All posts by phila

Luggable overhaul: Part 2

I placed an order for some more tantalum bead capacitors a while back and they finally arrived in from China. 10uF, 25V so rated at a higher breakdown voltage than the originals (16V). I’m not a huge fan of tant beads but they are compact and this is preserving a moderate amount of originality.

Tant beads

I started removing the old capacitors and soldering in new. Three layer boards are awkward enough to work with through-hole, but this went smoothly enough.

back of video board

Worked my way through, this is the multifunction card (RAM, serial, clock, parallel ports etc).

multifunction card

You can see where the tantalum beads are failing- they crack open in some cases and vent. The mark on the top of this one is just visible.

broken tant

I also wanted to change the LED on the board. Not because it didn’t work, but because Compaq used a very pale red epoxy cased LED that looked cheap. It spoiled the look of the board.

LED comparison

Side by side the old one and its replacement. The replacement one is older by a few years, but it from the era where the packages were nearly clear but much darker red plastic.

on the board

It’s a better contrast to the color of the board. Lights up a very deep red compared to the newer LED.


A pointless aesthetic? Yes. But it makes me happier to look at the board.

Luggable overhaul: Part 1

I had set my Compaq portable up on the table in preference to the Macintosh, with an idea to use it more regularly. It started up okay but made a rather unpleasant burned smell after about twenty minutes so apart it came.

expansion slots

Nothing particular showing up, so lifted all the expansion cards out and then removed the motherboard.


There’s a couple tantalum capacitors with cracks in, so they’ve gassed up and are not long for this world. The video output has been a little wobbly since I got the machine, particularly in low resolution mode. It’s all packed in fairly tightly.

vdu and psu

So, out came the VDU. Picture tubes always look so forlorn when they don’t have any cases or bezels fitted.

picture tube

There’s always one part that makes a bid for freedom. Tonight’s candidate was this washer:


The power supply is all plugs, making a note of what goes where as there are quite a lot of them..

power supply plugs

Everything all lifted out quite easily.

all boards

These are the two boards that need the most attention. The power supply (the highest power most compact board designed to date at that time) and the video board, powered by the power supply on the 12V rail.

vdu and psu

The connector was showing signs of high current draw so it’s definitely time for a rebuild. The power supply is marked “upgrade” on the back, so that’s positive.

Cycle rectification

I had pulled all my test equipment out to align my radio again;

test bench

So, I started my bike up and checked the output of the generator with my oscilloscope.

scope on bike

The output was rather spikier than hoped for into the negative, so redoing the rectifier was in order. Possibly the vibration was too much.


I finished up the latest revision of the regulator board, with a new Zener to bleed off any excess input voltage, a resistance across the input capacitor to bleed off any stored charge, a mechanically better connection to the board and some adjustment pots.

More generator issues

Checked the output of the generator with nothing connected.


With no load it was causing the capacitor to saturate at about 46 Volts. Not so good!


Also, the main voltage regulator chip had vibrated loose and fractured off. I made a bracket to secure it to the board better.


Bolted down securely, and relocated the capacitor; however with only the rectifier in place I’m reading a fairly significant AC component on my multimeter. I’m going to hook my oscilloscope up to it and see what the output looks like. I have a feeling possibly one (or more) of the diodes have failed.

House renovation

Took some time out whilst my parents came to visit and fixed a few things up around the house.

red shutters

First, the shutters were painted a real deep red (called “Old Mahogany”). This is a significant improvement over the battleship gray that they were; now the house is all reds, oranges and browns and it all comes together nicely.


Next up, the flower bed out the side of the house was completely redone and some plants were added to the front of the house in pots.


Finally, some vegetables were put in pots. Tomatoes, squash, blackberries, some herbs, eggplant and cucumbers.

Summertime beckons!


I had originally clamped the new exhaust pipe by cutting a couple slits in the end of the pipe, pushing it over the outlet of the muffler and clamping it down with a Jubilee clip. This proved unsatisfactory as the Jubilee clip could not be adequately tightened without slipping. They are ultimately not designed to be done up very very tight anyway, so I decided a U-clamp would be a better option. I went to the local hardware store and had a rummage around. I discovered a 3/4″ wire rope clamp, which had a decent clamping surface.


It’s a little oversized, but it has clamped the pipe very effectively. I also polished the pipe up, which came up really nicely.

diodes and coil

Next up was to pull the generator winding out and build up a bridge rectifier. I wanted to get the most out of the coil, so some modification was required. It was wound with one side to ground.

bridge rect

I de-soldered the end of the wire to ground and built a bridge rectifier so the device could use both sides of the wave output.


Tucked in a capacitor.

generator fitted

Fitted everything back in and connected it up in a testing fashion.


Hooked up an LED on the low beam light, as it’s more efficient and will not drain the battery so much. The color temperature is also acceptable, at a moderately warm 2700K.

voltage regulator

Began work on building a voltage regulator. Built it up on breadboard first and tested with a 12V supply to check it regulated correctly down to the 6V required by the system.

breadboard regulator/charger

Translated the regulator and charger circuit to Veroboard, attempting to keep it as compact as possible.

warning light

I had wanted to have a no-charge warning light, so decided the best way to do that was to have a comparator circuit. Compare the voltage coming in to that of the battery (across a voltage drop, in this case a diode) and illuminate a light when the input was less than that of the output.


The switches I had purchased were set up that the on/off rocker was green with a green LED and the on/off/on rocker was red with no illumination. The front panels were printed with I O II style lettering to show the positions. I took the on/off switch apart and fitted a red LED inside.

new faces

I reassembled the switches after having sanded the old labeling off and adding some new, more appropriate symbols.

lamp test

Testing showed the lamp illuminated adequately.

live test

Hooked the breadboard up to the bike and ran the engine to test operation. That proved successful.

comparator circuit

Completed build of the comparator circuit on the Veroboard.

bench test

Final bench test, under full load of the regulator and warning light circuits.

handlebars bare

Took a break from electronics at this point to clean up the handlebars, which were very rusty and flaking paint that was applied badly in the past (not by me!). Sanded the handlebars back to bare metal.

painted handlebars

Masked up and painted the handlebars gloss black to match the fenders.

handlebars reassembled

Reassembled, the finish is acceptable.

back to wiring up

Resumed wiring up the switches to the lights (with a set of diodes for the rear light so as not to back-feed the front lights.

first test

First test, on battery. Main beam at that point did not have a light bulb, the original was 12V.

wiring diagram

So now, it’s a bicycle, with a wiring diagram. The colors of the wires did not match as I had bought a trailer harness with a nice detachable plug for the back and the wires coming off the switch were all different colors.

leather bag

I fitted everything into the little leather satchel below the seat.

wired up

I need to finish up and cover this up with some looming tape or some other covering but for now it’s tidy.


All set up, neat and tidy.

Reflecting upon red plastic

One thing missing from the back of my bike was a reflector. It likely had a rectangular one under the seat when it was new- that to me is not really very much in keeping with the ethos of the bike so I had a rummage and found this on Amazon:


A 1 1/4″ round reflector, metal backed, made in New Jersey. I made up a small metal bracket, painted it black and attached it below the light on the rear fender.


Ordered also a small module housing a couple switches to operate the lights and ignition- the push-button on the handlebar that currently kills the engine is going to be for a horn of some description, something a little louder than a bell.


Annoyingly, it arrived broken. I glued it up and now it’s better. Next up, dismantle, rub down and paint up handlebars… then refit all the parts.

New paint; a stark contrast, illuminated.

Decided to rub down and repaint the fenders on the bike. I had never been very fond of the gray/white color scheme and with the addition of the gloss black fuel tank it started to look out of place. Plus, the white paint was beginning to look in poor condition from being stored out in the elements for years.

DA sander

Started with some 120-grit paper on the DA sander to take the old paint down to a good surface and provide a key.

rubbed back

Once rubbed back it was wiped clean. The paint is really very thick and has protected the metal well.


Gave the fenders each a couple coats of rust-protect gloss black paint and left them hanging to dry.


Between times I decided to see how the exhaust pipe would react to a bit of polish. As it turns out, really very well.


Moved the rear light to the back of the rear fender and reassembled everything. Just needs the handlebars rubbing back now and painting up (again, black).


It’s quite a difference from how the bike started out. This is a picture of it a few years back.


Next, I turned my attention to the lights. The magneto stator was meant to come with two windings, but only arrived with one. I ordered a replacement but that arrived with one winding and two wires soldered to the output. Utter nonsense.

generator stator

Bought an extension piece to the stator that turned it from a horse-shoe shape into a full hoop with a second winding to generate power for lights.


At a fast idle it creates enough energy to light the 4.5W bulb in the headlight. I might end up doing what I did not want to and fitting an LED lamp to it instead, as it is significantly more efficient and should power from the generator acceptably from idle on up.

Computer stuff and a motor assisted bicycle

I got fed up of having a mismatched set of drives and a hole in the front of my TRS-80.

neat and tidy

This prompted me to go find some software and find a way to transfer files to and from the TRS-80. Turns out running an emulator, using it to convert binary files to hex, transmitting them across serial and converting them back works well.
Also, on a plus note, have managed to get a word processor software working and printing properly. Real proportional print on the old daisy wheel printer!


It snowed. This prompted good “out in the garage” type work, as it was pleasantly cool.

pile of parts

I decided to try a bit of a fun project. Bolted an engine to my bicycle. A few things needed a bit of ingenuity- the sprocket at the back is clamped to the spokes between two discs of rubber. That pushed it too far out and didn’t let the brake work (hub brake on the rear wheel).

rag joint

An afternoon of adjusting and tinkering and setting up and I got it to run.


50cc, 1.5hp.. geared to do about 20-25 tops. Decided it needed a speedometer. Ordered an old-fashioned mechanical one. Decided I did not like the face that was on it so redesigned it, in the style of 60’s BMC Smiths gauges.

gauge design

Printed out rough draft and compared to the one it came with.


The gears also had no lubrication, instead relying upon the nylon being inherently slippery- that only works for a short while, so added some silicone grease to try extend the lifespan of them a little.


Mounted the face, decided it looked well enough. Painted up the center of the needle with silver paint.

spray paint

Finish is acceptable. Not mirror but certainly shiny.


All finished up, looking better than it did.


Took a while to calibrate, and it’s far from accurate but it’s good enough for the job it’s doing. Also, pulled the trip reset dial off and blanked it, turning it into an odometer.

black chain guard

Painted the chain guard up, made a few adjustments to the way the chains route.


Bought a light set for it, the front lens was all hazy. Polished it up so it was a lot clearer.


All back together it looks a fair bit better.


All attached to the bike, adding to the look and usefulness.


Next up is an engine driven generator, switchable to the wheel generator. Might add a battery in there someplace but for now it’s all AC lights.