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February 1966 Electronics World
 Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
from
Electronics World, published May 1959
- December 1971. All copyrights hereby acknowledged.
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By 1966 the dominance of
vacuum tubes, particularly in new products, as stated by Electronics World
magazine editor William Stocklin, "...is gradually passing behind us." The
Transistor Replacement Problems highlighted in this article refer primarily to
finding second (or third or more) sources for transistor types already designed
into existing products as semiconductor manufacturers move on to new and better
(often much better) devices. There was little motivation for companies to
dedicate scare resources to making low volumes of legacy devices just to service
radios, televisions, phonographs, etc., which, to be honest, they probably
preferred owners would abandon after breaking down and replace them with a
newer model. Of course that mentality was nothing new since all manufacturers
prefer a throw-away mindset since it serves two primary objectives: selling new
products and disposing of products already in the field so as to not have to
service them. Mr. Stocklin worried that the situation could get even more
serious once integrated circuits entered widespread service.
For the Record: Transistor Replacement Problems
 Wm. A. Stocklin, Editor
The era of the vacuum tube is gradually passing behind us. In its stead we now
have solid-state components. The change was inevitable, and just as progress is
impossible without change, so is change without problems. Design engineers, technicians,
and manufacturers have been confronted with their own problems over the past few
years. Now, with most of them solved, solid-state products are flowing off production
lines by the thousands. Most efforts had been directed toward military, industrial,
and commercial products, but since the beginning of this year we have all seen many
more new types of consumer items that are designed around solid-state components.
Almost all hi-fi systems now use solid-state components and many transistorized
TV portables, CB, and ham equipment are being marketed.
Although theoretically transistors are supposed to last forever, they may be
damaged by excessive heat, improper hook-up, or by the failure of some related component.
Hence it is safe to assume that the consumer may be faced with the need for replacement
some day.
It is obvious, when reviewing the schematic diagrams and parts lists of most
consumer products, that many transistors are special devices available only from
the manufacturer. This is a serious problem not only in increasing the cost of an
item but in causing serious delays in servicing and maintenance.
Rest assured, though, that with few exceptions manufacturers themselves dislike
the situation. To supply items for replacement is never a profitable enterprise
for equipment manufacturers.
We are all familiar with tube replacement where one simply had to select a tube
type from any manufacturer and get practically identical performance. Transistors,
however, even with the same type number, may differ widely in performance.
It is common knowledge that semiconductor manufacturers, when producing a specific
type of transistor, will obtain as many as half a dozen differently designated transistors
with different characteristics from one run. Even after selection, each type has
a wide range of limits.
This presents further problems to end users. In one particular case, H. H. Scott
for example may order as many as 20,000 2N2926 transistors. They, in turn, test
each one and segregate them into five groups; each is then color-coded with a dot
signifying a different beta. Almost all transistors designed for high-quality or
critical applications go through similar selection processes by the end user. Fisher
Radio does the same thing and so do the TV manufacturers such as Zenith, Motorola,
Emerson, etc. In view of this, it should be apparent that any direct replacement
for such transistors must inevitably come from the manufacturer and not from the
customary electronics parts dealer. This is extremely unfortunate for the consumer,
the radio-TV service technician, and certainly for the parts dealer.
There are no obvious solutions at this point that seem promising. Companies like
Scott, Fisher, Zenith, Admiral, G-E, and others have service centers across the
country, each of which is completely stocked with special components that are therefore
readily available at reasonable cost.
The independent TV service technician is certainly in trouble. He must, as soon
as possible, set up liaison with the manufacturers so that there will be no delay
in obtaining special components. He must work out his cost problem so bulk purchases
at certain points will prove more economical. He must, under all circumstances,
provide service within a reasonable time and at comparable cost. Otherwise, he will
gradually give way to the captive service groups. Certainly, simple substitutions
for portable transistor radio sets are in order since quality is the least important
factor. But when one wants to get the utmost performance from any hi-f system or
TV set, haphazard replacement should not be considered. The technician can't make
a hit-and-miss substitution, though no doubt many will. A recent test group of transistors
were replaced at random and a variation of as much a 20 db in gain was encountered.
Why then don't semiconductor manufacturers produce transistors with tighter limits?
The answer is quite simple if one takes a look at any of the present industrial
parts dealers' catalogues. We have more different types of solid-state components
at the present time, in the short history of the industry, than we ever had over
all the years of the vacuum tube. To ask for further selection would seem out of
the question.
A solution that might have some merit would be for EIA to standardize on a specific
beta test unit which could be used by every service organization in the country.
If this were done, each manufacturer could indicate on his schematic diagram or
parts list a standard transistor type number along with the specific gain requirements.
Service technicians could then select as required.
We should all ask ourselves if the service industry is going in a direction similar
to that of the white goods field. It might be. Certainly refrigerators, washing
machines, dryers, etc. are made mostly of specialized components. Will it go further
in that direction when we reach the integrated-circuit period? At the moment, it
seems that these will definitely be extremely specialized components.
Posted July 21, 2022
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