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

[Echo North]

haha, of coarse this project is impossible! JK  :'(

I triple checked and thats the reading...I'm probing all the possible spots I can reach, bottom and top...

Well everything seems to be working other than your GR meter.

If you don't have continuity between Q13's C and TP11...one of those pads is lifted off the trace.

 

[Echo North]

10.38VAC

That's like 14dBu at your output.

Sure you're doing the calibration step right?

 

[lackstudios]

Well everything seems to be working other than your GR meter.

If you don't have continuity between Q13's C and TP11...one of those pads is lifted off the trace.

both the traces look solid....the soldering looks good too...I also checked the Ω between Q13's C and TP11 and got OL on the DMM

 

[Echo North]

Then one of those pads ain't good.

Should be like 0.2Ω.

Solder a short wire or leg clipping across those points.

 

[lackstudios]

Then one of those pads ain't good.

Should be like 0.2Ω.

Solder a short wire or leg clipping across those points.

Ok, (with wire) now I'm getting the right voltage at both points...

The meter didn't move, and I checked the DCV between TP10/11 still 0.0 VDC even when I move the null adjust

 

[Echo North]

Ok, (with wire) now I'm getting the right voltage at both points...

The meter didn't move, and I checked the DCV between TP10/11 still 0.0 VDC even when I move the null adjust

Do all those Q12/Q13 DC Voltages again.

 

[lackstudios]

Do all those Q12/Q13 DC Voltages again.

OK, so now I'm getting...
Q12  E= 0.0  C= 16.61  B= -.775
Q13  E= 0.0  C= 16.59  B= -1.106

 

[Echo North]

OK, so now I'm getting...
Q12  E= 0.0  C= 16.61  B= -.775
Q13  E= 0.0  C= 16.59  B= -1.106

You most likely have something wrong in this attached section. You need to Ω test all of the trace connections, look for more dead pads. The schematic shows you what connects to what and looking at the traces will confirm that.  Your ohm meter is your friend.

That's about all I can do with out you sending it in for repair.

Good luck,

Mike

 

[Diamondj421]

That's like 14dBu at your output.

Sure you're doing the calibration step right?

Dammit dammit dammit dammit. My DMM is definitely reading around .775VAC at the input. Do I need a cable running from the output or anything? Would that make a difference?

 

[Echo North]

Dammit dammit dammit dammit. My DMM is definitely reading around .775VAC at the input. Do I need a cable running from the output or anything? Would that make a difference?

You should load your output yes.  Double check your qbias.

 

[Diamondj421]

What is your VAC across output + and output -?

Same conditions.

Mike

Ok. Reset the Q Bias. Readings are now:
+ Output: 9.48 VAC
Pad 15: 2.45 VAC
Across Output+/-: 9.46 VAC

Note: After completing step 2 and resetting the shorting pin, the needle drops so low that R71 (the front zero pot) can only bring it back up to about -12dB, before attempting to begin step 3.

 

[Echo North]

Ok. Reset the Q Bias. Readings are now:
+ Output: 9.48 VAC
Pad 15: 2.45 VAC
Across Output+/-: 9.46 VAC

Note: After completing step 2 and resetting the shorting pin, the needle drops so low that R71 (the front zero pot) can only bring it back up to about -12dB, before attempting to begin step 3.

hmmmm, it should drop when you reset the pin, but only to like -3 or -5.

Are you able to get the 10dB drop at the output? Ignore the meter for now.

Those voltages look ok to me.

 

[Diamondj421]

hmmmm, it should drop when you reset the pin, but only to like -3 or -5.

Are you able to get the 10dB drop at the output? Ignore the meter for now.

Those voltages look ok to me.

When I'm getting the input to read .775vac across input -/+ do I want the input and output knobs turned all of the way down? Those would affect the reading pretty substantially, right?

 

[Echo North]

When I'm getting the input to read .775vac across input -/+ do I want the input and output knobs turned all of the way down? Those would affect the reading pretty substantially, right?

Don't touch the knobs. Start with them at 12 O'Clock.  Adjust the level of your signal source to get 0dBu at the input.

 

[Diamondj421]

Don't touch the knobs. Start with them at 12 O'Clock.  Adjust the level of your signal source to get 0dBu at the input.

Alright, so today is my birthday and I'm feeling good that we're gonna get this SOB figured out!!! So, Input is set to 0dBu with both knobs at 24. Turned output pot to about "48" and the output is reading 0dBu. I begin turning up the input pot and again it maxes out at about 2.09-2.10VAC. When I turn the Attack knob all the way CW, the output drops down to about 1.54VAC before climbing back up to 2.09-2.10VAC. It does this climb in about 5.5 seconds (I'm trying to be thorough so I broke out the stopwatch). 

I'm fairly certain at this point that the Q Bias has been calibrated properly. The Null Adjust I can get to about .003 but again, upon reinserting the shunt "normally", the needle drops to the far left and with R71 fully CW, can only reach about -12dB on the meter.

Let me know what the next step is oh great one!!!

Cheers.

 

[Echo North]

Alright, so today is my birthday and I'm feeling good that we're gonna get this SOB figured out!!! So, Input is set to 0dBu with both knobs at 24. Turned output pot to about "48" and the output is reading 0dBu.

Did you turn the attack from off to FCW before adjusting the output?

 

[Diamondj421]

Did you turn the attack from off to FCW before adjusting the output?

I set everything as stated before the step then went forward. So Attack FCW set Output to 0 dBu, turned Attack off and then attempted to set Input to 2.44 VAC. 

 

[Echo North]

I set everything as stated before the step then went forward. So Attack FCW set Output to 0 dBu, turned Attack off and then attempted to set Input to 2.44 VAC.

and that when you run out of gain?

 

[Diamondj421]

and that when you run out of gain?

Yea. Input FCW maxes out at 2.10 VAC.

 

[Echo North]

Yea. Input FCW maxes out at 2.10 VAC.

Guessing you have a side chain issue...too much compression maybe.  Go back several pages in this thread...look for the posts about measuring pad 22 and pad 21 at  all ratios.  I've gone through it a few times with people in this thread.