72 Turrets Mk II Guts (No Audio)

Gut view of 72 Turrets (based on ‪@elams1894‬ JCM 800 "Punchplate" video, schematic, and component diagram. Bias circuit from Rob Robinette; https://robrobinette.com/RR2104_Master_Vol.... Highlights o "72 Turrets" name: The 120V mains version has 71 turrets, but I added a standby switch thus raising the count to 72 while also providing a nod to a certain band and its most recent album. o "Mk II" designation: This was my second time building one of these, the first designated "Mk I" and a nod to amp nostalgia and Mesa. o Build time: About 160 hours start-to-finish. o Mistakes & Do-overs: Not many compared to first build. Components: o Main vendors: Amplified Parts, TubeDepot, DigiKey, & Mouser o Caps: F&T, Mallory, & Sprague. o Jacks: Switchcraft 11 mono non-shunting for both input and output. o Switches: Carling for SPST (power & standby) & mini 3PDT (lo/hi selector); Tube Depot's "Three Position Rotary Switch" for SP3T ohm selector. o 1/2W resistors: Dale, except for 27K o 2W & 5W resistors: Various from TubeDepot and/or Amplified Parts o Power Transformer: Hammond 272FX (simplified & less costly version of the Hammond 372, although necessitated a bias tap/circuit). Will explore other brands; not impressed with Hammond's wire. o Power tubes: NOS Soviet-era 6P6S (6П6С), which is essentially a 13W 6V6 (not shown: JJ's 6V6S, which are 14W and support 500V plate voltage). See https://www.tubedepot.com/products/6v6gt-6.... o Pre-amp tubes: JJ ECC83 (12AX7) o Sockets: Belton o Solid core wire (limited mainly to 18AWG): Various higher-temp tolerant PVC on spools from Mouser & DigiKey. o Stranded wire: TubeDepot's "aerospace grade"; PTFE (Teflon) for 20AWG, Tefzel for 22AWG. o Turret board: Bulk FR4 epoxy resin. o Turrets: Keystone 1503-4 (double height) and 1527-4 (triple height). Had high hopes for these, but very disappointed in solderability. o Lamp: A variation of the "Fender style" lamp and more conducive to tighter spaces, but solder lugs very difficult to tin/take solder. Will likely adopt a 120V Alpinetech LED in subsequent builds, plus makes more logical sense to place primary power lamp in primary circuit. o Pots: Alpha o Chassis: Hammond 1444-1273 (12"x7"x3"). o Solder: Kester 44 63/37 o Flux: MG Chemicals syringe-style o Shielded cables: DIY using solid core signal, stranded ground drain, braid, and heat shrink following elams1894's and Uncle Doug's guidance. o Isopropyl: 99.9% to minimize H2O content. Deviations from ‪@elams1894‬ original: o Standby switch: Added one o Bias circuit off a PT 300VAC tap in lieu of dedicated 50VAC tap. o Power Tubes: See above in lieu of the JJ 6V6S. o Turrets: No stacked turrets; requires soldering two turrets, which is otherwise fine, but subject to desoldering/compromise when subsequently attempting to thereafter solder & rework leads/wires and despite a retention bolt/nut (and retention bolt also adds thermal mass...). I'd hoped the Keystone triples would provide a decent solution, but I was quite disappointed (see above). Other resources/channels: o Rob Robinette (https://robrobinette.com/Amp_Stuff.htm) o Uncle Doug (‪@UncleDoug‬) o Blueglow Electronics (‪@Blueglow‬) o Kley DeJong (‪@KleyDeJong‬)