my 1k sine test tone going in is at the specified .775v.  Any suggestions?

 

[Echo North]

Hi,

I'm having trouble calibrating my Rev A unit.  When trying to set the Q bias, the maximum output I get with the output knob maxed is .237 volts, far away from the 2.18v needed.  Also, I can clearly hear my test tone coming out of the unit.  I'm thinking this is not normal.

At the Q bias settings specified (noon on input/output, max attack release and 20:1, etc.) I have a .073v reading, where my Q bias adjustment stops increasing.  This seems low. 

I've confirmed my 1k sine test tone going in is at the specified .775v.  Any suggestions?

Audible test tones happen, especially if the input is hot.

IF you font have a 500 series extension or jig it's hard to signal trace in the box.  I'd start by checking every single component.  Check that it's value is correct, it's oriented correctly, and all the leads are soldered.  Report back.  This process should take an hour or so.  Since the build has no wiring, it has to be a misplaced component.  Also make sure your meter board is in place, you need it for the unit to calibrate/work.

Most of the issues we had in prototyping involved neglecting to solder a lead.

Mike

 

[rockprocess]

Hi,

I'm having trouble calibrating my Rev A unit.  When trying to set the Q bias, the maximum output I get with the output knob maxed is .237 volts, far away from the 2.18v needed.  Also, I can clearly hear my test tone coming out of the unit.  I'm thinking this is not normal.

At the Q bias settings specified (noon on input/output, max attack release and 20:1, etc.) I have a .073v reading, where my Q bias adjustment stops increasing.  This seems low. 

I've confirmed my 1k sine test tone going in is at the specified .775v.  Any suggestions?

Audible test tones happen, especially if the input is hot.

IF you font have a 500 series extension or jig it's hard to signal trace in the box.  I'd start by checking every single component.  Check that it's value is correct, it's oriented correctly, and all the leads are soldered.  Report back.  This process should take an hour or so.  Since the build has no wiring, it has to be a misplaced component.  Also make sure your meter board is in place, you need it for the unit to calibrate/work.

Most of the issues we had in prototyping involved neglecting to solder a lead.

Mike

Thanks Mike.  I went back and double checked each component and reflowed each solder joint.  When trying it fully patched in and out in my DAW, I noticed that the levels were fine, easy capable of more than unity gain.
This made me question my meter reading.  Turns out, I had carelessly used a female XLR to get my pin out, not thinking through that the male XLR that I'll be measuring has the 1 and 3rd terminals flipped.

Sure enough, attaching my meter leads to the correct pin 2 and 3 showed the correct voltage and I was able to calibrate without any issues.  What a great sounding unit!

 

[Lavalier]

I've built a stereo pair of these and they really sound great,
however, whenever the attack or release knobs are lightly touched there seems to be some intermittent static coming through the audio path. It's not an issue if you set it and let go. But if you're trying to adjust on the fly while tracking it's pretty unusable.

I've experienced this with both dynamic and condenser. Standard API lunchbox into a 192.
Lifting the ground doesn't make any difference either...

Anyone else had a similar issue?

 

[mnats]

Check continuity between the potentiometer bushings and the metal bracket. You may need to fit the lock washers behind the bracket to allow the bushings to make contact. Please post the result.

I've built a stereo pair of these and they really sound great,
however, whenever the attack or release knobs are lightly touched there seems to be some intermittent static coming through the audio path. It's not an issue if you set it and let go. But if you're trying to adjust on the fly while tracking it's pretty unusable.

I've experienced this with both dynamic and condenser. Standard API lunchbox into a 192.
Lifting the ground doesn't make any difference either...

Anyone else had a similar issue?

 

[solitud]

Hey,
I am building the FET/500 D.
I have a API Lunchbox with  DB25 connectors so the manual suggests that I have to cut a trace on the PCB to prevent default link mode.
But I only have ONE FET/500.
Is it still necessary to cut this trace?

 

[Echo North]

Hey,
I am building the FET/500 D.
I have a API Lunchbox with  DB25 connectors so the manual suggests that I have to cut a trace on the PCB to prevent default link mode.
But I only have ONE FET/500.
Is it still necessary to cut this trace?

No shouldn't be.  Only if another module in the rack uses stereo linking.

 

[solitud]

No shouldn't be.  Only if another module in the rack uses stereo linking.

Thanks for the quick reply! I am very new to 500 series so forgive me if this is a dumb question:
I have a SSL G Comp in the API Lunchbox. This is a stereo module occupying two slots.
Is this considered to be a module that "uses stereo linking" or is it still save to not cut the trace on the FET/500 with the G Comp in the same rack?

 

[Echo North]

I would cut it to be safe.  It's simple and then you don't need to worry about it.

The trace is not needed.  It's a redundant trace.

Mike

 

[solitud]

O.k., thanks, will do.

 

[solitud]

Another question regarding DOT and BAR modes. 
It's stated in the build docs that the FET/500 draws 150mA in DOT mode.
But I couldn't find the specs for BAR mode.
The API lunchbox supplies 215mA per slot.
Will this be sufficient?

 

[solitud]

For knowing not better I sticked to the default DOT mode.
I have finished the build, went through the calibration and everything works like a charm, yeah!
Thanks for this great kit. Packaging was outstanding stylish and the image-map based online build doc was perfect, especially for a noobish builder like me.

I am perfectly happy but found some small things to improve:

• My package contained two LM317LZ transistors for the meter board but the BOM just mentioned the one for IC203. I have put the other one in IC205. It seems to belong there.
• The image map has a small issue there, too. If I hover about IC205, capacitor C205 also lights up.
• The silkprinting of the trimmers VR1,VR2 does not match the parts orientation-wise.

Thanks again, all the best,
Knut

 

[Echo North]

For knowing not better I sticked to the default DOT mode.
I have finished the build, went through the calibration and everything works like a charm, yeah!
Thanks for this great kit. Packaging was outstanding stylish and the image-map based online build doc was perfect, especially for a noobish builder like me.

I am perfectly happy but found some small things to improve:

• My package contained two LM317LZ transistors for the meter board but the BOM just mentioned the one for IC203. I have put the other one in IC205. It seems to belong there.
• The image map has a small issue there, too. If I hover about IC205, capacitor C205 also lights up.
• The silkprinting of the trimmers VR1,VR2 does not match the parts orientation-wise.

Thanks again, all the best,
Knut

Ah yes there is an error with IC205/C205 on the build map.  Will fix.  VR1/VR2 should be oriented correctly but may still work backwards.

Not sure of the current draw in BAR mode but you can always try it.  It also depends on the other units in the rack as the all share the same power supply.  So if you have a bunch of units drawing 50mA, that leaves considerably more current for the other modules.

 

[Lavalier]

Check continuity between the potentiometer bushings and the metal bracket. You may need to fit the lock washers behind the bracket to allow the bushings to make contact. Please post the result.

Thanks mnats I'll give that a try when I get a chance.

On another note regarding the dot/bar mode. I wanted the option to do either, so I installed switches.
You can actually get them at Radioshack. Model: 275-007  Catalog #: 2750007
http://www.radioshack.com/6vdc-0-3a-dpdt-slide-switch/2750007.html#q=slide%2Bswitch&start=3
You have to clip off the three leads on one side, and then they fit perfectly...

 

[rockprocess]

I've noticed that the Attack control on my RevA Fet/500 is extremely subtle.  Is this normal?  I'm pretty familiar with 1176's in general and I don't ever recall the attack control being that subtle.

I've already gone back through mine to ensure the pot, cap and resistor in the attack section of the circuit are all correct values, functioning and soldered in fine.  Any thoughts?

 

[Echo North]

I've noticed that the Attack control on my RevA Fet/500 is extremely subtle.  Is this normal?  I'm pretty familiar with 1176's in general and I don't ever recall the attack control being that subtle.

I've already gone back through mine to ensure the pot, cap and resistor in the attack section of the circuit are all correct values, functioning and soldered in fine.  Any thoughts?

Pretty much yes.  The attack  is 20 microseconds to 800 microseconds.  That's micro not milliseconds. 

Older units had a pretty unique pot curves which *might* account for a bit of that.

 

[rockprocess]

Would switching the cap, resistor, etc. in the attack circuit to the values of later versions give me longer attack times on the longer end of the range?  I'm looking to keep the fast attack on the short end of the range but be able to dial in longer attack times too. 
I can't tell if doing that would affect the function of other aspects of the circuit or if the attack section of the circuit operates independently. 

Thanks!

 

[Winetree]

Version "D"
I can't read the BOM for the meter board because of print overs and parts seem to be different.
Where do they go?

IC 200  ?    Parts in Kit
IC 201  ?    2 - TL 072P
IC 300  ?    1 - CPA 426

IC 203 ?    Parts in Kit
IC 201 ?    2- LM 317
Q 200 ?      1 - 5088

Also E-Mailed
Thanks

 

[Echo North]

Version "D"
I can't read the BOM for the meter board because of print overs and parts seem to be different.
Where do they go?

IC 200  ?    Parts in Kit
IC 201  ?    2 - TL 072P
IC 300  ?    1 - CPA 426

IC 203 ?    Parts in Kit
IC 201 ?    2- LM 317
Q 200 ?      1 - 5088

Also E-Mailed
Thanks

Hmmm must be a browser resolution thing.

You can always see PDF BOMs on the MNATs site.

http://mnats.net/fet500.html