Hello all- First post, I am a beginning bg student who has rebuilt a couple of bass guitars. I acquired a Harmony 525 in pretty bad shape. This is my first amp project (besides building 2 Little Smoky's and things like that). I have some electronics experience, enough not to get killed by a tube amp, but some things like impedance matching are a great mystery to me. The question I have about it is the output transformer. According to the schematics I've found, originally it was a Supro T3788 with a 5000:8 impedance ratio. At some point in this amp's life it was swapped out for a Merit A-3128, which has a cnter-tapped 8000 ohm primary and an 8 ohm secondary (among several other secondary options, which are bundled out of the way.) http://www.bunkerofdoom.com/xfm/merit_misc_web/merit0004.jpg So, is this transformer acceptable? If I leave it in there instead of buying the currently-manufactured equivalent, is it going to fry the 6L6 tubes, the transformer itself, or the speaker? Or will it just sound like crap? I'm trying to find out before next weekend, which is a big HamFest over in Raleigh, where I will be able to buy new tubes if I need them (so I need to power up the existing tubes before then to check.) Thanks for any help. At this point I could theoretically put the tubes back in and power it up, but... JSC More to read about this project if you want, but TL/DR: My goal isn't to restore this to "original" but make a functional amp out of it. I got it cheaply enough that if I have to replace it component by component, I don't mind, especially considering the education involved. Tolex: the original has this cool pimply sort of ostrich pattern on it, so I opted to leave it, and reglue it where it needed it and use leather repair to fill in some gouges. Cabinet: removed dead bugs, disassembled it for cleaning, replaced the finishing washers, cleaned/buffed the oval headed original screws. Flipped the name plate over and refinished the back and stenciled on a new name. The main panel is really badly pitted and I have to replace it. Hope to cut and bend that this weekend. The speaker is fine- coil intact, reads 8 ohms, cone intact. Grille material was filthy so I cleaned it carefully, but I'd like to keep it because of the racing stripe. Power: replaced the terrifying nonpolarized plug with a grounded 3 prong socket, replaced the rusty/gritty power switch and neon lamp, removed the power inverter switch, covered the power transformer wires with shrinkwrap where the insulation looked iffy, checked for continuity and resistance on the windings, removed the ancient 10/10/20 uf can filtering cap and replaced with new electrolytics. Checked other wiring, have new jacks and pots to install once I get a new panel cut. Patched up the shielding foil here and there. There's a whole other question about preamp 12AX7's versus AT7's, but I'm not worrying about that now. I can swap more caps, resistors, tubes, whatever later. I hope to do a little post on this on my hackerspace's blog once I'm done, with before/after pics, so I hope to be posting that soon.