Author Topic: White Horse Gradually Increasing Hum Sound  (Read 576 times)

Timko

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White Horse Gradually Increasing Hum Sound
« on: February 07, 2020, 01:15:26 PM »
I picked up a White Horse after hitting a dead end trying to correct Aion's Blueshift.  And would you know it; I've managed to find some other weird issue with a considerably simpler build.  I noticed that when I engage the pedal and am not playing, a hum that gets progressively louder comes out of the effect.  When I begin playing, the hum compresses down with the rest of the signal, so I think that the overall compression effect works. 

I used Lumberg style jacks so I didn't do the grounding ring thing connected to the footswitch.  That said, I'm going to make sure that there's adaquate contact between the metal enclosure and the jack later tonight.  I looked at the inside of the effect this morning and could see a little paint in there.  I don't think that's really the cause because the hum isn't near as present when the blend knob is counterclockwise, bringing in the clean signal.  But that aside, the fact that the effect gets progressively louder when I'm not playing seems odd.

I used a 2.6V white diffused light for the LED, and have maxed out the brightness of that light on the switching board.  All of the switch functionality works.  The voltages look about right on most of the pins, but I did notice on the pins that say "varies" on the TLE2074 the voltage is approximately 0.

I plan to do some more signal tracing this evening, but if anyone has encountered an issue like this (maybe it's not even an issue) I'd be interested to hear.

Timko

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Re: White Horse Gradually Increasing Hum Sound
« Reply #1 on: February 17, 2020, 10:11:58 AM »
I have finally been able to get back to troubleshooting some of my pedal issues this weekend.  I took the entire pedal out of the enclosure for now so I could more accurately troubleshoot.  Here are some of my findings:

1. Settings
Bend - Dimed
Volume - enough for me to hear
Response/Speed - Set to 0 for quick compression
Bass - Dimed to add it
Pre Gain - Turned all the way off

I have noticed that when the Sustain is set anywhere north of 12:00ish, I can hear a delayed increase in volume when not playing my guitar.  It goes away when I start playing.  The hum mentioned earlier may be more of a grounding thing but the delayed increase in volume comes regardless.

When the drive control is dimed (I think this means only the MOSFET compression is happening; none of the vactrol is there), this doesn't happen.  I notice it anywhere from 8:00 to 3:00 on the drive setting.

This delayed volume increase is considerably less noticable when the Sustain control is set to 11:30 or less.

I removed the LED to see what effect I could hear based on what Madbean had written in his build doc.  The issue could still be heard (delayed increase in sound after enabling the effect).

I wanted to document my investigation in the event some other people have similar problems.  At this point I'm starting to feel the vactrol may be the issue.  However, if anyone has any other suggestions or investigation ideas I'd be happy to hear them.

Timko

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Re: White Horse Gradually Increasing Hum Sound
« Reply #2 on: March 02, 2020, 09:13:08 AM »
More testing and probing this weekend.  The volume increase is definitely on the vactrol side of the effect.  I think the hum was a red herring; I think the decrease then increase in volume is what I'm really looking at.  When audio probing, the audio signal going into pin 6 of IC1B is very faint and has just a tiny bit of this increase.  However, the signal coming out of pin 7 is very loud.  I did some other probing on IC pins to see what else was happening.

* Pin 12/13/14 - no volume change
* Pin 8 - no volume change

I spent some time watching the old VFE videos on this pedal.  One of the things I noticed was that the volume in those videos was set somewhere between 11 and 2.  I can't set the volume above 9 without blowing past unity gain.  TLE2074's are expensive so I just bought the one to go in this effect, but would this be an indication that there's a IC issue?