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

1965 Fender Showman amplifier. Killer bass or guitar head.

When I was in high school I had a cousin named Bryan. He had issues with telling the truth. But while I didn't trust him I loved the cat anyway. He wasn't a blood relative, just my god brother.

One day he showed up to my house with a Fender Showman, property of the Baltimore City Public School system. Yeah, he stole it.

But whatever. I'm sure they didn't notice it. The amp was missing tubes, badly neglected much like Bryan and that school system. It just needed help.

I was fascinated with the thing. I just wanted to get it working. I opened it up and shocked the hell out of myself on the still charged filter caps. It had power just no sound.

So I found a few tubes for it at Radio Shack and got some resistors that matched. I'm not sure if I even knew what a resistor was in those days. One just was burnt so I had to match it. Yes, Radio Shack in the Columbia Mall sold tubes! Good tubes. Not the crap made today.

I got it working. I remember it sounding like it was underwater, not in a bad way, it was just so warm.

Thus started my fascination with tube amps. And my fascination with the Fender Showman. I think I traded that chassis in on something I bought at Angela Instruments a couple years later. Early on when Steve had his shop in Savage Mill, or maybe in his house. Those were the days!

I did buy a working one when I was in Berklee. I used it for a while. I think I was fascinated as well cause a Marshall Plexi was intimidating to me. A Marshall seemed like an exotic nuclear power source. Yet, when I watched Jimi play Monterrey in the film, he had his Marshall and a glorious Showman amp too. Seemed more manageable to me.

So this one was from Indigo Ranch and had been sitting neglected for a couple or more decades. Simple re-cap, re-tube and there you go. I replace the (either 500pf or .1000pf) cap that feeds the phase inverter with a .002-.005. We're using the amp for a clean 80 watt bass amp. The Showman is 8 ohms, whereas the dual Showman is 4. I prefer these.

Such a beautiful sound......










Old caps. It's dumb but on an amp like this I re-use the sleeves cause they have the dates on them. But folks, do change the filter caps. It's just stupid not to!




Did the usual. New grounded cable yadda yadda..... Transformers are all original and this amp is no longer sad and neglected, its cutting tracks once again at Sonic Circus in Vermont!

J