Replica Ekco A22T (A22 export model)

[Aerodyne]

I can only echo the sentiments of others on this thread when I say that your skill is amazing. That, and your obvious dedication to perfection, both do you great credit. A very interesting and enlightening item, Robert. Superb work.
-Tony

[Yorkie]

Really great stuff Robert... your perserverance is inspirational.

I found the use of colour swatches most interesting as I too have created dials. See BVWS Bulletin 2009 Autumn. Some were only black or pretty basic colours that were easy to match by eye. Of course how much have the colours changed with time but you can only match to what you have.

For a silk screened dial for an HMV 650 / 655 I was in the hands of the screener and it was up to him to do the best he could to an original but damaged dial. Actually the result he achieved is amazingly close to my eyes, so well done to him.

Now a plug I still have a few dials left from the small quantity I had made (CNC glass + screening) so if anyone wants one please get in touch. When they have gone there will be no more.

cheers Gary

As with Robert's outstanding A22 dials, created from a 'blank sheet of paper' so to speak, and featured in the Bulletin with Robert's splendid A22 total restoration, your article in the Autumn 2009 Bulletin 'Making Dials' took us to a new level, exploring the use of decals (water-slide transfers), 'window film' and the screen printing of the HMV650 dials. It's one thing to patiently clean up a scan of an old dial, it's quite something else to use CAD software to create a brand new replica dial, getting all the legends in the right place, the right size, the right font, and the right colour.

As with Robert's Ecko dials, your HMV650 dial is so distinctive, and such an important eye-catching part of the set, that without it, however much effort is put into the unseen work on the chassis, the set is never going to look its best, and in some cases, will basically only be fit for spares. I have an Ekco AC77 which I was intending to restore, but as often happens with that set, the white markings have flaked off the dial glass, and given that white can't be printed on a conventional printer, it's a non runner. Same goes for a nice little Bakelite Marconi set.

In the case of your HMV650 dial Gary, your article in Autumn 2010 Bulletin on the total restoration of that radio, including issues with the IFTs, and lining up with a wobbulator and scope, was highly informative and a very interesting read. Forum members who are BVWS members will know that like Robert and Colin ('Retired'), you've been a prolific writer in the BVWS Bulletin for several years, including your Gecophone 'Stork' loudspeaker restoration in the latest Bulletin which hit my doormat yesterday. It's not easy to single out particular favourite articles, but if I had to chose one of yours Gary, I think it would be the 8-page article on your total restoration of an Ekco AC97 in Autumn 2008.

As with articles by Colin, Tony Thompson, (Aerodye), and Robert, these detailed well researched articles cover all the tricky, seemingly insurmountable problems, such as speaker repairs, cabinet repairs, dead sets, rusty chassis, missing knobs and so forth, inspiring the rest of us to tackle ambitious tasks that we'd never have contemplated had it not been for what we glean from the experiences of skilled restorers such as yourselves.

I don't know if it ever crosses the minds of many who might wonder how much authors are paid for the splendid Bulletin articles. The answer is simple - didly squat - not a single penny.

So thanks guys, and thanks for being active members of this friendly little meeting place for like-minded consenting adults who get their thrills from restoring what - to others - is junk, fit only for landfill. Till they see the end result that is!

[Radio Fixer]

Thank you David: it really helps to build up the enthusiam to write another when folks say to you "Hey! I enjoyed your last article.

Its a pity more people dont have a go at it... at the recent BVWS, AGM, Mike B once again asked for 'copy' and said dont worry about standard or pictures... we can knock it into shape. I can tell you from years of talking to Carl that they are always short of material.

As to Robert's efforts perhaps the most impressive thing, to me anyway, is the reverse engineering to make the SW coils. I dont think I would have come up with that, or been able to do it. I wonder what computer prog he used? Maybe Excel? You can do a lot with that. Years ago I was a Visual Basic fan and spent hours at that driving my wife mad... so I packed it in and started on the radio restorations.

As to your Ekco AC77 dial, that as far as I know, is simply a flat piece of glass with no beveled edge or hole for the pointer needed as with the 650. So cheap to get those cut. Also, its possibly a much more common set and so with a lower selling price it should be easier to sell off enough to get back an outlay on glass and screening. I reckon I could take on the artwork over time fitted in with other jobs.

But as you are not local you would have to find a screener, or use my chap by post. Its scary with screeners as you lay out a lot of money with no idea if they are going to come up with great results and perfection is needed for dials IMHO. When my guy said they were done I went to the works with some trepidation I can tell you.

cheers Gary

[Robert Darwent]

Thanks Gary, Tony and David for your very kind comments.

I found the use of colour swatches most interesting as I too have created dials... ...Of course how much have the colours changed with time but you can only match to what you have.

I would agree Gary, that is impossible to know for certain what the exact colours/shades of a 'pristine' original dial were like back when the set came off of the production line. We are only left with what sunlight, etc has transformed them into 60+ years on.

My intention was simply to produce something that was visually pleasing and acceptable, and approximated the dials commonly seen on sets today. In fact, some of my artworks incorporate selective fading and other faults to make them appear 'aged' in an attempt to make them look more authentic.

I found the use of the colour swatches most helpful. They certainly narrowed down the field when it came to finding the best shade for the dial background. Also, being able to do a large part of that 'virtually' speeds up the process no end and saves on time and printer consumables as well.

I wonder what computer prog he used? Maybe Excel? You can do a lot with that.

Nothing that modern or sophisticated I'm afraid. I wrote a simple BASIC program via an emulator of the old Atari ST computer on my laptop. Back in the late 80s to mid 90s I used the STOS BASIC programming language on the Atari ST extensively and I'm very familiar with it still.

Although it is archaic by modern standards it is still fine for doing such things as coil calculations. Plus knowing the software back to front, as it were, I simply can't see the point not using it in favour of something more up-to-date when it still performs admirably.

I have a similar attitude towards the graphics package I use, Micrografx Picture Publisher. It too is a 'dinosaur' compared to more recent offerings, but I'm loathed to change and go through the learning process again when it does all I ask of it.

Regarding your articles in The Bulletin, Radio Bygones and the like, of which I'm only too well aware and read with eagerness. I can only share David's sentiments and add they form the 'benchmark' standard in terms of excellence, thoroughness and quality that the rest of us strive to emulate. Consequently, I was quite humbled to read your earlier comment that you find some of my work "inspirational". That is very kind of you Gary, and very much appreciated!

Best regards

[Radio Fixer]

Dont want the thread to keep getting into a chain of thank you's... but never the less thanks for the kind words about my articles and that you enjoy them. Yours is inspirational to me (as are some of Retired's) in the dogged attention to detail. I know I sometimes cut corners but thats probably because I work on too many sets and am too prolific at writing articles. As examples, your attention to matching, even going to viewing in the virtual cabinet + adding aging of text. As an example of Colin's dedication he stripped a set and put all the bits back with rivets, using a drill press and homemade tools. I cheated and used nuts and bolts. But mechanics are his love... actually I would have been scared at breaking irreplacable valve bases.

Cheers Gary

[Robert Darwent]

Continuing with the project from post #7;

Winding the SW coils

Fortunately, I had a head start when it came to making the four 'new' coils required. I had scrap Ekco A23 and A28 sets from which to scavenge parts. The A28 chassis in particular was most useful, having several bandspread short wave ranges and sixteen coils in its coil-pack. The coils are of the same overall size and shape as those used in the A22, so it was possible to use some of those as 'donor' coils rather than start completely from scratch with a bare coil former.

I found three donor coils that gave the inductance values I had calculated simply by rotating the alignment slug in or out, the value needed being comfortably within the coil's existing range. For the fourth, the best match I had was a donor coil that was slightly higher in inductance, but by removing a couple of turns of wire from its winding I brought the value down into the required range.

It was a simple matter to remove most of the wax sealing this coil's winding with a soldering iron, unsolder one end and take off a couple of turns. I was careful to ensure that enough wax was left on the winding to keep the other turns firmly in place whilst carrying out this procedure.

Each of the four coils now needed a coupling winding adding over the main inductance winding. From dismantling a similar spare coil, I determined that this coupling winding consisted of approximately five to six turns evenly spaced on top of the main winding. Using a similiar gauge enamelled copper wire, I added this coupling winding to each of the four coils in turn. The wire ends were terminated by bringing them out through unused holes in the top of the former, later permanently secured by soldering to small solder-tags.

Below is one of the coils resealed with wax after the addition of the coupling winding;

       

Next came the task of stripping the existing A22 coil-pack. Below are images of how it looked originally;

               

After careful removal of all the components I was left with the following unpopulated board;

           

Note; the addition of an extra trimmer capacitor to the board. This was necessary due to all three coils in the aerial section requiring a tracking trimmer. The coil-pack used in an original A22T also has this extra 'sixth' trimmer, compared to only five found in a standard A22 set.

The additional trimmer was scavenged from the scrap A23 chassis. I found that I could modify the mounting arrangement used by the group of two existing trimmers to securely hold it in place. This leaves the sixth trimmer standing a few millimetres higher than the others, but since its fixing is mechanically sound, I considered it acceptable 'tacked' on to the end of the board in this way.

[pwdrive]

Good article Robert, you have done well.

Lawrence.

[Robert Darwent]

Rebuilding the coil-pack

I modified the existing A22 circuit diagram to reflect the different bands offered by an A22T, the donor parts and the calculated padder and tracker capacitors for each range;

   

The following diagram shows the layout for the A22T coil-pack;

   

I began with the slightly easier 'Aerial' side of the coil-pack, adding the three coils one at a time and soldering the required connections between the bank of trimmers running down the side of the board and the band-switching wafer mounted in the middle. Working carefully and methodically, I successfully completed this side of the coil-pack;

           

Continuing on in exactly the same fashion, I rebuilt the 'Oscillator' side of the coil-pack. This section was more difficult, due to having to accomodate the additional large padder capacitors in the limited space available;

               

Note; the two large 6800 pF 1% mica capacitors. These are connected in series to make-up the calculated, non-standard, 3400 pF padder value required for the S2 oscillator range.

Finally, I should add that none of the original coils and padder capacitors were used in the rebuild and have been carefully stored. Even the medium wave coils came from the scrap A23 chassis. Therefore, if so desired, the coil-pack could be converted back to a standard A22 model.

Next instalment: Chassis restoration.

[Robert Darwent]

Good article Robert, you have done well.

Thank you Lawrence, appreciate your reply and kind comment.


Chassis Restoration

As mentioned at the beginning of this thread, the A22 chassis which forms the basis of this project was acquired semi-complete. Specifically; it was minus a dial, loudspeaker and a set of valves. Although the chassis was very dirty and the wiring had seen better days, it was otherwise complete. It even had a chunk of its original broken bakelite case still attached;

                   

Note; not shown in the above images, the chassis also came with the metal trivet that the speaker cloth is attached to and mounts on to the central spindle. Unfortunately, the bronze bezel that goes around the circumference of the cloth was missing.

I adopted the same approach that I outlined in my 'Ekco A22 rebuild' article (BVWS Bulletin, Vol.36 No.3, Autumn 2011 issue), which was to completely strip the chassis and undertake a full restoration.

All the important wiring connections were first labelled and marked for each of the major components before they were removed. Working steadily and methodically in this way, I quickly had the chassis completely stripped whilst being certain of exactly how everything was originally connected.

I could now begin the task of cleaning and painting the two major sections of the chassis. After a thorough clean and the removal of any flaking original paint, each part received a coat of silver or black smoothrite paint, as appropriate.

I also began the replacement of all resistors and the wax type capacitors used on the tag-board that attaches around the edge of the circular chassis. I used modern 2W carbon resistors because of their similar dimensions to the originals and yellow 630V rated polypropylene capacitors to replace the wax types.

The images below show the restored chassis and the start of the rebuild process;

                   

When I reattached the rebuilt coil-pack to the chassis and tried to reinsert the band switching spindle, I found that the medium wave oscillator coil (upper right in the image with the capacitor across it) was fouling the clean rotation of the spindle.

After a number of attempts at repositioning the coil and wiring, I eventually solved the problem by the inclusion of several small washers under the two mounting bolts that secure it. The washers raised the height of the coil a few millimetres which proved just enough to clear the spindle and cure the issue.

Next instalment: Chassis restoration continues.

[pwdrive]

Hello Robert, it's looking good, I use the same polyprops and those same type resistors, on one job I did I found that the old Erie resistors (the ones in ceramic tubes popular in the 50's) will pull apart leaving just the tube but it generally takes some heat to achieve that, once the tube is cleaned out they will take the .7 watt resistors, I think they are Welwyn, I got mine from Farnell, I applied a dab of super glue inside the ceramic tube and then inserted the new .7 watt resistor filling the ends of the tube up with Araldite with a bit of brown colouring to match, for that particular job I then painted the body of the tube with a light cream paint then marked the resistors value on it with a fine black permanent ink marker, it would also be possible to re paint with the original colour code. I find the 2 watt and .7 watt ones that I have described are just the job for valve stuff as I think they have a 300 volt plus rating.
A general safety note that if using a blow torch to heat those old Erie resistors up the wear safety goggles.

Lawrence.