The Fullerwell

18watt-specific Tech Talk - Building, Fixing, Parts, Mods...

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crgfrench
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Re: The Fullerwell

Post by crgfrench »

crgfrench wrote:
Wed 02/06/19 6:03 pm
...You can build the Fullerwell circuit on [Tube Depot’s 5E3 board] with a few tweaks.
I changed the spec for R20 from 125 Ohms to 150 Ohms. I recommend an 8W minimum Brown Devil here.
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Re: The Fullerwell

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Finally broke out the old Hakko and populated the Turretboard today. It's amazing what you can get done when 2 of your jobs shut down and the third one has you working from home. Still need to order a few resistors I didn't have on my bench but other than that it's pretty much complete.
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Re: The Fullerwell

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That looks like you've made a great start!
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Re: The Fullerwell

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Fullerwell 18 Watt Amplifier #1 on a 2"x6" prototyping board (2018) [white board]
FB_IMG_1574961549956.jpg
Fullerwell 18 Watt Amplifier #2 on a 3"x7" commercial PCB (2019) [green board]
20200326_221018.jpg
Fullerwell 18 Watt Amplifier #3 on a 3"x9"
custom turretboard (2020) [black board]
20200326_221000.jpg
Planned #4 on a Wattkins Universal PCB
Planned #5 on an eyelet board
Planned #6 PTP using tag strips
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Re: The Fullerwell

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More turretboard progress.

1) completed the tube-side wiring, installed in the style of Danny Russell, i.e. all wiring comes up from underneath the board on the inside of the turrets. I love this construction method -- more work but gives the board a beautiful clean appearance.

2) swapped the positions of the American and British cathode bypass caps & resistors for the first Mullard CV4004 preamp tube (at the far right end of the board). This allows for perfect alignment with the cathode pins on the V1 socket (pins 3 and 8 ).

3) reinstalled all 6 film/foil coupling caps so that their outer foil ends are on the low-impenance side of the circuit. When I first soldered these I must have had a brain cramp; I originally installed them [pointing up] with the outer foil ends were pointed towards the preamp ground bus, mistakenly thinking "that's the low side" ...but of course coupling caps don't connect to the ground bus! They connect to the plate of the prior stage, which in this case is [pointing down] towards the tube sockets. The circuit will work fine either way, it just has slightly better shielding now, to reduce excess noise.

4) modified filter caps ground bus connection. Hard to see in these images because I used black cloth push-back solid wire, but originally I had only the first filter cap connected to the power amp ground bus and the second two connected to the preamp ground bus, like in the 1957 Fender Tweed Deluxe layout. I changed that so only the third filter cap is on the preamp ground bus; to reduce hum.
20200331_121008.jpg
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Re: The Fullerwell

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With a bit of drilling, a 5E3 chassis accommodates a Marshall 18W power tranny (Classictone 40-8035) and a Merren reproduction of a Drake #784-103 output tranny. And it all fits right into a standard 1x12 Tweed Deluxe cabinet. Barely.
20200401_165848.jpg
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Re: The Fullerwell

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This gives it a better weight distribution.
Is there any reason to NOT locate the OT right over the inputs?
20200402_113737.jpg
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Re: The Fullerwell

Post by crgfrench »

This is how to build a Lite 2b on the Fullerwell turretboard. This board has an extra set of turrets on the right if you want to remove the V1 cathode jumper and have 2 channels with different voicings.
Screen Shot 2020-04-03 at 10.22.04 AM.png
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Last edited by crgfrench on Fri 04/03/20 9:55 am, edited 4 times in total.
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Re: The Fullerwell

Post by colossal »

crgfrench wrote:
Thu 04/02/20 11:17 am
This gives it a better weight distribution.
Is there any reason to NOT locate the OT right over the inputs?
20200402_113737.jpg
I think that is a better plan, all around. With the previous arrangement, you would probably get some hum induction because of how close the PT and OT were to one another.
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Re: The Fullerwell

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I made a slight edit.
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Re: The Fullerwell

Post by zaphod_phil »

crgfrench wrote:
Thu 04/02/20 11:17 am
This gives it a better weight distribution.
Is there any reason to NOT locate the OT right over the inputs?
You might get squeal.To help reduce the chance of that happening, twist the three OT primary connection wires tightly together,almost like they're heater wiring.
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Re: The Fullerwell

Post by JMPGuitars »

zaphod_phil wrote:
Fri 04/03/20 4:41 pm
crgfrench wrote:
Thu 04/02/20 11:17 am
This gives it a better weight distribution.
Is there any reason to NOT locate the OT right over the inputs?
You might get squeal.To help reduce the chance of that happening, twist the three OT primary connection wires tightly together,almost like they're heater wiring.
+1 for this. I like to add heat shrink tubing over the twisted wires to reduce the chance of any wires shifting, and protect them at the same time.
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Re: The Fullerwell

Post by crgfrench »

Thanks guys, I will do just that. Also I'm going to leave the OT leads on the outside of the chassis until they reach the original grommets. Cant see them there anyway in this Tweed Deluxe combo cabinet.
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Re: The Fullerwell

Post by crgfrench »

Quick summary of how to build 3 circuits on this turretboard:
https://youtu.be/RsKN2cn9ck4
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Re: The Fullerwell

Post by zaphod_phil »

Is “Fullerwell” the name of an amp design or the circuit board(s) you’re using?
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