SOLVED Glory Hole - Gain Pot Kills Output

[Dirty_Boogie]

I’ll preface this by saying I’m an experienced builder, so have gone through the usual troubleshooting. When turning down the gain pot, the last 5% of rotation kills the volume. Also, at the lowest gain setting (before it kills the volume) it’s still pretty gritty, and goes up to really dirty at full gain. I’ve built the Morning Glory on vero several times, and they sound completely different - 0 Gain doesn’t kill the volume - goes from an almost clean boost to medium overdrive at full Gain.

Double-checked all component values, and my solder joints all look clean. I’m not in front of the pedal now, so no pics (yet). Wondering if the B100K pot is bad? I know it’s not always a good idea to measure a pot/resistor when in a circuit, but measuring across lugs 1 and 3 give me infinite resistance (I expected 100K). Resistance across across 1 and 2, and 2 and 3, gives 0 ohms, at either end of rotation (as expected).

Any other suggestions from the resident pros here?

Thanks!

 

[jimilee]

Are you sure all the values are correct, the pot itself?

 

[Dirty_Boogie]

Yes, I'm sure...

 

[music6000]

Yes, I'm sure...

View attachment 22675View attachment 22674

Is the R6 1/8w resistor suppose to be 6k8 = Blue, Grey, Black, Brown, Brown ????
What is the resistor R9 - 6K8 colours under the Tranny Board ????

 

[Dirty_Boogie]

Is the R6 1/8w resistor suppose to be 6k8 = Blue, Grey, Black, Brown, Brown ????
What is the resistor R9 - 6K8 colours under the Tranny Board ????

Yes, both of those are 6k8 1/8W

 

[jimilee]

Bad pot maybe?

 

[Dirty_Boogie]

Bad pot maybe?

That's what I suspect. First time I've used the Tayda-branded pots, so maybe a bad one. I'll try to replace it tonight.

 

[jimilee]

That's what I suspect. First time I've used the Tayda-branded pots, so maybe a bad one. I'll try to replace it tonight.

That jumped out at me after I reread the post. I’ve not had an issue with them so far….but, you know how it goes.

 

[Dirty_Boogie]

Solved! Bad Gain pot, as suspected. Verified that measuring across lugs 1 and 3 give me infinite resistance (I expected 100K). New pot... works as expected.

 

[music6000]

Solved! Bad Gain pot, as suspected. Verified that measuring across lugs 1 and 3 give me infinite resistance (I expected 100K). New pot... works as expected.

Does that cross Tayda Pots off for future builds????

 

[Dirty_Boogie]

Does that cross Tayda Pots off for future builds????

1 bad apply shouldn’t leave a bad taste in my mouth, but for an extra $0.11 per pot, I think I’ll go back to Alpha.

 

[Dirty_Boogie]

Does that cross Tayda Pots off for future builds????

I’ve never bothered checking pots in the past - just caps, resistors and transistor hfe (if relevant). But now that I think of it, a mechanical device like a potentiometer has higher likelihood of failure. Also, I happened to measure two dual-gang 100K pots for a Kliche build this week - one measured only 85K and the other 87K. Will definitely start testing pots now in my builds.

 

[music6000]

I’ve never bothered checking pots in the past - just caps, resistors and transistor hfe (if relevant). But now that I think of it, a mechanical device like a potentiometer has higher likelihood of failure. Also, I happened to measure two dual-gang 100K pots for a Kliche build this week - one measured only 85K and the other 87K. Will definitely start testing pots now in my builds.

I went through about 6 Alpha 24mm 100K dual gang's when I built my Klon replicas ranging around the same, as low as 85K!

 

[Dirty_Boogie]

By the way, how do I get the fancy SOLVED icon to show on the thread list? Or is that an admin-only function?