JTM50 Black Flag build, finally under way.
- Thread starter ivan H
- Start date
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ivan H
Ambassador of Tubes & Grooves
Sorry I didn't get back to yesterday, my service provider was down (state wide) for a good deal of the day due to all the bushfires raging all over.
The "anode" (aluminium) foil has an "oxide" layer. The manufacturer forms this oxide layer by immersing the aluminium foil in an electrolyte & applying a DC charge. The thickness of this oxide layer is directly proportional to voltage, so we want to form it at the voltage we will be using the cap at. The oxide layer can somewhat be dissolved by the electrolyte when sitting unused for long periods (on the shelf etc). I believe that "forming" the caps also conditions the electrolyte. There's probably more to it that I'm not aware of, too. Cheers
SG John
Ambassador of Cool Guitars and Amps.
Ivan, I really enjoy reading through this to learn more about amp building (and understanding). I'm almost done with my Princeton build to pop my cherry.
Question on the schematic. What did you use for the build sheet? Did you use the same layout as on the Ceriatone page?
I'd like to start sourcing parts to eventually build a JTM 45 or JTM 50. I have some amp geek friends who work at M.I.T., and have "amp club" on Saturday afternoons at one of their houses, so I'll have good supervision.
This is the build sheet I have.
Also, is there a set "rule of thumb" for which color wires you would want to use for specific applications?
Thanks.
Question on the schematic. What did you use for the build sheet? Did you use the same layout as on the Ceriatone page?
I'd like to start sourcing parts to eventually build a JTM 45 or JTM 50. I have some amp geek friends who work at M.I.T., and have "amp club" on Saturday afternoons at one of their houses, so I'll have good supervision.
This is the build sheet I have.
Also, is there a set "rule of thumb" for which color wires you would want to use for specific applications?
Thanks.
BFT Gibson
Ambassador of Originality
you guys that build..much admiration & respect !!!
ChasFred
Ambassador of Smooth Operations
SG John
Ambassador of Cool Guitars and Amps.
syscokid
Ambassador of War & Peace
What about a full kit from Mojotone or Stewmac???? Sure makes it a lot easier when you have all the parts from one source. And usually, these kits come with decent instructions and good support.
I like the looks of this offset model:
British Style 45 Offset Amp Kit
Kit Build Difficulty: Easy Difficult**Shell is shown with Mojotone Logo installed. Please leave us a comment when you order if you would like a Mojotone logo installed.** This kit has a lead time. Check here for more information.Please read our article 'Mojotone Amp Kit Building Primer' along...
British Style 45W Guitar Tube Amp Kit
Amp Kit Difficulty LevelEasy HardIf this kit shows as out of stock please check here for more information.Please read our article 'Mojotone Amp Kit Building Primer' along with our amp kit disclaimer located in the Specs tab before buying this kit. This was the first amplifier Marshall® ever...
- StewMac
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ivan H
Ambassador of Tubes & Grooves
With 50 watt Marshall type builds, over the years I've done enough that I pretty much do them from memory, though the Ceriatone layout is a good one. I'd suggest using the Metroamp 50 watt build instructions that you can download from the "build checklists" on the ValveStorm site. It is a comprehensive, step by step instructional.
For a Marshall type build the wiring color code is;
Cathodes = Yellow.
Control grids = Green.
Anodes (plates) = Blue.
Grounds = Black.
HT = Red.
Power tube Screen grids = Yellow.
All the correct wiring colors will be shown in the Metroamp instructions.
Cheers
Edit: You can also order everything except transformers & choke from valvestorm.com
Use the build checklist feature. Robert is great to deal with & you get a choice of components like filter caps, coupling caps, potentiometers etc. Cheers
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SG John
Ambassador of Cool Guitars and Amps.
What about a full kit from Mojotone or Stewmac???? Sure makes it a lot easier when you have all the parts from one source. And usually, these kits come with decent instructions and good support.
I like the looks of this offset model:
British Style 45 Offset Amp Kit
Kit Build Difficulty: Easy Difficult**Shell is shown with Mojotone Logo installed. Please leave us a comment when you order if you would like a Mojotone logo installed.** This kit has a lead time. Check here for more information.Please read our article 'Mojotone Amp Kit Building Primer' along...www.mojotone.com
British Style 45W Guitar Tube Amp Kit
Amp Kit Difficulty LevelEasy HardIf this kit shows as out of stock please check here for more information.Please read our article 'Mojotone Amp Kit Building Primer' along with our amp kit disclaimer located in the Specs tab before buying this kit. This was the first amplifier Marshall® ever...
- StewMac
www.stewmac.com
I can actually grab quite a bit of stuff out of bins at "Amp Club." For the Princeton I'm in the middle of, I only had to purchase a chassis, transformers, tubes, and light. There may have been a couple of other small things, but everything else was there to help myself to. I know a few of the caps or resisters, I may have to get a bit fussier over, but Tim's cellar is fairly well stocked. I'll just have to bring along a bag of good coffee beans when I start the next build.
That offset 45 does look cool though.
SG John
Ambassador of Cool Guitars and Amps.
SG John
Ambassador of Cool Guitars and Amps.
Thanks. Yeah, a good friend of mine introduced me to them. He had been friends with Tim, the owner of the house (and club). They had been friends since nursery school. He works at M.I.T., as do the other guys. Tim did the tv screens for U2's Zooropa tour, and is involved in other sorts of visual stuff. He likes building over the top amps that have absolutely no practical use, but are fun to play out of. Then Scott is the British amp guy, and Alex likes the old Fender and other American circuits. They were surprised I went for the Tweed 5F2A build when I went for the Princeton build. Most people opt for the Blackface. They have been been very helpful, especially since I would like to learn the correct way to do something (not the cheapest way). I've been too busy with stuff to make it for a while, so I just hit all the solder joints on the tag board. Tomorrow, I'll start to neaten the wiring. I had a minor bit of distortion that suggested a cold solder joint, but it worked when we first powered it up.
syscokid
Ambassador of War & Peace
This Amp Club sounds like some cool stuff to be part of. I wish there was something like that around here. At least there's the internet...
This thread has got me thinking (too much so) about taking on a build, like the 45 Watt Brit-Plex from Stewie-Mac. To that end, I wanted to ask a few questions...
For several years, I used a JTM-30 amp, which historically suffered from overheating. And since I often work in stuffy corners of bars and studios, even outdoors in direct sunlight, I wanted to ask if it is feasible to add some sort of cooling fan to a build such as yours and why they do not have this feature as standard equipment????
For several years, I used a JTM-30 amp, which historically suffered from overheating. And since I often work in stuffy corners of bars and studios, even outdoors in direct sunlight, I wanted to ask if it is feasible to add some sort of cooling fan to a build such as yours and why they do not have this feature as standard equipment????
Question: What is an "OT primary lead phase issue?" I read many reviews of the amp kits with people describing this as a common fault....
syscokid
Ambassador of War & Peace
AFAIK, those JTM30s were unique with the overheating problems. Some amps have built-in cooling fans, but I don't like that design. The rest of the amp with the exception of the power tubes will outlast those cooling fans many times over, and more than likely the fans will become noisy too. I rather have and/or bring a tiny portable fan if needed.
I'm thinking that fault here, lies with the builder. The connection from the OT's primary leads to the power tubes was mistakenly reversed. Easy fix... just reverse the connections and pay attention to the schematic or layout.
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ivan H
Ambassador of Tubes & Grooves
I thoroughly recommend an amp build Robert, it is a very rewarding endeavour & having seen your guitar builds I'm sure your attention to detail will see you produce a decent build. Good questions too, & well answered Sysco. Yes, with a 50 Watter simple convection cooling is fine, no cooling fan needed. We see some extreme temperatures here (yesterday was 42*C/107.7*F & summer has just started). In these sort of temperatures I remove the rear panel from the headcab, just to allow better airflow. I've not encountered any heat problems.
Yes, OT phase reversal is "builder error". You see, most amp designs have a "negative feedback loop" around the power amp, where a portion of the output signal in injected back into the phase inverter. It is called "negative feedback" as it is 180 degrees out of phase with the signal at the input of the phase inverter. The presence & resonance controls are part of this negative feedback loop. If the OT primary leads are reversed, the feedback component being injected back into the phase inverter (or "driver tube" in a single ended design) will be positive (in phase with the signal on the PI input) instead of negative. This creates a "self feeding" instability where the amp will howl like a banshee. As Sysco said, pay attention to the OT primary colour coding on the instructional layout & it won't happen.
Look forward to hearing we've influenced another to start building. Cheers
Yes, OT phase reversal is "builder error". You see, most amp designs have a "negative feedback loop" around the power amp, where a portion of the output signal in injected back into the phase inverter. It is called "negative feedback" as it is 180 degrees out of phase with the signal at the input of the phase inverter. The presence & resonance controls are part of this negative feedback loop. If the OT primary leads are reversed, the feedback component being injected back into the phase inverter (or "driver tube" in a single ended design) will be positive (in phase with the signal on the PI input) instead of negative. This creates a "self feeding" instability where the amp will howl like a banshee. As Sysco said, pay attention to the OT primary colour coding on the instructional layout & it won't happen.
Look forward to hearing we've influenced another to start building. Cheers
Cadorman
Ambassador of the Catocaster
I just finished reading this thread. Great work Ivan! Now I want to build a black flag kit and I haven't even finished my 2203 yet. For a complete kit that Valvestorm unit looks like the way to go. You could easily have it done for under $700 US using Classic Tone trannys, plus shell of your choice.
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ivan H
Ambassador of Tubes & Grooves
Thanks Cadorman, good to see your into building amps too. Looking forward to a 2203 build thread in the near future.
The power transformer is a Marstran/Heyboer unit that I had sitting on the shelf, so I didn't have to outlay for that. I have used Classic Tone transformers in small, single ended type builds. The filter choke in this amp & my '69 Superlead build are from Classic Tone. Cheers