Saturday, December 06, 2008


The digial clock works!

There really wasn't much that needed to be done. There were a few lose connections on the lamps, but none needed replacing. The two pin mains power connector and dual fuses were replaced with a single fuse and 3 core flex. But it was running slow, this was fixed by cleaning out the gearbox with contact cleaner and replacing the oil.

From Uniselector Clock

The first video shows how the calendar mechanism advances and resets. The whole mechanism is driven by a single large solenoid that is activated every 12 hours.

From Uniselector Clock

The second video shows the time being set. The rotary switches on the control panel are turned to the correct time and the "reset" switch lifted. The time then advances, as show by the lamps, and stops at the required minutes. The hours keep advancing until the right hour is reached and the switch released.
div>Follow this link for more pictures and information on the clock.

Wednesday, December 03, 2008

Who needs a nixie clock?

Quite possibly built in the late 1930s here's the electro-mechanical digital clock I've just acquired.

It doesn't have a digital display, i.e. one with digits, instead it has 12 lamps for the hours, five for the tens of minutes, and another 10 for the minutes.  The lamps are switched by telephone exchange type uniselectors.  There are rotary switches on the side to set the alarm.

The calendar part is entirely mechanical, but it has a cam on the month wheel to set the number of days in each month.

I'd love to know if anyone has ever seen this clock or a similar one before, where it was used, who made it, or anything else.

Over the weekend I'll see if I can get it working.


Some nixie clocks have used Strowger (uniselector) switches.  See the gallery here (search for the Tomlin clock).    
Digital (display) clocks did exist in the 1930s - see

Friday, November 28, 2008

Privatization, what is it good for?

It's been an interesting week. On Monday, in the UK Government's Pre-Budget Report, one of the less reported items was "reviews of the Met Office, Oil & Pipeline Agency...

So maybe, just maybe, in a few months my employer will no longer be owned by the Ministry of Defence.  Okay, for most folks in computing that probably doesn't seem like a big deal.  But for an organisation that's existed for over 150 years, that's a big change. Especially so for those employees who give the impression of having been there for most of that century and a half.

National meteorological services (or NMS's as we call 'em) are almost always state owned, and pretty much every country has one - even Somalia is trying to re-establish(*) one right now.  I doubt it's because having crazy bearded scientists  who claim to predict the weather is a source of great national pride, just that in an age of air travel, climate change, and  expectation that governments anticipate, rather than just deal with, disaster having a decent weather service is a necessity.

Anyway, now there's some new things for me to learn.  This looks to be a useful resource -


* Typing this "re" reminded me of a recent internal email advising staff who had signed a security document, that had since been amended, that they would be "asked to resign".  How we all laughed!

Sunday, November 23, 2008

Mullard 3 3

Almost exactly a month ago I "won" a "homebrew vintage amplifier" chassis on Ebay.  It looked to have a couple of decent quality transformers and I reckoned that it's hard to destroy them both accidently so bidding for what I reckoned one to be worth wasn't taking too big a risk.  Both turned out to be OK, but I decided not to use the mains transformer for the rebuild.

Here are the before photos -

From gadgets

From gadgets

And here's the rebuilt amplifier -

From gadgets

From gadgets

From gadgets

For schematics and project notes see Mullard three-three.

Saturday, November 08, 2008

Cheap triodes

Judging by the high prices valve (tube) amplifiers and their component parts are making on EBay these days the following notes might be of use to others.  As I've now managed to gather more than enough parts to build a Wireless World Quality Amplifier I should really get on with building it  - not buying yet more valves, transformers, etc.

Decent triodes seem to be unreasonably expensive at present.  OK, the likes of PX4, PX25, PX25A output triodes are bound to be pricey, more than £100 even for a used tube.   Which is why most folks on sensible budgets use output pentodes (or kinkless tetrodes, KT66) with the more extravagant using them as triodes, as in the famous Williamson amplifier.   

But... why pay more than a few quid for a used L63 (6J5G)?  Here's an old idea that might save valve amp experimenters a few pounds - 6Q7G was designed as a first audio triode for wireless sets, sure it's also got two diodes, but you don't have to use them.  When I bought my wartime Vortexion PAs one had a couple of 6Q7G the other used EF37A connected as triodes - see the datasheet that can be downloaded from the Virtual Valve Museum, Mullard give data for using this valve as triode or pentode.

Thursday, October 23, 2008

The answers to that question

A couple of days ago I posted a question from Wireless World in 1942.  Here's the answer that was published at the time, and a letter from Arthur C Clarke published a month later.

THE mere fact that we are able to observe the light which is reflected from other planets shows that there is nothing to prevent an electromagnetic wave traversing the space intervening between the earth and those planets—or rather between the. earth and the planetary atmospheres. For it must be noticed that this light —which originally comes from the sun —is not necessarily reflected by the surface of the planet itself, but may come from its outer atmosphere. Some planets have very dense atmospheres, others atmospheres of great rarity, while, in the. case of 'Mercury, there is hardly any atmosphere at all. The spectra of some planets contain strongly marked absorption bands, indicating that the light has penetrated the planetary atmosphere, the gases of which have caused absorption of certain frequencies. The light waves in these cases have probably reached the surface of the planets themselves. In other cases the planetary spectra are very similar to that of the solar spectrum, which would indicate either that the planet had no atmosphere, or that the light had been reflected from the outer part of the atmosphere itself.

In some cases, therefore, though not in others, an electromagnetic wave—even one of such a high frequency as that of light — can penetrate the planetary atmosphere and reach the surface of the planet itself. And if a wave of light frequency can do this, why cannot also one of radio frequcncy? Where there is an atmosphere which is penetrable by the sun's rays there is probably also an ionosphere, brought into being by the action of the rays upon the gas molecules of the planetary atmosphere. And since the nature and distribution of the gases of planetary atmospheres differ from those of our own it is reasonable so suppose that the ionospheres of the planets—if they exist—would exhibit different characteristics from those of the terrestrial ionosphere. There is also the question of the intensity of the sun's rays at the planets to be considered in this connection. It is probable, therefore, that there may be planetary ionospheres which are impervious to different ranges of radio frequencies than those to which our own ionospheres is impervious.

It would appear to be possible, however, for a wave of radio-frequency to penetrate to the surface of a planet in some cases. - The frequency used would have to be of such a value that the wave would easily penetrate both our own ionosphere and that of the planet in question, and would not be greatly attenuated by absorption in either of these regions. So far as the terrestrial ionosphere is concerned these conditions are suited by a radio wave in the "ultra high " part of the spectrum—of a frequency of, say, 50 Mc / s or higher.

The answer to the first part of the question would therefore appear to be " Yes—in the case of some planets." In order to " hold wireless communication," however, habitation of the planet by intelligent beings is implied, in order that the communication may be two-way. This would rule out a number of the planets, for it does not seem reasanable to think that intelligent beings could exist on those planets whose density is very low—in some cases it is less than that of water. In other cases there are other reasons for thinking that habitation of the planet is improbable. But in a few cases—such as that of Venus and of Mars—the existence of intelligent life is not so highly improbable.

Attenuation and Absorption

The practicability of holding wireless communication with an inhabited planet is quite another matter, and does not at present appear to exist. When a radio wave travels outward from a transmitter—even when it is sent out in the narrowest possible "beam "—it gradually "spreads" out in directions at right angles to its direction of travel, so that it covers a greater and greater area the farther it advances. But the energy present in the wave front at a great distance from the transmitter is the same as it was when the wave front was near the transmitter, and, since the wave front covers a greater and greater area as it advances, the energy present at any one point in it becomes
 less and less the farther it travels. This weakening of the wave with distance travelled is called "spatial attenuation" and will occur even when no absorption at 'all is taking place. Considering the relatively great distances involved between the earth and other planets-4o to o million miles is about the shortest distance—it is evident that spatial attenuation would be very great, and that colossal power would have to be used at the transmitter in order to overcome it and provide a workable signal—according to our standard—at the receiving end. A rough estimate indicates that a transmitter power of the order of 6,00a,000 kW would be necessary in order to provide a radio field intensity of 5 microvolts per metre at the nearest planet in the absence of any absorption. True the power necessary could be considerably reduced if a highly directional transmitting aerial array were used, but even so it would still be far in excess of that radiated by any existing transmitting station. So we may rule out the possibility of getting through to the planets at present.

As to whether there are any inexplicable radiations reaching us from outer space, so far as the Wireless World Brains Trust ` . aware, no ionisation which is detectable by present-day apparatus occurs at the earth's surface which cannot be attributed either to cosmic rays, gamma ray radiation from the earth itself or to radioactiye emanations in the atmosphere. The cosmic raya themselves are thought to be due to radiations occurring during
 the creation (or possibly during the  disintegration) of atoms in interstellar space, and therefore, not to be associated with any -agency on one of the planets. There may, however, be rzdi tions reaching us which are of an entirely different character to those capable of being detected by existing apparatus. The answer to the second part of the question would therefore appear to be "Not known." T. W. B.
More Views on Interplanetary Communication

"CATHODE RAY," in a postscript to his letter which is printed on page 271, writes:—
IN my capacity of Member of the Wireless World Brains Trust, and referring to the question of whether there are any inexplicable radiations reaching us from outer space, I recall that in 1933 Karl Jansky reported in Proc. I.R.E., as a result of at least a year's experiments, that he obtained continuous reception of radio waves from a certain stellar region. So far. as I know, this matter has never been cleared up. -

ARTHUR C. CLARKE, Hon. Treasurer of the British Interplanetary Society, adds a note :THE fantastic figure of six million kW, quoted as necessary to produce a 5 microvolt/metre field on the nearest planet, presumably relates to spherical radiation, which no one for a moment considers. The use of beam technique would reduce power requirements to a minute fraction of this. Moreover, there seems very good evidence that radio waves from comparatively low-powered transmitters have travelled distances which are almost interplanetary. The existence of echoes of several seconds' duration (equivalent to the distance of the moon) is well established, and delays of up to ten minutes or so have been reported—corresponding to distances of several times those of Mars or Venus at perigee.
Secondly, the evidence that radiation reaches the earth from space is quite strong, and I am surprised that your contributor did not mention it. I refer to Jansky's reports on the subject (Proc. I.R.E., Oct., 1935). Jansky reports this " star-static ''as lying between 9-21 Mc/s and being 10-30 db. above the level of thermal agitation. (See also Jansky, Proc. I.R.E.. Dec., 1937, and Friis and Feldman, Proc. I.R.E., July, 1937, for a further discussion of this matter.)
Finally, if radio is incapable of really long-range communication (which I doubt) the solution to the problem lies in the modulated light beam. Light can be focussed with extreme accuracy and the sensitivity of a photo-cell collecting light at the focus. of a giant reflector, and backed by an electron multiplier and the usual amplifying stages, is so enormous as to be almost meaningless. It is certainly capable of maintaining communication between all the planets in so small a space as the Solar System! As to the objection that most planets have opaque atmospheres, I would answer that all except Venus have airless satellites very close to them to which they could be linked by UHF.


More amplifier repairs

After a failed attempt to "win" what looked to be a valve-less Mullard 5-10 chassis in the hope of getting a replacement output transformer for my 5-10 at a reasonable price I did a bit more googling on the topic of transformer rewinds. Somewhere in the many forum posts I found a mention of checking for failures where the transformer windings are joined to the connecting leads. Given the style of transformer I've got, this seemed worth a check. So I opened it up carefully removed the outer layers of tape. In the picture you might be able to make out that the connections to the yellow wires are good but all four strands that should have been connected to the red centre-tap had failed. There was some charring and a little bit further away from where the connection had been some green traces. Further poking around and I had all four strands again. A little shorter than originally, but by scraping off the enamel I was able to test for continuity. Three of the four windings were OK. I don't know enough about transformer winding to know why each half of the primary was made up of two parallel windings, or why for the half that still had two good windings (I presume they were both good) one had a higher resistance than the other. Anyway I decided to use the two of the three good windings with the nearest resistances. Put it back together, and hey presto, a working "five - ten" with its original transformer returned. It probably can no longer safely deliver the full ten watts, but that's not really a problem.

With that job being easier and more successful than I'd expected I decided to keep going and "re-cap" my workshop Leak Stereo 30. This was bought very cheaply on ebay - "spares or repair". With the view that it would provide
spare parts for another that I have in the house. I'd ordered the capacitors from RS and decided to get axials, as originally used, so I spent a couple of hours pulling out the old, and bending and fitting the new. The left channel was always a bit weak, so I did that first and checked at the 1/3 and 2/3 count.
After the first third through the left channel it still wasn't great, but by 2/3rds it was as good as the right channel and with all replaced it was better. So then I did the right channel. Then checked the voltages and currents at the test points and all done. Now it sounds better than the good one in the house. So now I guess I'll have to do that one too. But for now I'll just swap them over :-)

Monday, October 20, 2008

Can a good question change the world?

It's hard to know what really changes the world for the better. Is it good people, or good acts, or good ideas, or, perhaps, good questions?

Why do I ask? Well, in my idle moments I'm reading, scanning and learning the history of the Wireless World Quality Amplifier, the valve amplifier, that gave the British hi-fi in the 1930s and 40s. See here for what I have so far. (I shall be attempting to build a copy this winter).

Anyway it's now well known that in 1945 Wireless World also published a paper by the young Arthur C Clarke of the British Interplanetary Society (oh, and Royal Air Force). Less well known is the question that led to that paper. Here it is -
Is it theoretically possible to hold wireless communication with other planets? And is there anything in the nature of inexplicable radiations (i.e., apart from cosmic rays) reaching us from outer space?

(Wireless World, October 1942)

I'll post the published answer soon.

Tuesday, October 14, 2008

Thursday, September 18, 2008

Return to 21st century

It's been a while since I've posted anything about technology from the present century, so here goes -

On Tuesday I attended the London Google Developer Day, I have the T shirt to prove it!

As with last year I don't intend to blog about it in any detail, since there were other bloggers there who are far better at such things than me.  See UK Developer Blog: A blog is born (the official blog) for links to those blogs. 

For me it didn't have the buzz of last year, but I don't expect that's likely to be beaten any time soon.  Though for my colleague Angela it was pretty special as she was one of the non Googlers invited to speak.

So what did I learn.  Well that there's a lot of interest in Google's AppEngine, but some folks aren't such fans of Python - why on earth not?  And some folks worry about SLAs but don't have their own on site power generation (OK, maybe that's a Devon thing).  I learnt that GWT is very, very cool and I probably should have been using it for months if not years - so I'll try and fix that soon.  And that I need to watch all the presentations on You Tube ASAP, because it's not enough to just learn more about the things that seem interesting now.


Sunday, September 14, 2008

Mullard Five-Ten - out with the old.

Over the last week I've spent evenings removing bad components and replacing with good ones. I found a few old Dubilier 0.1uF paper in oil capacitors that looked sound and measured OK on the test meter, so I've decided to try them. They certainly look the part. I decided it best to buy new electrolytics (except for the large HT filter cap - expensive) - Rifa's from RS look good and have decent specs.

As for the output transformer I've decided to borrow one from one of my Vortexion's. It's far too big (you can see the original in the background of the photo), but it will allow me to try the amp out before spending a lot on a new one, or a rewind of the old one - I wonder how much that might be? These days it always seems cheaper to buy new rather than repair, unless you do the repair yourself. Umm, maybe I need to learn how to wind transformers.

Yesterday I switched it on for the first time, and it worked!  There was a lot of hum and some motor-boating so it was fairly obvious that the 50 year old HT smoothing capacitor wasn't up to the job.  In my junk box I happened to have an LCR 68uF 500V electrolytic that happened to be exactly the same diameter as the existing 40+40uF one, though much shorter  (I peeled off the bright blue plastic wrapper). So I've fitted this as C1 and for C2 used a 47uF 450V axial I had.  Both were bought about 12 years ago, so should be good for a few years yet.  It did the job.  There's still a little hum, though it vanishes completely when the EF86 is removed, so I suspect it's due to the wiring layout.   
Posted by Picasa

Monday, September 08, 2008

Acoustical (Quad amplifier) and Leak "Point one"

I don't own either of these, but I've been skimming through the many copies of Wireless World I've acquired and came across these adverts.
More constructively I'm listing the developments that led to the Williamson Amplifier - see here.

History of Quad
Leak (Wikipedia)

Sunday, August 31, 2008

Next patient - Mullard Five-Ten

One of my colleagues has just given me this valve (tube) amplifier built from a kit based on the Mullard Five-Ten design published back in 1954. Though this design is still being built by audio enthusiasts today, it seems this one is the genuine 1954 article. It's far from working condition though, so it's going to need a fair bit of work and a few replacement parts.
As it's likely this will be an extended project with a few stops and starts as I seek components - I don't really like to buy new, because it's expensive, and because new parts often don't look right - I'll be keeping notes in my mullard-five-ten wiki page.

Here are a few more "before" photos. Things to note are that this kit uses the higher power rectifier option of the GZ30. The quality of construction of the chassis is good, so it was certainly built from a kit. The quality of the build is competent, but not great.

From the rear we see the two EL84 output valves, these look as though they've been very, very, hot and a check of the output transformer reveals the primary is open circuit. Between the output valves can be seen the ECC83 phase splitter and behind that the EF86.
There's also an empty hole (far left) that's exactly the right size for a Bulgin 3 pin mains connector.

From the underside we can see that there are some very old electrolytic and paper capacitors. Note that the dates on these are "JUL 53".

A closer view of the hole for the missing Bulgin mains connector. It seems there was once an earth tag here that has been replaced with a picture hook!

Mullard Five-Ten resources

Adding a stereo demultiplexer to the Leak Trough Line 3

When I bought my first Trough Line 3 on Ebay a few weeks ago I did a little googling and found this article on replacing the stereo decoder in the stereo version and this one on an external decoder. It struck me that converting a mono tuner to stereo might be a fun project that could be achieved fairly cheaply with salvaged components. All I needed was a tuner with a stereo decoder, which I had. Fortunately for the Sony, before I ripped it apart an older manually tuned Chinon receiver came up on Ebay locally, so I grabbed it for a fiver. Here it is accepting the multiplex output from the Trough Line.

Being a fairly ancient receiver, mid 70s I guess, the stereo demultiplexer chip was the only IC in the box, so fairly easy to spot, a mix of tracing the wiring, from mono/stereo switch, stereo indicator lamp (N.B. lamp, not LED), voltage checks and poking the pins with the CRT revealed what did what and the fact that it used a single 12V supply. I reckoned the easiest way to get it into the Trough Line would be to cut out what I needed from the circuit board using a hacksaw. So that's what I did! Here it is with a voltage doubler power supply taking 6.3V a.c. from the Trough Line heater supply.

So far, so good. Now to try and fit it in the Trough Line. The obvious thing to do is to put it where the decoder is fitted in the stereo version. Wow, it fits! But it's a tight fit. Looking at the board more closely reveals that the tallest component is the smoothing cap for the regulated power supply. A modern cap of the same value taken from an old PC motherboard is half the size!

That done the installation can continue. I decided that screening probably isn't necessary. Perhaps I'll be proved wrong on this later. The voltage doubler goes underneath. Done!

Sunday, August 24, 2008

BBC FM radio transmitters and broken switches

This weekend brings a new FM aerial and the second Leak Trough Line is brought back to life.

As hoped the second Trough Line arrived, albeit with no valves, in fact no glass at all, the fuse and 'fuse lamp' were both missing. Before replacing the valves I checked continuity of the mains transformer and on/off switch. The transformer was OK but one half of the switch was faulty. So I removed the switch from the circuit. Connected to the mains, with chassis earthed, gave ac on the heater and HT windings. So I put an EZ80 rectifier in the appropriate socket and checked the HT dc. All fine. With the rest of the valves in everything was still good. With aerial and amp connected I now had a working tuner. Unbelievably easy.

Checking the on-line Maplin catalogue for fuse lamps was a disappointment, it seems they've gone the way of variable capacitors and 3mm (1/8 inch) wander plugs. Such things are still available from some sources, e.g. Farnell have Belling Lee wander plugs, not cheap though. Then I noticed that my "donor" tuner, bought for £4.99 on Ebay, had 6 of them. They're 8V, rather than 6.3V, but perfectly usable. The main purpose of the donor was to provide a stereo decoder. I'll describe how I extracted it in a later post.
A few minutes use revealed that not only had the mains switch failed, but so had the two slide switches. Fortunately my Trough Line surfing had already take me to Keith Snook's page on repairing and tuning the Trough Line. I pretty much did exactly as Keith described, though I noticed that there were some fine cracks in the rubber cushion behind the brass strips. Which made me think that the rubber was probably quite a bit harder than when new. As a, probably temporary, remedy I cut a couple of small pieces of self amalgamating rubber tape and super-glued one to each of the cushions. Oh, and to clean the contacts I rubbed the ball from an old PC mouse over them. Now both slide switches are working well, and I've replaced the volume control, and its faulty switch, with a rotary switch.

As for the aerial, I've replaced my cheapo omni-directional loft aerial with a cheapo 3 element directional one. Which way to point it though? Perhaps this is another job for Google Earth - see BBC FM.

More Trough Line links -

Monday, August 18, 2008

Experiments with the Leak Trough Line

Reckoned by some to be one of the finest FM tuners ever, the all valve Leak Trough Line is a very simple radio. Trough Lines can be bought fairly cheaply on Ebay (well for under £50, though some do fetch much more). I've recently picked up a couple for under £20 each.

Initial impressions of the first buy was that the sensitivity really is very low indeed, but it sounds great. The accepted audiophile solution is a big outdoor aerial. Fair enough, but are there alternatives, e.g. using a decent low noise RF amplifier? This was to be my first experiment with my newly acquired Trough Line 3, but then I saw an opportunity to acquire another very cheaply, albeit with no valves. Rummaging through my boxes of valves revealed that I had spares for everything, including the tuning indicator, except for the ECC84. So what is an ECC84 and did I have a suitable alternative? Looking at the circuit diagram I could see it was the first RF stage, but the circuit diagram was hard to read so I looked at the circuit for the stereo version. Hey, it uses a different valve, the ECC88, these I have.

ECC84, PCC84, ECC88, E88CC, PCC88 - what's the difference? If like me you've got a lot of old valves from old TV receivers, radios, and test equipment you probably don't have any spare ECC84s, but you may well have a few of each of the others. The good news is, they're all usable in early Trough Lines that use the ECC84, though some modification to the wiring of the Trough Line will be needed to use any of the 88s. It seems the ECC88 was an improved replacement for the ECC84, though the base connections aren't exactly the same. It also needs a slightly higher anode current. To check this without modifying the Trough Line I put together a simple adaptor. Here's the circuit.

And here's what it looks like.

And yes, it works! In fact it works very well, bringing in stations that couldn't be received at all with the ECC84. So I'm making this a permanent change to my first Trough Line. Hopefully nobody reading this will imagine I have any special powers or knowledge; all the information required to put together the adaptor can be extracted from the two circuit diagrams, but to be completely sure I checked the valve specs at the Virtual Valve Museum. Here you can also find details of the other valves I mentioned. It's worth noting that they aren't exact equivalents, since ECC84 and PCC84, etc. were designed for slighlty different uses and have different heaters.

Some explanation is possibly required regarding the heaters. The standard heater voltage for mains powered radios from about 1940 (earlier in the USA) was 6.3V. However for AC/DC sets and TVs the heaters were connected in series and so valves were designed to all draw the same current. Valves with a first letter 'E' are for parallel use at 6.3V, whereas those with a first letter
'P' are for serial use at 300mA. What you'll find is that for all these valves the heater voltage and current is within 10%, so for practical purposes they are all usable at 6.3V, and most likely all but the ECC88 are usable at 300mA (I've not tried this). Note this is not generally true for E and P valves, especially not output valves. Other heater variants are also possible, for example a UCC84 would have a 100mA heater.

Before -

And after -

I've seen PCC88 as substitution before. Though these are radio frequency (VHF) amplifier cascode triodes they were used unstead of the last ECC82 in my Ferrograph tape recorder when it was built. I'm not sure why though. What this does show is that the two triodes in the (E/P)CC88 are the same, this doesn't seem to be the case for (E/P)CC84.

Sunday, August 17, 2008

Messing about with capacitors

After a couple of messing about with valves posts I was going to call this messing about with transistors, but mostly it has been capacitors. My wanderings through my electronic junk has now reached the 1960s. Again the challenge is what to keep and what to get rid of. Fortunately I've not kept much from this era, the age of black and white TV, transistor radios, and FM. I've got one item to sell, so on to Ebay to check prices and see what's hot or not. Errrmm, interesting maybe there's more to the 60s that I thought - British hi fi seems to be selling well, but with some bargains too. The temptation was too great so I snapped up a Leak Stereo 30 amplifier and Trough Line 3 tuner. These were described as "in good condition", which I took to mean complete, but not working. I reckon it was worth the (not much) money to have a couple of boxes with MADE IN LONDON ENGLAND on them to mess about with.

A few days later the postman struggled to the door with a large box. I quickly unpacked the box and opened up both cases. Everything seemed present and correct, so off they went to the workshop.

The tuner worked perfectly, sure it needs more signal than I have at present, a better aerial is needed.

As for the amplifier, the left channel worked but not the right. So I clipped a lead across the wipers on the volume control and the right channel came alive. Both power amps were fine, so the problem was with the right pre amp stage. A glance at the circuit diagram shows that there are two routes for the tape amp input one through the pre amp, and one direct to the power amp via the tape monitor switch. However plugging a Sony tuner in and flicking the tape monitor switch gave output on the right but not left! Tracing the signal showed the fault here was with the hi/lo slider switch on the rear panel. Replacing switches that will most likely never be used seemed pointless, so I just soldered all the hi/lo switches to the lo setting. That done I traced the signal through the the right preamp. It vanished at C16R! So something was wrong at T3R. The capacitor didn't look quite right, the plastic cover was clouded, so I pulled it and replaced (25uF, 25V axial). Still no joy. Checking the voltages around T3R showed they were very wrong, emitter at almost 0V. C17R (125uF 10V axial) was also faulty, replaced and now everything is fine!!!! Interesting that C16 had failed open and C17 closed. Odd things electrolytic capacitors. Perhaps I should replace them all, but it seems like a lot of work for little gain.

Here's the tuner. It's mono so I'll have a go at adding a stereo demultiplexer soon. I think I'll try and take one from another tuner (maybe the Sony), rather than build one with new components.

Sunday, June 22, 2008

Still messing about with valves

Here are some pictures of one of the older electronic components in my "collection".

It's an early 1920s valve. Valves like this were used in the very first broadcast receivers around the time the BBC was formed. This one still works, which given its age and type is probably unusual - it's a bright emitter or "r-type" so only has a few hundred hours working life. With the heater connected to a 1.5V cell it lights up like a light bulb! You can just about make out the internal construction in the photo - a thin wire filament (cathode) with a spiral grid inside a cylinder (anode).

Since there's not a lot on information on very old valves on the web here's some technical details. Manufacturer: Métal Radio (France). Model: BW 303. Markings: 1,6 - 1,8V 30 - 75V XX.

Now I must go and try and fix my AVO valve tester, it's cutting out and putting 110V across the heater terminals. Perhaps this has something to do with the 0V and 110V coarse setting for heater voltage being next to each other....

Monday, May 26, 2008

Messing about with valves (tubes)

It's been months since my last blog posting, so there's not a chance of covering the many random things I've been up to of late.

Actually there are a couple of posts that I didn't finish, so never posted. Back in March I nearly posted about my largely unsuccessful efforts to spring clean the garage (well workshop come junk store).

I've got a very large stash of electronic 'stuff'. My stash includes crystal set components from the 1920s, a couple of working 1930s battery powered wireless sets, mains sets from the 1930s, 40s and 50s. There are many other 'treasures' including test equipment such as Avometers, and a Mk 1 Avo valve characteristic meter. And of course lots of components such as valves, connectors, even pieces of wire and nuts and bolts. Most of it is mixed up in large cardboard boxes in the garage and attic.

So how to deal with all this stuff and sort the junk from the treasure? There are certainly a few things that I believe to have some value, the Avo valve characteristic meter and the Ferrograph tape recorder. A couple of 1950s bakelite cased radios, both with cracked cases - they can't be worth keeping - off they go to the local auction. What about the two RF signal generators? Maybe I should keep one (now you can see how I come to have so much stuff to start with). I've decided to keep the TE20D and sell the ancient Triplett 1632 (it made £16 at the auction).

Well I did eventually get around to throwing out some the junk, after many enjoyable hours salvaging things I might find useful, motors from disk drives, crystals and sockets from computer motherboards, and other interesting (to me) bits and pieces. Along the way I got the Avo valve characteristic meter working, and even tested a few ECC82 and ECC83 valves to replace the broken ones in the Ferrograph - so that now works again.

As a consequence of these diversions I've now set up another website, Wireless Words, and a wiki, self-aware.

So on Saturday I took the van, loaded with scrap metal, circuit boards, and other rubbish to the "recycling centre". Where I discovered this "treasure" -

It was mine for one pound! OK, so I bought some rubbish, but it's interesting rubbish. A 1930s wireless set with push button tuning and a "magic-eye" with sockets for pickup and television sound. Being as geeky as I am I could tell it was pre-WWII, but probably only just. Well it turns out it's a 1938 set, here's the evidence -

Women demonstrating an Ekco radio, Radiolympia, London, 1938.

Thanks to the Science and Society Picture Library. It would be fair to say I've got no idea what I'm going to do with it. But the motorised tuning mechanism lends itself to a remote control system of some sort. A computer controlled valve wireless perhaps.

Tuesday, January 29, 2008

Google Earth in your pocket

Though I expect many of my colleagues will just shrug and wonder whether I can get any more geeky, it seems that a couple of my geek interests have, probably temporarily, crossed paths.

Over on Ogle Earth there's some speculation as to whether Nokia buying Trolltech might bring Google Earth to Nokia phones, whilst on Internet Tablet Talk the speculation is about the impacts on Maemo.

Well as an Internet Tablet carrying "alpha geek" maybe I can add further confusion, or not, by posting pictures of Google Earth "running" on a Nokia N810.

In truth it isn't actually running on the tablet, the tablet is using the laptop to run Google Earth and using VNC to display the graphics and get the stylus and keyboard input. The end result is much the same though - so long as you've got a wifi connection to a suitable "host". Though not ideal for Google Earth, I've used this method to run applications "in the cloud" using Amazon EC2.

Sunday, January 27, 2008

Encrypt your data. How hard can it be? [1]

UPDATE - Development of TrueCrypt was discontinued back in 2014 and has subsequently not been maintained. A number of security flaws have been uncovered and as a result we are reaching out to people to highlight a list of alternatives.

Here's the list (along with further details about TrueCrypt no longer being maintained) -


In the light of recent events here in the UK[2] I thought I'd investigate data encryption - well try it out. Fortunately my work doesn't require me to handle confidential data, and these days, for the most part, I don't carry much of my own personal information with me. Though I've long been either pragmatic, or perhaps wealthy, enough to consider that the loss of any portable electronics - phone, laptop, etc. would be more of a nuisance from the data loss, than the physical loss. So maybe the data does matter to me enough to consider encryption.

As a scientific programmer much of my life is spent in the Unix/Linux world, added to which I'm a (Linux based) Nokia Internet Tablet enthusiast, so I felt I needed something that would allow me to exchange encrypted data between the Linux and Windows worlds. A quick Google led me to TrueCrypt, Windows and Linux versions available for free download, and the source too, so maybe I could build it for my new N810. To cut a long story short, in between checking on a sick alpaca, I was able to build TrueCrypt for OS2008 - the latest Nokia tablet OS over the weekend. OK, I've not proved it's totally secure, but how hard is it? Not very.

[1] What's the point of rhetorical questions?

Sunday, January 13, 2008

My first week with the N810

I've had my new Nokia N810 for just over one week. It's the gadget in the bottom right of the picture, also shown are a HP calculator from 1985 (which I still use but it lives in my desk drawer) a Palm IIIe and last year's Nokia N800. So what's it like? Well a colleague who owns a N800 described it as "techie bling", which is what HP calculators were in the 1980s, so it's probably a fair description.

Initial impressions are that the keys on the keyboard are too small, the miniSD memory slot is too fiddly, the keys on the top are very hard to find with the keyboard open and the display quality much better than the N800. The built in GPS is interesting, and I'm bound to find uses for it.

Weather satellites

Over the holidays I built myself a weather satellite receiver. It receives data from MSG, Meteosat 7, and GOES 11, via the EUMETCAST relay on Hotbird 6. Not being a satellite TV user it's a few years since I last messed around with kit like this and it's amazing how cheap and simple it is today. Though getting everything working as I wanted it in Linux was more of a challenge. There are more photos of the "receiving station" in my Picasa album.