Old Amps

Old Amps Quite often I get calls relating to guitar amplifiers that people have found or purchased second hand from a variety of places. Whether it is from a family member, neighbor or a second hand store. Some have even been purchased from dealers who deal in vintage guitars and amps.
What prompts me to write this "White Paper" dealing with old amps is some of my clients actually have been shocked. I don't like to see anyone get physically hurt or financially burdened by old amplifiers that need work.

The first thing after acquiring an old tube guitar amp is does it work? You will assume that if you turn it on and the pilot light is glowing and there is some kind of noise coming from the amp that it works. Now for the Physically Hurt part. It is safe to say that 95% of the old guitar amplifiers from the 50's and early 60's came with 2 prong power chords for supplying the AC voltage to the amplifier. The bad part of this is that these amps with 2 prong chords are not grounded and this is where the danger is. There are documented cases of people getting old amplifiers and been electrocuted. The problem is you become the ground path. This can be accentuated due to bare feet on the basement floor, add high humidity and you will really get a jolt. You could be hanging on to your guitar and your lips or tongue touch the microphone and you will get zapped. The problem lies in that your hand is touching a metal parts of the guitar, this has a hot side on the output jack and a grounded side that would go from the ground side of the guitar cord to the ground of the input jack. Naturally the grounded side of the jack goes to the ground of the amplifier. If the chassis is not grounded you end up with a floating ground or artificial ground that does not touch true earth. (Ground pin on three-prong plug affixed to amp chassis) In some cases there is only a small tingle feeling. The other side of this is a full-blown jolt of electricity, enough to stop a full-grown mans heart. There was a documented case on TV, Rescue 911 about a young boy who had gotten an old Gibson amp from some where. The boy took the amp out to the garage and started to play his electric guitar. After awhile the parents didn't hear any guitar playing and went to see what was going on. They found their son laying on the garage floor unconscious. A quick call to 911 and the boy was revived.
The cause of this mishap : Gibson guitar amp with NO GROUND. They actually showed the amp in a close up, so I'm not picking on Gibson amplifiers. Actually they and all amp manufactures of the 50s and 60s in North America used the 2 pronged cables. This was the standard for the times. In some country's the three prong cable was regulated to the point you could not manufacture an electrical device without it been grounded.

PLEASE LOOK AT THE POWER CABLE. IF IT IS A 2 CONDUCTOR CABLE HAVE IT CHANGED TO A 3 CONDUCTOR CABLE FOR YOUR OWN SAFETY.

Keep the old 2-conductor cable in a safe place, that way if you sell the amp to a collector he can put the 2-conductor cable back on the amp to make it original. There are other benefits to 3-conductor cable the amp will be quieter due to the ground pin grounding the chassis. This is a must if you are planning on recording with the amp. A word of caution, some small amplifier companies use the chassis as part of the circuit to run voltage on. This is seldom done but I have seen this done and when you try to ground the chassis you get a dead short. If in doubt have it checked by a competent repair person. If you plan on doing the power cable conversion your self, please read the following disclaimer,

DISCLAIMER: GUITAR AMPS CONTAIN LETHAL VOLTAGE THAT CAN MAIM OR EVEN KILL EVEN WHEN TURNED OFF AND UNPLUGGED. IF YOU DO NOT HAVE A FULL UNDERSTANDING OF THE DANGERS OF WORKING WITH ELECTRICITY AND HIGH D.C.VOLTAGE , YOU ARE ADVISED TO SEEK A QUALIFIED REPAIR PERSON TO DO REPAIRS AND OR MODIFICATIONS TO YOUR EQUIPMENT.

FUSES
I don't know how many times I've checked the fuses on an amplifier and found a 20-amp fuse where it should be only a 3-amp fuse! Let's see in Canada and the U.S. 15 amp fuses or breakers are standard in homes and bars. The most likely place we would use an amp. If you put a 20-amp fuse in the amp, the house fuse/breaker will pop before the amp fuse. This is a very dangerous situation as you personally could be killed or the amp severely damaged. The manufacturers specified the rating off the fuse for two reasons:

1:Your personal safety.
2:The safety protection of the Power, Output transformers and other circuits in the amplifier. These fuses in most country's are legislated by Governing Electrical Bodies

There is a very sad case of over fusing an amplifier. (A fuse higher than the specified fuse by the manufacturer) For the old timers reading this you might even have a couple of this bands records, For the younger people take this very seriously. Les Harvey of Stone the Crows (Alex Harvey's brother) was electrocuted to death on stage during a performance in England back in the 70s while playing his electric guitar. In the follow up investigation it was discovered that the road crew had replaced the fuse with a nail. The nail had been put in because the amp was blowing fuses and or they had no spare fuses at the time.
In either case this is plain stupidity at its best!!!
Fuses are a safety device. They are required by law in most of the world to prevent the above story from happening to you. You may think that "I'll fix that thing once and for all. I'll put a bigger fuse in there". Unfortunately the only thing you have done is tipped the scales in electricity's favor of damaging your equipment and or up to killing yourself .

Please if you amp is blowing fuses there is a reason, it usually means a dead short or internal parts are damaged.

Read the disclaimer again!!! and get it fixed!!!

The longer you leave it, the chances are that it will cost more to repair in the end.
Factor in that if this is a collectable piece and you end up blowing the output or power transformer that you will loose some of the value of the amp due to the fact that the transformers have been replaced. Hence your investment just took a dive into the toilet.

Now for the financially burdened part.
Any given amp has a given dollar value on the vintage amp market and I am going to use a particular case that I know off. It involves a Fender Black Face Twin 66-67 that was bought at a guitar show (1997). Cosmetically clean original amp.$1200.00 The person who bought this amp will remain nameless but these events actually happened. Tried the amp out, paid the $1200.00 (seller would not move on the price) and got the amp home. The amp had not been played in at least the last 10 years. Over the next 2-3 weeks the amp developed some classic problems.
1: microphonic pre amp tubes
2: a hum that does not get louder when the amp is turned up.
3: A funny buzzing on certain notes when played on the guitar.

The first one is easy, replace the tube that have problems(Nameless decides to replace all the tubes) a wise move on his part as most are original and weak. Second problem is leaking filter capacitors. There is dried residue and fresh electrolytic flowing from 2 freshly blown capacitors in the filter pan. The third took some work as there where loose parts in the amp, but it turns out to be a bad speaker. The speaker will have to be re coned. There where other things that nameless wanted done but for a round dollar value $300.00 will be the repair.

The amp is repaired but now something that sets in with the owner (nameless) I have an amp that has a street value off $1200.00 dollars I have spent $300.00 on repairs my total investment is $1500.00 dollars. Now if after all this I decide to sell the amp I will have to sit on it and wait for the value to hopefully go up or take a loss on the amp to get my cash out of it. I have seen this happen many times not only as the repair person but also as the person who gets the panic phone call because there is smoke coming out of the amp. In six years I have only had 2 people ask me what to look for in old amps before they parted with their money. These 5 items below are physical things pertaining to the functionality of the amp, not cosmetics or collect ability that I look for.
1 Power cable has been changed ?
2 Filter caps have been changed?
3 Speakers working. I play every note up the 6-5-4 strings to the 12 fret listening for buzzing in the speaker.
4 Tubes. Are the pre amp tubes squealing?
5 Does the amp have power? No not turning it on. Does the volume get louder as you turn the volume up? or does it have weak output? Are the power tubes plates glowing red? Is there a visible blue gas in the power tube? These are the things that I look at from a consumer point of view.

They represent dollars that I/You will have to spend to make the amp playable.

Nameless should have not paid $1200.00 dollars for the twin more like 8-9 hundred dollars would have been about right. BUT then this comes into play "Them who have, set the price for those who want" in plain English supply and demand. You're not going to find a black face twin in good shape on every street corner. So as the old sayings goes"Buyer be ware" or "You pays your money and takes your chances."

If you have a particular amp that you are planing on purchasing find out what repairs to common things will cost.
How much for pre amp tubes?
How much for power tubes? (Factor in that a 50 watt will cost less than a 100 watt model.)
What is the price off a filter cap job?
Speakers what do they cost new? what's the price of re-coning?

Remember if you find one or more off the above listed things, politely point this out to the owner/store and use it for haggling on the price of the amp.
Somewhere before you go out looking for amps or you hear that such and such store has an amazing Twin, you have to set a limit to how much you will pay for the item and be prepared to walk away. Unless you fall into the "Got to have it at any Price club."

If you follow this one piece of advice you will not end up in the Twin dilemma. If you buy at $1200.00 and it needs $300.00 in repairs and you do not fix it you will have a hard time getting $1200.00 for an amp that squeals, hums and is fuzzy on certain notes unless you find some one who has to have one at any cost.
Now the repairs are his worries.

Shop carefully and ask questions about the amp. When purchasing amps for my personal use I all ways factor $125.00 onto the price. This is my buffer for tube problems, bad pots, jacks or bad board components along with the 3 pronged AC chord if it has not been changed already.

DISCLAIMER: GUITAR AMPS CONTAIN LETHAL VOLTAGE THAT CAN MAIM OR EVEN KILL EVEN WHEN TURNED OF AND UNPLUGGED. IF YOU DO NOT HAVE A FULL UNDERSTANDING OF THE DANGERS OF WORKING WITH ELECTRICITY AND HI D.C.VOLTAGE , YOU ARE ADVISED TO SEEK A QUALIFIED REPAIR PERSON TO DO THE REPAIRS AND OR MODIFICATIONS TO YOUR EQUIPMENT.

Gibson and Fender are registered trademarks and are such recognized.
This White Paper was written on factual real life incidents and is not meant to be slanderous in any shape or form to the above mentioned manufacturers.