Big trouble in little Corolla

The little Corolla has been getting steadily worse in the starting on cold morning. Saturday it stopped working all together. Hey I can use a screwdriver and sand paper! This looks easy, the internets tells me this is a common problem with Corollas and is a twenty minute job. Famous last words!

So, after disassembling the solenoid on the starter motor of the car, including un-soldering the solenoid winding from the cap. I cleaned the main starter motor contacts. They were a mess, so I sanded them back and tried to clean all the black gunk off. I cleaned all the other conductors and reassembled. As you do...

Then bolted the starter motor back in the car, tried to start it. Nothing.

Thinks.

Fiddle around with key switch wiring, contacts, etc etc ... nothing. There was only 6 volts on the ignition key switch to the solenoid. Not sure if there is lots of lossy connections between the battery, switches etc. Bother.

Find battery is a bit low on the volts. Put the battery on to charge, went over to a friends place for diner. Got home, the battery seemed to be charged suitably. Went to bed.

Got up this morning, to ponder the issue of there not being enough volts on the ignition wire, scour the internet for more ideas. Walk to servo to find a relay and connectors, etc. They had nothing. Zip. Bother...

Go home, listen to the WIA broadcast and ponder other possible solutions.

After a couple of phone calls shuffling my calendar, I walk half an hour into town to find Sprint Auto to find these parts. Sprint Auto was closed. Was not liking my luck at this point. Walk to Repco. \o/ Its open! Speak to geezer about what my problem is and what I thought might be a suitable solution about not enough volts on the key switch. He suggested that it sounded reasonable, but I would be better off waiting until tomorrow to find an auto-electrician or get a reconditioned second hand one. I needed the car running today. Things to do. With a lighter wallet and a pocket full of parts I walked half an hour home.

Got home grabbed some lunch, had another look on the internets to see if I could find someone else with a similar problem or at least a circuit diagram and repair manual type information. At this point I knew there was something that I did that was amiss. Couldn't quite put my finger on it.

Build up a relay that is trigger by the ignition swith from the key, powering the solenoid from the battery direct to get more current through to pull the solenoid in. The solenoid wasn't moving, but the motor was turning. This was very, very wrong.

Realize that maybe the solenoid was actually dead, maybe a broken winding. Decided to pull the starter motor off the car and ponder some more. I couldn't actually find anything on the Bosch model at all. There were a lot of NipponDenso models that looked similar. At this point I started comparing any starter motor for the 4A motor I could find. At some point I noticed that the large contact studs on the back of the solenoid were wrong. The short stud was on the top, away from the motor and the long stud was on the bottom, closest to the motor and connected to the positive cable for the starter motor. Hang on a second...

So at about this point I looked at a service manual for an AE86, which is a different model, but gave me the most detail for an 1988 corolla I could find. The schematic on the AE86 go me thinking about why the motor was spinning without engaging the solenoid. You got it, I had put the thing in upside down and solder the wires in back to front in the circuit.

After another half an hour, I had assembled it the right way and put it back in the car.

Not expecting it to even move the solenoid, the car car started smoothly and ran! So I switched it off and added my ignition relay, and that started nicely too. So I tidied everything up and took the car for a lap around the block, to be sure.

Half hour job, eight hours later! At least its working properly now and we can now go do those things we need to do. =)

Kim VK5FNET

80 meter DC Rx - Debugging lack of mixing

Hit the issue with nothing coming out of the mixer. Using the signal injector feeding into the RF input port, I could hear RF static type noises.

So, I spoke to a few folks at the last AHARS meeting. Specifically what drive level from the LO is needed to turn on the 1N4148s. Jim, VK5TR suggests that I will need +7dB. Darryl, VK5JDS suggest about +6dB.

So I made an RF probe, a 10nF capacitor / 1N34 diode / 47M resistor style probe that I attached to the front of the DVM. A simple T shaped arrangement, on a little scrap of copper clad board and put a BNC socket on one end for a CRO probe, the other to a pair of banana plugs to attach to the DVM.

Wonderful; 0.4 volts from the LO. Now to match +7dB up to what volts output that should be...

72,

Kim VK5FNET

One 8 step sequencer running on the bench

I spent a bit too much time googling for synth music and sequencers over the last few days. I had a lot of fun just reading about folks projects and how they built up various kits or designed from scratch different arrangements. I have not really spent much time working with 4000 series or 7400 series ICs in the last ten years. Well not since first year Uni to be honest. That was a long time ago and my memory for truth tables is long forgotten.

So, I almost cheated but finding the friendliest schematic I could find and trying to build that up. You know how it goes, adapting part of this circuit as a stage one of your project. Well I had a few problems. My 4017 wasn't behaving at all! I spent several hours on the bench trying to figure out why I couldn't get the thing to behave. The first problem was that I missed a ground connection on pin 12, eventually running a bypass cap to the reset pin before it settled down and started to do the right thing. But the first LED wasn't behaving itself at all ...

Some further testing revealed that the LED in the first position was a flashing LED! So its now in its own draw, in the component cabinet. The 555 was a whole lot easier to work with and was pretty much doing what it was supposed to from assembly. The potentiometer has a dead spot right at the fast end of oscillator, so may need to swap the wires on the pads, or get a new 1megaohm 'pot'.

I will say that after having the 'friendly' schematic, I did change most the resistor values, add a few extra capacitors and lay it up differently on the plug-in breadboard. Its not a new circuit, but I learned a lot, mainly how to trouble shoot this little thing.

So what have I achieved here? More motivation to tinker in the shed/shack on the plug-in breadboard and play around with the circuit. Getting things working build up the motivation to do more. I have a tall ladder before me. I'm aiming to make the rungs nice a close together. Easier to climb that way ;)

Anyhow, happy homebrewing to all!

72,

Kim - VK5FNET