Harbinger One and POP

[Road2k]

Good morning, i build Harbinger one 2015 and it works very well, but it have a big big pop when i engaged it. Can anyone suggest me which is the problem?
Thanks
Stefano

[Orbis_Ignis]

Sounds like it may be building up a charge. (Not sure if there is a pull down resister) Is it every time you engage the pedal or just when you first start playing with it?

[Road2k]

The first time that i engage it!!!!

[Orbis_Ignis]

Yep, it's building up a charge. Before you turn it on, stomp on the Footswitch a few times.

[Road2k]

Thanks Orbis, but where a can solve? Why this happen?

[Orbis_Ignis]

It's usually solved with a pull down resistor. It's usually put right by the input to drain that charge. Not sure if the circuit already has one (R50 maybe?) or if it can be added. Someone that knows more than me is going to have to chime in. Sorry

[Road2k]

Thanks a lot, yesterday i retried the pedal, it make pop 10/15 times when i engaged, it make pop also when i change from vibe to chorus.

[Bursarboy]

Hi all:
I'm resurrecting this month-old thread because I'm experiencing the same issue.  Just built the Harbinger & it sounds just beautiful!  I really love the tone & lush vibe-ing.  Only issue is a moderately loud POP when I turn it on or off.  Also a pop when I switch from chorus to vibe or back, but honestly I really only use chorus mode so I don't care too much about this part. 

Can the value of the pull-down resistor be increased?  I'm thinking it's one of the 1M resistors so maybe I could just double the value to address the POP.  I'm just not sure which resistor it is.  Is it R50 as was suggested?  Could I just put another 1M resistor in series with it?

Many thanks.  I really like the Vibe; also built the Smoothie (which is also amazing) & will be doing more.  If my wife lets me.  Kidding.  Sort of.

T

[madbean]

So, there's actually no pull-down resistor in the Harbinger. There is a biasing resistor for Q14, but that is on the opposite side of C28. There shouldn't be any DC on the input in either the Modern or Vintage mode to cause a pop esp. if you are wiring it to ground the effect input on bypass. But sometimes switches just pop despite what we think should happen It certainly won't hurt to try a pull-down to see if it eliminates the problem. Put a 1M resistor on your footswitch -it'll go from the FX input to ground.

I have not experienced a pop with the C/V switch, but again you can try another 1M or higher resistor there. Solder the resistor to the two outside legs of the SPDT switch.

At the same time, it wouldn't hurt to do a quick DC check with your multimeter. Specifically you would want to check R49 and lugs 1 and 3 of the CV switch for any DC voltage. That would indicate one or more leaky caps.

[Bursarboy]

Thank you so much for that - I'll try it & report back.  FWIW, I'm running it at 18v & also using a Guitar PCB 3pdt board for the switch - probably should have included that info in 1st post...  Anyway, I think I get what you're saying & I'll give it a go.  Many thanks again,

T

[Bursarboy]

That worked!!  Many, many thanks again, MB.  Absolutely love this vibe.

T

[Bursarboy]

Well, my bad...  Didn't work after all - turns out I had basically just dialed down the volume on the Harbinger which reduced the pop, but it's still there, just as bad.  Here's what I have done:

• 1M resistor connected at harbinger (board) input and connected to ground
• 3M resistor across outside legs of chorus/vibe toggle

I took voltages at R49 - zero on both sides.  Also at the C/V toggle.  Looking down at the inside of the pedal, left leg reads about .870 volts, right leg about 1.4 volts.  If I move the toggle the left sides goes down slightly while the right leg goes up to about 2.3 volts.

So I seem to have a leaking cap somewhere.  My guess is that the best solution is to find & replace the leaking cap, but I really no idea where/how to begin the search.  Any help would be very much appreciated.

T

[Bursarboy]

Tried a 2M resistor at the output to ground.  I measured about .3 volts at output before putting in the resistor, then about .1 after.  No change on the popping.  Is there any way at all to isolate the offending cap? 

T

[madbean]

C5 and C6 are the two DC blocking caps here. So, it would be one of those if you are reading DC at the output. If you are adept at desoldering then try removing one of them (doesn't matter which) and re-measure to see if you are still reading DC at the output. If not, the cap you removed is the bad one. If so, then one or both caps are leaky.

.3v is not insignificant...if it were 0.03v I would call it ground, but what you are describing is problematic. The other solution (if you don't want to desolder those caps and potentially damage the PCB) is to add a larger electrolytic (like 4u7 or 10uF) between the FX output wire and your 3PDT switch (negative end to the switch). That would eliminate the leaking voltage and be large enough not to affect the AC signal coming through.

[Bursarboy]

Great, thank you again.  Another rookie mistake: I had the volume low, but not off. If volume is full down I measure 0 volts, all the way up, about 1.4v, whether in bypass or not.  (I'm not a rookie, I promise).

Anyway, thank you for helping me zero in on this - I'll probably try the cap at the switch before removing one of those other 2, but narrowing it down like that really helps.

T