Wednesday, May 20, 2020

Recreating 1920s crystal-set wiring

Continuing the restoration of the 1923 Edison Bell crystal wireless set, the wiring needed to be re-created. The remnants of wiring in the set as it arrived was clearly not original - at some stage the original wiring had been modified to probably use a 'modern' diode roughly screwed to the roughly drilled extra holes in the baseplate. The old wiring and all the lamp-parts were likely removed to make space for this. The thin cotton-covered wire itself also looked incorrect - the length of PVC-insulated wire was certainly not original.

Even though there is not that much information on the inside of these Edison Bell sets, or even on 1920s crystal sets in general, some pictures could be found online that showed the inside wiring. These are of three different units, so that common features to these three are likely to be original factory fitted parts.

From these images, it becomes clear that the set was originally wired with 'thick' wire rod. This was actually quite common in 1920s radios and electrics; bare wire forming a neat three-dimensional circuit. From the pictures made a guess at the diameter (probably just over a mm) and got some tinned copper fuse wire of just over a mm diameter.

To straighten the thick wire ('rod' material, really); the regular procedure. Unwind and manually un-bend a length of the wire. Then clamp one end in a vise (or clamp to the bench-edge) and the other end in a drill. By pulling and then twisting the wire left and right it gets nicely straightened. A hand drill is good to use as it gives a bit of 'feel' for how you're deforming the wire and when to twist back. For safety, always keep a bit of tape over the wire ends (cut wire is rather sharp and springy...).

With needle-nose pliers and a bit of 4mm tubing as former, bent loops in the wire ends and made the sections to fit the terminal posts. The first leads to fit were the connections to the crystal detector - these must've been formed in-place, as they pass through the small hole in the base-plate and should have loops at both ends. The loops at the detector crystal-covers need some tweaking with a kink in the lead to clear the glass. (Suspect the original may have used slightly thinner gauge wire, or perhaps even not made a loop there at all - just a straight wire-end?)

Following the same procedure and consulting the reference images of original sets, the complete wiring could be recreated and fitted again. Also the leads to the slightly-different reproduction lamp-fitting was added.

Bringing the leads to the far end of the variometer seems a bit odd - reversing the variometer to have the terminals closer to the baseplate would've saved some copper. But perhaps the ease of fitting (or whim) was more important than a few inches of copper wire back in 1923.

With some thinner cotton-covered wire to the battery-compartment, the lamp again works too. (From the pictures it could be seen that this should also be thick 'wire' with a green insulating sleeve - but there's a limit to authenticity here, this is more practical.)


Sunday, May 10, 2020

Missing fittings and an assembly puzzle

Continuing the restoration of the Edison-Bell Type B crystal wireless set, a next step was to find replacements for the missing fittings. A British product of nearly a century ago, it naturally does not use any metric standard-size fasteners or fittings. This made it a bit of a puzzle to determine the right sizes - and then a puzzle how to get these today.

From playing with 1920s vintage Meccano (the Electrical Outfit), had learned that BA-threads were common in electrical equipment of the era. Checking with a Meccano part 304 (6BAx1/2" screw) confirmed that e.g. the mounting holes for the lamp in the panel were indeed 6BA. Measuring the remaining fittings on diameter and threads-per-inch confirmed all fittings to be 4, 5, and 6BA thread. (To measure t-p-i, firmly roll the screw in a bit of paper or cardboard to make clear marks and then measure ~10 marks to get the value.)

Again the internet-age allowed ordering of individual BA-sized brass screws and nuts. These duly arrived from Britain (despite current conditions!) and were quickly nickel-plated like the originals. One 4BA screw first had the cheesehead filed down to a flat top - from the tool-marks on the original contact-studs, this was exactly what the Edison-Bell must have done in 1923.

Now all fittings cleaned and missing fittings replaced by new - the panel looks very presentable again:

No more unsightly empty holes. Also underneath, the missing screws and nuts are added - more complete, but still without wiring. (The variometer is still assembled wrong in the below image - that one turned out to be quite the puzzle.)

The battery-studs and lamp-holder-screws are 6BA, the variometer fittings and mounting screws are all 5BA, as is the detector mounting screw. All terminals and studs are 4BA. (In case anyone has one of these radios and needs to replace a fitting.)

The variometer (or variator?) is a rather clever set of parts by Edison Bell - they also sold it separately for building into other sets and it can be assembled in several ways. The mounting brackets can e.g. be mounted any side - also it took me a while to work out the correct, intended assembly of the circuit for the coils.

Both the outer and the inner sphere have 48 windings, at ~65 and ~70mm diameter. These should be in series, allowing the centre sphere to rotate and work with or against the overall inductance. A surprising element (to me, at least) is how the outer shell coil-halves are connected. This is simply a pressing of the bare wire agains the small nut in the other half that clamps that other half's wire.

The two pivot bolts that hold the inner sphere are the leads into and out of its coil. The brackets on those bolts allow routing the circuit to the outer coil terminals. Took a bit of puzzling, this.

One other item was the dial scratching the panel. It turned out to not be warping of the dial (as originally suspected), but a manufacturing defect in the top knob. The middle insert-nut must have been placed slightly askew in the mould, before over-moulding. This was mitigated by shimming (waxed paper) between the top-knob and dial.

The markings in the dial were then re-done with white wax - following again the advice from the excellent book on typewriter repair by Teege.

Radio repair with thanks to the Typosphere and Georg Sommeregger :-)

Saturday, May 2, 2020

Obtaining obsolete accessories (B&L part nr. 31-59-59)

One of the entertaining challenges with obsolete technology can be finding the correct accessory or spare part. The item itself is long obsolete, the manufacturer no longer services the item (or more often the manufacturer is long defunct). However the digital age with the global flea-market that is the internet often helps out - if not available right away, then it's a matter of laying in wait for a time.

Sometimes on the other hand, you just stumble on an item by accident - as was the case with this accessory for my plain-stage Bausch & Lomb type H microscope. This microscope is the simpler (cheaper) version, catalogue number 31-21-50-08 with a plain stage priced at USD 135 back in 1935.  (Who at B&L came up with these type numbers? There probably is a logic there...)

(Catalogue image from scan at

To later add a mechanical stage to one of the lower-cost H microscopes, Bausch & Lomb sold attachable mechanical stages. These were available both with and without a graduated scale. Not a cheap item, either version. The graduated stage shown here in the 1940 catalogue for USD 33.

(Image also from the great library of B&L literature at

Purely by chance and not specifically searching for it, I spotted this B&L mechanical stage with graduated scale for sale online.

As it was offered for a reasonable amount, and the chances of the exactly-right accessory being available a next time being slim, went ahead and 'bought it now'. A rare item to find - Bausch & Lomb microscopes are relatively plentiful in North America, but in Europe they're uncommon. Specialised accessories more so. Even with international shipping (Portugal), it still came in reasonable at around 20 Euro.

It is of course 'vintage', so there's some play on the horizontal movement and the vertical-movement wheel is a bit bent (must have gotten a heft knock). But other than that, it is functional and complete with the thumbscrews to attach it to my plain-stage type H microscope.

So now a B&L type H fitted with the attachable mechanical stage.

The stage has straight-sided knurled knobs. From some scouting around and checking serial-numbers and images, it seems that in 1940 Bausch & Lomb changed their microscope knobs and wheels from double-knurled to straight. This makes this accessory indeed likely a 1940s item (still dimpled face to the wheels); a good match for the 1939 microscope.

Already used to chase pond-life around a slide - and neat to be able to add the accessory to this obsolete piece of technology. (I.e. entertainment for the 'completist' in me :)

Sunday, April 19, 2020

Sprucing up an induction coil for the crystal set

Crystal wireless set restoration: a whole range of coils could be purchased to be used with the Edison Bell wireless set. These tuning-coils change the overall system inductance and thus make the radio tune to a different frequency range.

As part of the restoration process of this crystal set, I managed to source one such coil - a relatively low-inductance specimen, a number 50 coil. Many manufacturers made such coils, with various winding methods. The Edison Bell versions of this component are nicely elaborate, wound on nested hexagons and bound to the plug-base by cord. The outside is then wrapped with tortoise-shell pattern celluloid - at least I think it's celluloid.

As is to be expected after 90-odd years, the item was somewhat dirty and the celluloid is cracked. (Celluloid does not always age well...) 

Thankfully, like most vintage technology of that era it can be taken apart and repaired. Not sure what to do about the badly shrunken and brittle wrapper, for now it's been given some backing-tape to stop it 'flapping about' to limit further damage. It could be replaced by a reproduction wrapper, but for now we'll keep the frayed original.

Untying the knot allows the green cord to be removed. Removing the two screws at the side of the base then makes the whole assembly come apart for cleaning. The glue that originally helped to hold the plug-base onto the coil has long dried out and lost any adhesive power.

All the metal parts were given a good cleaning and then a polish. As can be seen in the comparison of the two brackets - the power of Brasso...  (:

The wire makes contact with the plug-prongs by being pressed between the celluloid wrapper and the bracket. The copper wire ends are of course rather corroded by now, even when shielded behind the bracket. So before assembling, given a sanding down to bright wire-ends for good electrical contact.

Placing the plug-base back in position, the prongs and brackets can be screwed back into place. A quick check on continuity to be sure the wires make proper contact.

The cord was rather faded. To 'spruce it up' a bit, the faded cord was given a quick soak in green dye in a small petri-dish. Before (left) and after (right). This does not restore it to original, but does evenly colour the cord and removes some very faded spots.

The next step is to tie the coil and plug together again. A bit tricky to get the lengths right, starting with the cord once through the hole and then winding left and right wraps with the ends, finally bringing the longest end over to the other and tie off. (It makes sense when you've the coil in your hands.)

With refreshed cord, cleaned metal bits and wrapper held-in-place, it can be mounted again on the set. (The Edison Bell crystal set is currently in the process of being restored. Several parts still to be sourced, but it is cleaning up quite nicely already.)

Thursday, April 9, 2020

Edison Bell Model B Crystal Set

The small wooden box still has the decal stating it to be an "Edison Bell Radio".

In their catalogue it was named the "Model B Crystal Set" and according to the online Radiomuseum site the model dates from 1923. Being a British set of that time, it has the BBC logo and the notice that it is approved by the Postmaster General, permit number 615.

The radio is not quite in original 'as-found' condition. It's been worked on - one of the things done to it is that unfortunately the whole case was given a coat of varnish - fairly rough - covering the rusty latch and leaving faint drip-marks on the front. On the other hand, the thick layer of varnish probably helped preserve what is left of the decals.

Opening the lid, inside are all the controls and terminals. It is mostly complete; one of the studs for a switch is missing, but the twin detectors are there. Also all the terminal screws are present and correct. A shorting plug for the connectors for an extra tuning-coil would've been nice, but that'd be asking too much. Everything is a bit dusty and dirty, but this should clean up fine.

The set is rather fancy, with twin galena crystal detectors ('cat's whiskers') and an extra little lamp to illuminate the detectors. That is what the little drawer at the side is for, to hold the dry cell for the lamp.

One of the detector glass cover tubes was replaced by a length of measuring cylinder. The rear glass is original from the early 1920-ies, with a section whitened for better visibility of the whisker.

Unscrewing the "Eboneum" panel and turning it over, the key component is still there. The variator looks fine, yet to be tested. Everything related to the lamp is however gone; no lamp-holder, wiring or even battery studs in the tray. Also the wiring is a bit suspect - not certain the green cotton-covered wire is original. This radio was definitely tinkered with, perhaps already 40-odd years ago. In addition to the case having been lacquered, the wiring was certainly modified and some components were removed.

Nevertheless it's in decent shape with the important bits still present.

When new this must've been exciting new technology, but this crystal radio has been obsolete technology for a very long time.

A neat project to slowly bring back into shape and make function again.

Wednesday, April 8, 2020

Newly arrived - wooden box

Just arrived, another little item in the category 'vintage technology obsessions'. Continuing to 'dream lo-tech', I rather splurged on this little item. In these times especially, this makes a grand little escape by exploring and restoring.

It is mostly complete - the bits missing can probably be re-created or mocked-up by me. It is not a typewriter, but definitely contemporaneous with the emergence of the portable typewriter as a 'consumer product'. This item was the high-tech of its day, relatively expensive too.

Next up is a first cleaning and then more pictures (and details :)

Friday, March 6, 2020

Newly discovered Melotyp (from the shed)

In the March 4th program of the 'Tussen Kunst & Kitsch' television programme (similar to the BBC's Antiques Roadshow), a Melotyp machine was shown.

This is the music-typewriter also known as the Nototyp or the Rundstadtler machine. Seen earlier in an old magazine article (here posted about some years back) and it was the subject of a very informative post at the excellent Australian Typewriter Museum blog.

This particular specimen was brought to the show by the owners who'd found it in their dad's shed. Failing to sell it at a jumble-sale (thinking 10 Euro was just a bit too little, holding out for at least twenty...), they did a bit of online searching and then decided to take it to the show.

The fragment on the typewriter starts at ~15m into the show. The machine is shown and some background to it is given by the expert.

The decals on the top-plate are in great condition.

Same for the keyboard, in great condition for its age.

And the machine still types music too:

What looks like a rubber-band attached to the carriage (first screengrab image) in the show suggests that the carriage spring of the machine is broken or otherwise out of order. Given that it is essentially an Adler with modified type, it should not be too hard to fix or replace the carriage spring.

Unlike regular Adler's, this Melotype is very rare indeed. This newly found machine probably increases the total number known by ~10%. (And nearly sold for a tenner - who knows; for home-decoration or steampunk project?)

There are it seems still rare machines out there in sheds and attics. And for the Melotyp - maybe the company did manage a first production batch of machines beyond the first prototypes as suggested from the advertisement - otherwise another of the five remaining in Europe has now been located.