Broken Macintosh

Very short-lived, this one. I took everything apart and adjusted up the screen so it was central.

Nice and even

Set it on the side to do a bit of a burn-in test, and the decoupling capacitor for the horizontal yoke let out all its magic smoke, the screen went a bit funny and I switched it all off quickly.

c1

Decided to build the little capacitor network suggested in the manual, of several ceramic capacitors in parallel to build up the capacitance but reduce the ESR.

c1c1c1c1

Put it back together and again we have screen but.. the horizontal isn’t aligned any more. The two interlaced pieces of the screen, all stretched out – do not line up.

interlaced

I’m going through the schematic, I’ll check all values and make sure that the capacitor failing did not draw too much current through the flyback and fry one of the windings.

Rejuvenated Macintosh

I decided that the wobbly-screen Macintosh needed to have a bit of work done to make it a bit more trustworthy and reliable. The electrolytic capacitors had been installed in it since 1985 (8113th device produced in the 24th week of 1985 in Fremont, per the serial, so a real early 512k).

mac on table

Took it to pieces after ordering a bunch of spares (total about $15, so not bad), with the replacement caps rated at least one voltage rating over what was fitted and 105C rather than 85C as fitted originally to try and keep them a little more stable.

logic board

Not many capacitors on the logic board, though it is a 4-layer PCB so extra care had to be taken. I’ll give them this, it’s a well made PCB.

logic board closeup

Tried to keep the solder-work neat. Don’t think I did too bad a job, to be honest.

work in progress

Got stuck in doing the power and sweep board, which has the majority of the capacitors.

powered up

First test, and things were promising until the brightness control decided to stop working.

broken brightness pot

Turns out the center carbon track had completely fallen apart. Checked the schematic, fairly standard 16mm 1MOhm linear pot, so went on the hunt for something similar in the electronics catalogs online.

new pot

Closest modern variant I could find. The board is the right size and the connecting pins the correct length, important in this application because of the way the computer is assembled.

take apart

Carefully undid the new piece, as the thing was essentially backwards from how it needed to be.

sweep

This side is where the old one had the handle coming out. I removed the crimped section and split it all down, had to file the ears of the board a little to make it fit but managed to put it back together again, and have it test good and smooth operation across its range of travel.

reassembled pot

Put that back in the circuit and the brightness is now adjustable again. Checked the voltages and the 5V rail (the master) was a bit low at 4.72V so that was tweaked up to 5.00V. The 12V rail, slaved from it sat happily at 12.2V so that’s all well within limits.

5 volts

The screen became a bit intermittent- traced that eventually down to a couple broken solder joints on the connector to the end cap of the tube.

broken joints

Removed the old solder and re-added new.

working now

All up and working again. Need to adjust the centering of the screen a little, I think I must have knocked the centering rings when I put the wiring back in. Overall, a lot better than it was.

Centrifugal.

The Renault had been making some unhappy noises from the engine bay recently, bad bearing kind of noises. I drove it to work and back and on the way home it decided to buck and jolt badly, feeling like a bearing jamming up (more on that later).

old pump

After having to purchase an 11mm wrench (not a real size, why it’s used is beyond me) I removed the water pump. Due to the design, it was impossible to remove by hand, as the bolts undo and the pump came off with a gentle tap, but the impeller got stuck in the aperture with the pulley wedged against the frame rail. A bit of wiggling and there was 1/8″ holding it back so a thump from the bottom of the mallet handle saw it liberated onto the floor.

coolant

I’m quite impressed by the coolant. It’s very clean, all things considered. This is a good thing.

water pump removed

Water pump aperture, including original gasket, which probably could have stayed, in hindsight. Note the really large space to work in (by general Renault standards, at least. I can get my hand in there and even see what I’m doing. Luxury).

gasket scraper

Spent an hour swearing at the old gasket, which was particularly awkward to remove.

no more gasket

Eventually it did come up clean. I’m just glad the block is cast iron because the angle I was forced to work at with the blade would have scratched and taken chunks out of any softer metal. Surprisingly also, the pump housing is remarkably rust free where the impeller spins, so I’m guessing this coolant does have some anti corrosion properties.

new pump

The new pump came with a new gasket (which didn’t fit very well, the holes didn’t line up properly) and has a different impeller design. Previous one was a pressed steel affair which was effective enough, had 4 vanes. This one is cast metal and has many more (and upon actually having run it now, pumps a much higher volume of coolant, particularly at idle).

sealant

Gave the gasket a coating of sealant and installed the bolts, which were held in place by the gasket (useful side effect of the holes not lining up well).

pump in place

There was a moderate period of jigsaw/Jenga type thought and experimentation that occurred before the pump went in. In the end, the bolts had to be in place, the pulley had to be on the shaft but not attached so the pulley could wobble about enough to allow access to put the pump in place. Thankfully there’s enough room to see one bolt past the frame rail and also space to stick a locking rod so the pulley bolts can be tightened.

alternator bracket

Then it was time to put things back on! Alternator and aircon compressor bracket assembly first.

alternator

Alternator with top adjustment bracket.

compressor

Finally, aircon compressor and belt, which took a while to remember which way round all the pulleys it goes.

battery

Finally, the battery tray and battery went back in. Filled up the coolant and let it burp as best it can with the engine off.

grubby

Been a while since I’ve had grubby hands, made a change from moving boxes and furniture.

running

Finally, all buttoned up, topped up and running. Aircon even works still, which is nice. There howling bearing noise is gone, but initially it was still bang thump, kangarooing and running intermittent badly on the test run. This was traced back to a rubber bungy that had split and fallen off one of the big spigots on the brake booster. Replaced that with a short length of pipe with a wire nut stuffed in the end because that shouldn’t split now. Normal, smooth running resumed. This fuel injection system really doesn’t do well with vacuum leaks at all.

It’s nice to have it back on the road, even if the front brakes are now sticking because they’ve not been used. Next job, that.

New Arduino Project – matrix LED display

I salvaged a couple of displays from some old equipment that was being thrown away. Pulled up the datasheet and started trying to make my Arduino Uno display things.

gibberish

After bit-bashing in some dots, I managed to get it to correctly display a letter, this case a lowercase “a”.

a

Now it actually works- I’ve made it scroll text input from the Serial port, full ASCII table. 3.8kb of code, not bad compiled from C.

nmmm

The above was from a leafed/paged test of the full ASCII table I made it loop.

Getting back to it.

It’s been a busy few months.
386 weather center

Flooded at work

Bad weather from Hurricane Harvey

With summertime storms looming on the horizon, weather that has made the yard grow like a jungle and homework assignments, sleepovers and movie nights burning up the rest of the time and energy I have, plus the house sapping the bank account meant I didn’t think I’d be getting back to any projects at all.

oxalis trianglularis

These strange little triangular plants have been popping up all over the yard recently. Turns out they are Oxalis triangularis, or “Fake Shamrock”. They are toxic to animals, and so far quite difficult to get rid of, but amusing and interesting to look at. Coupled with these, I’ve been getting waterlily looking plants popping up in the shade of the front path.

pinhole camera

We had a 75% covering of the sun from the eclipse, I was stuck outside at the cross-box in Thibodaux all day due to a fiber cut, but that wasn’t going to stop me from seeing the sun covered! Piece of cardboard with a small hole poked in it by mechanical pencil saw an adequate pinhole camera created, and the image above captured on a sheet of paper.

dirty generator

Picked up the generator from where it was chained up at the mother-in-law’s house. It’s been sat semi-covered in the shade for the past 7 years, and as such covered in all sorts of grime. Set about with a brush, bucket of water and Formula 409 and got it looking presentable again.

clean generator

Took the solenoid apart because it would click but not spin the starter motor over. The copper on the terminal connected to the positive terminal of the battery had gone all green (the steel nut on it was perfectly rust-free), where as the negative was all shiny but the steel nut had turned to a blob of brown rust. Chemistry is fun!
It needs a new battery but fired up on the old stale fuel in the tank- very surprising. Filled it up, along with 40 gallons of fuel in cans, in preparation. At that time it was unclear if we were going to be hit by hurricane Harvey. We saw some very bad weather (on the TV screen at the top of this post) but thankfully that was it.

living room furniture

Got some new furniture for the living room, which has allowed me to set up the old garage with the old furniture, a TV set and game console.

crepe myrtle and roses

The recent pleasant, cool, dry weather has meant I was able to get outside with a saw and heavily prune the plants on the northern edge of the property. There was a tree growing up through that crepe myrtle plant and the rose bushes were all woody. Does not look like much but that was a full afternoon’s work.

bbq

stripey clouds

Nice weather drawing to a close, meant that a bit of R&R could be had; much welcomed.

A moderate hiatus

The last few months have not exactly been a hayride, but the main reason I’ve not been around here is that I now have a house. It took 7 months of paperwork, lawyers and headaches to finally close on, but it’s been worth it.

house

It’s a nice little mid-seventies brick ranch in a quiet neighborhood; not very far away from the place we had been renting for the last 6 years (had it really been that long?!).

living room

Getting it all set up inside, still with boxes everywhere.

jetwash

The usual new-house steady flow of maintenance happening, despite the summer heat.

sunset

Getting used to being in a house. There’s a lot of yard to mow, twice a week this time of year.. just finished tidying up the garage- yea, got a garage now to put the car (currently broken again) in!

garage

Next big project is to put up a bench in the office, to start working on electronics again. Trying to find the time for anything lately is a challenge. Such is life.

Wipe and wait

My car has a 4-position windshield wiper stalk; off, intermittent, slow, fast.

While the motor needs to be pulled and serviced because there’s little difference between slow and fast, the intermittent wipe had always been somewhat pathetic.

Selecting intermittent would make the relay click, and as soon as the wipers returned to the parked position, click again and they would almost immediately wipe again.

Pulled the dash shroud down and located the clicking box at the top left. (Top right is the key-in/seatbelt buzzer, bottom left the cruise control stalk, above that with the finned heat sink the dashboard dimmer control).

relay delay box

Took the circuit board out and drew up the circuit diagram by following the traces, to get a better understanding of the circuit and its method of operation.

board

Culprits were most likely the electrolytic capacitors. One had a high ESD and the other was meant to be 22uF, it measured in at about 100nF. Replaced them both. Now the wipers wipe and wait about 5 seconds before wiping again on intermittent, and added bonus, they now wipe 3 times after spraying screenwash onto the screen. Not bad for 45 minutes’ work and spares I had in stock.

Odds and ends

Been busy with Scouts events lately. First off was the Raingutter Regatta, which is an event where you build a boat from a kit and then race against other people with boats by blowing at the sail through a drinking straw.

Didn’t win any races but the boats were decorated that morning with Sharpie permanent markers. We have the Cheshire Cat from the latest edition of the Alice In Wonderland films, and Edvard Munch’s “The Scream”.

boats

That was a bit of fun. Next up was the Space Derby, which is basically elastic-band, propeller driven craft that fly along a zipline. Furthest wins, or first to the end of the run, which is about 30 feet or so of fishing line, held taut.

airplane

We went for a heavier design which won it first place in the races (not the fastest but it managed to gain the most momentum and coasted on by faster but shorter-traveled competitors). Designed after the P52 Mustang.

wheel off again

Took the wheels off the front of the car again, and changed the brake pads for new ones. The brakes had good pedal but offered little actual braking effort.

glazed

The pads were so glazed I could almost see my face. Plenty of friction material but all cracked up. In the bin they went. The brakes now work properly. That’s better.

Co-processing.

I decided to buy a little something for myself, so eBay was opened up and I hit “Buy It Now” on an item.

Package

3 weeks later, it arrived from Kowloon, Hong Kong. The reason for the package? This empty socket.

socket

As if by magic, it was filled with a suitable device:

387

Upon fitting a 387 co-processor, a jumper needed to be shorted to inform the board to use it.

jumper

CheckIt determined that the thing was working (which is good, as there are surprisingly quite a lot of fake/broken chips circulating the market).

checkit

It was then tidied up into the desk. Makes a significant improvement where a math co-processor is utilized.

lotus 3

A bit of fun, reminder of days gone by.

Some new subjects to focus on

As mentioned in an earlier post, I recently acquired a Canon A-1 35mm film camera. It dates to 1978, and it was Canon’s first foray into fully automatic exposure cameras.

It gives a digital readout of the f-stop (aperture) and exposure time through the viewfinder using red LED numerals (which can be disabled), you can hold the reading for backlit scenes, calculate both, just the aperture or just the exposure time. Very innovative for the day, just focus and click. I got the pictures back that I had taken from being processed. Here’s a small selection:

Bayou Lafourche at Leeville
Bayou Lafourche at Leeville.

Hydrant
Experimenting with depth of field.

Leeville North, LA Hwy 1
Louisiana Highway One, at North Leeville. Once the busiest road in the area, now a ghost town.

Captain Thuan
Fishing boat, Bayou Lafourche, Larose.

It does have a light leak on the right hand side of the mirror. After a little reading, it seems that’s fairly common on these as the felt stripping that blocks the light disintegrates with time.

Pointe des Chenes

Compare with a modern digital image, adjusted with a warming filter. Quite different. I like both, but all the images taken with the Canon look like they could easily have been shot in 1985.