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Old 01-12-2013, 11:04 PM   #1
R45VT
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The Blue Voodoo modification thread


This thread is meant to accompany the Blue Voodoo thread in GG&A.

http://www.ultimate-guitar.com/foru...oo+for+us+cheap



Okay- for this thread we are talking specifically about the BV120H. Either version. There are slight differences between the preamps but they are slight. The potentiometers are constructed differently as well, the blue Tolex are plastic shaft and low turning resistance. The Black Tolex ones are metal shaft and higher turning resistance. These shafts also have a tendency to pull out during removal of the knobs. Never install the knobs until EVERYTHING else is completed.

The tone stack will be simplified and reshaped. Parts will be replaced with different values components or removed altogether. Nothing more fancy than that. Also keep in mind the modifications are not set in stone- you can pick and chose which ones to do.

clip C8
clip C17 - it robs some of the high mids
clip R101 (the 47k in parallel with the mid pot and R26) - more range of mids
change C14 to 390pF - more high mids
change R28 to 1k - bigger range of bass, you can have less bass or more bass.
change C16 to .047uF - if you need more low mids
Change R24, to 100k more resistance will give you more highs and apparent tightness in the bass.
lower R25 if you think you need more highs. most tone stacks don't have R25, replaced with jumper.

Change treble to 250kA and mids to probably 100kA or 250kA.
(part numbers will be added later. The potentiometers must be obtained from Crate, cost is $4 each plus shipping)

The rest of the parts can be obtained from tube depot. Make sure the coupling capacitors are rated above 400V. Examples and links are given a few posts down.

Supplies and tools before you even thinks about beginning:



You will need a soldering iron, preferably one that is temperature controlled as there are fine eyelets on the PCB and you would hate to lift one wouldn't you.

You will need a de-solder gun or if you are a caveman desoldering braid. The pencil style desoldering guns are my favorite.

You will need solder. I used 2 different sizes- .050 and .032. Both 60/40 rosin core. The smaller eyelets get the smaller diameter solder- it won't glob and look like shit.

You will need a small flathead screw driver and small cutters to help aid removal and installed of components.

Various sizes of philips head screwdrivers.

A small need nose pliers saved my butt a few times. I would recommend them.

A sharpie with a good tip.


Ground rules

Tube amplifiers have capacitors that could potentially kill you if they are charged. They are designed to drain themselves(in these amps), however you should never assume they are discharged. If you are not comfortable with this or do not have a volt-meter to verify I would not proceed. Neither Ultimate guitar or myself are liable for your stupid actions. You are a free thinking individual. Use your head.

I will not cover basic soldering/desoldering skills. If you don't have the skills to pay the bills stop wasting your time reading. Don't destroy your amplifier.

Also there are many a component next to each other- make sure you get an overview and make a list of which piece to do and in what order. You don't want to pull a capacitor you just installed to change a resistor...

Tear down



Remove the back cover if it is installed.

Disconnect the wires leading to the reverb tank and remove the philips screw holding the wires to the head shell. (Keep all parts in a plastic bag. I would recommend 1 for exterior screws and the other for the knobs and such.)

Pull the power tubes out store them safely.

Turn the unit over and remove the 4 philips screws securing the chassis to the head shell.

Pull the chassis out from the head shell by the transformers.

Remove the preamp shields and pull the tubes. Mark the PI tube as they are balanced most of the time.

Unscrew the 8 philips head screws for the power tube clips. This will allow the power tube PCB to be removed.





Flip the chassis over, remove the 2 philips screws that hold the lower plate and then cut the zip ties holding the 6VAC wiring to the power tube PCB once the plate as been removed.


Remove the power tube PCB set aside.
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See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.

Last edited by R45VT : 01-14-2013 at 03:07 AM.
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Old 01-12-2013, 11:05 PM   #2
R45VT
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Once the power tube PCB has been removed the fun part begins- remove all the wiring that connects to the PCB. I would recommend taking photos and marking the wire terminal cover with a sharpie with its "J" number. This will ensure a correct wiring install. If you are struggling to get them off the chassis you can use pliers as long as you pull by the crimp and not the wire.

Remove the knobs and the nuts behind them on the front of the amp along with the input jack.

On the back of the amp remove the rear panel- pull the plastic nuts off all of the jacks, remove the 2 screws for the power cable socket, remove the chassis ground screw.

Remove the small philips screws from the top of the chassis that hold the rear panel on. Once the rear panel has been removed pull the plastic spacers off of the jacks and keep.


Next locate all the screws that hold the PCB to the chassis and remove them (6 total). 2 of them have washers on them that ground current tracks to the chassis. Do not lose them.

The PCB should be free of the chassis now. Set the chassis aside transformer side down so it does not warp.

With the chassis on the work bench its take to take an overview of it.



Download this layout to your computer. If you cannot find a component on your PCB take a look here.

https://dl.dropbox.com/u/77904849/105xxp2.pdf

Here is R28, it will be changed.


C17 is between the 2 pots on the left. It will be removed without replacement.


C8 will be removed without replacement as well. You can see R24- next to C15 and C16. Make sure to change R24 when you have C15 and 16 removed.
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See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.

Last edited by R45VT : 01-13-2013 at 03:42 AM.
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Old 01-12-2013, 11:05 PM   #3
R45VT
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It would also be a good time to replace the other coupling caps if you feel so inclined. This one was faulty causing a popping noise when turning stand-by on and off along with a lot more popping...



Bye bye C17



When you are going to desolder a few components at once time it is helpful to mark the solder with a sharpie so you remove the correct component.




Never force a component off the PCB, if you can clip if off from the reverse side it makes removing the pins from the solder much easier, they literally drop out . Suck all the solder off as complete as you can. If the pin is bent over you may have to straighten it before you can pull in through. If you

When installing new components bend the pins to hold them in place. I would cut the excess length before soldering.
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Originally Posted by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.

Last edited by R45VT : 01-13-2013 at 01:34 AM.
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Old 01-12-2013, 11:06 PM   #4
R45VT
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Parts

I ordered my parts from tubedepot- xicon and silver mica caps. All resistors were 1/2 watt metal film.

http://tubedepot.com/cp-xi-0047-630v.html .047uF
http://tubedepot.com/cp-sm-390-500v.html 390pF
http://tubedepot.com/r-273.html pick your values and quantities 1/2w metal film







If you use Orange drop- which I do not recommend as they are double the size of xicon/silver mica make sure they do not touch anything else. You will have to pre bend all the terminals to the original width as well.



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Originally Posted by DeathByDestroyr
See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.

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Old 01-12-2013, 11:06 PM   #5
R45VT
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Still in progress and very rough.

Any questions ask away.
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See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.

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Old 01-13-2013, 05:26 AM   #6
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When you say kA, you mean kohm right?
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Old 01-13-2013, 04:27 PM   #7
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Quote:
Originally Posted by eddiehimself
When you say kA, you mean kohm right?


1000 ohm, A is for Audio taper/log. You don't want a linear pot.


Also the clean channel volume pot is a 1M ohm linear. It's very loud. If you want more control install the Audio taper one instead.
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See, it's important that people clarify when they say "metal", because I pretty much always assume they are a Cannibal Corpse fanboi.

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Old 01-13-2013, 04:38 PM   #8
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Quote:
Originally Posted by R45VT
1000 ohm, A is for Audio taper/log. You don't want a linear pot.


Well, of course. I was just saying, the way you wrote it made it seem as if it was all one unit. Obviously 100 kiloamps would be a hell of a lot of current, but you never know.
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Old 01-13-2013, 04:55 PM   #9
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Quote:
Originally Posted by eddiehimself
Well, of course. I was just saying, the way you wrote it made it seem as if it was all one unit. Obviously 100 kiloamps would be a hell of a lot of current, but you never know.


What country are you in?

When I look them up they are almost always listed as 10kB or 250kA.

A for Audio/log and B for liner.

I can change it but now I am curious as to where you live.
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Old 01-13-2013, 05:42 PM   #10
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Quote:
Originally Posted by R45VT
What country are you in?

When I look them up they are almost always listed as 10kB or 250kA.

A for Audio/log and B for liner.

I can change it but now I am curious as to where you live.


I live in the UK. Usually, I see pots written as A100K or B250K, which I think is probably the best way round in order to avoid ambiguity. It isn't really surprising that you 'merkins do things differently
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Old 01-13-2013, 10:50 PM   #11
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Quote:
Originally Posted by eddiehimself
I live in the UK. Usually, I see pots written as A100K or B250K, which I think is probably the best way round in order to avoid ambiguity. It isn't really surprising that you 'merkins do things differently



Damn Brits. I don't trust people who drive on the wrong side of the road.
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Old 01-13-2013, 11:23 PM   #12
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I missed the part where you said all of the electricy things, I understood PCB and clip, does this mean I need to clip my PCB?
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Old 01-14-2013, 02:52 PM   #13
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Quote:
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Damn Brits. I don't trust people who drive on the wrong side of the road.


We drive on the right side of the road, which is the left
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Old 01-14-2013, 05:33 PM   #14
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Quote:
Originally Posted by eddiehimself
We drive on the right side of the road, which is the left

right is left? datlogic
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