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

[Echo North]

New idea. Can someone PLEASE post a picture of a fully functional Rev D PCB that I may compare to. I had some left over resistors that I had to install from the interactive map. I'd just like to see if I possibly have an extra resistor somewhere or not. Can't find a pic of the new Rev D anywhere though. Thanks.

Visual comparison is mostly useless. It's a circuit issue. Soldering seems good, but I can't really tell, again pictures rarely help.

1) The QBias is set right?
2) Now you're stuck at null adjust right?
3) You have the jumper in the correct location?
4) You've verified the component values agains the Rev D map? Remember in the guide there is a link for helping read color codes.
5) Look at the GR Meter Driver section here (older schematic but mostly accurate):
http://mnats.net/files/1176REVA_125_VOLTAGES.pdf
How do those DC voltages measure.
6)make sure you didn't mix up the 100Ω and 2K square trimmers.

Mike

PS: Also remember we have flat rate repair if that interests you.

 

[Diamondj421]

Visual comparison is mostly useless. It's a circuit issue. Soldering seems good, but I can't really tell, again pictures rarely help.

1) The QBias is set right?
2) Now you're stuck at null adjust right?
3) You have the jumper in the correct location?
4) You've verified the component values agains the Rev D map? Remember in the guide there is a link for helping read color codes.
5) Look at the GR Meter Driver section here (older schematic but mostly accurate):
http://mnats.net/files/1176REVA_125_VOLTAGES.pdf
How do those DC voltages measure.
6)make sure you didn't mix up the 100Ω and 2K square trimmers.

I'm going to check all of that when I get home but more than likely I'll be mailing it off to you tomorrow. Maybe I'll have better luck with my other Rev D and 2x Rev A's. Thanks Mike

Mike

PS: Also remember we have flat rate repair if that interests you.

 

[Echo North]

In my years of experience in working on these it's usually something silly like a bad joint that doesn't look all the bad. Either way, if you do send it in, we'll send you a full report on what was wrong.

Mike

 

[Diamondj421]

In my years of experience in working on these it's usually something silly like a bad joint that doesn't look all the bad. Either way, if you do send it in, we'll send you a full report on what was wrong.

Mike

It's Murphy's Law. If I keep trying to fix it, I'll never figure it out and if I send it to you, I would've figured it out in the time it takes for shipping. Haha. I just want to use this glorious thing at this point! One more attempt at solder joints tonight then off to you tomorrow if no results.

 

[Diamondj421]

It's Murphy's Law. If I keep trying to fix it, I'll never figure it out and if I send it to you, I would've figured it out in the time it takes for shipping. Haha. I just want to use this glorious thing at this point! One more attempt at solder joints tonight then off to you tomorrow if no results.

Andddddd I had two of the pots switched around. Lets hope that was the last problem. Thanks again, Mike!

 

[Diamondj421]

Andddddd I had two of the pots switched around. Lets hope that was the last problem. Thanks again, Mike!

I found a replacement 2k pot but it's 3296 instead of 3396. Will that still work?

 

[ebenchristensen]

As a follow-up to my request for help (and hopefully continue on with calibration and building a mate) here is what was discovered:

Yes, it was the fuse, and two more of them just to get the rail readings. (which eventually were 30.4 /-9.7)

The issue is the main power supply cable length to the PCB (well at least that is what I am going to assume right now, because the unit has been powered up now for about 3 hours). The cable length was about a mil too short on one of the connectors when it was plugged into the pcb, and was causing one of the leads to pull out. This is probably why it was solid when I had things loosely put together. once I un-braided a loop or two it seems to have enough play to allow for a solid connection.

thanks again.

 

[Echo North]

As a follow-up to my request for help (and hopefully continue on with calibration and building a mate) here is what was discovered:

Yes, it was the fuse, and two more of them just to get the rail readings. (which eventually were 30.4 /-9.7)

The issue is the main power supply cable length to the PCB (well at least that is what I am going to assume right now, because the unit has been powered up now for about 3 hours). The cable length was about a mil too short on one of the connectors when it was plugged into the pcb, and was causing one of the leads to pull out. This is probably why it was solid when I had things loosely put together. once I un-braided a loop or two it seems to have enough play to allow for a solid connection.

thanks again.

Ah makes sense.

We have since discovered this issue ourselves and have stopped braiding those wires. Sorry for the hassle!

Mike

 

[Diamondj421]

As I was checking CR8 with my meter it popped and sparked. I seriously can't catch a break. I'm assuming this means I need a new one. I searched Mouser for a 30v DC zener diode and nothing similar looking came up. Where can I get a replacement pronto? Also, I tried to carry on after this happened. Got to step 3 of calibration and couldn't get the attack knob to cause the 10db drop. Are these two things linked? I'm gaining a whole new respect for you guys through this build...

 

[Echo North]

As I was checking CR8 with my meter it popped and sparked. I seriously can't catch a break. I'm assuming this means I need a new one. I searched Mouser for a 30v DC zener diode and nothing similar looking came up. Where can I get a replacement pronto?

Sounds like you shorted it.  We can sell one to you or Newark has them.

 

[Diamondj421]

Sounds like you shorted it.  We can sell one to you or Newark has them.

How do I go about getting that from you? I'd like to order it and have it rush shipped asap.

 

[Echo North]

How do I go about getting that from you? I'd like to order it and have it rush shipped asap.

Email us. We don't usually ship on Tuesdays but I can get it out.

 

[Echo North]

Email us. We don't usually ship on Tuesdays but I can get it out.

Is it even damaged?  To you get 30V ish at the 30v test point?  If so its fine.

 

[Echo North]

Both of your issues so far were caused by misplaced components. I suspect more of that first.

If you're not getting a 10dB drop either:

1) Your Qbias isn't set right
2) You have a misplaced component in the "GR Control Amp" section (including the ratio PCB)
3) You're doing the calibration step wrong.

I'd start by going through all those "GR Control Amp" parts including the ratio PCB. Having a 470Ω, 47K, or 470K resistor swapped will ruin your time.

Mike

 

[Diamondj421]

Both of your issues so far were caused by misplaced components. I suspect more of that first.

If you're not getting a 10dB drop either:

1) Your Qbias isn't set right
2) You have a misplaced component in the "GR Control Amp" section (including the ratio PCB)
3) You're doing the calibration step wrong.

I'd start by going through all those "GR Control Amp" parts including the ratio PCB. Having a 470Ω, 47K, or 470K resistor swapped will ruin your time.

Mike

I accept defeat and am going to surrender my build to you geniuses. Hopefully you can tell me what I did wrong for the next time

 

[Echo North]

I accept defeat and am going to surrender my build to you geniuses. Hopefully you can tell me what I did wrong for the next time

Send us an email. We'll figure it out.

 

[StudioJakubka]

Wait you have a Rev A? Is it the new version that just came out? PCB is V1.12?

What is your DC at pad 18 again?

Mike

Yes, Rev A 1.12, 4 weeks old.

Vladimir

 

[Echo North]

Yes, Rev A 1.12, 4 weeks old.

Vladimir

So what's your DC at pad 18 when you rotate the qbias pot?

 

[StudioJakubka]

So what's your DC at pad 18 when you rotate the qbias pot?

it goes from -1.764 to -1.016, Other points are:

1 0
7 -1.407
15 0
18 -1.744
19 -1.404
21 -5.98
22 0

 

[Echo North]

it goes from -1.764 to -1.016, Other points are:

1 0
7 -1.407
15 0
18 -1.744
19 -1.404
21 -5.98
22 0

Don't worry about the other stuff. Those other points may not even have DC or are relevant. It just confuses the fact finding process.

What is your DC on either side of R60?