Hairball Audio said:
I'm sure if this will solve the issue, but I would definitely start there.
Okay! I'm glad to report that one of my Rev A's successfully went through all 3 calibration steps after I started the process with the wipers in the center position. I followed along to the Don Bonin youtube videos ( https://www.youtube.com/user/dbonin360 ) for all three steps and it worked like a charm. However, on my second unit, I'm not able to finish the final calibration step for the Tracking Adjustment. Here's a step by step of what I was doing:
1. I started out with the input and output controls all the way down. 20:1 was selected, GR was the meter mode, Attack off, and release all the way clockwise.
2. I confirmed .775VAC on my input XLR. With this signal coming in, my VU meter was hitting at about -1.5 so I zero'd it out using the front adjustment pot on the unit.
3. Switch to VU mode (+4) on the unit. The needle drops to around -20dB. I now crank my input up to about "12" (at this point, my DMM reads .736VAC at the input XLR as it drops when I turn up the input from -infinity). I turn my output knob up to just shy of "48" to zero out the needle on the VU meter.
4. I now turn on my attack knob all the way clockwise and the VU needle drops to about -6 on the meter. This was where things started to go differently from unit 1 (which successfully calibrated) vs unit 2 (which didn't). On my first unit at this point, the needle dropped to about -14 on the meter. This was what happened to Don's needle as well in his calibration video.
5. From here, I attempted to adjust the input and output knobs in order to have the needle at 0 when attack is off, and -10 when attack is on. It worked on unit 1 like a charm, but with endless fidgeting on unit 2 I was never able to get the meter to hit both. It seemed as though I was in an endless circle of having the needle at -10, turning the attack off, the needle would fall to -20 then jump up to about +2.5. From here, it would very, very slowly pull back down to about -1 on the meter. I would re-adjust the output control to zero the meter, turn attack on, the needle would drop to -20, then move up to -7, and slowly fall down to about -8 where it would find its resting point. From here I would adjust the input to get it to -10, turn attack off and the cycle would repeat endlessly with almost the exact same readings every time despite the input knob and output knobs changing each cycle.
On my unit that successfully calibrated, the input knob was just above the dot between 24 and 18 and the output was just shy of 48 when it successfully reached the 0/-10 point. The successful unit also did not do the drop to -20, then back up, and slowly creep down to its resting place thing that the 2nd unit is doing.
I've confirmed that r44 is in the middle of it's value prior to starting this calibration step although I don't think that has anything to do with what's wrong. I'm no expert, but it seems as though the meter is acting finicky but I'm unsure of where to start in troubleshooting this. The unit is passing signal and (I will triple check this later tonight) to the best of my abilities from a thorough inspection, it appears that the wiring between unit 1 and unit 2 are identical so I don't think anything is backwards. Suggestions on how to proceed with troubleshooting?
Much thanks!
