1963 Fender Bandmaster, tremolo issue. And, how to slow that tremolo down

 Today was fun. 3 silver panel Fenders and a blonde. All of them were a hot mess of craptastic tech work! Poor soldering, poor choice of components, general laziness.

The best was this 1963 Bandmaster......

These are one of my all time favorites. They're genuinely weird amps in the Fender canon. With active tone controls that people largely rejected and that lush absolutely glorious 3 tube harmonic vibrato that was likely quite expensive to produce. It sounds closer to a Univibe than what any other Fender produces. It's got a phase shifter quality. Not like the pitch bending Magnatone, it's just a shade subtler. 

These amps used to be cheap as chips. Not any more, yet they aren't all that popular. People prefer the tweed and black series, these are just, odd. I bought one for $300 in 1991 and played it with a JTM45 together during the Grunge Scare of the early 90's. Big tone!

So this one was a mess. Just general poor tech work on the inside. It was re-capped years ago. I re-did the electrolytics. The whole thing was Orange Dropped. Not my favorite but since I was on a budget I let them be. Besides, most of them were the old polyester series which I like very much. Only a few were the 715 series.

The choke and output transformers are replacements, the choke being from 1966 and the output transformer is from 1972. Not the least bit unusual on this model. I've seen more Bandmasters throughout the whole range that had bad output transformers and a handful with bad chokes. I think they were just a hair under rated, but that's part of what gives a Bandmaster it's special sound. These parts were likely replaced years ago as this amp has been around the country making music. It's had a life and a half!

So once I got the basics done I noticed the obnoxious "thump thump thump thump thump" of the vibrato system hadn't gotten any better. Simple fix. One of the cathode bypass caps in the circuit was supposed to be a 2uf cap. Someone upped that to a 10uf cap. The tremolo circuit in any amp can be very sensitive so it's best to go with the original component values. Problem was solved right away.

Sometime it's a bad tube that causes this, or a bad cap or resistor. Today I was lucky. No time tied up in trouble shooting mode.

But..... while I love the tone quality of the vibrato in these amps I wasn't satisfied. It was just to fast. Not enough range. Rather boring. Simple mod took care of that.

Locate the 3 caps in series that create the oscillation. On the plate its .02, the other two are .01. I simply doubled the 3rd cap by placing another .01 cap in parallel to the one connected to ground. First try it out:

You can try different cap values here and if you like it cut those leads and give it a permanent home:

Not a bad idea to do it this way rather than replace the original component so if down the road you want to remove it there ya go!

Anyhow, this one is making music again and is for sale at Southside Guitars here in Brooklyn. It's a fantastic amp. Player grade yes, but you're a player right?

JB

1955 Fender 3x10" Bandmaster, 5E7. Yes, rare as can be.

This was a fun project. A 1955 Fender Bandmaster with 3 10" Jensen P10R speakers. This is the first original one I've had the pleasure of playing, I built one when I had my shop in Portland and sold it soon after. If I ever need to go 'big' again, I may build another one of these for myself, this may be the candidate for what I need.

What do I like about these? They are raw and primitive. They are part of the evolution to the more refined legendary Bassman amp. They don't work nearly as well in other words. The tone controls are a bit weird and the transformer to speakers is a good mismatch! (4 ohm transformer into a 2.6 ohm load!) That's a part of the sound for better or worse. Plus, I love the size. A Bassman is just a bit too big for any of my needs.

Speaking of that mismatch, you almost never find one with the original output transformer. They simply burned out. A friend had an even more rare Brown 3x10" from the early 60's and that had it's transformer replaced just like this one. I believe only Mercury Magnetics makes a proper 2.6 ohm transformer for these. When I built one that's what I used. Great part but I was a little let down. It was a lot more iron than I expected. I think they call it the "Fat Stack" or something like that. I prefer to have a smaller part, I don't need all that clear bass! So hopefully someone out there makes a trashier part now. A great sounding amp is a mixture of excellent quality parts and frankly, crap. Too much of either direction and you lose me.

This amp belonged at one point to a rhythm guitarist who played with Muddy Waters. When it came to me I saw pictures or the insides and outsides. I could see it had Orange Drop Sprague capacitors throughout, not my favorite, and the work looked a bit sloppy.

It also had a solid state rectifier and just okay modern tubes:

Once I played it other than a bad distortion (one of the speakers had a bad voice coil) I had to wonder what could I do to improve it besides the obvious: better tubes and a proper tube rectifier.

Once I opened it I could see the Orange Drop caps weren't the icky 715 type, but old polyester. I like those. They are nice and warm. You can identify them by the black stripe on the outside foil side:

Notice the blue resistors and the 2 "Chocolate Drop" capacitors in the preamp. Those do have to go. Not acceptable parts in a Cadillac!

Those blue metal film resistors are ok for load resistors, in fact they work better and are more stable. But stable isn't what were after here, we want that extra push over the cliff into special!

The only drag with modern Carbon Composition resistors is they seldom have long enough leads. So I had to extend the 2 watt cathode follower resistor:

Tone stack complete:

I use Mojo Dijon caps as these are my favorites. I also opted for a 250pf 500V silver mica cap for the treble cap. For the phase inverter I left the Orange Drop caps intact. I like them there. The Mojo caps are more like an old cap. Nice soft edges, warm. Mixed with the polyester Orange Drops I think it's a good balance.

Next was the tone caps on the pots themselves:

These were really poorly soldered. In fact the one on the treble pot simply came off then I touched it with a chop stick! You really need to have a high quality iron to get that joint right. Don't cheap out with your economy iron! Buy a Weller already!!! Also hit the back of the pot with sandpaper and use rosin. You'll have a much easier time of it and some pots you simply can't solder on to the back without sanding or using a scratch awl!

The caps themselves here don't matter as much, they are only bleeding some signal to ground, but I replaced them anyway cause, why not? The Mojos look more like the original Astron caps so....

Now the switches. They were fine, just not a classy part in my opinion. I can't stand seeing some big ass disco switches on one of these amps. It just looks stupid!

The one on the right is the replacement. I'll use the old ones for a Plexi, which likes the big bats!

Also on the standby switch I needed to add a .047@600V cap to ground. Not entirely necessary but it's in the schematic so:

And if you notice in the above photo the original wire had oxidized badly. I needed to replace that length with some nice cloth stuff as well. If I wanted to be all picky I'd age the wire with coffee, but who is going to see it???

Then the bias circuit and the grid stop resistors. I did add a trim pot to adjust bias:

Next the sexy part... The tubes. These amps sell for a lot of dough. Sovteks are nice, and I do like the Chinese 12AX7 tubes it was loaded with but, let's reach for the top shelf. Sovtek 5881 tubes replaced with Tung Sol made RCA!

Also that blasphemous solid state rectifier replaced with a NOS Sylvania 5U4 made the same year as me, 1968:

Those scuzzy preamp tubes are replaced with Mullard made "Phillips" branded tubes. And the first gain stage replaced with an RCA 5751. A bit less gain but that's what Fender wanted. Want faster breakup? Use a 12AX7, or....just turn the volume knob up!

Photos of the transformers:

The power transformer and choke are original. The output is from 1961. It's a proper Schumacher Bandmaster transformer.

And a nice chassis shot:

I did use a bigger (30uf @ 500V) cap in the first stage of the power supply. Personal preference. The rest are proper 16uf and an 8uf for the preamp.

So how did it turn out? Was all this work worth it? The amp did sound great but yes, it sounds better now. That extra color to the tone, and it's a more defined. Warmer. So I say yeah, it was worth it!

So if you own one of these, you know how lovely they are. One of the most unique American made amps that ever was produced. It's unusual cause Fender knew how to build an amp like no other, so why the mis match with the transformer. As the drive to produce cleaner tones and more powerful amps to achieve this ensued, I wonder what he was thinking with this one?

For those of you who don't have the dough for an original, I see Fender is making them again. They are pricey but not as pricey. My opinion? Pay someone else like myself or maybe Victoria to build you one. We'll do you better!

-JB