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. There used to be a Web site that described the company history, but it has gone. It stated that originally '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'. I don't know if this is accurate, but there is now a website called 'Pye Story' that includes a history of Newmarket Transistors.

Newmarket did not make any point-contact transistors, their first commercial products were junction types released in about 1956. Intriguingly, they were true to their name and, to my knowledge, never made a single diode (although they sold one diode by shorting two leads on a transistor, see NKT155 below). 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.

The details of Newmarket/Pye's first transistors are slightly confusing. The oldest data that I have found are in the book 'Transistors and Crystal Diodes' by B.R.Bettridge for which the first edition is dated 1955. It lists the following as Pye transistors:

I have Pye Industrial Electronics original data sheets dated June 1956 for the following four groups:

V10 transistors

I do have examples of the V10 types without the suffix letter, but most are unbranded like these.

PYE V6/R2 transistors PYE V6/R4 transistors PYE V10/50 transistors

I have a few V10/50 marked 'Pye' and also a few V6/R2 and V6/R4 marked 'Pye', which causes me to suspect that Pye versions of the other types in the two triplets must also have been made. My Pye examples are all dated 1956. A characteristic of them is that the entire body is painted including the top, which may bear a paint dot or a small printed letter. Confusingly, some can be found printed PIE, which stands for 'Pye Industrial Electronics'.

I'm looking for examples of the Pye (or PIE) V6/R8, V10/15 and V10/30 to complete the set. If you know where I might find any, please

V6 transistors V6 transistors

Here are two variants of the later unbranded V6/Rn triplet. Those in the first set have a fully painted can but the top is overpainted in gold. I am missing the V6/R4, the two shown are dated 1957.

I'd like an unbranded V6/R4 to complete the set. If you know where I might find one, please

The second set has something like a red decal around the body, which does not cover the top or bottom. Again the top is painted gold, and the bottom of the decal has a dotted line, perhaps to help with cutting it from a sheet. These are also dated 1957 but I believe are later than the first set.

V10 suffixed transistors

And here is the suffixed set of V10 types. The V10/30A in the middle has the fully painted can, the other two have the decal. My supposition is that all three were initially fully painted, and the decal was introduced later. All are dated 1957 although I have one green V10/50B dated 1958. All have gold tops.

Goltop transistors

For all V types, low- and high- power, the gold painted/labelled top is significant: Newmarket adopted the branding 'GOLTOP' for its V series transistors in 1957. The company history on the 'Pye Story' site explains that originally this was to be 'GOLDTOP' but this fell foul of the trades descriptions laws as no real gold was present!

V10/15 in envelope

The V6 and V10 types can be found in paper envelopes as shown, with handwritten characteristics, sometimes dated. Presumably these were prepared at the factory as specially-selected devices for critical applications. If anyone knows more about this, please

wanted V6/R3

The V6 and V10 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

Newmarket's V series power AF types use a large 'stud' outline with a threaded bolt on the bottom, the case being connected to the collector, and two pins for the other leads. Their part numbers indicate the maximum collector voltage and current gain of the transistor. They come in three varieties: the earliest examples are simply black with a white part number and a date code, the majority have black/gold colouration, and late examples are unpainted with NEWMARKET usually printed on them.

V15/30P transistor V15/20P transistor V15/10P transistor

This is the V15 triplet. The earliest ones use a month-year datecode format, while later ones use the military CV-series two-letter datecode format.

V30/30P transistor V30/20P transistor V30/10P transistor

And this is the V30 triplet.

later V6 transistors

It seems that the limited performance of the early V6 types was of concern, because in 1958 Newmarket issued unpainted versions with a higher maximum power dissipation. The image shows unpainted V6/R2 and V6/R8, the first with a red top and undated, the second with a gold top and coded PM for December 1958.

Naturally, I'm looking for an unpainted V6/R4 to complete the set. If you know where I might find one, please

unpainted V6 transistors

Newmarket seem to have decided to distinguish the unpainted V6 types are by reversing the two characters of the gain banding, creating types V6/2R, V6/4R and V6/8R. Again, all my examples are unbranded. The earliest date on any of mine is 1960.

later V10 transistors

Unpainted versions of the V10 triplet exist but with unchanged numbering, again unbranded. However I don't have an unpainted V10/50B, instead I have a few V10/50A. The earliest date on any of these is 1959.

I'm seeking an example of the unpainted V10/50B. If you know where I might find one, please

TO5 V6/8R transistor

According to Newmarket literature, the improved V6 and V10 types were also available in a 'cylindrical' outline, with a further suffix C added in the data listing. I have this one V6/8R in the TO-5 outline. It has no suffix C but I wonder if this is that 'cylindrical' version.

I am seeking any V6 or V10 transistors in the TO-5 or other cylindrical outline. If you know where I might find some, please

Spot-on transistors

As with other manufacturers, Newmarket transistors, presumably out-of-spec examples, were sold to the hobbyist market. This image shows what is clearly a V series transistor, marked as a 'yellow/green' type in a small square paper envelope. There is also at least one other such bicolour type: yellow/red. I don't know if these were sold directly by Newmarket or whether they were bought in bulk and resold by another company. The envelopes bear no company information, just the overprinted 'SPOTON BRAND (reg)'. The transistors have nothing printed on them, and no gold top, but the two colour spots are on the top.

V15/20R transistor

Newmarket made one unusual early transistor, the type V15/20R germanium PNP drift transistor, for which I have an April 1959 provisional data sheet. As far as I know, this is the only V type with suffix R.

V60/30P transistor V60/10P transistor

In addition to the above V15 and V30 types the 1959 Newmarket 'Semiconductor Device Data' booklet contains a higher voltage power transistor triplet with the same three gain values as the previous two triplets.

The images show a V60/10P dated QA for January 1959, and an undated V60/30P, both in black-gold livery.

I am seeking examples of V60/20P to complete the set. If you can help, please

V30/10LP transistor V25/15P transistor

I have some V-type power transistors for which I have no data. The images show:

I do have a March 1958 Kinetrol 'Price List' that includes V30/10LP, but gives no characteristic data. This is the only example of this suffix that I have ever seen.

I am seeking data for these types. If you can help, please

V15/20IP transistor V15/20IP transistor V15/20IP transistor

In 1959 Newmarket claimed to be first to release an 'intermediate power' type of transistor. The IP types use a medium-sized circular domed outline 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. They come in three colourings: all black (possibly the earliest), Goltop black and gold, and unpainted metal.

The 1959 Newmarket 'Semiconductor Device Data' booklet contains V15/20IP and V30/20IP. A Newmarket advertisement in 'Wireless World' January 1960 adds V60/20IP, of which Peter kindly sent me a pair.

V15/20IP transistor

I also have an anomalous V30/100IP for which I don't have data. If the 100 denotes gain, that is exceptional for a medium-power type at this time.

I am seeking data for this type. If you can help, please

Green Circle 6 transistor

I am grateful to Paul, a correspondent who alerted me to this page from the magazine Wireless World in February 1959. On it, Newmarket announce several matched sets of transistors intended to provide the entire semiconductor complement needed by a transistor radio manufacturer. They use a new identification scheme called 'Circle Line' based on a colour and a single digit number. Newmarket may well have been the first UK company to offer sets of semiconductors like this, although Mullard, STC and Thorn-AEI did so later. Five sets are offered in the advertisement:

I'm curious as to what diode they supplied, as Newmarket did not make diodes. The upper image shows Green Circle 6, probably an AF-output transistor. It is not branded. The RK is a CV-style date code for October 1960.

White Circle 2 and 6 transistors

The middle image shows White Circle 2 and White Circle 5. The advertisement states these are IF and AF-output types respectively. Neither is branded. The 2 is undated, the 5 has a datecode SD for April 1961.

Black Circle transistors

Paul is restoring a PAM radio that contains a Circle Line set. My image shows some of them, all with damaged leads. They are listed on the 'Trader' service sheet as 'Black Circle Seven' transistors. a set that does not appear on the advertisement. The date codes on them are for June and July 1960.

I am seeking examples of the other Circle Line types, and original data for any. If you can help, please

V10/1S transistor V10/2S transistor V10/1SC ? transistor

In 1959 Newmarket announced two low-power switching types in the same oval SO-4 outline: the V10/1S and V10/2S, also available in the cylindrical outline with suffix SC. The oval V10/1S was used in the Ferranti Argus series of British process-control computers.

I have one example of V10/1S in a TO-5 outline, painted black as shown. Is this really a V10/1SC and they did not print the extra suffix C? Or does the J stand for JEDEC?

I am seeking more examples of the V10/1SC and the V10/2SC. I also would love to have information about the TO-5 outline. If you have any, please

V60 noodle transistor V30 noodle transistor V15 noodle transistor

In 1959 Newmarket isued some of the high-power V-series types in the standard TO-3 'diamond' outline. For some strange reason, they initially gave them the suffix NP for 'noodle power'. If anyone can explain this unusual choice of characterisation, please They seem to have changed this later to 'PD', but I have no data books that include these.

My 1959 'noodle power tentative data sheet' lists:

NKT transistor flange

of which I have V15/30NP and V30/30NP. All my examples have the NP handwritten on them in small letters. 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, and is hollow. I also have a V60/15NP for which I have no data. It has a gold label on top which does have the NP printed on it, and the hollow flange contains a brass former. This construction is unique to Newmarket.

V60 PD transistor V30 PD transistor V30 PD transistor

When it comes to the PD types they look more modern with a gold label but no black paint and, regrettably, no date codes. I have examples of the following but have no original data for them:

However, the Newmarket 'Cross Index' dated September 1962 lists the following 'equivalences':

which shows that V60/10PD and V60/30PD must also exist, forming the same triplet (with V60/20PD) as the previous stud outline types. This makes me suspect that there is a V30/..PD triplet and I am missing V30/20PD. I'm unsure that the V15../NP types were changed to a V15/..PD triplet as this maximum voltage is too low for more modern types and they may have been considered obsolete.

Newmarket's second series of transistors, the NKT series, became available in 1961 and developed into a very broad range of devices. I have several reference sources for these:

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

NKT15 transistor

The devices NKT1 to NKT99 are classified in the Products Portfolio as germanium alloy PNP RF transistors with low maximum collector-base voltage. The Portfolio only lists a small number of types in a standard TO-1 outline:

The Aide Memoire lists considerably more, some in SO12B outline and some in SO3/TO5:

My image shows an NKT15 so the above is incomplete!

NKT100 transistors

The Products 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:

Again the Aide Memoire lists considerably more, some in SO3/TO5 outline and some in SO4/TO22:

I also have a data sheet that includes NKT151 and NKT155 in a group with NKT152-154.

The Transistors Data booklet also includes:

I only have examples of a few of these many types, including some with handwritten part numbers. The image shows a uniquely black-painted NKT102, an NKT104, and a handwritten NKT152.

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. (I don't mean the Circle Line here, that was earlier). 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 Products Portfolio as comprising germanium alloy PNP AF transistors, in TO-1 and TO-5 packaging:

The Aide Memoire includes more, some in SO3/TO5 outline and some in SO4/TO22:

The Transistors Data booklet also includes:

NKT300 transistors

In the NKT300 range we break out into germanium PNP intermediate power types:

These use the domed TO-8 outline with screw-down washer, but with pins rather than the group of wires of the V/IP types. However I have one example marked just '362' that does use the V/IP case.

The range NKT400 - NKT499 contains germanium PNP high-power types in TO-3 outline, both switching and audio devices. Like the V-series TO-3 power types the diamond-shaped flange is a separate piece of thin metal cold-welded around the central dome with a brass (or rarely plastic) former underneath. One of their PC-series of amplifier cards (see below) uses NKT453 transistors without the diamond flange.

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 NKT405 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 NKT406. If you know where I might obtain any, please

wanted NKT transistors

Then come NKT415 and NKT416, medium-voltage, medium-gain amplifier types. 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 NKT415, NKT416, and NKT420 transistors. 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.

NKT500 transistors

NKT501 to NKT504 are not included in the Products Portfolio, but the Aide Memoire lists them, and I have an original data sheet dated February 1962 for them. These are described as 'extra-high-current power transistors'. They are germanium PNP types in the JEDEC standard TO-36 outline.

I have never seen an example of any of these, If you know where I might find any, please

NKT600 transistors

The NKT600 group comprises germanium PNP alloy-diffused transistors in TO-8 outline, for VHF applications. The 1962 Products portfolio lists:

While the 1964 'Transistors Data' booklet lists:

NKT700 transistors

The NKT700 range contains all the NPN germanium transistors in the NKT series. All are low-power devices. The 1962 Products Portfolio lists:

The 1964 'Transistors Data' leaflet adds:

And I have a booklet 'NPN-PNP Circuits' by Newmarket dated May 1962 that lists

Newmarket sold groups of transistors as 'packs'. I'm unsure what the actual presentation was. The packs were:

NKT Servikit transistors 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 two images show eight Servikit types and three more. They all bear a type number SERnn and are packaged in small plastic tubes that contain a label with some of the characteristics, including a line saying that the SER type is 'formerly a special selection' of a specified NKT type. I also have two other types loose without tubes. I'm unsure of the full set of SERnn numbers used, but I have no SER18, and I'm also missing the power transistor: I have seen one for sale as SER4, which is puzzling.


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, two in small NKT boxes, and one visible power transistor. All have NKT part numbers, not a SER naming. The other two magazines show loose transistors without tubes or boxes.

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

Newmarket made an MC series of custom microcircuits, which are hybrids. They come in either a very small DIL outline, or else in a TO99-style round multi-lead can. I have some information on them, but no device data, as they are custom. Thanks to the excellent Silicon Ark I have one, shown here. It has nothing printed on it at all, but it did come with information stating that it is a Schmitt Trigger circuit. It has four leads (with four more cut off), so that is quite possible.

NKT microcircuit NMC809A hybrid

I also have this NMC809A. It seems to use a standard 14-DIL package, but only has 5 widely-spaced pins.

I don't have any information on an NMC series, but a correspondent sent me this data on the NMC809A. It does not say whether it is a hybrid or monolithic IC but does use normal 14-DIL pin numbering.

If you have data or examples of the MC or NMC microcircuits, please

Like most UK semiconductor manufacturers, Newmarket made CV equivalents of their devices. These are military-grade versions of commercial types, given a Common Valve type designation. I am interested in obtaining examples of the following CV types from the 1963 CV Register:

CV5309 = V15/20P CV5327 = V30/20IP CV5330 = V10/15A CV5791 = V30/20DP CV5929 = V60/20IP CV7011 = V30/30P
CV7012 = V60/30P CV7086 (NKT only) = NKT403 CV7116 = V60/30DP CV8004 = V30/20P CV8386 = V15/20IP

I assume that 'DP' should be 'PD'. If you know where I can find any of these, please

NKT OC36 transistor

The Product Portfolio also lists other device numbers and types. These include NKT10419 - NKT20339 silicon industrial transistors in TO-18 outline; NKT80111 - NKT80216 junction FETs in TO-17 and TO-18 outline; 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 apart from the germanium curiosities these types are not of great interest.