SOLVED Viceroy

[SYLV9ST9R]

I finished my Viceroy build last night.

I used MMBF5457, and a trimpot for R4 to have 5V on Q1’s drain (as referenced here), and a BC549C instead of the 2N5089 (hence the reversed pinout).

Everything seems to be in working order (i.e. all the controls are doing something), but I feel that it’s not as "gainy/crunchy" as it should be. Even with the gain dime, it still feels in the low OD range (comparing to say, how a Monarch sounds in review videos).

I don't see anything outstanding, so is there in particular I should check out for?

 

[fig]

Is R15 correct? Sorry I can't see the orange band well.
Edit: yeah my bad sir. I was looking at 100Ks and looked at R15 instead of R9.

 

[SYLV9ST9R]

Is R15 correct? Sorry I can't see the orange band well.

Yes, it's a 10K (Brown-Black-Black-Red-Brown), so red not orange

 

[zgrav]

have you tried using your trimpot to lower the voltage on Q1? Try it at 4.5, the 4.0 and see if you prefer it. And if that sounds worse to your ears, try 5.5 volts to see if you like that better.

 

[SYLV9ST9R]

have you tried using your trimpot to lower the voltage on Q1? Try it at 4.5, the 4.0 and see if you prefer it. And if that sounds worse to your ears, try 5.5 volts to see if you like that better.

Thanks for the suggestion, will try that during lunch break to see if it improves the sound.

 

[zgrav]

if you like the changes you hear at different trimpot values, go ahead and dial in whatever sounds best to you and then measure the voltage for your reference.

 

[Chuck D. Bones]

Don't change any parts before we do some testing.

You can check the bias. Not every JFET out of the box will work without some tweaking.

Q1-D should be around 5V.
Q4-E should be around 4.5V

These are ballpark numbers. If you're within ±1V, the pedal should be LOUD and have plenty of gain. If either of these are off, we can tweak some resistor values or change the JFETs. It is recommended that you measure Vp before installing JFETs in any pedal.

Do a detailed visual inspection of both sides of the board, verify the correct pots, etc.

 

[SYLV9ST9R]

Don't change any parts before we do some testing.

You can check the bias. Not every JFET out of the box will work without some tweaking.

Q1-D should be around 5V.
Q4-E should be around 4.5V

These are ballpark numbers. If you're within ±1V, the pedal should be LOUD and have plenty of gain. If either of these are off, we can tweak some resistor values or change the JFETs. It is recommended that you measure Vp before installing JFETs in any pedal.

Do a detailed visual inspection of both sides of the board, verify the correct pots, etc.

Thanks.
I’ll verify all this, check that all in it’s right place + visual inspection and I’ll report back my numbers.

 

[SYLV9ST9R]

@Chuck D. Bones

Q1-D : 5V
Q4-E : 4,05V
Everything looks fine otherwise.
As I said, it seems to do what it's supposed to, but not that loud. Like with the level at noon and the gain maxed, I'm not getting that much crunch.

Might just order a bunch of SMD and test their Vp (I've bookmarked a post where you explain it so I should be good).
What value should I aim for? And should I go for MMBF5457 or use another JFet?
Thanks.

 

[Chuck D. Bones]

Q4-E seems a little low. Check one more place: Q4-B. Should be 5V or a little higher. If not, inspect the solder joints around Q3.

Look for incorrect resistor or capacitor values, bad solder joints, etc. It hard for us to do that because you pix aren't great. You have to take youtube videos with a grain of salt because things happen during the recording and playback processes that alter the sound. What happens when you hit the JUICE button?

 

[fig]

What happens when you hit the JUICE button?

Margarita time!

 

[SYLV9ST9R]

Q4-E seems a little low. Check one more place: Q4-B. Should be 5V or a little higher. If not, inspect the solder joints around Q3.

Look for incorrect resistor or capacitor values, bad solder joints, etc. It hard for us to do that because you pix aren't great. You have to take youtube videos with a grain of salt because things happen during the recording and playback processes that alter the sound. What happens when you hit the JUICE button?

The JUICE is working, when pressing it, it does get definitely more loud/crunchy.
Without it being pressed, I played it at different settings on my amp, I found it could get loud, but felt it was missing some gain (even with the knob fully CW).

Q4-B reads 4,65V. I will reflow the joints for Q3, looking earlier, I was finding it might need it.
The rest of the solder joints look good, and I verified and all the Caps and resistors are in the right place

Sorry for the bad pics. I'll get my camera out next time, would be more clearer.

Thanks again for the help.

 

[Chuck D. Bones]

Look for solder bridges between G & S on Q3. Measure Q2-S. We're zooming in on the problem.

 

[SYLV9ST9R]

Look for solder bridges between G & S on Q3. Measure Q2-S. We're zooming in on the problem.

Thanks Dave, sorry for the late reply, last week was hectic,
The doen, t seem to have any solder bridges, and Q2-S measures at 4.6V

 

[Chuck D. Bones]

Q2-S Should be 1V or less. Q2 is saturated. Make sure R12 is 560Ω. With power off, measure resistance from Q2-S to GND with meter meter - (black lead) on GND. Then measure resistance from Q2-G to GND, the the meter + (red lead) on GND. GAIN should be set to zero for this last measurement.

 

[SYLV9ST9R]

Q2-S Should be 1V or less. Q2 is saturated. Make sure R12 is 560Ω. With power off, measure resistance from Q2-S to GND with meter meter - (black lead) on GND. Then measure resistance from Q2-G to GND, the the meter + (red lead) on GND. GAIN should be set to zero for this last measurement.

R12 is indeed the 560Ω.
Q2-S to GND : 535.5Ω
Q2-G to GND: 31.6kΩ

 

[Chuck D. Bones]

Those are good readings. At this point I believe that the MMBF5457 you used for Q2 has a Vp that is too high or it's shorted from D to S. My money is on a short, either internal or external.

Do you have any more you can test? We can attempt to measure Vp in-circuit, but you have to disconnect one lead of R12 to do it. How about a good close-up photo of Q2?

 

[SYLV9ST9R]

Those are good readings. At this point I believe that the MMBF5457 you used for Q2 has a Vp that is too high or it's shorted from D to S. My money is on a short, either internal or external.

Do you have any more you can test? We can attempt to measure Vp in-circuit, but you have to disconnect one lead of R12 to do it. How about a good close-up photo of Q2?

I'll try to snap a good pic this evening.
I have some spare MMBF5457 I just received, so I'll measure them tonight.

 

[Chuck D. Bones]

If they came from a different batch, they may not be representative. xx5457 would not have been my recommendation as a sub for PF5102 unless you know you're getting ones with a low Vp. Mouser sells MMBF4393, those would be a better option.

 

[SYLV9ST9R]

If they came from a different batch, they may not be representative. xx5457 would not have been my recommendation as a sub for PF5102 unless you know you're getting ones with a low Vp. Mouser sells MMBF4393, those would be a better option.

Noted. I'll start by measuring the ones I got (I had bookmarked this for that intent) and see if one could replace Q2.
What would be a good figure for the Vp?
I looked for an external short, but I don't see nothing.
If that doesn't cut it, I'll put it aside and order replacement.
Once again, your assistance and knowledge is more than appreciated.