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

[Echo North]

Sorry for the late reply, I was unable to access the support forum for a couple of days.  The answer to your question is "no", there is no voltage drop.

What is that Pad 15 voltage?  Like 2 VAC or 0.08 VAC?

 

[CBarx]

What is that Pad 15 voltage?  Like 2 VAC or 0.08 VAC?

3.8vac. With or without attack on bypass.

 

[Echo North]

3.8vac. With or without attack on bypass.

What is your AC V at each side of R78 (ratio PCB) with GR ON.

Mike

 

[CBarx]

What is your AC V at each side of R78 (ratio PCB) with GR ON.

Mike

.07vac and 1.7vac

 

[Echo North]

.07vac and 1.7vac

Weird.

What ACV do you have at pin 4 on the main PCB of that connector that attaches to the ratio board?  Does that ACV change if you disconnect the cable?

Mike

 

[CBarx]

Weird.

What ACV do you have at pin 4 on the main PCB of that connector that attaches to the ratio board?  Does that ACV change if you disconnect the cable?

Mike

1.68vac, then it drops off if the ratio board is disconnected.

 

[Echo North]

1.68vac, then it drops off if the ratio board is disconnected.

You're measuring at the main PCB?

 

[CBarx]

You're measuring at the main PCB?

Correct.

 

[Echo North]

Correct.

That is super weird.

So with the cable disconnected, with the standard testing set up, you should have 4ish VAC at pad 15.  Do you see that VAC on any of the ratio header pins (no cable)?

Mike

 

[lhamilt18]

Hey guys, so i put together the power supply for the fet rack revision F. Everything seems to be fine except that my meter is reading -30v and +10v. I check all the orientations of my diodes and caps and they all seem to be properly oriented. What could I be overlooking?

Thanks in advance.

 

[Echo North]

Hey guys, so i put together the power supply for the fet rack revision F. Everything seems to be fine except that my meter is reading -30v and +10v. I check all the orientations of my diodes and caps and they all seem to be properly oriented. What could I be overlooking?

Thanks in advance.

You must have your probes backwards.

Mike

 

[lhamilt18]

You must have your probes backwards.

Mike

yep that was it haha. thanks

 

[Echo North]

Hello, I recently bought a FET/RACK Rev F. I'm wrapped up with all of the soldering, and I'm on the calibration stage. I'm sending a 1Khz signal out of my DAW into the input of the 1176, and have adjusted for it to read .775 VAC  at input + and input -. However, when I check the output +/-, I'm not getting the desired reading. More of something like 0.002-0.003 VAC. I noticed I had put the 2K zero adjust trimmer on the top side instead of the bottom, so I de-soldered it and re-soldered it to the bottom side, hoping that would fix it, but still nothing.

The unit does receive power and will turn on when I engage the GR button, but I can't get that read, and the meter won't move when adjusting the input and output.

One thing I'm not sure about is that I can't really get the desired readings for the cathode (30V DC)and anode (-10V DC). For the cathode, I'm getting something along the lines of 0.004V DC on the cathode, and then nothing too solid on the anode. Surprisingly, however, the unit, as I mentioned before, is receiving power and turns on. Do you have any advice for what the issue might be? Thanks in advance!

We'll let's start with your power supply.  Did it originally test fine? meaning after you stuffed the power supply and before you stuffed the rest of the PCB.

Mike

 

[wmjohnson]

Hello!

Just finished putting a rev D together, went through the troubleshooting guide and the calibration procedure and everything seemed to check out within a reasonable margin of error.

My issue is that when I rotate the release control it shoots the meter to the left and, if signal is present I lose it.  Seems to be a control voltage circuit issue? With a 20:1 ratio and attack full on with the release full CW the control voltage is -1.76 VDC, at full CCW it's -1.36 VDC (measured at the passive signal link).

At least theoretically, with no signal the release control should not change the control voltage that much, correct? I checked all the joints on that attack/release assembly and reseated it in the connector. Any ideas?

Thanks!
Will J

Update: I have a rev F here, too. Since the attack/release assemblies are the same, I swapped it in to the D to help isolate the issue, seems that's not it.

Update: I tried cleaning the board multiple times, as was suggested for someone with a similar issue, and that hasn't helped at all.

 

[seanweaverguitar]

when I rotate the release control it shoots the meter to the left and, if signal is present I lose it.  Seems to be a control voltage circuit issue? With a 20:1 ratio and attack full on with the release full CW the control voltage is -1.76 VDC, at full CCW it's -1.36 VDC (measured at the passive signal link).

Update: I tried cleaning the board multiple times, as was suggested for someone with a similar issue, and that hasn't helped at all.

I'll watch this thread for Mike's reply since it'll interest me too. When I built my Rev A this past winter I was having the same identical issue with the release control sending the meter left, and it still moves a little, but nothing really concerning. I think it was that I hadn't let the unit warm up since I cleaned the boards so many times it was OCD and then sent the unit into Mike who was the greatest (can't say enough good things about Hairball and for but lack of funds would buy everything on the site...and am about to place a couple more orders or few) and assured me the build was totally good.

Just checked the GroupDIY now because it happened again this morning, overdubbing  a bass part and being in a hurry I just powered the unit on with my controls set as before (attack a little right of noon, release a little left) and that meter was pretty far to the left but it just took 5 or 10 mins. warming up and is now all good again. Like very little meter drift as the release knob is rotated

 

[Echo North]

I'll watch this thread for Mike's reply since it'll interest me too. When I built my Rev A this past winter I was having the same identical issue with the release control sending the meter left, and it still moves a little, but nothing really concerning. I think it was that I hadn't let the unit warm up since I cleaned the boards so many times it was OCD and then sent the unit into Mike who was the greatest (can't say enough good things about Hairball and for but lack of funds would buy everything on the site...and am about to place a couple more orders or few) and assured me the build was totally good.

Just checked the GroupDIY now because it happened again this morning, overdubbing  a bass part and being in a hurry I just powered the unit on with my controls set as before (attack a little right of noon, release a little left) and that meter was pretty far to the left but it just took 5 or 10 mins. warming up and is now all good again. Like very little meter drift as the release knob is rotated

The FET/RACK, like the original, has a fully discrete meter circuit. The components in this section are sensitive to heat and when powering a cold unit, your meter will rest a little sort of zero. It will take at least 1 hour for the meter to slowly climb back to zero and it may still fall short or overshoot zero. After hours of usage, it may fall a little again. The variance in this part of the circuit is why the designers placed a zero adjust accessible through the front panel. If you’re keen to have it at exactly zero, you’ll be using this adjustment hole a lot.

The release can cause it to drift a little, but that should't be more than a fraction of a DB. barely noticeable.  If  it's causing it to drift I would start by cleaning the PCB of any flux, particularly around the FETs.

Mike

 

[wmjohnson]

If  it's causing it to drift I would start by cleaning the PCB of any flux, particularly around the FETs.

I've already done this pretty extensively. "drift" isn't the right word in my case - it shoots to the left and compresses hard. I've lifted r65 and r7/c6/c22 to figure out if it was an issue around those areas or if it was somewhere before that. I think it's somewhere before that.

With no signal present,  what should the DCV be a TP7, attack off, both ends of the release knob? Currently mine moves between ~ -1.35VDC and -0.78VDC. Is this correct?

Thanks,
Will

 

[lhamilt18]

hi, I'm calibrating my Rev F and I have two questions. in regards to these steps:

"-Now let's set the meter to display this 10dBu drop.  When the attack is "off" (full CCW) and you see +10dBu at the output, set the meter to 0 by using the front panel zero adjust trimmer.

-When the attack control is "on" (full CW) and you see 0dBu at the output, use R44 to set the meter to -10."

In my case with the Rev F.... is the "zero adjust trimmer = to the Tracking Adj trimmer on my main pcb?
also, what would R44 be equivalent to on the Rev F? Because for me R44 is a regular, non-variable resistor on the meter pcb.
thanks

 

[saqeef]

We'll let's start with your power supply.  Did it originally test fine? meaning after you stuffed the power supply and before you stuffed the rest of the PCB.

Mike

To be quite honest, I think I actually skipped testing just the power supply before stuffing the rest of the PCB. I was overeager.

EDIT: Having thought about it, I do remember stuffing the parts for the power supply, then attaching the PCB to the chassis as instructed in order to test the power supply, but I really don't remember what the results were. Having said that, what's the next step?

 

[wmjohnson]

I've already done this pretty extensively. "drift" isn't the right word in my case - it shoots to the left and compresses hard. I've lifted r65 and r7/c6/c22 to figure out if it was an issue around those areas or if it was somewhere before that. I think it's somewhere before that.

With no signal present,  what should the DCV be a TP7, attack off, both ends of the release knob? Currently mine moves between ~ -1.35VDC and -0.78VDC. Is this correct?

Thanks,
Will

Update:

figured out I can pull q11 and recalibrate the Q Bias and it seems to behave like it should. the control voltage doesn't move like crazy when i move the release knob at least.

ordered a few more 5457s a few days ago, hopefully swapping one in will get the meter to work right, otherwise would anyone have any ideas about what might be going on in that section? seems like it's draining more current to drive the gr meter than it should be?