Ernie Ball VP Jr mod

[therealfindo]

Still getting used to making layouts.. here's another try, this time with board mounted jacks and a 3pt millenium bypass (based off this diagram http://3.bp.blogspot.com/_nsvZ1rXQwes/TE4lHsvQklI/AAAAAAAAAi0/VbBpTImaDes/s1600/Millenium+Bypass+2.png) for the LED:



https://dl.dropboxusercontent.com/u/1767893/vpmod%20with%20mil%20bypass.png

Will it work?? 

[therealfindo]

Still getting used to making layouts.. here's another try, this time with board mounted jacks and a 3pt millenium bypass (based off this diagram http://3.bp.blogspot.com/_nsvZ1rXQwes/TE4lHsvQklI/AAAAAAAAAi0/VbBpTImaDes/s1600/Millenium+Bypass+2.png) for the LED:



https://dl.dropboxusercontent.com/u/1767893/vpmod%20with%20mil%20bypass.png

Will it work?? 

Ok, I've tried this and it's being wierd (and not working!)

When I power it up, I get bad noises, but the wierdest thing as that when I have no power plugged in BOTH throws of the switch still have a signal (an ubuffered one). Surely the  transistor would stop the guitar signal if it wasn't being powered??

[mth5044]

therealfindo - I'm incredibly confused at your layout. What's up with the pot and switches just making random connections to the perf board? They aren't connecting to anything... specifically the middle lug of the volume pot and the middle center and middle left lugs of of the 3PDT.

[therealfindo]

therealfindo - I'm incredibly confused at your layout. What's up with the pot and switches just making random connections to the perf board? They aren't connecting to anything... specifically the middle lug of the volume pot and the middle center and middle left lugs of of the 3PDT.

Sorry.. I should have labelled them - they're not random, they're the tip connections for the board mounted jacks.
So: just above R1 is the input jack, and on the far right are the two output jacks -  as they are on the VP JR.

[therealfindo]

so, without power, the circuit shouldn't have any signal, right? so that it does, means something's awry in the connections, yeah?

[mth5044]

In the way you currently have your bypass wired, when in bypass mode, you are connecting the input to the output of one of the buffers, as well as the millenium bypass input and both the tuner and output. There may be a way to do the millenium switching with a 3PDT switch, but I can't figure it out. Here is a way to do the switching with a 3PDT switch without an LED, or use a 4PDT and tack the LED switching on the last row.

Lugs of the 3PDT are    

1   4   7
2   5   8
3   6   9

with each switch being a vertical row. To orient your switch correctly, the lugs should be horizontal.

1: Buffer input
2: Input jack
3: Jumper to 6 and 9
4: Buffer out for output
5: Volume pot
6: Jumper to 3 and 9
7: Buffer out for tuner
8: Tuner jack
9: Jumper to 3 and 6

Bypass:
Input to lug 2. Connect lugs 3, 6 and 9 together. Lug 5 sends to the volume pot, lug 8 to the tuner out. In bypass, you have your signal coming in and going directly to the tuner and volume pot, normal operation.

Buffer:
Input to lug 2. Buffer in to lug 1. One buffer output goes to lug 4 and the other to lug 7. These then connect to the tuner out and volume pot.

If you want to use a 4PDT toggle and Millenium bypass, connect pin 7, the tuner buffer out to the middle lug of the extra switch then the bottom lug of the extra switch would go to the millenium bypass. Might as well just use a resistor and LED at that point. Maybe someone can come up with a better idea using the millenium bypass and a 3PDT.

[therealfindo]

Thanks... yeah a 4pdt would be no problem, except that I don't have one on hand and couldn't be bothered ordering one for this. I'd rather try and figure this sucker out 

I went back to the 2pdt millenium bypass wiring had a rethink of the switch over a bowl of porridge:



It looks like the problem you noted ("in bypass mode, you are connecting the input to the output of one of the buffers") is solved... I''ll pull the soldering iron out later today and see if it works. I'm still a bit worried that the circuit itself is faulty, but it might just have been a result of the bad switching setup.

[mth5044]

Nicely done.

[therealfindo]

Well the LED switch works... and the circuit is working better now too, in that I'm getting signal when I should.

However, there's now a buzz when the circuit is bypassed - it's clean when active and the volume pedal is all the way on. When the pedal is mid-sweep, there is a buzz too, which I don't recall the VP JR having prior. It sounds like a grounding thing, but I used an alligator clip to check those, and couldn't find the problem..

Odd that I'm only getting buzz when bypassed though. Any ideas?

[therealfindo]

Well the LED switch works... and the circuit is working better now too, in that I'm getting signal when I should.

However, there's now a buzz when the circuit is bypassed - it's clean when active and the volume pedal is all the way on. When the pedal is mid-sweep, there is a buzz too, which I don't recall the VP JR having prior. It sounds like a grounding thing, but I used an alligator clip to check those, and couldn't find the problem..

Odd that I'm only getting buzz when bypassed though. Any ideas?

oh, duh... finally got back to this project.. and realised the buzz was because the circuit ground wasn't connected to the pedal chassis.. totally fixed when I screw it all back together!

[therealfindo]

So... I turned this circuit into a PCB but I've run into a problem and I can't find the solution..

While the Volumecontroled output works,  I'm not getting any signal from the Tuner output when the buffer is activated - in bypass mode, it works too.
With some probing around I found that the problem must lie somewhere between Q2 and F somewhere before F is grounding, but I cannot see where, neither on my board (no bridges to be seen) nor in the design.. am I missing something obvious?



J1, J2, J3, R9 are unused (they are links when for building it without a bypass switch)
And yes, D1 is back-to-front.
Yellow is top layer traces, and Orange are the bottom layer.
The letter pads are linked to their corresponding pad.

c1 100nF
c2,c3, 1uF
D1 1n4001
d21n914
Q1, Q2 J201
Q3 BS170
R1 10M
R2, R3 2M2
R4, R7 10K
R5, R6 100K
R8 2K2

I measured the pins of Q1 and Q2 and they match, as do the readings at the + end of C2 & C3.

Can anyone see anything? Thanks!!

[therealfindo]

Ok.. nevermind... I had a closer look at the copper fill layers, and somehow F and the - of C2 are connected to the copper ground fill... ANNOYING!

[prabeshk26]

I just run an AMZ Super buffer in front of my 25k EB VP Jr. I used a dual opamp instead of a quad. The combo works quite well.

can you give me schematics of VP Jr.