Bumble bee ain’t swellin. Resolved

[madbean]

Like benny said the proper VGS of Q2 is critical to make the effect work. But, I don't think using one out of spec for the build will throw off voltages for the 2n3904 at all.

Worse comes to worst, I might be able to dig up a proper spec'd 2n5457 for you if your new batch doesn't pan out.

[jimilee]

Like benny said the proper VGS of Q2 is critical to make the effect work. But, I don't think using one out of spec for the build will throw off voltages for the 2n3904 at all.

Worse comes to worst, I might be able to dig up a proper spec'd 2n5457 for you if your new batch doesn't pan out.

Thanks to you both. I really didn't think it would but I don't know how the two effects are configured to work with each other.


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[Cybercow]

JimiLee - "Sorry, yes. The VGS measures 3.1. Would that stop the 3904 trannies at the top on the right and the one below it from measuring properly? I've got more 5457s on order. "

The FET Vgs needs to be between 1.25 and 1.5 as indicated in the build docs. But the poor FET performance should not be responsible for the incorrect voltages of the trigger sensor section BJTs (2N3904s). What are the voltage output of the switching board PCB? It should be a dual rail at ±15v. Have you verified that?

[jimilee]

JimiLee - "Sorry, yes. The VGS measures 3.1. Would that stop the 3904 trannies at the top on the right and the one below it from measuring properly? I've got more 5457s on order. "

The FET Vgs needs to be between 1.25 and 1.5 as indicated in the build docs. But the poor FET performance should not be responsible for the incorrect voltages of the trigger sensor section BJTs (2N3904s). What are the voltage output of the switching board PCB? It should be a dual rail at ±15v. Have you verified that?

I have, but I didn't write it down. I'll get it to you in a bit. I was wondering about that.


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[jimilee]

JimiLee - "Sorry, yes. The VGS measures 3.1. Would that stop the 3904 trannies at the top on the right and the one below it from measuring properly? I've got more 5457s on order. "

The FET Vgs needs to be between 1.25 and 1.5 as indicated in the build docs. But the poor FET performance should not be responsible for the incorrect voltages of the trigger sensor section BJTs (2N3904s). What are the voltage output of the switching board PCB? It should be a dual rail at ±15v. Have you verified that?

The v+ is 8.05 and the v- is -7.45.


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[Cybercow]

The v+ is 8.05 and the v- is -7.45.

OK, the supply seems fine. (I mis-stated the ±15v previously, it should be closer to ±9v like you have.)

Q5 seems to have near enough correct voltages, but Q6 & Q7 are far too low. Those 2N3904 collectors (Q6 & Q7) should be at around 5.9v. Did you set the switch in the middle position, the Mix control all the way counter-clockwise and the other controls centered?

What voltages do you get when you remove the 2N5457 & 2N3904s (Q6 & Q7) from their sockets? Please try that and report your voltages.

[jimilee]

The v+ is 8.05 and the v- is -7.45.

OK, the supply seems fine. (I mis-stated the ±15v previously, it should be closer to ±9v like you have.)

Q5 seems to have near enough correct voltages, but Q6 & Q7 are far too low. Those 2N3904 collectors (Q6 & Q7) should be at around 5.9v. Did you set the switch in the middle position, the Mix control all the way counter-clockwise and the other controls centered?

What voltages do you get when you remove the 2N5457 & 2N3904s (Q6 & Q7) from their sockets? Please try that and report your voltages.

I knew what you meant with the voltages, its all good.

Yep, switch is in the middle and voltages don't change with the 5457 removed. The only way I can get the voltages to change is with the 100k trim pit.


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[Cybercow]

Did you remove Q6 & Q7 (2N3904s) also? The ones with the low voltages?

And something is definitely wrong if the 100K Tweak trimmer is changing the voltage on the collectors of Q6 & Q7. C4 is supposed to isolate them from ground.

[jimilee]

Did you remove Q6 & Q7 (2N3904s) also? The ones with the low voltages?

And something is definitely wrong if the 100K Tweak trimmer is changing the voltage on the collectors of Q6 & Q7. C4 is supposed to isolate them from ground.

I didn't remove them no.  Are you talking about to check the 5457 after they're removed? When I turn the tweak trimmer all the way down, the 5457 and q6 an 7 voltages are where they should be. So C4 is the isolater, the 2.2u


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[Cybercow]

JimiLee - that 2µ2 cap is actually C14. I was referring to C4 (0.68µF) - it's always connected. C5 & C4 are actuated via the toggle switch. And never mind the bit about pulling the FET or any transistors. The following should help.

Have you gone thru this part of the setup procedure (#4 from page 7)? - - - - "4) To set up the swell effect do the following: set the switch in its middle position, the MIX knob all the way counter-clockwise and all other pots to their middle position. Leave TWEAK in the center and the 20k trimmer all the way down. Now, adjust the 20k trimmer clockwise until you hear notes start to swell up in volume. Continue adjusting it until the volume of the swell matches your input. From there, you can adjust the TWEAK trimmer to  re-tune. In my build, the 20k is set at about 11 o'clock and the TWEAK trimmer pretty much in the middle."

What occurs to me is that the voltages are to be measured with the above mentioned settings. Mind you please, that this is an assumption on my part as it is not clear at what settings things should be when measuring the voltages.

So, if you're getting proper voltages on the collectors of Q6 & Q7 with the 20K trimmer turned all the way down (counter-clockwise), then you should be able to get it swell by following the instructions in #4 on page 7 as noted above.

[jimilee]

JimiLee - that 2µ2 cap is actually C14. I was referring to C4 (0.68µF) - it's always connected. C5 & C4 are actuated via the toggle switch. And never mind the bit about pulling the FET or any transistors. The following should help.

Have you gone thru this part of the setup procedure (#4 from page 7)? - - - - "4) To set up the swell effect do the following: set the switch in its middle position, the MIX knob all the way counter-clockwise and all other pots to their middle position. Leave TWEAK in the center and the 20k trimmer all the way down. Now, adjust the 20k trimmer clockwise until you hear notes start to swell up in volume. Continue adjusting it until the volume of the swell matches your input. From there, you can adjust the TWEAK trimmer to  re-tune. In my build, the 20k is set at about 11 o'clock and the TWEAK trimmer pretty much in the middle."

What occurs to me is that the voltages are to be measured with the above mentioned settings. Mind you please, that this is an assumption on my part as it is not clear at what settings things should be when measuring the voltages.

So, if you're getting proper voltages on the collectors of Q6 & Q7 with the 20K trimmer turned all the way down (counter-clockwise), then you should be able to get it swell by following the instructions in #4 on page 7 as noted above.

Yep, did the setup thing. Lemme ask you this, Brian said I didn't have to use a polarized cap for the .68u.  Not doing so would then not isolate anything from ground if I'm right.


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[Cybercow]

JimiLee - no. The 0.68µF cap will DC isolate whether it is polarized or not.

If you did the setup thing, then, (IMO) the only thing(s) left to look at is the original postulation I made where "matching" those specific components in the sensor trigger section are crucial.

As a recap, those specific components to match are:
• R17 & R32 (4K7 Ω)
• C20 & C21 (1µF)
• D3 & D4 (1N914)
• R33 & R34 (100k Ω)
• Q6 & Q7 (2N3904)

I'll keep my eye on this thread just see what else you might discover. I have little else to offer at this point.

[jimilee]

JimiLee - no. The 0.68µF cap will DC isolate whether it is polarized or not.

If you did the setup thing, then, (IMO) the only left to look at is the original postulation I made where "matching" those specific components in the sensor trigger section are crucial.

As a recap, those specific components to match are:
• R17 & R32 (4K7 Ω)
• C20 & C21 (1µF)
• D3 & D4 (1N914)
• R33 & R34 (100k Ω)
• Q6 & Q7 (2N3904)

I'll keep my eye on this thread just see what else you might discover. I have little else to offer at this point.

Thank you for all of your help.


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[Cybercow]

Have you been able to accrue any progress on this pedal? Anything new to report?

[jimilee]

Have you been able to accrue any progress on this pedal? Anything new to report?

Nope, not yet.


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