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Radio City Products 423 Restoration [Permalink]

For those who don't know; I quite enjoy buying old broken test equipment and restoring it to a fully working condition. I recently added another ebay purchase to my collection. It's by far the oldest piece I have dating from about 1942. That's about seventy three years old. That's fourteen years older than my AVO 8 (MK1).

It is the "Radio City Products model 423". There is a great site for reading about the history of RCP if you are interested:


As you can see, it got to me in a rather poor state. The top of the box was falling apart, the leather handle had snapped and most of the varnish had disappeared.


The joints at the back of the box were also loose. This is likely to be because the lid puts stress on these joints when it's fully open.

Some other problems also needed sorting. So, The plan was;

The first interesting part was the handle. I don't really know much about making leather carry handles and so I just took the old one to a shop that does leather repair and asked "Can you make a new handle like this?". The result was a handle that had both ends. Hooray! The woman in the shop tried to give it an antique look and finished it with a two tone dye. This is the place I used:


So that wasn't much effort and was only £18. The meter itself from ebay cost £12.59, then there was £16.61 shipping from somewhere in the USA. So far the handle has been the most expensive part, in total I've spent £47.20 on the meter.

Now to the box and to the loose joints. The joints are dovetail joints. I clamped them back into place and then drilled a hole down each one. I then unclamped them, applied glue, clamped them again and put nails in the holes I drilled. I'm hoping that by adding the nails I have increased the life span of the newly repaired joints. You can just about see the nails in the joints in this next photo.


While the lid was off, I took the opportunity to remove the broken plywood.


Wanting something easier to do, I then turned to the clasp, it was a little stiff and a bit out of line. I decided to replace it completely which was slightly more awkward than I anticipated. I wanted to bolt it on instead of screwing it on. It's more secure and more difficult to get wrong. This was easy enough on the lid but the box required some notches to be removed.







Next on the list was that shattered plywood top. This was fairly easy to replace. I cut out a section of ply to roughly the same size as the lid, slightly too big. Then, because the joints on the corners of the lid were also loose, I had to put the hinges back on and attach the front section using the new clasp so that I could hold everything in the correct position to glue it back together. I placed the box upside down on the new ply while I let the glue dry. Held in place with some heavy things I had handy.




Then I just had to trim the excess off and sand it down. The sanding part was made really easy by this magic device...


It rounded off the corners of the lid nicely and powered through what was left of the varnish.



Quick confession, this is the first time I've really been focused on restoring a wooden box. Usually I'm restoring the electronics. I had to ask a friend about what varnish to use. He recommended polyurethane varnish, so I got some in the closest colour to the original. On the inside of the box the varnish hadn't peeled off and so I could match the old colour. I ended up buying some ronseal varnish in walnut flavour.


This next photo was taken after the first coat, I gave it two coats.


With a nice shiny new clasp and handle, I couldn't leave the hinges and the handle holders looking dull and old. Time to break out the astonish and a small handheld rotary polishing tool. I cleaned them up with one of those rotary wire cleaning tools first to get the muck off. See the before and after shots.





That's all the visual stuff done. Now I had to stop the rattling inside the meter coil assembly. After playing the invisible maze game for a while it turned out that there was the head of a screw loose inside. Hmm. Time to open it up a little further. The meter coil housing is difficult to remove because of one particular nut. It's hidden under lots of wiring and is very difficult to access with a tool of any kind. I did get it in the end. Once it was out, I simply removed the back and the screw head fell out. A quick check to make sure everything was still held together correctly inside and then it all went back together.





Hooray, all fixed. Almost. With the new clasp in place, the handle stopped you being able to open the box easily. I had to move the handle clasps down a little. This would have left two rather ugly holes visible so this is why there are two screws that appear to do nothing. The finishing touch was to fill in the white paint on the pointer. It had gone dull and grey and in some spots fallen off.


And now for the before and after photos together...



Bonus shots... (Including the hand drawn schematic found inside the meter, where the batteries go.)






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New year, new post, better guitar. [Permalink]

First post of 2015 and it's on the first day of 2015 too.

New year's resolution... post more cool stuff? Maybe.

I haven't done much new and interesting stuff but I did make the pickup selector on my peavey raptor plus exp slightly easier to use.

With lots of effort with masking tape and permanent marker, I have drawn some lines from the switch positions to the pickups that they select.

While I had the marker handy I added some pointers for the volume and tone knobs.


Here's a pic. Click for bigger.


Guitar pickup selector

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An upgrade to lollipop [Permalink]

Now that I have upgraded to Android(TM) 5.0, a.k.a "Lollipop", I now have to swipe up on the lock screen before I can enter my pattern. This is a step backwards. The buttons at the bottom of the screen are now less intuitive. When has a circle ever intuitively represented "home"? Does a square really say "show me recent apps"? The triangle for the back button is just about acceptable.

So is there anything good about it?

Multiple google accounts. This solves problems I have had as a developer, being unable to test app features as users other than the developer user. This should fix that problem, I haven't tried yet though. The lock screen does have some new features that are useful, you can choose to trust a connected device. Suppose that your smartwatch is always connected (unless your phone has been stolen) you can have the lock screen let you in with no pattern when the watch is connected. When the phone is unlocked in this way, it will not automatically lock when the watch goes out of range, that would be nice, otherwise a thief could grab your phone, unlock it and then run away. A slight oversight.

As usual, it is slightly uglier for a few days until your eyes adjust and you no longer doubt if you have the right phone in your hand. The notification bar is now just a bunch of items that float on top of everything else instead of being a full screen thing that covers the background, I'd prefer to have the thing behind the notification area to be completely invisible when you want to see notifications.

Other good things include better battery management and faster boot. I am therefore fairly neutral about this upgrade. Some really good things happened and some really bad things happened. Meh.

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Reverse engineering an LED display from eBay [Permalink]

I decided to try doing a video for this post instead of just writing about it.
As a result, most of the content for this post is in the video, some of it is repeated here.

I recently came across some LED displays from eBay. They were so cheap (£15 each plus about £5 postage) that I bought two.
I think the seller had pulled apart a sign from a railway station departure board or a bus stop sign or something like that.

So here is a quick look; The signs were made by "shorekarn". They each have 40 columns and 7 rows of LEDs (280 in total). Each board has a chain of shift registers that effectively make one large SIPO (Serial-in-parallel-out) 40-bit shift register. There is a 3 to 8 line decoder (that has a redundant line) which selects the row to light up. Therefore the signs must be actively scanned to maintain an image. The boards can be daisy chained together to make larger signs.

This was fairly easy to figure out, googling part numbers I didn't know and then following traces back and referring to pin diagrams of the chips, I was able to identify the function of each pin on the main data connector.

I wrote some arduino code to control it, it turns out that was remarkably easy thanks to the simplicity of the sign's design.

So, without further ado, here is the vid:

I'm not sure what I want to do with these signs, I just couldn't resist them at that price.
I have written a snake game for it that also has sounds, I might turn it into a really odd arcade machine.

Hope you liked it.

Links to datasheets for the chips on the board:


3 to 8 line decoder 74138
Quad NAND gate 7400 Not that there's anything we haven't seen in this one.
8 bit SIPO shift register 74164


Row drivers (darlington transistors) TIP125
Row driver IC (hex buffer) 7407
Column driver IC (darlington transistor array) MC1413P

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Reprap box lid failure [Permalink]

I haven't posted anything for a while, I thought I should fix that.

This will only be a short post, I recently broke the lid on my reprap box. It was a fairly clean break and so I fixed it by bolting some small sections of plastic I still had lying around to each side.

This is probably slightly less worthy of a blog post than some other things I have done but I need to post something, It's been too long.

So here are some photos, as always - click for bigger.

The problem;


The big hole left in the lid;


After drilling some holes for the bolts;

Holes drilled

And then countersinking with this very useful tool;

Countersink Bit

Then I could bolt the fixing plates on;

First half of plates

Job done;

All fixed

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