While waiting on iron for my #183 Dumble build, I made the mistake of browsing the Trainwreck threads
I came across Martin's super fine build and thought it was very cool and different from other builds I've done so far and whipped up a board (after seeking Martin's permission)...plus was able to nab some iron pretty quickly. Much simpler build of course than the #183...super fun. Will be great to hear whatever differences among all the other amps in the house...
PF-TWExpress-Manning_01.jpg
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Ha! A Trainwreck style amp has been on my radar from the start of this amp building OCD journey...Just took the right inspiration. Thanks for that! A couple of my Fender builds have Trainwreck style MV mods. I'm waiting on a couple of parts...
The holes were cut with some killer automotive cutters I have (see pic). I don't actually tend use these on amp chassis oddly enough, I tend to prefer step drills since they don't grab as much and the holes are covered with the sockets. That set does make perfectly clean holes in metal however. (Whenever I get around to restoring my 1985 BMW R80...I'm sure they will get properly used!).
Martin—I was reviewing the MV mod you implemented (schematic below)—which is what I'm going to follow since it's different from what I put in my Fender AB763 and the Marshall 2104 I built. I came across a discussion here about liner vs audio taper pots. Seems that linear could be preferred?.. Any thoughts since it looks like you went with audio? I hadn't considered this but the MV in my Fender which is Type-3 has an audio taper pot is not even through it's travel at all—VERY sensitive at the lower range—I have it around 1 for in home use (reg vol around 6, and guitar almost maxed was sounding best to me since then on the guitar I can surf the distortion point, depends on guitar of course)—reading that post would suggest that I should try a linear pot there...see what happens.
Type-2orLar-Mar_Master_Volume_Schematic.png
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Figured I'd add this to this thread for anyone who might want to build an Express.
I've been emailing Edcor (super helpful and responsive) about trafos for various projects and these are now available direct with permission from RJ:
PT EM0726
OT EM0721
Looking good! When I built mine I soldered the flying leads to the socket lugs first (J-hooked and held in tension while soldering) and then to the eyelets, after the board and sockets were mounted in the chassis. Might be just as easy your way, but that is what I did.
I thought about it a bunch... and flipped a coin. It's possible that tube first is the right approach, likely in fact....hemostats will be used I'm sure...It's one of the advantages of turrets in my experience... multiple attachments, securing components over time, without full reheat is possible.
Coming along... minus the fingerprints. Great layout Martin—can't come up with any improvements. (I know the tube clips aren't really needed...but hey!)
I bonded some paper backed veneer to aluminum as a foundation of the faceplate—pretty sure that will work. I have some ebony veneer I could now bond to that—it's not paper backed—that could continue up the front a la that Trainwreck look—could also continue the maple sheet—maybe make it a washed color. Not sure yet—need to consult the other design officials in the house. I'm sort of leaning towards Tolex outer cabinet w/ inset wood beveled TW style front only. For the back—I'm definitely doing the low rent punch labels—I like it. I'm going to test some vinyl cuts for the front panel labels—we have a cutter—they would be the single letter TW style I've seen—maybe even Old English. I could always make a custom faceplate if this gets annoying to use—but I think it would be cool to do a bit of an homage...open to thoughts of course!
PF-TWExpress-Manning_05.jpg
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Should be making music soon! The thin veneer looks like a good solution, neatly avoiding any issue with bushing lengths. I imagine you could still do the wood burning thing for the purists.
Transfer technique onto raw wood—first try. Pretty successful I think. Will be sharper with a smoother sealed surface. I was playing around with pressure etc...
PF-TWExpress-Manning_06.jpg
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Last edited by pfarrell on Fri Jun 10, 2022 1:34 am, edited 1 time in total.
Another update... Not too bad working the wires presoldered to the board down into the tube sockets...Might be slightly easier this way in my imagination? Hard to say.
Verified fit of the wood veneer over aluminum faceplate—works out just so. Only modification was drilling the MV hole a bit bigger in chassis only since that dual gang pot has an unthreaded collar at the base—needs to sit in the chassis, slightly larger than the threads.
What's your pin layout there for the bias pot Martin? Wiper to ground? (Noob.)
PF-TWExpress-Manning_07.jpg
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