# 1966 Fender Vibrolux Reverb - bad caps?



## Rodavision (Feb 26, 2010)

Hello. I'm new to GC and I was wondering if anyone could offer me some help with my amp. 

The amp is a 1966 Fender Vibrolux Reverb that from what I can tell is all or almost all stock other than tubes. It's been an awesome amp but over the last couple of years it's developed some problems making it hard to play. Being a pretty handy guy with a fairly diverse knowledge and experience with electronics helped me when I recently installed new tubes and rebiased along with fixing a bad wire in the reverb tank. This brought back the killer tone and volume that had disappeared along with my reverb, but I still have other problems which are getting worse.

I'll do my best to describe what it is doing but it is hard to completely detail it. 

First when I take it off standby it takes a few seconds to come up to volume.
Second when I play it has loud pops which occur every 30 seconds or so followed by diminishing crackling sounds.
Third it intermittently drops in volume and then after a few seconds it bounces back up with no ramp up.
Forth it seems to cut bass frequencies when driving the amp with a fairly high gain. The bottom notes on power cords will just not play sometimes or will cut in and out.

I could be completely wrong here as I am no expert but I can see a little bit of leaking from some of the big old caps and I'm thinking that it's time these 44 year old caps were retired. Does it seem correct that these could be causing all of my problems? If so which caps should I replace (I don't have enough cash to take it to someone and have it completely redone)? Also how do I find out which wiring schematic is the correct one for my amp (the tube sticker is torn and partly missing)?

If it is the caps what should I replace them with? I've searched for recommendations on caps and all I can find is subtle descriptions of the sound of the various types out there. I love the sound of this amp and don't want to change it at all so I would like to use components that would retain that sound while not costing me a fortune. If the tone had to change at all I tend to like Fender and Marshall tones.

Thanks I really appreciate any help that can be offered!


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## Big_Daddy (Apr 2, 2009)

I highly recommend that you take it to a good amp tech. I just took my '67 VR to a guy in the Detroit area for a checkup and, for less than $100, he got it running like a charm. Also, there are some _*serious*_ voltages in these babies and, unless you are experienced, you can really hurt yourself (or worse).


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## shoretyus (Jan 6, 2007)

Not a techie but I own a whack of tube amps....my deluxe had all those symptons....I would suggest that a total recap is in order. By the time you pull the amp out and try and fix a couple of caps you might at well do the works.. kind of like rebuilding a motor and not changing the clutch. You will be amazed at the difference or should I say how much better it will perform when it's done. Stick to stock specs.. that is a very desired tone that you like. 

If you tackle it yourself the parts won't be very much.


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## Rodavision (Feb 26, 2010)

Thanks for the tips. I'm happy to hear that the same symptoms were cured by recapping. There are so many brands and types out there what caps would retain the tone?


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## Rugburn (Jan 14, 2009)

I wouldn't touch any of the tone caps unless they're shot. The filter caps are the ones you want to change. These have nothing to do with the tone, unless they're failling. Cheers

Shawn


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## Rodavision (Feb 26, 2010)

I was draining and checking for voltage on the caps when I noticed something I thought to be very odd. I'm going to take pictures but it is obviously part of the problem I've been having. Give me a bit and I'll have it up here to show.


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## Rabbit (Oct 9, 2007)

Take it to Wild Bill Costello Hes right in Hamilton for crying out loud (how lucky can you get?) Good guy,good service and really reasonable rates! Go for it!


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## Rodavision (Feb 26, 2010)

Ok I just discovered that according to Pentax my camera is not Windows 7 compatible so I will not be able to show you right now the problem I discovered! 

What I found in my amp was the one lead on one of the caps was clipped off. I say this because it looks tapered down the way that a wire cutter would pinch as it cuts. I find this very strange and disturbing. It seems that the wire remaining on the cap for the most part held contact to the solder but likely as I played hard it would bounce and lose contact. There are signs of leaking on a few of the caps as well so I picked up 5 Sprague Atoms from TheTubeStore and will install those as soon as possible. If that doesn't solve the problem I will get a few more caps and work my way along. Has anyone seen a cap wire shear off on it's own?

I enjoy doing this kind of problem solving. Most of my experience is with building effects boxes and trouble shooting electrical problems in cars so I'm learning the specifics of how this old amp works as I go. It's more fun to me to do this myself than to take it somewhere. Having said that does anyone know how to identify which wiring schematic is the correct one for my amp other than going through all of the components one by one?


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## Rugburn (Jan 14, 2009)

Here's a link:


http://www.schematicheaven.com/fenderamps/vibrolux_reverb_aa270_schem.pdf


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## WCGill (Mar 27, 2009)

Yes, it sounds like your amp is at that age when it needs a going-through and the filter caps would be a good place to start. If it's indeed a l966, then it's a AA964, although power supply configuration didn't change with later models. Check those plate resistors too as they can get noisy over time too. Best of luck.


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## shortstrings (Oct 20, 2008)

I have the exact same amp and was having all sorts of problems constant humming low volume ect. . I had my amp reworked by a local amp builder who appriciates vintage amps and what a difference its loud and clear now. If they are original caps they will gone. THis is one of the best sounding fender amps period. I think you can order a cap kit online, make sure you drain the voltage of the caps though. I will post the shots of the work I had done the tech supplied before and after pictures.


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## Rodavision (Feb 26, 2010)

So far I have removed the old caps and just picked up some resistors, I'll finish installing them as soon as possible and post my results. In the meantime I just found an old post about a similar issue that I wish I had found when I ran my searches. Is it possible to Sticky this?:

_



DYI cap job

One of the forum users sent me a PM about a problem with his old Fender. I'm posting it here so that everyone can read it. I'm sure that everyone can understand that I can wind up answering the same questions over and over as private emails! I'm just too old and fat to spend the extra time!:smile: Hopefully this will prove useful to a lot of people at once.

I came across some of your posts as I was googling for caps for my fender. I have this old fender that would belive is pretty original and the sound has been deteriating and now today there is a constant hum that does not change with any of the volume adjustments. It still plays but really crappy in behind the hum. I would like to upgrade the caps or whatever is needed. I'm pretty sure I can change out the parts myself once I know which ones and can find a good source. I also have a old buddy the work on tube stuff in the military and has lots of test gear. So where would be best place to start to get this amp sounding as good as it was meant to sound. I am not really looking to do any mods. Any help would be much appriated. I live in northern BC and dont really want to send it out (I do travel to edmonton so if there is a really good shop there that does this work that you know of that would be a option)


Sounds like your filter caps have gotten old and dried up inside! A bad hum that just gets worse and worse until you can't play over it anymore is a dead giveaway.

This is about the last job I'd recommend for a beginner, as it involves the highest voltage section in your amp. It would be very easy to get a nasty shock!

Still considering where you live I agree that your options are limited. The amp is probably very heavy to ship somewhere as well. I live near Hamilton, Ontario and have zero experience with good techs out where you live. Still, a post on guitarscanada could possibly turn someone up closer than you'd think. There are some great techs that help out on this board. I just don't know exactly where everyone lives.

What's happening is this: Your amp has a power transformer and one of its output windings boosts the voltage from the wall/power cord up higher to be suitable for your tubes. This is AC voltage and tubes need DC so the voltage is put through a rectifier to become pulses of DC. The rectifier can be either a tube rectifier or some silicon diodes.

Now tubes need a more pure, steady DC supply so big value capacitors are used to smooth out these pulses. They "filter" the pulses into purer DC. The easiest and cheapest way to make caps of these large values (like 20, 40, 100 microfarad or more) that are rated at these high voltages (like 450 or 500 volts DC) is to use what's called an "electrolyte" inside. Hence the name "electrolytic caps". This electrolyte is a wet paste. The cap has to have a tiny vent hole in it in case heat builds up inside and it could explode. So over the years the moisture in the paste will slowly get out. It doesn't matter if the amp is played or stored. The caps are going to dry up. They will last longer in cooler climates but sooner or later they'll be beat!

Replacing these caps was always kind of a routine maintenance thing. In the glory days of tubes filter caps were sold usually with a guarantee of only 5 years or even less. It was expected that they would likely last 10-15 years. Some have lasted a lot more. It's a crap shoot.

In a Fender look for a metal pan on the top of the chassis, held by 4 self tapping screws at the corners. If you lift it off you will find the filter caps underneath. If you are going to replace them you should understand that these caps can hold several hundred volts of charge long after the power is turned off! Touch the wrong wire and you can get zapped! Caps can hold such a charge for months! You need to take a power resistor of a few hundred ohms and some "gator" leads and short it across the wires of each cap before you start unsoldering them. Give it 10-15 seconds each time to make sure the cap is fully discharged. Shocks hurt! In extreme cases it could stop your heart!

Few regular industrial electronics distributors carry filter caps for tube circuits anymore. It's not worth it for them to sell only a few each year! I'm not saying you won't find them but I'd sure be glad that it was YOU spending all the time looking and not me! I buy mine from an online store like:

thetubestore.com Audio and vacuum tubes for your amplifier.

They have lots of other stuff than just tubes!

If you do it yourself and you don't die don't forget that there are some small electrolytic caps on the preamp tube cathodes that also can dry up. These are cheap and should be replaced at the same time. In Fenders they are always 22 mfd rated at 25 volts or more.

Here's some great links for schematics:

The Fender Amp Field Guide

Schematic Heaven - FREE Amp Schematics Tube Amp Schematics Valve Amp Schematics Effect Schematics Effect Pedal Schematics Guitar Amp Schematics Bass Amp Schematics Fender Amp Schematics Marshall Amp Schematics Gibson Amp Schematics Vox Amp Schematics

Another fabulous site that will help with a lot of DIY like cap jobs is:

New Page 1 Look up in the top left corner and click on "tube amp debugging page"

I hope I've helped the original questioner and perhaps some others as well.

Wild Bill

"After the JCM 800 it was all down hill..."
Gear: Big heap of caps, resistors and transformers that
I constantly re-wire into any amp I want...

_


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## airnutz (Dec 31, 2010)

I had a Fender Bassman that snapped and popped it turned out to be dirty pots a good session with contact cleaner fixed it up no repairs needed,If theres fluid seeping from the filter caps they need to be replaced if your going to gig with the amp its best to change them all considering the age,The two large filter caps under the tray on the tube side need to be replaced in "pairs",the blackface amps have "paper" caps on the wire side of the chassis also they leak like the others,there other caps on the wire side if they are stock they are dark blue with a white label and a couple of dark brown ones they develope a split in the side,an obvious indication they are bad,loose pin contacts on tubes,cold solder joints,loose and dirty input jack and rca contacts can be cleaned up,you can tap on contacts with the amp on and chassis out with a wooden dowel or chopsticks to find problems you need to be super careful you get zapped it can kill you,I hope you can find a great "amp" repair person,get that amp fixed up and it's all you will ever need for club gigs.I have a "66" also if yours has the jensen C10n/C8284 speakers in it dont get rid of them,if it does'nt Weber makes a great replacement,Good luck


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## parkhead (Aug 14, 2009)

you have bad filter caps ... bad plate load resistors and or a bad pre amp tube ... all basic regular maintenance stuff 
p


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## Tyler Savage (Nov 16, 2009)

you're all wrong - these amps are unfix-able, but I'll gladly take care of their disposal for you


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## Guitar101 (Jan 19, 2011)

There's Vibrolux schematics on this sight. Check it out.

The Amp Guide » Fender


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## Rodavision (Feb 26, 2010)

I know this is an ancient thread but I never did share my results as work got busy and I had other things to focus on.

Anyway I changed the filter caps and any others that showed signs of leaking and also changed the plate resistors and did a 3 prong conversion then rebiased my still new tubes. The result? My amp sounds incredible! 

Thanks so much for all the help, I absolutely love my amp again! I still have a scratchy pot that I've been nursing along but everything else sounds great. One of these days I'll sit down and search for a quality replacement but for now I just set the volume and don't fiddle with it lol!

Along that thought does anyone know how I can reach Wild Bill?

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## bw66 (Dec 17, 2009)

Glad you got your amp going.

You could send Wild Bill a message through the forum: http://www.guitarscanada.com/member.php?647-Wild-Bill


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## Rodavision (Feb 26, 2010)

Ok thanks, I wasn't sure if he was still on here. I'll message him.

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## greco (Jul 15, 2007)

bw66 said:


> Glad you got your amp going.
> 
> You could send Wild Bill a message through the forum: http://www.guitarscanada.com/member.php?647-Wild-Bill


I am quite sure that Wild Bill doesn't respond to PM's..as he prefers emails. 

Unfortunately, I don't have his email address.

Cheers

Dave


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## Rodavision (Feb 26, 2010)

I PM'd him, hopefully he responds. There's also another guy in Hamilton named John but he dropped out of the scene a few years ago and everyone I talked to said they haven't seen or heard from him.

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## Wild Bill (May 3, 2006)

Rodavision said:


> I PM'd him, hopefully he responds. There's also another guy in Hamilton named John but he dropped out of the scene a few years ago and everyone I talked to said they haven't seen or heard from him.
> 
> Sent from my XT925 using Tapatalk


Just for the record:

[email protected]
905-527-9835


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## Rodavision (Feb 26, 2010)

Awesome thanks! I'll give you a call tonight or tomorrow, going for Gino's pizza right now!

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