Here's the original condition of the amp.

Not bad, I'd say, as far as these things go.

The circuit is pretty standard stuff. Something anyone could have pulled out of the back of an RCA tube book during the day. Standard circuit, nothing unusual, the only odd thing is that it has a split phase inverter that's driving the 6V6 pair at high current. That's the big fat black glass tube in one of the later pics, it's a 6N7. Kinda unusual tube, but it does the job. A pair of 6V6's delivering roughly 15 to 18 watts into a 10" speaker, sounds like a pretty standard amp configuration of the day, yes? Above you can see that someone got into this thing before, probably several people.... probably tried to give it a cap job or something (they didn't used to think in terms of "salvaging vintage capacitors" back then....). Not that any of these parts are worth salvaging, mostly it looks like a heap of junk. I'm inclined to throw everything away and start over, but we'll see. Maybe we can find a resistor or two we want to keep. Notice that little white thing in the pic below? It's the one right between the blue and orange caps on the left. See that? That's a resistor! It's a 100k plate resistor that seems to have gone belly up, it's completely open and nothing's going through it. Wow, I wonder how an amp could continue working with so many problems - bad plate resistor, broken wires.... I guess they just don't make 'em like they used to! So, here you can see a couple of old parts, one that looks like it's a little burnt, nothing too bad though. That cap on the end looks a little hairy though, that one might even be an original. Imagine that - a fifty year old electrolytic cap... I think, it's probably a good idea to swap out all those types of caps every five years or so, if you're using your amp a lot. If it's in daily use, maybe even less than five years, maybe three years. And ah... did you catch those kloodgy little 470 ohm resistors wired in parallel? Grin.... :) These pics are interesting 'cause they show "other peoples' work" on this thing.... Now, these next two are even more interesting 'cause you can see what they've done with the speaker. On the original, they used a Jensen "field coil" speaker, where the power supply choke was actually the speaker magnet! But, someone seems to have done an "upgrade" on this one. Ouch.... Don't know what kind of speaker that is, it looks like an OEM version of a 10" EV maybe, something like that. Doesn't sound bad, I ran my Princeton Reverb through it and it sounded okay. Nothin' to jump up and down about, but, adequate. Now that it's all apart, you can see the way the chassis really looks. Wow! Here's the cab, and the raw chassis is in the next pic. It looks just like one of those old tube radios I used to pull out of the dumpster when I was a kid! Yep, it's even got those old black glass tubes... we used to take bags full of those and throw 'em into the wash, the tubes make this wonderful "sucking" sound when they implode.... :) So yeah, we're definitely going to have to go find some new tubes for this baby. Those black glass tubes are gettin' a little hard to find. They're also unusual, relative to the more commonly available ax7's and so on, so, if you want to try to find a black glass version of a 6SC7, you're probably going to end up paying top dollar on eBay. I got lucky, found a couple of original RCA's brand new in their original boxes for twenty dollars each. Not bad, in this day and age of ten dollar JJ's and Sovtek's. But I think I'll stick with the 6V6-EH's in the output section, those things sound great to my ear, almost as good as the original RCA's. And finally you can see what they tried to do with the cabinet. Yep, this'll definitely take a bit of work! So, now I'll show you what I did with this baby. I started with the electronics, of course - gotta get that working perfectly before thinkin' about how to house it. Anyway, so this was the approximate state of things when I got the amp. It's "not too bad", I've dealt with a lot worse. Recently someone asked me to restore a Katrina victim, his 1971 Twin had been under water for two weeks when he came to me and indicated he might need my services "eventually".... 'Course with these guys, eventually usually means "before the next gig", and so, if the guy's not workin', it could be forever, but these guys down in NOLA, they had plenty of work after the hurricane. So, I had plenty of work too! What does that look like to you, in terms of the cabinet in the pic there? Maybe an old Polytone or something like that? Yeah, that might be it, a 10" Mini-Brute cabinet. Oh well, at least the speaker is the right size....

The De-Restoration

And now, the fun begins.....

So, the first thing we do, is take this puppy completely apart. After, that is, we draw the actual schematic by hand = 'cause you can never tell with old Fenders. There's all kinds of rumors about Leo being nit-picky about his parts, but the truth is, that he just used whatever he happened to have on the shelf at the time, and when that ran out, he'd use whatever else he could find that would work. You can really never tell what you might find inside an old factory-original Fender. But well, so, half the parts on this piece aren't original anyway, but let's see what's under the board. So, we notice a few things while we're taking the amp apart - like for instance, he's a perfect example of Leo's handiwork - here's a pot, that looks like someone took the switch OFF of it, and then used just the remainder. I have NO doubt that Leo would have done such a thing. :) Ah, here's another good one - no wonder the thing doesn't work! Here's a couple of cut wires, first on one side, then the other.... So, hmm.... I wonder what that wire is, and why it's snaking ALL the way across the amp, from one end to the other. There it is on the right, you can see the green wire, the good end is on the top left and the broken end traces all the way down to the bottom right. Well, gee.... wonders never cease! It's an input wire, it's one of the shielded cables that connects the input jack to the grid of the preamp tube. Well, heck.... at least they shielded it! :) Grin... But ah, all that hum didn't matter too much in the old days, 'cause people were just grateful to hear "anything at all". Imagine when a fifteen watt amp like this could actually make a difference! Those were the days. :) So, we're taking things apart now. Everything comes off the board, 'cause you can clearly see in the earlier pics that the board is warped, and we want to make sure there's not little bits and pieces of solder hangin' out under there (from "other peoples' handiwork", of course... And so we keep stripping, and stripping, and stripping, until we finally get here: This is exactly where we want to be. We want to start with a completely clean board. There's lots of guys out there, that get a little ancy when you start talkin' about throwing away their old carbon resistors and molded caps, but the truth of the matter is, that those old parts mostly "sucked", generally speaking. However, some of them did indeed have "the" sound, but the problem is, that's like finding a needle in a haystack. You have to get "just the right Sangamo", 'cause 99% of 'em won't sound right, but if you get "just the right one", man, you're off to the races. It's kind of like buying a Russian-made mic, if you know what I mean. This is good. This is where we want to be. Now, we can start building up again.

The Restoration

So, first we come in with some nice new parts. Top-of-the-line Sprague Atoms in the power supply, 'cause nothing else will do. Believe it or not, power supply caps are absolutely critical to the proper functioning of these old amps. They're largely resopnsible for the "sag" characteristic in the sound response, and any of you old blues players out there will know exactly what I'm talking about. If you're amp doesn't sag right, it's not going to respond correctly when you play it, and there's no point in "fighting" your amp to try to get a decent sound out of it. So yes, Spragues it is - and then, there's a local surplus place out here in San Fernando, called "Apex", that has tons of old caps like these ones you see here, I founs some blue barrels, some of the old black and red Mallory's, a couple of nice quality carbon resistors (notice I tried to keep those old 1.5k cathode resistors in place).... So, from here, it's just a matter of putting the wires in the right place, and then, we can start putting the board back into the chassis. When I pulled the board off, I made a careful diagram of where each wire went (since they're all the same color, you know) - so now, it's a simple matter of re-connecting all the loose wires, and visually inspecting them to make sure they're all intact and well conencted. And, it's actually starting to look like an old tube radio again! Wait a minute, that crappy old line cord is bothering me, and it's really annoying to look at. Hmm... what could we find, that would be appropriate for this situation? Let's see.... this is one the things, that being in the "biz" for fifty years, will get you - it's the knowledge of "where" to get particular things. Like, a period-appropriate line cord, which is the kind of thing that you really "don't" want to be spending an arm and a vintage leg on, right? So, hmm... let's see what we can come up with. All right, here's one - What do you think? And then, we set the whole thing on a table and pop the tubes in, and it's ready for a test. Martha, where's that fire extinguisher? Nah, not for the Fender, I meant for that Laney Klipp 100 in the background... Hey, and, are my eyes deceiving me, or is that a Gibson Falcon back there? That's a pretty cool lookin' AC line cord there, yes? I ended up finding it at another surplus electronics place on the other side of the valley. It's actually intended to provide the authentic "old appliance" look (I think it's Chinese made though, and I mean, I always wondered how those guys scoped the existence of niche markets like "wires that make your old appliances look good").... So, okay, I think we're ready for our first electronic test now. So, we do this in the usual way - take out all the tubes, plug in the amp, turn it on, and make sure we have voltage on the power transformer secondary, and in all the filaments and so on - and then, plug in the all the tubes in backwards order, with the output stage first, followed by the inverter, followed by the preamps tubes from back to front. That way, when something stops working (ie sags your voltages too low), you'll know exactly where to look. But, all seems well, we have a nice 350 volts or so to the plates, and the unloaded output stage is just above 400, and all that, is well within tolerance. Cathod resistors look good, nothin's getting hot or burning up, so... let's plug in a speaker, and see what happens. And YES, everything works PERFECTLY! But hey, wait a minute, this is interesting - this thing, doesn't sound anything like most of the old Fender tweeds. This thing sounds like a baby Marshall!!! You wouldn't know it by lookin' at it though... And I mean, considering it has an input that's actually labeled "microphone" (grin). And I think I'm in love with that Falcon in the background, and that one, has an accordion input! And well, I'll be dipped in sh... they actually played accordions through these amps? Who'd-a-thunk.... But yeah, it works! We're rockin'! Well, at least somethin's coming out of the speaker, so now, we gotta figure out how to make this thing sound good "in context", in its natural setting. A good cab can make or break the electonic part of the amp, even a Dumble would sound crappy through the wrong set of speakers, and with the wrong cab. Some cabs, only sound good with ONE specific kind of amp or speaker, and who knows, maybe they designed the thing into the speakers alpha dispersion lobe or something like that. But I mean, I'm a really simple guy, and I don't usually think in those terms. I think like, "okay, I got an EV, a JBL, and an old CTS here, so let's see which one of those sounds the best, and then I can give Ted a call and tell him what I know and ask him for his expert input and advice". So, the EV ended up sounding pretty good. This amp sounds "dark", not "bright" like a tweed. It sounds "dark" like an old Marshall 18. So, it needs a speaker that can deliver a fair amount of bass at high volumes, which immediately excludes things like Oxfarts. The Oxfords sound pretty good in really tiny amps, that don't need any bass. A Pignose, would be a good setting for an Oxford. But I mean, they don't call 'em Oxfarts for nothin'. I actually sent an Oxfart cone flying all the way across the room once - yeah, I mean, just by playin' the guitar! It was a real shocker, let me tell ya - there were others in the room, and you could hear a pin drop in that five second interval before the laughter broke out... :)

The Cabinet

So now, comes the most difficult part, which is the cabinet. I say "difficult", only because, the original parts are impossible to get. Don't even bother trying. I did, and I can report back to you, that they're not out there. The only way you're going to get some, is to find an old Fender 26 at a garage sale, like thid guy did. BUT, we're clever people, so, we can actually create these parts, but we might need a really good machinist to help out. Some of this stuff... is not exactly high-tech anymore, shall we say. I mean, let's be real, field coil speakers? Whew.... I think this amp, is going to get a nice Weber 10F150T, one of those will make this thing sound real sweet. (That's just about the perfect 10" speaker for anything built prior to 1970, it sounds superb everywhere I"ve heard it, including in Princeton Reverb's where it really excels, but also in other settings like old basketweave Marshalls and etc. You can do a lot with speakers, but you'll probably need a guy like Ted Weber to help you out. I can't say enough good things about Ted. You don't find many like him in this business anymore, he's a real treasure, and I owe him a LOT of thanks for successes like this one. Well, so, I'm tired again, and I'm gonna take a break, so you're going to have to come back tomorrow if you want to see the cabinet. This is a lot of work, I'm gettin' a new respect for those webmaster guys (and girls - the best one I know is a girl, and I was always wishin' I could get her away from those computers for a little while). ;) So yes, please stop on by tomorrow, and I promise I'll have some more good stuff for you. I'm working on the audio schematics too, have you seen those? They're here, and they're free - I do ask that you sign up for my site though, 'cause I'm going to start paying for bandwidth if too many people start grabbing CD's full of schematics, so, please play nice, and that way this stuff'll stay free for all of you! Thanks for visiting my web site, I hope you're enjoyin' it! Please check out the Group of 12 web site too, those guys are almost as clever as I am, and they've got all kinds of great history in the audio biz, and I'm sure you'll be seeing some of it appear on these pages. But meanwhile, their webmasters are doin' some pretty cool stuff over there, they've already got a turnkey solution for small independent record labels, and they're expanding into content delivery and so on, so, I'm pretty sure we can expect some good stuff from these folks.

So, ciao for now - see you again soon!



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