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BJF Reverb

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MBeach
(@mbeach)
Active Member
Blev medlem: 2 veckor sedan
Inlägg: 7
 

Hi,

I've recently built the universal reverb driver.....it seems to work great, but I find that that dwell 1 keeps a consistent output volume up to 3 o'clock, then decreases in volume after that (as more of the signal goes to the reverb tank).  My tanks have been tested, and this has happened with multiple tanks.  Is that normal?  Any help is greatly appreciated!

Thanks,

Mike


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MBeach
(@mbeach)
Active Member
Blev medlem: 2 veckor sedan
Inlägg: 7
 

@bjf

see previous comment.....forgot to tag you in the last one. Thanks!


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Björn
(@bjf)
Medlem Moderator
Blev medlem: 3 år sedan
Inlägg: 20
 

Hi there,

 
Yes tagging sends me a notification
 
So let’s see how I can help you.
 
Volume at ouput of circuit should be constant regardless of setting of  Dwell 1. So do you mean that output of circuit drops as Dwell 1 is advanced beyond 3 oc?
 
 
At your service
BJ

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MBeach
(@mbeach)
Active Member
Blev medlem: 2 veckor sedan
Inlägg: 7
 

@bjf

Thanks so much for the reply....I appreciate the help.  I checked the voltages of the output on the board (blue wire solder point that says output on the board), and they are the same (.8) regardless of where the knob is set.  To be more specific, the clean guitar volume stays at a consistent level up to 3 o'clock, then as the reverb sound gets louder, the clean guitar volume has a noticeable drop at that point until the end.  Obviously it's getting drenched in reverb as well, but there seems to be a significant drop in gain somewhere at that point.  At first I thought it might have been something to do with the level of reverb coming back in, but it's done the same with multiple tanks.  On closer examination, it's definitely the clean signal of the guitar though--it's at a consistent volume as reverb gets higher, then dips in volume  from 3 to 5 (when the dwell knob is fully turned).  Hope that makes sense. 

Thanks for your help!

Mike


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MBeach
(@mbeach)
Active Member
Blev medlem: 2 veckor sedan
Inlägg: 7
 

@bjf

I went back to check that reading, and the blue output cable is saying 0 now--must have been touching another component.  

Thanks,

Mike


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Björn
(@bjf)
Medlem Moderator
Blev medlem: 3 år sedan
Inlägg: 20
 

Hi Mike,

 

Yes I see and yes connections are tight and next to output is B+ et.c.

 

That is great to hear that it is now solved

 

BJ


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MBeach
(@mbeach)
Active Member
Blev medlem: 2 veckor sedan
Inlägg: 7
 

@bjm

 

Thanks Bjorn.  Sorry I if wasn't clear...I'm still having the same issue--basically that the output of the pedal drops in volume after 3 o'clock.  All connections are tight. 

Thanks,

Mike


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MBeach
(@mbeach)
Active Member
Blev medlem: 2 veckor sedan
Inlägg: 7
 

@bjf

Hey Bjorn, I did some more testing of components to see if I can find the problem.  I saw on an earlier post that resting voltage on T1 and the Dwell 1 pot should be about 2V.  Mine is reading 1.46.  Could that be the issue?

Thanks,

Mike


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Björn
(@bjf)
Medlem Moderator
Blev medlem: 3 år sedan
Inlägg: 20
 

Hi there,

 
OK so you still have a problem?
 
I will try to help you figure this out.
 
Re: J Fet’s, those typically have the worst possible tolrances and they also differ from make to make. So there typically are no exact voltages to be expected.J113 is anyway an exceptionally tightly specified J Fet at IDSS 2mA and this would typically give resting voltage in the circuit of 2V +-600mV.
You can wire a 10M Ohm resistor between Gate and Drain ( here the leg that goes to B+ tree to get a resting voltage of 2V at Source)
J Fet’s are typically symmetrical and because of that Drain and Source can be interchanged
 
At your service
BJ

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MBeach
(@mbeach)
Active Member
Blev medlem: 2 veckor sedan
Inlägg: 7
 

@bjm

Thanks for your reply...yes, still having the same issue with volume loss past 3 oclock on Dwell 1.  I can wire the resistor if you think it will help the problem (though seems like if T1 is readying 1.48 its probably still within allowances).  

Do you think that should fix the volume drop at Dwell 1?  Or could there be something else causing it?  

Just wanted to check before making changes.

Thanks for your time,

Mike


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