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 :)