Beginner workbench

[Gus Bus]

Hi everybody,
I just acquired a 1966 vibrolux reverb from a friends late father. She doesn't play so its mine now and it sounds amazing. Right way I noticed it needs new tubes. I want to do the work on it myself but I have never worked on tube Amps before. I have an electronics degree but mostly in digital hardware and programming. I'm on the hunt for an oscilloscope. What Should the max frequency of scope be? And what other tools / instruments do I need to bias, mod, and trouble shoot these circuits? Function generator? Thanks.

[xtian]

Cool amp!

And welcome. I'm from the Bay Area, but up in Chico now.

Any scope will do most jobs for tube amp repair. 5MHz, 10MHz, whatever. A good sine wave generator is useful too, especially for troubleshooting, measuring clean power output, etc.

A soldering iron with adjustable temp is good. Basic set of tools: needle-nose pliers, cutters, stripper, drivers, chukars, clutches, whangdangs.

Learn about how to safely discharge power capacitors before you dive in, and learn how to confirm with a multimeter.

Oh, and a camera for posting gut shots. Mandatory.


Why do you think it needs new tubes? Also, if it still has original caps, it would be wise to replace them. Also look at the power cord: two conductor or three? Death cap?

Cheers!

-a

[menger66]

Sounds like a once in a lifetime thing, and a very nice gift. I'd take it very slow, If it needs new tubes take to a good tech and have him give it a look over and see if it needs tubes for sure, your friend did'nt realize he may have gave you a weekend in Vages or a new flatscreen.

[Phil_S]

I'd echo the caution on new tubes. First get the amp working right. It is almost a foregone conclusion that an amp that old needs all the electrolytic caps replaced and a 3 prong cord installed. After that, let's see how those old tubes perform. Old tubes made in USA or Western Europe, particularly preamp tubes, will have a very long life cycle.

Congratulations. It is quite an enviable thing that you received.

IMO, you can get along without a 'scope for ordinary service work. Your DMM will tell you an awful lot. An auto ranging meter is a huge convenience, but not a must have.

I'd rather have two DMM's than a 'scope. (I have several acquired over the years and a 15MHz 'scope, which I hardly ever use. If I had a repair business, it would be different, I'm sure.)

If you really want a 'scope, a 20MHz two channel scope is a great thing to have. A 5MHz-15MHz is going to be fine. Most guitar amps drop out somewhere between 5KHz and 10KHz. The higher frequency range is good to see the harmonics. If you are really bent on getting one, here's a sale on a way-more-than-adequate 50MHz for $329 http://www.tequipment.net/RigolDS1052E.html?v=0 but you can find a used one for $100 or less if you are patient. I'm not sure you'll get to use it on this particular amp.

[Jana]

Woah--slow down. That is a 2000 to 4000 dollar amp you have (depending on condition). That is not the amp that you should use to learn about amps. Yes, it probably needs some servicing but it should be done with precision and care by someone who is experienced. Congratulations on the amp, but please, don't go and f**k it up.

[cbass]

+100000000
dont touch that thing untill you lkearn what you are doing. Build a kit find an old no name amp that isnt worth much to learn on

[Gus Bus]

Sorry if I made it sound as if I didn't pay a dime for it. I paid $1350 which I know is a great deal. It has sentimental value to her and she didn't just want to sell it to somebody she didn't know. Anyways, I appreciate the notes of caution. I feel confident in my aibility to exercise the caution needed and to follow the schematic (as soon as I find it!) It's the aa864 circuit. The amp is pretty beat up as he used to play at jazz clubs often. He died early of lung cancer from those smoky clubs. He wasn't a smoker himself.

What parts on this amp cannot be replaced? I want to get the amp sounding really nice before I decide to do any mods. I came across some on this page.
http://fenderguru.com/amps/vibrolux

[Colossal]

Post a gut shot of it Gus!

[cbass]

you should have no problem finding a good tech in your area.Im sure someone here could recomend one.

No offense but being trained for EE in a digital era has nothing to do with tube amps other than math.Im not trying to say your not smart enough to figure it out but it takes some time to get the physical aspect of it down.To not burn wires or components not break off lugs on a tube socket not drip solder down into a pot Etc.

If you really insist on DIY Then listen very closely to what the guys and girls here tell you to do.

[cbass]

Depending on its condition I wouldnt do anything more to it than needed to get it running good.
I certainly would not mod it unless its really ruff or been hacked by someone else

[ToneMerc]

This is what I usually do to old Fenders.

1. Replace all the caps under the dog house.
2. Replace bias cap and all the rectifier diodes.
3. Replace the cathode caps.
4. Install 3 wire ground powder cord, remove death cap and wire fuse to the hot side.
5. Retension tube sockets as needed.
6. If the main board is warped, I will touch up solder joints where component have shifted.
7. Clean the pots.

TM

[mhartman]

This is what I usually do to old Fenders.

1. Replace all the caps under the dog house.
2. Replace bias cap and all the rectifier diodes.
3. Replace the cathode caps.
4. Install 3 wire ground powder cord, remove death cap and wire fuse to the hot side.
5. Retension tube sockets as needed.
6. If the main board is warped, I will touch up solder joints where component have shifted.
7. Clean the pots.

TM

+1. Also check out the brass grounding plate. If there is any corrosion, you'll want to clean it up with a wire brush.

[drew]

https://tubeamparchive.com/viewtopic.ph ... 8e9dd4bf2f

http://el34world.com/schematics.htm#Servicing fender amps

[Gibsonman63]

This is what I usually do to old Fenders.

1. Replace all the caps under the dog house.
2. Replace bias cap and all the rectifier diodes.
3. Replace the cathode caps.
4. Install 3 wire ground powder cord, remove death cap and wire fuse to the hot side.
5. Retension tube sockets as needed.
6. If the main board is warped, I will touch up solder joints where component have shifted.
7. Clean the pots.

TM

+1. Also check out the brass grounding plate. If there is any corrosion, you'll want to clean it up with a wire brush.

Also, all of the input jacks are shorting jacks. Clean the contacts with a burnishing tool and make sure they are tensioned enough to short well when the instrument cable is unpluged.

Regarding things not to replace: Definitely do not replace any of the original coupling caps unless they are leaking DC. Obviously, don't change transformers.

I have owned a 1965 Vibrolux Reverb for over 20 years. There should be no reason to mod this amp. It does what it does fantastically. More power than and clean headroom than a Deluxe reverb and better breakup at lower volume than a Twin reverb. Don't try to make it something it isn't, just build another amp if you need to.

Once you get it up and running properly, collect a few tubes and roll them through the amp until you get what you want.

[Gus Bus]

Here are some photos. The power chord has already been switched over to three legs. The inside looks pretty well taken care of as apposed to the outside. What kinda of corrosion am I looking for. On the grounding plate there is some orangish/brown color at the solder joints.. flux maybe? The caps look good too right? What I've noticed from playing it is that the pots are very scratchy. The reverb is washy where is seems to oscillate noise indefinately, and there is a non-musical noise that I attribute to the tubes going.