diyAudio

diyAudio (http://www.diyaudio.com/forums/)
-   Instruments and Amps (http://www.diyaudio.com/forums/instruments-amps/)
-   -   picked up an old Fender amp (http://www.diyaudio.com/forums/instruments-amps/221254-picked-up-old-fender-amp.html)

cyclecamper 9th October 2012 08:27 PM

picked up an old Fender amp
 
Rather than trying to make my Peavey Classic 50 into a Fender which it was never meant to be, I just picked up a second amp, without spending any money. He wanted cash too, but traded me just the loaded chassis straight-up, and kept the combo cabinet and speakers. I noticed he was trying to sell his Fender amp on Craigslist with two listings, then on ebay with two listing, lowering his prices periodically. So I drove to his shop and traded my unused stuff for his unwanted stuff. I gave him a Kramer aluminum-neck narrow-"V" style bass (nice but I don't really like the sound of short-scale basses that much, you can't play a "V" body sitting without a strap, and I have another uglier but more utilitarian Kramer aluminum-neck bass I prefer) and an old ART digital reverb (no MIDI) and a old-new Ernie Ball volume pedal I never used (I have another) and an old JBL biamp crossover (plug-in card, unbalanced in/out, '60's vintage, will never use it).

What I got from him in exchange was the wildly unpopular Fender Super Twin, not to be confused with the later Super Twin with Reverb or the Super-Sonic Twin Reverb, or any Twin Reverb. This is the twin non-reverb, with probably too much power for just two speakers. Its claim to fame was Ted Nugent touring with a row of 6 of these, each sitting atop a matching-size 2-12 bandmaster or showman bottom. It looked really nice in an insane way, but (I assume no coincidence) Ted Nugent has had serious hearing problems ever since. Fender rates it at 180 watts, quite a lot for a tube amp.

I haven't even tried it yet, these are my first impressions just looking at the chassis and a bit of initial internet research. I didn't get (or want) the whole amp, and I got a decent deal on just the chassis (with tubes). A year ago they were going for surprisingly cheap, but now their value seems to have recovered a little. I can hardly wait to plug in when my renter is not home, and see what it will do. I'll try it tonight, even if I have to limit levels.

I don't really understand what Fender was thinking with this amp. First, IMHO it's one of the least attractive Fender amps. There was creepy white trim around the grille cloth which didn't hold its shape and a lot of people removed the white trim; the block lettering on the face plate is truly uninspired; black grille cloth that showed dirt and age and was a bit too transaprent; it doesn't look anything like a classic Fender twin and all it needs is red knobs to look like some creepy transistorized amp. Many have a big washer surrounding the large jewelled pilot light, as if the chassis hole was mis-sized or insufficient thickness or something. There's several things like that which give the impression it was a limited run and never got all the bugs ironed out completely (they made it for 2 years). So I'm happy I only bought the chassis, it will be much prettier and verstaile and portable in an attractive cabinet as a head. For once, I have no tears for breaking up a classic when starting with an ugly duckling. No reverb and no effects loop might make sense for a dirty amp, but though this has a "distortion" knob (which nobody seems to like) its biggest virtue is probably clean headroom and enough iron and power to make really good bass. Who really wants a 100-pound (wild guess) open-back combo without reverb, tremolo, or an effects loop? Plus the speakers were unmatched and in mediocre condition, hardware rusty, etc. Maybe it would have been a great pedal-steel combo? Much better as a bass head or clean head for guitar; or maybe I just like less-efficient closed-back cabinets with uncolored speakers and as a head this will ceratainly drive them.

Unlike my Peavey, which was designed purposely to get interesting complex tones at reasonable volumes, I sure got my money's worth of transformer iron and output tubes with this beast! The power transformer is really enormous, the output transformer is pretty big for a change, and there's 6 (count 'em, a half-dozen) 6L6GC output tubes. There's no choke, which is strange for a tube Fender, but I haven't really checked out the power supply...don't know yet whether there's perhaps dedicated B supply power for just the preamp?? I have to find a readable schematic that's not so fuzzy. This approaches SVT power territory, but the PI in this one doesn't use an interstage transformer like the SVT or the kit from Weber.

Except for a weird loud Fender 400-watt bass amp that had to be used with 3 bottoms to use all its outputs, I think these super-twins might be the most powerful tube amp Fender built? Did they make a Super Showman with 6 6L6s; I really can't remember or find one? Was there a 4X10 combo with 6 6L6s about the same time? Anyway, I think it ought to make a really GREAT bass amp as soon as I get it into a really nice case, pretty much like the tall head case for a Showman with Reverb (which I think this chassis should slide right into). I'm trying to decide between the obvious classic '60's fender grille cloth w/ black tolex, or perhaps going all-blonde tolex and blonde grille which looked beautiful on a cabinet website. Either way IMHO it will be a lovely head. I don't feel bad at all about converting this combo into a head; lots of pros like Eric Johnson convert twins into heads for the road (his are in very nice cabinets that look like a cross between a tall showman and a short twin). There's nothing at all convenient about an overweight combo. But as a head this is still reasonably portable and lighter than an SVT. I must admit that the big open-back combo format allows decent cooling without a fan; if I put ths in a head cabinet it needs interior space and better cooling vents than most heads, unless I build in a fan. It might be nice to forego the fan, and add some taller rubber feet and vents in the bottom of the cabinet, and make the front grille actually ventilate thru the front. A metal-mesh grille would hardly look right, but would work. It's unfortunate that Fender's upside-down chassis with the tubes and transformers hanging down does tend to cook the components inside the chassis as the heat rises and gets trapped inside the chassis. But any simple venting of the inside of the chassis really lets the dirt in. I'll really have to think about cooling this beast inside of a head cabinet. Usually a Fender head's back is designed with some chimney effect, letting cool air in a large lower slot and venting the hot out a large upper slot.

There's really a lot for me to like in this amp. First, I don't do a lot of channel-switching because I don't do a lot of live performing. But Fender's non-switching dual channel tradition never made much sense to me. This single-channel amp uses all its resources for that one signal path, which seems to me like a good way to utilize the available resources and my limited money for hardware.

I think they changed the input network resistors a bit, I think they lowerd the value of the resistor in series with the first grid which I will probably like. Will know more when I get a readable schematic and try it out with high-inductance pickups.

I think I saw high-quality pots. The knobs are unattracive traditional Fender skirted knobs with the shiny center, some cracked, but I am impressed they are on robust 1/4" shafts and retained with set-screws. Not like the under-sized broken shafts still awaiting replacement on my Peavey.

There's the typical Fender bass/mid/treble tone stack between the first and second stages, and their traditional 'bright' switch cap across the volume pot. But then later in the signal path there's an unusual all-tube center-flat 5-section rotary-knob graphic EQ with a cap and inductor for each band. It really offers boost or cut in each band! Hopefully little interaction! It can be bypassed via footswitch. All these EQ knobs are currently installed wrong; they need to have center (0) flat...whoever tightened the set-screws was used to 0-10 knobs, not these with 0 in the middle. Might be interesting to look at these pots and see whether they are common or special unobtainable types.

Looking inside, there's no printed circuit boards. I have nothing against printed circuits, but this should be really easy to work on. There's a ton of carbon resistors, which I'm told can be noisy; I don't need "authentic" noise. But this might be the perfect vintage for me...old enough to be hand-wired on posts but new enough to have reliable modern capacitors. No muti-section cans, no leaky wax-sealed paper caps. The electrolytics are all modern types. The film caps look like lovely epoxy-dipped orange drops except they're not orange. There's a few fancy sprague film caps. The pots look decent. Everything's dirty, everything's been cooked a little, the metal chassis has inconsequential bits of rust, but in general I'm VERY impressed. Too bad they didn't use a better chassis coating (is this steel painted silver?), 'cause everything in it appears to be first-rate, even the tube sockets. I'll say one thing for this point-to-point hand wiring: they sure used MUCH larger components and spaced the leads compared to printed circuits. The resistors might be carbon, but they're enormous compared to what some mfgrs put on their printed circuit boards, and they sure get better cooling when hung in open air between two posts. Do larger carbon resistors contribute less noise than small ones??? Preamp tubes are 7025's, supposedly a bit quieter than their 12AX7 brothers.

Way, way too early to tell whether I might change anything. Of course, I'd like to compare it to the later model that included a reverb. Weber has some circuits for adding reverb and tremolo. Maybe just adding an effects loop, so I can plug in the Peaey valverb would suffice and leave it more stock. I might just leave this one alone after putting it into a nce case. Or I might add an aluminum cover over the chassis, and some switches to turn off pairs of output tubes. A half-power switch is often useful. Can I turn off 4 output tubes and run the remaining 2 into the impedance of this output transformer? I'm not sure whether the output transformer has multiple taps.

I'll know much more as I check out what I just got. It's already somewhat different, and as a hardware junkie I'm already thrilled.

cyclecamper 10th October 2012 01:33 AM

1 Attachment(s)
I found several other people who had the same idea of making a great bass amp head out of a non-reverb 180-watt Super Twin. Here's a pic of one. I wonder whether I can get a new faceplate anymore, as the aftermarket does not address these oddball amps they only made for 2 years.

cyclecamper 10th October 2012 02:06 AM

Another guy did the same thing, in black grille cloth.

http://giuseppe.smugmug.com/Other/Mu...IMGP2311-L.jpg

JRGuitarGuy 12th October 2012 01:59 PM

Man your right that one would be killer just for straight up loud as **** clean headroom lol

JRGuitarGuy 12th October 2012 02:00 PM

I bet the output tranny on it is a monster too

JRGuitarGuy 12th October 2012 02:02 PM

i think the carbon comps as they age are more prone to noise all depends I guess some guys swear by them

JRGuitarGuy 12th October 2012 02:04 PM

and your right Hand-wired amps are safer and easier to work on nothing wrong at all with PCB amps just some manufactures need to learn to mount **** up off the damn PCB so **** don't blow up and put holes in it lol

JRGuitarGuy 12th October 2012 02:09 PM

I had carvin legacy 2x12 I bought some new Ruby El34s for it they lasted 2 months I properly biased them and everything I had it cranked 1 day and all of a sudden BOOM lol 1 red-plated blew up shot glass out back side of the amp piece of that glass was sticking out in the drywall lol smoked and blew up all the screen resistors the tube arced so bad part it of melted blew trace for heater circuit off pcb had like a half dollar sized hole in it rofl and it also smoked the output tranny lol

JRGuitarGuy 12th October 2012 02:11 PM

So yea be careful with them Ruby El34bstrs they blow up lol

Conrad Hoffman 12th October 2012 02:11 PM

The big issue with carbon comps is drifting way off spec. Measure every one. I've also seen some with subtle cracks around the middle. Almost impossible to see, but the value goes way off. Probably overloaded or just got old and cracked. The number of bad caps I've seen is far less then one might expect. Replace anything with physical defects or bad value and/or dissipation factor, but leave the rest alone if the value and DF and DC leakage are good. DC leakage is a real issue in tube amps, and it won't show up unless you specifically test for it. Most people replace caps because they don't have the ability to test them, or just won't. DeOxit is your friend!

Ditto about the Rubys, I've seen them go destructively bad for no reason. IMO, EH is a way better tube.


All times are GMT. The time now is 06:29 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio


Content Relevant URLs by vBSEO 3.3.2