What's it Worth to You?
How do you decide weather your amp is worth having repaired or not? This is a frequent discussion that comes up when an amp arrives in the shop for service. Here are a few things to consider that may help you with this decision. First, if the amp has a high personal value to you sentimentally or functionally, or is a rare collectable item, than in most cases the repair is readily justified.
Another aspect to evaluate is what is the resale value of the amp in the current market versus. how much you have already invested in it plus the additional cost of the repair. A fully functional, serviced amp will be much easier to sell or trade than a broken one, so even if you may be planning on selling it, a competent repair and service can be an asset here. Of course there is some point where you just won't be able to recoup your investment even after subtracting the useful life you had before the failure.
What seems to be the best deciding factor in most cases is; for the cost of the repair, what else could you purchase as replacement? Even if the repair is a few hundred dollars, can you get a similar amp of the same quality for that amount? With the exception of some new, high end, expensive amps; chances are that your older unit was better made than a comparable newer one. It is also probably easier and more cost effective to service than many of the newer mass produced units by the same manufacturers, so be aware of what could happen after the warrantee expires. Here are some things to consider before you scrap your old gear to purchase something new.
Most older tube equipment was designed to be easily serviced, with all components accessible and for the most part, field replaceable. Usually there was sufficient space for substituting slightly different sized parts, and in general these amps didn't use purpose built, short run components (which can be very important if you encounter problems while on tour far away from an authorized service center). The grade of components and manufacturing was of professional quality, more along the line of industrial equipment, using heavy chassis material with welded joints and all circuit connections soldered. Trouble shooting problems in such amps is usually pretty straight forward as the circuit flow is visible, and can be performed by most competent electronics technicians using minimal test equipment. The resale value of these amps has either leveled off or in many cases increased due to significant demand.
Most newer amps are built in a similar fashion to modern computer and consumer electronic equipment (most of which is designed to be disposable rather than repaired): thin printed circuit cards wired together with ribbon cables terminated with insulation displacement or push on connectors in a very light weight, folded chassis. In much of this type of construction, all or most of the tube sockets, potentiometers, jacks and switches are directly soldered to one or more circuit boards, making maintenance and replacement more time consuming and requiring an exact replacement part to assure mechanical fit. Some units use short run, custom components which may be available only from the manufacturer and in years to come may be very difficult to source anywhere (this is particularly true with semi-conductors and integrated circuits). Trouble shooting problems can be quite difficult as many components aren't accessible, disassembly is time consuming and circuit flow isn't at all obvious. Intermittent problems are common with this type of construction due to the wiring methods used and problems caused by heat creating very tiny stress fractures on the printed circuit cards' traces. Resale value on these units will probably be quite low, with little if any demand in the future.
Another issue to consider is that some products marketed as "tube equipment" really aren't! With the increased interest in older gear and the supply/demand curve dictating high prices for it, quite a few companies are producing equipment featuring a "gratuitous tube" (which may have minimal circuit functionality) to fool buyers into thinking they've bought the genuine article at quite a low price. The facts are that it's expensive to design and build tube gear (particularly in North America; but that's for another article) and if you want the real thing, it's going to be costly. Be sure to investigate a product before buying it to be sure you're getting what you want and not being taken by the glossy adds depicting a glowing tube. Most are cheaply made in Asia with the companies investing far more in advertising than in engineering and manufacturing. The majority of the active circuit elements are typically inexpensive integrated circuits, and the tube is usually run at a very low voltage (not within it's optimum range) to keep the costs down, not to deliver optimum tone. These items are very rarely worth repairing, as the cost of the repair is probably more than the value of the unit.
From the above, you may deduce that we feel an older amp is intrinsically superior to a new one; for the most part that's true. There are certainly some new amps that are even better built than older ones; manufactures' such as Analog Bros.,Tony Bruno and London Power have taken the best attributes of older equipment and mated them with modern materials technology, better attention to detail in manufacturing and updated circuit design to produce what will no doubt be the highly prized amps of the future. These few exceptions withstanding, the quality of most new manufactured amplifiers (and most other audio and musical instrument equipment) is nowhere near the standards set over 30 years ago.
Here are a few things to help you determine if your amp is worth repairing, as they are all indicators of the quality of its original manufacture.
How heavy is it? Not the weight of the amp as a whole (enclosure and speakers), but its electronic chassis assembly. If the chassis was made with a strong, rigid design and thick material this gives a good indication that it was made to last. Many new amps are built on a thin, folded unbraced sheet of metal that has no structural integrity when removed from the enclosure. This can lead to reliability problems as there can be a considerable amount of flex, and little protection for the circuit elements.
The weight and size of the transformers is another indication of build quality. A mains, output and choke transformer set for a 50 watt amp weighs about 15 pounds, with each one more or less the size of a large fist. Small transformers are a sign that costs were cut in the most important parts of the amp (exceptions are reverb driver transformers, interstage or small signal transformers and some chokes that may seem small but are quite adequate for their purpose).
How is the actual circuit laid out? Are the tube sockets mounted directly on the chassis or to printed circuit boards? Tubes generate heat which can cause flexing of pc boards from the normal heating/cooling cycles. This frequently results in broken traces (sometimes very hard to find) that can cause failures and intermittent problems. Mounting the tube sockets directly to the chassis provides for a large surface area of metal to act as a dissipater of some of the heat, rather than heating up a fragile PC board. Some PC boards are so thin that merely inserting a tube can cause a broken connection.
Though the use of PC cards is another discussion all together, at this point let's just consider weather they are of good quality or not and how they relate to the overall design of the amp. As with tube sockets, it's also bad practice to mount the control potentiometers, switches and jacks directly to PC boards. This makes routine maintenance and repair much more time consuming and expensive, and also has an adverse effect on reliability. The relatively common occurrence of a lateral impact on a plugged in cable end can cause significant damage to a amp when the input jack is PC board mounted. Just the many normal insertions and removals of the jack can fracture the connections on the board. A well built amp will have all of its' controls and connectors mounted to the chassis rather than to a PC card.
PC cards themselves vary widely in quality. There is nothing intrinsically wrong with a well designed PC card (though there are valid reasons that we've decided not to use them). A high quality board should be made of a thick glass epoxy material, with heavy traces, plated through holes and a complete solder mask. Unfortunately, this is somewhat rare in musical instrument amplifiers. More typically, they are made of a cheap phenolic material with very thin traces and none of the other attributes mentioned above. A simple component replacement can result in the trace pulling up off the board requiring further repair work.
How is the quality of the wiring? A well made amp should have neatly dressed wiring, color coded to make servicing easier and be adequately rated for the voltage, current and temperatures encountered in a tube amp. A mess of wires all of the same color indicates that not much care went into the manufacture of the amp and in addition to creating problems, will also make service more difficult. Does the amp use "computer type" ribbon cables? This is a sign of an amp that was designed to a price point rather than to last.
How do the solder connections look? Are they shiny and neat or are they big blobs that have "whiskers" of wire sticking out from them? This is another indication of the care that went into the amp. Don't be confused by some bad repair jobs that may have been performed in the past; look at all of the connections to get an idea of how it was done in the factory.
If your amp has most of the positive attributes discussed above, chances are that you'll be better off having it fixed than buying a replacement. Though some of the features offered on a new amp (that your old one doesn't have) may seem to justify the purchase, remember that quality of design and manufacture is what will keep the amp going on the gig rather than the bells and whistles the marketing department is trying to sell you on. There's an old biker saying that goes "chrome don't get ya home"; keep this in mind and you'll make the right decision.