OP
How many tubes does one of these 18 Watters have and what does each tube do???
18 Watt MojoTone Kit Build With Conversion To JCM800 Circuitry:
- Thread starter Inspector #20
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How many tubes does one of these 18 Watters have and what does each tube do???
Amp Mad Scientist
Ambassador of Heresy
V1 is the preamplifier
V2 is the compression
V3 is the phase inverter
And V4 V5 are the power amp
V6 is the rectifier
Or sometimes the rectifier is called V1, and it's the other way around for the tube numbering.
OP
Thank you, I am really trying to absorb all of this...
Amp Mad Scientist
Ambassador of Heresy
There is a new way to couple the circuits to eliminate the slow cutoff affect.
But I will show you that later...
OP
So, the JCM800 conversion is mostly different cap values and the substitution of the yellow jacket in V6???
Amp Mad Scientist
Ambassador of Heresy
You have to change the schematic so that the output of V1a feeds into the input of V1b.
There is some changing of cap values.
Do you have the schematic for 2204?
OP
No Sir...
OP
I'm not sure. The Mojotone 18 watt is very reasonably priced, so I thought it was a good platform to work with...
Cadorman
Ambassador of the Catocaster
That's like buying a 351 Cleveland 2bbl and converting it into a 351 Cleveland 4bbl. They aren't the same animal.
My homebrew 18watter has a solid state rectifier. I like it very much. I didn’t have the space for another tube socket. Advice: Don’t skimp on the OT, that’s where the beef is unleashed from/contained.
P.S.-congrats on making your own thread for this @Robert Herndon .
Amp Mad Scientist
Ambassador of Heresy
That's what it is.
The difference is not major.
A 2204 is just a slightly modified Plexi.
And a Plexi is just a slightly modified JTM45.
And a JTM45 is really just a slightly tweaked Bassman.
Between all those amps there is not a heck of a lot of difference.
I change a Bassman into a JCM 800 pretty easily, but the Bassman transformer has a lot more noticeable deep bass response.
That's one of the few O transformers where there actually is a big difference compared to a normal guitar amp OT.
OP
So, I was checking out Ted Weber's site and they offer an 18watt TMB in multi color combos.
tedweber.com
With their September 2020 discount, the complete kit is over $200 less than Mojotone and shipping is half as much too.
I'm always looking to make a smart purchase, not cheap per-se, but well researched.
I also want to buy from an American company.
6M18 Amp Kit – Weber Speakers
tedweber.com
With their September 2020 discount, the complete kit is over $200 less than Mojotone and shipping is half as much too.
I'm always looking to make a smart purchase, not cheap per-se, but well researched.
I also want to buy from an American company.
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OP
Guys, I know zero about these amp builds...however,, I have built wire harnesses for antique cars and repaired antique vacuum tube radios, so I can read a schematic and I can produce shiny, reliable solder joints without overheating the components. I have also performed repairs to old Mercedes-Benz analog computers with circuit boards without destroying the traces.
So, I think I can perform the work required.
Now, figuring out how to tighten up bass response, caps, and that sort of thing, I will need a lot of help.
So, I think I can perform the work required.
Now, figuring out how to tighten up bass response, caps, and that sort of thing, I will need a lot of help.
OP
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My homebrew 18watter has a solid state rectifier. I like it very much. I didn’t have the space for another tube socket. Advice: Don’t skimp on the OT, that’s where the beef is unleashed from/contained.
P.S.-congrats on making your own thread for this @Robert Herndon .
That's good advice. I've seen the Classic Tone OT's mentioned in some kit descriptions, but I'm totally out of my comfort zone here other than knowing what tubes to buy...
OP
Then I want to mill and drill the towers for screw in studs and guide plates, Isky 805-DO springs and Isky 507-STA retainers, Isky LC2000 lash caps and Big Block Chevy 1.72 ratio rocker arms are a drop-in swap...
Let's make a 351 Boss.
OP
Here's a review I found on the Ted Weber 18 watter. Some good info here about the turrets and board:
Rated 5 out of 5
Marcus (verified owner) – September 29, 2018
Im giving Weber 5 stars on the strength of the great value of this amp kit. The 18 watt Marshall combo amp is the most well trodden ground among DIY amp builders, its also the most "sacred" ground in a way.The 18 watt Marshall is said to be the one that, not only touched off the DIY tube amp/vintage gear building thing, but it revived a GREAT AMP that was forgotten by most everyone including Marshall amplification, who as a consequence of DIY interest began offering a reissued hand wired version and they still do. Ok blah blah blah. I do have at least one criticism of this kit -the turret board..the turrets do not have a great tinned-coating and can be difficult to solder. On top of that the board itself seems slightly thin (lets say metric ) and seems slightly less resistant to heat than it could be so you get this situation where the turrets need more heat for the solder to stick and the board doesn’t like it. Clean the turrets with acid wash and or alcohol before working and use enough flux for best results. The cabinet I received is beautiful with no flaws. The chassis is punched out for the old 1960’s layout which is what the Weber layout is. Some other 18 watt kits have incorporated design elements of the new reissue HW amps , including a closed ended chassis, and a modern style power cord and a "top" mounted cap can.. .This Weber kit is laid out like the vintage amp and uses a vintage style open ended chassis and through hole power cord, and the 32-32 cap is mounted in line with the tubes – just like a 1960’s amp. I used a step drill to drill a hole for the cap can on the "top" (front facing surface) – between the transformers ,like the reissues , and used the now empty, hole on the back/bottom to mount a Marshall style, round impedance selector switch. These are fantastic amps that sound all Marshall with the peaked mids and the tight lows and the overdrive grind.
Rated 5 out of 5
Marcus (verified owner) – September 29, 2018
Im giving Weber 5 stars on the strength of the great value of this amp kit. The 18 watt Marshall combo amp is the most well trodden ground among DIY amp builders, its also the most "sacred" ground in a way.The 18 watt Marshall is said to be the one that, not only touched off the DIY tube amp/vintage gear building thing, but it revived a GREAT AMP that was forgotten by most everyone including Marshall amplification, who as a consequence of DIY interest began offering a reissued hand wired version and they still do. Ok blah blah blah. I do have at least one criticism of this kit -the turret board..the turrets do not have a great tinned-coating and can be difficult to solder. On top of that the board itself seems slightly thin (lets say metric ) and seems slightly less resistant to heat than it could be so you get this situation where the turrets need more heat for the solder to stick and the board doesn’t like it. Clean the turrets with acid wash and or alcohol before working and use enough flux for best results. The cabinet I received is beautiful with no flaws. The chassis is punched out for the old 1960’s layout which is what the Weber layout is. Some other 18 watt kits have incorporated design elements of the new reissue HW amps , including a closed ended chassis, and a modern style power cord and a "top" mounted cap can.. .This Weber kit is laid out like the vintage amp and uses a vintage style open ended chassis and through hole power cord, and the 32-32 cap is mounted in line with the tubes – just like a 1960’s amp. I used a step drill to drill a hole for the cap can on the "top" (front facing surface) – between the transformers ,like the reissues , and used the now empty, hole on the back/bottom to mount a Marshall style, round impedance selector switch. These are fantastic amps that sound all Marshall with the peaked mids and the tight lows and the overdrive grind.
OP
I'd appreciate your collective input on which kit to purchase.