1979 Fender Vibrolux Reverb with tremolo issues. Should I charge more for silver panel amps???

 Here was a mess.......

Fender 2x10" Vibrolux Reverb circa 1979. When it came across my bench it had your typical noise issues and one nasty "bumpity bump" from the tremolo circuit. 

Once I opened it up the first thing I noticed was someone had done a rather half assed job at a black panel conversion (AA964 circuit.) So I figured I may as well complete the job. I changed all the elecrolytic caps first which helped but there was still that tremolo issue. Curiously enough it  was far worse when you turn the reverb up! So I started by eliminating that boost circuit, which takes away a length of wire that is about 8" long traveling from the reverb transformer output to a switch on the back of the volume pot. That made a little bit of difference, less wire generally equals less issues. But that didn't knock out the problem. 

Sometimes this problem is as simple as changing the tremolo tube or the "bug" network (the photo cell neon bulb thing) or just putting a .1 cap across the bug from the 10M resistor to ground. This was already standard factory goodness by then and the amp had that, though they used a .01. I upped it to a .1.....

Next I noticed the 2.7k cathode resistor and the 820 ohm resistor were opposite of where they were on a black panel amp. The 2k7 resistor should be on the left closer to the tremolo tube and the 820 ohm resistor should be on the right closer to the reverb recovery / mixer tube. That made a sizable difference. And it came that way from the factory. I next changed the cathode cap on the 100k resistor on the tremolo tube to a 4.7uf. That helped too.....

But, I like things to be close to perfect. When you turn up the reverb it still did the bump like my parents did in 1978 at the disco in Germany. Cool for the dance floor though they were told to "get a room" by an English fellow.

So what to do next? 

The silver panel amps can be cantankerous. They're just not that well made. The foundation is there: great transformers, hand wired, this one retained the 5u4 tube rectifier, but they just used things like cheaper wire. I've had noisy silver amps that I literally needed to change the wire to get the noise level down.

In this case it became clear to me they just used too much wire! Lead dress is important. 

I mean, look at this jive:

An experienced tech can see the problem. The wires on the tremolo tube are way too long and crossing the wires on the reverb recovery tube! This is factory wiring folks from the CBS days. So I proceeded to shorten the wires and move them away from one another....

That knocked out the problem. I wound up shortening the leads throughout the amp. Overall, it lost about a foot + of wire!

I cannot imagine this isn't a problem that developed with time. The wiring was all factory and the amp has been played hard for the last 40 years. I'm stunned to see that no one attempted to correct this issue before, or maybe the previous owners never used the tremolo circuit. That's plausible. Tremolo isn't for everybody.

So now this amp is ready for proper use. It's got a great sound and I feel good about it going to a new home. When I had my own shop I'd roll my eyes whenever a 70's Fender came in. Most were okay, straightforward, but many were challengers. 

So hopefully this post will help another tech out. Do look at the lead dress. There was a good amount of haste in those days at Fender. I mean look at a 1979 Stratocaster. My first guitar was one and it was terrible. Seriously a sad, heavy, careless piece of corporate lack. This amp is better than that guitar, they were just five dollars away from making both well but chose to cut corners. Fortunately this amp is now terrific cause amps are easier to transform! My poor old guitar will never be good. I didn't feel bad giving that one away years ago!

JB

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

Silvertone 1434 2x12" combo. Tedious to work on but well worth the effort!

Don't have any proper photos of this one as I only have the chassis to work on. Decided to leave the cabinet elsewhere. It's a big amp and I have little room!

I've worked on many of these. I quite like the sound of them. Big and trashy!

They are a bit tedious to work on. One needs the proper approach to get them right. In this case the amp didn't work at all. That part was easy (6EU7 tube in place of what should be a 12AX7!). The rest isn't difficult at all, you just need to be patient and re-cap the thing.

When I say re-cap I usually mean change those dried up electrolytic capacitors. That part is obvious and on one of these amps quite easy. But for these amps you'll need to change EVERY CAPACITOR along with every load resistor. They are noisy. Every Sanagamo cap was leaking or dead. The tremolo was completely dead. That entailed replacing an open 330k resistor along with all the tremolo circuit caps. Also need to replace the load resistors. The 6AU6 tube was good, they usually are.

Tremolo circuit:

The 330k 'feed' resistor I'll be replacing with a 25k trim pot. Once I got the tremolo to work it was simply weak. I reduced that resistor to 50k and it's way better, but it can be great so let's go for that.

More shots inside the chassis:

Phase inverter/driver circuit:

One of the peculiarities of these amps is the filament arrangement for the 12AX7 tubes. Those are D.C. and powered from the cathode resistor on the 6L6 power tubes. They are wired in series with about 28 volts going across both tubes. The nice part about this was I have 2 modern Tung Sol 12AX7 tubes that hummed under any normal arrangement. I couldn't sell them. But in this amp with the DC filaments they run nice and quiet.

Bloody modern tubes! Got a set of modern Tung Sol 5881 tubes I dropped in this amp. One is bad....

I couldn't find a schematic so here is one that has some similarities:

Tremolo circuit is 90% identical along with the preamp....

Amp runs pretty quiet now. These will never be as quiet as a good Fender but don't let that stop you from considering one. If you get one don't bother trying to trouble shoot the issues, just bank on spending a few hours replacing every cap and every load resistor in the house. No sense in playing whack a mole with your valuable time! And please don't buy into that "but the original sound" bullshit! You can buy carbon composition resistors all over the place now thankfully, and I like those Mojo Dijon capacitors for my signal path. Get in there, get your hands dirty and get it right! Worth the effort!

I can say the same with every other Silvertone amp I've worked on. They were pretty crappy amps to begin with but that is their charm. They used the cheapest parts available so 55 years later......

JB