Blog posts of '2013' 'October'


Today, we have for you, the second part of the Blackburn Times article for you to enjoy: -

After passing through the iron gate at the entrance, I peeped at the foundation stone on the main building.  It was dated 1938 and I was later told that Alderman J Fryars then Mayor of Blackburn had made an expert job of laying it.

Looking round at the factory blocks on the 43-acre site, it did not seem out of place to conjecture that such strides could only have been made over a century and certainly not within a decade and a half.

Mullard loomed like a monster cave to be explored and investigated in sections.   The assorted processes in the evolution of the valve were so interlaced that to take each one and look at it seperately was almost a crime against the system.  So, instead of plunging into the technicalities of valve production, I learned how the factory ticked over and how an army of over 3300 employees were kept marching.

An army they say, marches on it's stomach so one of the key spots on the tour was the factory canteen where 1200 can be seated at one sitting.  An interview with the canteen manager revealed how the 48 strong canteen staff manage to cope in feeding the factory and the daily consumption list is enormous with 1200 to 1500 meals being served comprising of 750 sweets, 40 gallons of soup, 15 cwts of potatoes and 950 rounds of sandwiches and all this washed down with 7000 cups of tea.

Up in the morning early, the canteen staff are on hand to serve a steaming brew to workers on the early shift and so it continues from 06:30  until 22:30 meeting the needs of a steady stream of eager customers.    For those who have not the time to leave their benches during the staggered 10 minute breaks, a dozen tea trolleys skim round the various departments with a respectable assortment of cakes and snacks. 

Part 3 of this fascinating tale follows over the next few days. 


Today, the Mullard archive has revealed the copy sent for approval by RF Kennedy, a journalist with the Blackburn Times.    Although I have abridged this text somewhat, this was first published in the  Friday evening editon of the Blackburn Times on 12th February 1954.

 It was a 40-minute lunchtime break at the Mullard Blackburn works and the rush scene showed hundreds of workers on their toes, determined not to loose one second of the interlude which was typical of a factory where the accent is on..... Speed, Efficiency & Perfection.

To a newcomer, it all seemed so much bustle but a tour of the mammoth factory - I could have stayed all week and still not seen the whole - showed there was organisation behind the bustle.

This organisation has brought contented employment to over 3300 people of Blackburn and district and through the production of milloins of valves each year, is bringing untold pleasure to countless numbers of television viewers and radio fans in every corner of the globe.

Yes, Mullard have certaily notched a place for themselves in the industrial prosperity of this town whose bread and butter for generations have been dependant upon the cotton industry.  And Mullard have achieved this proud place in the space of a mere 16 years.

Tune in for the next exciting installment of this story, coming to the blog near you SOON!



The march of time and progresss marched inexorably on at Mullard's and an interesting development occurred for CRT in 1954.  If you look at some of my earlier blog postings on the manufacture of CRT, you will see that the EHT connections provided pre-54 were somewhat different to those you may be more familiar with but this did indeed change in 1954.

If you recall, the earlier EHT connection comprised of a number of wires fused into the side of the envelope which was in turn soldered to a metal cap on the tube's exterior wall.  To make such connectons required a fair deal of skill and the whole operation was labour intensive with Mullard suffering a trying time during 1952 when quite a number of these connections failed due to rough handling in transit which was expensive and wasteful - especially as the packaging for these early CRT was very good as well.

Anyhow, the replacement connector was a one piece jobbie made of a nickel-chrome-iron alloy which you can see in the photo below: - 

And here is a photo showing the corresponding EHT connector - are things looking familiar now?: -

Item D was a handy little adaptor comprising of a thimble cap of standard dimensions, the lower end of which was fitted with six spring prongs to locate the terminal.  This adaptor allowed TV receivers from past years to be rejuvenated with one of the newer tubes without changing the existing wiring - those chappies at Mullard thought of everything you know.



People seem to have the most horrendous problems converting their various capacitance units so to help, I have produced the following table which I hope may find use as a handy "aide-memoir."  Why not print it out and have it on the workshop/lab/study/junk room wall: -


uF nF pF/ uuF
1uF / MFD 1000nF 1000000pF(MMFD)
0.82uF / MFD 820nF 820000pF (MMFD)
0.8uF / MFD 800nF 800000pF (MMFD)
0.7uF / MFD 700nF 700000pF (MMFD)
0.68uF / MFD 680nF 680000pF (MMFD)
0.6uF / MFD 600nF 600000pF (MMFD)
0.56uF / MFD 560nF 560000pF (MMFD)
0.5uF / MFD 500nF 500000pF (MMFD)
0.47uF / MFD 470nF 470000pF (MMFD)
0.4uF / MFD 400nF 400000pF (MMFD)
0.39uF / MFD 390nF 390000pF (MMFD)
0.33uF / MFD 330nF 330000pF (MMFD)
0.3uF / MFD 300nF 300000pF (MMFD)
0.27uF / MFD 270nF 270000pF (MMFD)
0.25uF / MFD 250nF 250000pF (MMFD)
0.22uF / MFD 220nF 220000pF (MMFD)
0.2uF / MFD 200nF 200000pF (MMFD)
0.18uF / MFD 180nF 180000pF (MMFD)
0.15uF / MFD 150nF 150000pF (MMFD)
0.12uF / MFD 120nF 120000pF (MMFD)
0.1uF / MFD 100nF 100000pF (MMFD)
0.082uF / MFD 82nF 82000pF (MMFD)
0.08uF / MFD 80nF 80000pF (MMFD)
0.07uF / MFD 70nF 70000pF (MMFD)
0.068uF / MFD 68nF 68000pF (MMFD)
0.06uF / MFD 60nF 60000pF (MMFD)
0.056uF / MFD 56nF 56000pF (MMFD)
0.05uF / MFD 50nF 50000pF (MMFD)
0.047uF / MFD 47nF 47000pF (MMFD)
0.04uF / MFD 40nF 40000pF (MMFD)
0.039uF / MFD 39nF 39000pF (MMFD)
0.033uF / MFD 33nF 33000pF (MMFD)
0.03uF / MFD 30nF 30000pF (MMFD)
0.027uF / MFD 27nF 27000pF (MMFD)
0.025uF / MFD 25nF 25000pF (MMFD)
0.022uF / MFD 22nF 22000pF (MMFD)
0.02uF / MFD 20nF 20000pF (MMFD)
0.018uF / MFD 18nF 18000pF (MMFD)
0.015uF / MFD 15nF 15000pF (MMFD)
0.012uF / MFD 12nF 12000pF (MMFD)
0.01uF / MFD 10nF 10000pF (MMFD)
0.0082uF / MFD 8.2nF 8200pF (MMFD)
0.008uF / MFD 8nF 8000pF (MMFD)
0.007uF / MFD 7nF 7000pF (MMFD)
0.0068uF / MFD 6.8nF 6800pF (MMFD)
0.006uF / MFD 6nF 6000pF (MMFD)
0.0056uF / MFD 5.6nF 5600pF (MMFD)
0.005uF / MFD 5nF 5000pF (MMFD)
0.0047uF / MFD 4.7nF 4700pF (MMFD)
0.004uF / MFD 4nF 4000pF (MMFD)
0.0039uF / MFD 3.9nF 3900pF (MMFD)
0.0033uF / MFD 3.3nF 3300pF (MMFD)
0.003uF / MFD 3nF 3000pF (MMFD)
0.0027uF / MFD 2.7nF 2700pF (MMFD)
0.0025uF / MFD 2.5nF 2500pF (MMFD)
0.0022uF / MFD 2.2nF 2200pF (MMFD)
0.002uF / MFD 2nF 2000pF (MMFD)
0.0018uF / MFD 1.8nF 1800pF (MMFD)
0.0015uF / MFD 1.5nF 1500pF (MMFD)
0.0012uF / MFD 1.2nF 1200pF (MMFD)
0.001uF / MFD 1nF 1000pF (MMFD)
0.00082uF / MFD 0.82nF 820pF (MMFD)
0.0008uF / MFD 0.8nF 800pF (MMFD)
0.0007uF / MFD 0.7nF 700pF (MMFD)
0.00068uF / MFD 0.68nF 680pF (MMFD)
0.0006uF / MFD 0.6nF 600pF (MMFD)
0.00056uF / MFD 0.56nF 560pF (MMFD)
0.0005uF / MFD 0.5nF 500pF (MMFD)
0.00047uF / MFD 0.47nF 470pF (MMFD)
0.0004uF / MFD 0.4nF 400pF (MMFD)
0.00039uF / MFD 0.39nF 390pF (MMFD)
0.00033uF / MFD 0.33nF 330pF (MMFD)
0.0003uF / MFD 0.3nF 300pF (MMFD)
0.00027uF / MFD 0.27nF 270pF (MMFD)
0.00025uF / MFD 0.25nF 250pF (MMFD)
0.00022uF / MFD 0.22nF 220pF (MMFD)
0.0002uF / MFD 0.2nF 200pF (MMFD)
0.00018uF / MFD 0.18nF 180pF (MMFD)
0.00015uF / MFD 0.15nF 150pF (MMFD)
0.00012uF / MFD 0.12nF 120pF (MMFD)
0.0001uF / MFD 0.1nF 100pF (MMFD)
0.000082uF / MFD 0.082nF 82pF (MMFD)
0.00008uF / MFD 0.08nF 80pF (MMFD)
0.00007uF / MFD 0.07nF 70pF (MMFD)
0.000068uF / MFD 0.068nF 68pF (MMFD)
0.00006uF / MFD 0.06nF 60pF (MMFD)
0.000056uF / MFD 0.056nF 56pF (MMFD)
0.00005uF / MFD 0.05nF 50pF (MMFD)
0.000047uF / MFD 0.047nF 47pF (MMFD)
0.00004uF / MFD 0.04nF 40pF (MMFD)
0.000039uF / MFD 0.039nF 39pF (MMFD)
0.000033uF / MFD 0.033nF 33pF (MMFD)
0.00003uF / MFD 0.03nF 30pF (MMFD)
0.000027uF / MFD 0.027nF 27pF (MMFD)
0.000025uF / MFD 0.025nF 25pF (MMFD)
0.000022uF / MFD 0.022nF 22pF (MMFD)
0.00002uF / MFD 0.02nF 20pF (MMFD)
0.000018uF / MFD 0.018nF 18pF (MMFD)
0.000015uF / MFD 0.015nF 15pF (MMFD)
0.000012uF / MFD 0.012nF 12pF (MMFD)
0.00001uF / MFD 0.01nF 10pF (MMFD)
0.0000082uF / MFD 0.0082nF 8.2pF (MMFD)
0.000008uF / MFD 0.008nF 8pF (MMFD)
0.000007uF / MFD 0.007nF 7pF (MMFD)
0.0000068uF / MFD 0.0068nF 6.8pF (MMFD)
0.000006uF / MFD 0.006nF 6pF (MMFD)
0.0000056uF / MFD 0.0056nF 5.6pF (MMFD)
0.000005uF / MFD 0.005nF 5pF (MMFD)
0.0000047uF / MFD 0.0047nF 4.7pF (MMFD)
0.000004uF / MFD 0.004nF 4pF (MMFD)
0.0000039uF / MFD 0.0039nF 3.9pF (MMFD)
0.0000033uF / MFD 0.0033nF 3.3pF (MMFD)
0.000003uF / MFD 0.003nF 3pF (MMFD)
0.0000027uF / MFD 0.0027nF 2.7pF (MMFD)
0.0000025uF / MFD 0.0025nF 2.5pF (MMFD)
0.0000022uF / MFD 0.0022nF 2.2pF (MMFD)
0.000002uF / MFD 0.002nF 2pF (MMFD)
0.0000018uF / MFD 0.0018nF 1.8pF (MMFD)
0.0000015uF / MFD 0.0015nF 1.5pF (MMFD)
0.0000012uF / MFD 0.0012nF 1.2pF (MMFD)
0.000001uF / MFD 0.001nF 1pF (MMFD)





Don't you just love the parlance "crystal diode".  1954 was the year that Mullard took their first steps into the mass market with semiconductors.  Trumpetting their new  product as having low shunt capacities and higher rectification efficiency than those old fashioned valve things, the range started with two devices specially developed for television use.  

There were teething problems as the TV trade tended to attach these new fangled devices into TV circuits using a poker heated in t'fire thence cooking these early and not particularly robiut devices but application of tweezer heatsinks thoughfully provided by an arrangement between Mulard and Antex to solve this unforseen setback.

Type OA61 was designed as a video signal detector with it's handy PIV of 30V.

Type OA61 was designed as a DC restorative and synchronising pulse clipper with a PIV of 100V.

Both types demonstrated a minimal shunt capacitance of 0.1uF and a working temperature range of -50 - +60oC.  The future had arrived!


You can read more about this Noval based output pentode on one of my valve product pages but here, today we have an excerpt from a Mullard 1954 press release extolling the vital statistics of this versatile and today much loved device: - 






Just look at this, taken at HMV Oxford Street in 1957, a time when post war yoof culture was really taking off.  What we see here is not the interior of a Concorde fuselage nor a row of wash basins in the ladies loos, in actuality it is a very swish row of listening booths where prospective purchasers - female of course - could go to ruin their records as well as listen to them before they bought them - pretty good huh.  Can anyone recognise the record decks???? 


We have had a run on stabiliser devices recently, so I thought it was perhaps time to write a blog article about how these work.   Interestingly, they are not a valve in the true sense as they do not amplify but ratherfind use in maintaining steady DC voltages in power supplies where mains supply variations occur or within circuits where a reliable reference voltage is required for operation.

The simplest form of voltage stabiliser consists of a rod anode surrounded by a cylindrical cathode which are mounted within a glass bulb which has an atmosphere containing a single or multiple low pressure noble gas mixture with neon, helium or argon commonly being used - more on this later..  As a DC potential flows, the cathode will strike with a visible glow and a burning voltage flows from anode to cathode.  This potential has the useful property of only minimally being varied by changes in current as you can see in the following picture: -


The voltage at which a stabiliser strikes and burns at is determined by the gas or gas mixture used within the envelope with the supply voltage typically being higher than the operating voltage required to ensure strike and burn occurs.  Mullard made a variety of these devices, the parameters for which are listed below: -

This phenomenon has two effects - if the input voltage changes, then the burning current, I, and resistance, R,  will also change BUT the voltage across the stabiliser will remain constant.  The only deviation that can occur is when the ratings of the stabiliser are exceeded at which point, the stabiliser will rapidly fail - if one were to perchance reverse the anode and cathode connections then again, the stabiliser would (spectacularly & rapidly) fail.

So, there we have it, a quick treatise on these fascinating devices, Made by Mullard amongst others but remember, they are not a valve!!!