Newmarket transistors

Newmarket Transistors Ltd., usually referred to as NKT, and located in the Suffolk town famous for its race courses, was one of the more idiosyncratic, and therefore interesting, small UK manufacturers of germanium transistors in the 1950's and 1960's. The original company 'The Transistor Development Company' was formed in December 1953 as a wholly owned subsidiary of Pye Ltd., to manufacture small signal low frequency germanium transistors for use in portable radios. In 1957 the company name was changed to 'The Newmarket Transistor Company' and in 1958, it was changed again to 'Newmarket Transistors Ltd'. Newmarket did not make any point-contact transistors, their first commercial products were junction types released in 1956. Intriguingly, they were true to their name and, to my knowledge, never made a single diode. Their logo seems to have changed a few times, possibly with the name changes, although they never printed a stylised logo on their transistors, the earliest types having no branding at all, and the later ones using the 'NKT' prefix.

Newmarket transistors Ltd

Newmarket seem to have been quite successful in the germanium transistor business, judging by the number of different types that they manufactured. Their earliest devices are the V-series, then they changed over to the NKT series, and finally they made a number of Pro Electron and other registered types in various series, including silicon types and FETs (although these may have been sourced elsewhere). They also made packaged circuit boards and even custom hybrid microcircuits in DIL and TO-99 packaging.

Unlike most UK germanium transistor manufacturers, NKT did survive the transition into the world of modern electronics, albeit at the cost of losing its original identity. Its survived as GE Aviation Newmarket until 2016, when the original 1950s site was closed. It was finally demolished in 2019.

Newmarket Pye

If you know anything about Newmarket Transistors, or have other information about NKT's early semiconductors, please

I do not possess all the transistors below, in fact I am seeking many of them. It is noted in the text where I am seeking examples of any particular type: if you have some for sale or exchange, please Conversely, I am happy to help anyone looking for information on these devices. I have an extensive collection of original data sheets and books, and can provide characteristic data on almost all Newmarket germanium types.

V6 transistors V10 transistors

The first commercial Newmarket devices were junction types in 1956: the red-painted V6 trio: V6/R2, V6/R4 and V6/R8, and the the green-painted V10 trio: V10/15, V10/30 and V10/50. These were very limited in performance: the V6 types are IF/RF transistors with a maximum collector-base voltage of 6 volts, and the V10 types are AF transistors with a maximum collector-base voltage of 10 volts. The three types in each trio are distinguished by gain selection, although there is considerable overlap between types according to contemporary NKT data books.

V10/15 in envelope

These early types are occasionally found in paper envelopes as shown, with handwritten characteristics. Presumably these were prepared at the factory as specially-selected devices for critical applications. If anyone knows more about this, please

These transistors are of particular historic interest because they were used in the Pam 710, the first British transistor radio. However, it had one oddity: it also used a red V6/R3, a type that is not mentioned in any contemporary data book. If anyone knows more about this, or has such a transistor, please

later V6 transistors

It seems that the limited performance of the early V6 and V10 types was of concern, because in about 1958 Newmarket issued unpainted versions with a higher maximum power dissipation. The modified V6 types are distinguished by reversing the two characters of the gain banding, creating types V6/2R, V6/4R and V6/8R. The improved V10 series is identified by a suffix A. According to Newmarket literature, all the improved types were also available in a cylindrical can, with a further suffix C added, but I have never come across any transistors of this shape. If you have some, please

Spot-on transistors

Like other manufacturers, Newmarket sold their out-of-spec low-power AF devices to the hobbyist market at reduced prices. This image shows a 'Spoton brand' transistor, marked as a 'yellow/green' type. I am unsure how much use these would have been of to anyone, they must have either had very low gain or else very high noise.

V30/10P transistor

Newmarket did not confine themselves to small-signal devices for radios but also released high-power AF types in 1956, using unusual 'stud' cans with a large bolt on the bottom and two pins for the other leads, still bearing part numbers indicating the collector voltage and current gain of the transistor. They come in three varieties: a few that I suspect are the earliest examples are simply black with a white part number, the majority have black/gold colouration, and late examples are completely unpainted. My image shows all three varieties for the V30/10P type.

The black body with gold painted top is significant: Newmarket used the branding 'Goltop' for many of its transistors. If anyone can explain the commercial reasoning behind this, please

V15/20IP transistor

In 1959 Newmarket claimed to be first to release an 'intermediate power' type of transistor: this image shows the top and bottom of the V15/20IP. The IP types, of which there are many with different voltage/gain values, used this circular domed can with a wide flange. In NOS condition they come with a mounting washer that clamps over the top and has two lugs with holes so that the transistor can be bolted to a heatsink. The image shows Goltop colouring: I also have some later IP types that are unpainted metal.

V10/1S transistor

The bulk of the types in the V series are AF transistors, with the V6 IF/RF types being exceptional. In 1959 Newmarket announced two low-power switching types in the same oval SO-4 can: the V10/1S and V10/2S, also available in the cylindrical can with suffix SC. The oval V10/1S was used in the Ferranti Argus series of British process-control computers. I am seeking examples of the V10/1SC and the V10/2SC. If you have any, please

noodle transistor

Newmarket eventually made a few of the high-power V-series types in the standard TO-3 'diamond' can. For some strange reason, they initially gave them the suffix NP for 'noodle power' (yes, really, this is documented in their data books). If anyone can explain this unusual choice of characterisation, please My image shows a V15/30 in Goltop colours with a handwritten suffix NP (difficult to see on the small image). I have a number like that. Later on, they switched to the suffix DP, which I assume stands for 'diamond power', in an unpainted TO-3 can.

Newmarket's second series of transistors, the NKT series, became available in 1961 and developed into a very broad range of devices. I show a selection of them below:

NKT15 transistor

The devices NKT1 to NKT99 are classified in the Newmarket 'Products Portfolio' (apparently dated 1962, although I suspect it is later) as germanium alloy PNP RF transistors with low maximum collector-base voltage, but the Portfolio only lists a small number of types in a standard TO-1 can, whereas I have many examples of types in the SO-4 oval can, such as the NKT15 shown, that are not listed. I suspect that the Portfolio shows a rationalised and very limited subset of the types actually produced during the early days of the series. If you can shed more light on this, please

Several people, mainly guitar effects pedals builders, have asked me for pages from the Product Portfolio and so I have scanned it and created a separate page for it.

NKT100 transistors

The Portfolio describes the range NKT100 - NKT199 as germanium alloy PNP RF transistors with medium maximum collector-base voltage and again lists only a handful of types, this time in TO-5 cases, whereas I possess a selection of unlisted types in SO-4 oval cans, often with handwritten numbers. The image shows a uniquely black-painted NKT102, an NKT104, and a handwritten NKT152. I do have a solitary NKT128 in the TO-5 can.

NKT155 transistor

Newmarket Transistors did not manufacture any diodes. However, they needed a detector diode in order to be able to sell a complete set of active devices to transistor radio manufacturers. They did this by shorting together the base and collector of the NKT155 transistor. This part was not sold as a normal transistor.

NKT200 transistors

The range NKT200 - NKT299 is described in the Portfolio as comprising germanium alloy PNP AF transistors, in TO-1 and TO-5 packaging. I possess a number in those standard cans, but also have several types in the oval SO-4.

NKT300 transistors

In the NKT300 range we break out into germanium PNP intermediate power types, some AF, some IF and some switches. These use the domed TO-8 can with screw-down washer, somewhat reminiscent of the V/IP types. I even have one example marked just '362' that uses the V/IP case, although this type number is not listed in the Products Portfolio.

The range NKT400 - NKT499 contains germanium PNP high-power types in TO-3 cans, both switching and audio devices. They are unusual for TO-3 devices in that the diamond-shaped flange is not a solid integral part of the domed body but is a separate piece of thin metal cold-welded around the dome with a plastic former underneath.

NKT401 transistor NKT402 transistor

The group starts with NKT401 and NKT402, germanium PNP high-power switching transistors, rated at 10 Amps maximum collector current.

NKT403 transistor NKT404 transistor

Then come NKT403 to NKT406, germanium PNP high-power amplifier transistors, rated at 10 Amps maximum collector current except for NKT405 which is rated at 5 Amps. The four have different gain values.

I am seeking the NKT405 and NKT406. If you know where I might obtain any, please

wanted NKT transistors

Next is NKT420, a germanium PNP high-voltage high-power amplifier transistor, rated at 120V maximum collector-base voltage and 5 Amps maximum collector current.

I am seeking the NKT420 transistor. If you know where I might obtain any, please

NKT450 transistor NKT451 transistor NKT452 transistor NKT453 transistor

Finally come NKT450 to NKT453, germanium PNP high-power amplifier transistors, rated at 3 Amps maximum collector current.

NKT600 transistors

The NKT600 range comprises germanium PNP alloy-diffused transistors in TO-8 cans, for VHF applications.

NKT700 transistors

The NKT700 range contains all the NPN germanium transistors in the NKT series. It includes both AF and RF types but all are low-power devices in TO-1 cans.

NKT Servikit transistors

The October 1964 issue of the magazine 'Wireless World' contains the following news article:

By careful choice of characteristics, Newmarket Transistors Ltd., of Exning Road, Newmarket, Suffolk, have put together a kit of fourteen transistors which they claim will enable any serviceman to repair virtually any entertainment type of transistor equipment. Known as the " Servikit," it contains four alloy diffused v.h.f., five alloy r.f., three p-n-p a.f., one n.p.n. a.f. and one power transistor. To help select a suitable replacement, the makers have included an index of British, continental Europe and Japanese types, which the range is designed to replace.

The image shows the eight Servikit types that I possess. They bear a type number SERnn and are packaged in small plastic tubes that contain a label with some of the characteristics. I'm unsure of the SERnn numbering used, but I must be missing 6 types, including the power transistor that I know is SER4.


Rather bizarrely, images of the Servikit appear in three Italian magazines that are downloadable on the Web; the January 1967 issue of 'Costruire Diverte', the May 1967 issue of 'Radiorama' and the July 1967 issue of 'Tecnica Pratica'. All state that there are sixteen transistors in the set. This image from 'Tecnica Pratica' shows thirteen in the plastic tubes, apparently two in small NKT boxes, and the visible power transistor that is clearly marked NKT452, not a SER naming.

The 'Costruire Diverte' article says the set contains 5 RF types, 4 VHF types, 2 AF types, a matched pair for Class B output, a matched pair for complementary NPN-PNP output, and one high power type.

If you know more about the SER types, please


Newmarket made packaged circuits types PC1 - PC10 and PC101 - PC106, which of course employed their own germanium transistors. All were relatively low power. The image shows the PC3 audio amplifier.

I have created a separate page that gives details of these.

NKT microcircuit NMC809A hybrid

Newmarket also made the NMC series custom microcircuits, which were hybrids. They are rare, the image shows the only one I have, the NMC809A. It looks a bit like a standard dual-inline package, but has 5 widely-spaced legs. Other ones use round TO-99 cans.

A correspondent sent me this data on it.

If you have data or examples of these microcircuits, please

Like most UK semiconductor manufacturers, Newmarket made CV equivalents of their devices. These were military-grade versions of commercial types, given a Common Valve type designation. I am interested in obtaining examples of the following CV types:

CV5330 = V10/15A CV8386 = V15/20IP CV5309 = V15/20P
CV5791 = V30/20DP CV5327 = V30/20IP CV8004 = V30/20P
CV7011 = V30/30P

If you have any of these, please

The Product Portfolio also lists other device numbers and types. These include NKT10419 - NKT20339 silicon industrial transistors in TO-18 cans; NKT80111 - NKT80216 junction FETs in TO-17 and TO-18 cans; junction transistors in the OC, ACY, BC, BCY, BDY, BFX, BFY, BSX and BSY series; junction transistors in the 2N series; and micro-miniature silicon active devices for direct attachment to film circuits. I do have a few of the junction transistors, but in general these types are not of great interest.