Thursday, February 21, 2019

Fridge Magnet Repair


One knows that one is scraping the bottom of the barrel for work when one has nothing better to do than to repair a broken fridge magnet. Pictured below is the injured magnet.


It's some sort of ceramic material. This looks like a job for CA adhesive. Here goes.

- - -

I gave the break a bead of runny, liquid CA adhesive on one side, and stuck the thing back together. Here it is parked in the vise for an overnight cure.


That should turn out fine. Tomorrow morning it can go back into service on the fridge.

- - -

Done -- FRIDAY, FEBRUARY 22, 2019

Here's the glued, fully cured magnet.


Almost seamless; ready for service.

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Sunday, February 17, 2019

Tool Review -- Mastercraft No. 052-0060-2, Pocket Digital Multimeter


I picked this up today from Canadian Tire for $9.99 CDN, on special from the regular price of $34.99.


Here's a view of the front of it without its bubble pack.


There's a flip-out stand in back.


Battery Installation

The unit takes a single 9V rectangular battery in a compartment at the upper rear. (A battery is included in the packaging.)


Removing that single screw gives you access to the battery compartment. Don't lose the screw; it's an M2.5 thread -- not something you'll easily find a replacement for.

Test Leads

They're 33 inches long, not counting the length of the probes. They come with little caps for the plug ends[1], which strike me as quite needless.


The probe tips are short[1] -- barely 9/64" long -- and not very sharply pointed.


Continuity Test

For resistances lower than about 30 ohms, the meter issues a discreet beeping sound. There's no way to turn off that feature.

Hold Feature

Pressing the button labelled 'H' forces the instrument to hold its current reading in its display. Pressing the 'H' button again releases the hold, and returns the device to normal operation. Be aware that nothing appears in the display to indicate that 'hold' has been invoked. One could get faked out and think that the meter was defective because of a 'stuck' display.

Instruction Manual

The little manual that comes with the meter is remarkably good -- easily one of the best such manuals I've ever encountered.

Accuracy

I'm not equipped with calibration standards gear, so I just have to take the manual's word for it. I expect that the meter's accuracy is entirely ok for this class of instrument. The voltage scales display zero when they're supposed to; the ohmmeter displays 0.1 ohm on the low ohms scale with the test leads firmly shorted together. Good enough.

In Conclusion

For $9.99, I'd say that I've done alright. I bought this to have a basic multimeter with me in my carry-about tool kit, and it looks like this should serve. I have no gripes with the thing, though I would like it to be possible to disable the audible continuity test feature

* * *

Note:

[1] The guarded, deeply recessed banana jacks/plugs and short probe tips are typical these days. They're supposed to make for user safety, but they limit a meter's versatility. A standard banana plug just barely inserts far enough to make, which complicates the fabrication of special/alternative test leads a bit. The probe tips are too short to enter, say, a household electrical receptacle for a quick test to see if a receptacle is live, and if it's wired correctly. 'No big deal, but I'd happily settle for a little less 'safety' in favour of versatility and ease of use.

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Friday, February 15, 2019

A Timing Light From Way Back In The Day


This thing has been languishing in a drawer for decades now.




Does anyone still use these? Canadian Tire lists a couple of models, so I guess there's still some use for them -- by those who work on vintage cars and trucks, I imagine.

I opened it up just for a look-see what's inside.


Yikes! I'm not even going to try to reverse engineer that -- too many mystery components.

- - -

I buttoned it back up and tried powering the thing with a 12V, 1.5A bench power supply. Pressing the trigger button way overburdened the power supply. I need to get a lead-acid battery to power it with, then I can maybe try it out with my spark generating apparatus. Meanwhile, I'll retire it back to its drawer.

 - - -

Progress -- THURSDAY, FEBRUARY 21, 2019

I decided that I don't really want to be the owner of a 12V lead-acid battery. Instead, I set about beefing up the output capability of my bench power supply. That worked out well enough, and let me carry on with trying out the timing light.

- - -

A Snag

It turned out that the timing light was drawing too much current because of component failures -- the inverter wasn't oscillating; it was just loading the power supply. So, I set about reverse engineering the timing light. Following are the two schematics I came up with; one for the primary (inverter) circuit, and one for the secondary (DC power supply) circuit.




Following are some notes on the schematic, and my experience with troubleshooting the thing:
  • I can't vouch for the absolute accuracy of my schematics. Reverse engineering is a tricky business, fraught with booby traps.
  • Transistor Q1 was fried and leaky. There was no part number on Q1, so I went for a rummage through my stash of transistors. On the basis of a SWAG[1], I chose a TIP122 NPN Darlington for a replacement. With the new transistor installed, the unit was still inoperative.
  • The passive components all looked to be more-or-less ok.
  • Electrolytic capacitors are notoriously failure-prone[2], so I replaced C3 with a 4.7µF, 63V item, even though the original looked reasonable on a capacitance meter. That fixed it.
So, back in business. With the timing light's inverter oscillating properly, the unit's current draw at 12V is about 1A. I tried out the light with my spark generating apparatus, and it worked as it ought to. Now if I just had my 1961 Austin-Healey Sprite back, I'd have a real use for the thing.

- - -

A Video -- FRIDAY, FEBRUARY 22, 2019

I made an attempt at video recording the timing light in action on my spark generating apparatus. The video opens with the apparatus idle at top dead centre. (White marks on cylinder cooling fin and flywheel fin aligned.) Further on, in dim ambient light, you can see the timing light capturing spark occurrence. Spark occurrence is a few degrees before top dead centre. Here's the video.



* * *

Notes:

[1] Scientific Wild-Ass Guess.

[2] I've known electronics 'technicians' who could scarcely read a schematic, or operate an oscilloscope, yet they did a credible job of troubleshooting and repairing electronic equipment failures. If they knew little else, they knew that electrolytic capacitors are failure-prone. That bit of knowledge goes a remarkably long way in the electronics troubleshooting field.

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Sunday, February 10, 2019

Lexicon -- Snowblower vs. Snowthrower


[WEDNESDAY FEBRUARY 13, 2019: I had a really nice opening photograph of a snowthrower in action right here, but I decided to take it down. The image as it appeared on Google Search was captioned, "Images may be subject to copyright." Hmmm. I've read anecdotal horror stories of individuals being dunned for royalties because of inadvertent copyright infringement, and I didn't want to become another anecdote of that sort. So, here's a lame photo that I own of a snowthrower that I own that's not in action.]


[Then I wrote the following back on the 10th of this month.]

 - - -

One sees the terms 'snowblower' and 'snowthrower' used interchangeably. But 'blowing' and 'throwing' are two different things. So which should it be? -- 'snowblower' or 'snowthrower'?

 - - -

I've thought long and hard about this, and I've decided that it has to be 'snowthrower', not 'snowblower' -- all one word; no space between 'snow' and 'thrower'.

Consider; what would a snowblower be? It would be a machine that creates a wind that blows snow off your driveway. The machines we have do no such thing. They pick up the snow with a rotating auger, and they forcefully hurl it out of a chute -- they 'throw' it.

So there we are; an end to the snowblower/snowthrower quandary. It's 'snowthrower'.

- - -

Then I chanced upon some internet items that just happened to touch on the subject, "Snowblower vs. Snowthrower", and I got a bit of an education. In a nutshell, a 'snow thrower' is a single-stage machine with only an auger that picks up and 'throws' the snow. A 'snowblower' is a two-stage machine with both an auger to pick up the snow, and an impeller to 'blow' the snow out the discharge chute. An outfit known as Jacks Buying Guides has a good, brief article on the subject.

I'm still inclined to maintain that what all the machines do is they 'throw' snow; they don't blow it. That said, at least now I know what the generally accepted difference is between a 'snowblower' and a 'snowthrower'. And I still think that 'snowthrower' ought to be all one word, just as 'snowblower' is all one word.

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Saturday, February 9, 2019

A Compact, Lighted Travel Makeup Mirror


A neat little item, but this mirror's lighting is flaky.


The unit is six inches square.It has a light with selectable colour filtering at either side of the mirror. The lights come and go at random. Let's see if we can discover the fault.

- - -

The lighting is from two little incandescent bulbs powered by four 'AA' cells.[1] Here's a view of the lights popped out of the mirror's frame for access.


The bulbs weren't firmly screwed in. Snugging them up tightly did away with the flakiness. The mirror's lighting now works as it should.

As for any further seviceablity of such a thing -- good luck. Should a cold solder joint surface inside, it would be game over because I can see no way to non-destructively dismantle the mirror. It looks to me like the factory screwed the front frame to the rear frame, then forcibly snapped the mirror in place over the screw heads. 'Odds of prying out the mirror without breaking it are slim to nil.

- - -

The Light Bulbs

They're what's known as G-3½ miniature screw base bulbs. They have their electrical characteristics printed on their bases, but there are no type numbers. (They're rated at 4.8V, 0.5A.)

The 'G-3½' business breaks down like this:
  • G = Globular (as far as I know) bulb shape.
  • 3½ = 3½ eighths of an inch bulb diameter; i.e seven-sixteenths of an inch.
You can see what an arcane bit of business we're dealing with here.

I have an extensive listing of miniature light bulb types in my possession, in the form of an elderly Electrosonic Inc. catalogue. Nowhere in that catalogue's listings is there a G-3½ bulb rated at 4.8V, 0.5A. The odds of finding such bulbs are slim to nil.

- - -

So there we are -- a nicely designed and executed little makeup mirror that will be landfill should it ever give more trouble than it has so far.

* * *

Note:

[1] The mirror is fitted with a 3.5mm phone jack for use with a six volt AC adapter. Plugging in a plug disconnects the battery, and puts the unit on external power.

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Monday, February 4, 2019

A Zenith Royal 66 AM Receiver


Here's an antique from the earliest days of the transistor radio.


It's so old, it has a bulky air-dielectric tuning capacitor in it, rather than a modern, miniature film-dielectric tuning capacitor. Here's a rear view of its innards.


It's quite dead. I'll check the battery cells and their contacts.

- - -

All four cells were totally discharged. The unit must have been left turned on and neglected. New cells got it going, and it works nicely. The volume control is noiseless. There's a bit of noise at the very low end of the tuner's reach.

The battery compartment contacts are excellent -- clean and free of oxidation. Zenith knew what they were doing.

 The only real flaw was a loose tuning dial numbers ring. Some CA adhesive took care of that.

- - -

It Was A Different Time

The battery compartment map on the inside of the rear cover gives instruction for the installation of mercury cells.


Mercury cells have been virtually banned for a long time now, because of their toxic contents.

- - -

So there we are -- a working radio set, probably from the 1950s, back when we used to manufacture consumer goods in North America.

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Sunday, February 3, 2019

A Lawn-Boy ST320E Snow Thrower


Here's a 'won't start' snow thrower that my son picked up for very little money.


I just brought it in from outside, so there's snow on it. I'll leave it to make a puddle on the floor, and return to it when all is dry.

- - -

It's a Model No. 55380, Serial No. 000242. That serial number doesn't show up on Lawn-Boy's website as being legitimate. Perhaps it's a Canadian serial number that Lawn-Boy couldn't be bothered to track.

Anyway, I got some useful information from the website on the model series:
  • Swath: 20 inches.
  • Engine: Tecumseh Model No. AH600-1657N; 3 hp; 2-stroke cycle; electric start.
  • Engine Speed: 4,000 rpm ± 100 rpm..
  • Ignition Coil Air Gap: 0.013".
  • Mix Ratio: 50:1; originally 32:1. [The subject machine is 32:1.]
  • Spark Plug: Champion CJ8Y.
  • Spark Plug Gap: 0.030".
So there are the fundamentals. 'Next step is to see if the engine has spark and, if so, does the kill switch work.

- - -

Top Cover Removal

Seven No. 10 x 1/2" hex washerhead screws (5/16" A/F) fasten the top cover. (Two of the screws are missing on this machine.) The fuel tank's cap must come off, then the cover can be forced up over the fuel tank's neck and slid up the handlebars a ways. A small bungee cord serves to hold the cover up out of the way.


Spark Plug Access

Here's where things get a bit messy. I don't have a compact 3/4" spark plug socket that will reach in neatly under the machine's rear cover, so I'll have to loosen off the rear cover a bit to get the spark plug out. A few more No. 10 x 1/2" hex washerhead screws have to come out.

And here's the spark plug out.


It's a resistance-type spark plug -- Champion RCJ8Y. Centre electrode resistance is about 13k ohms. The plug is in reasonably good condition. Gap is a 'loose' 0.030".

And a test shows that I have spark, and the kill switch works. I'll clean and gap the spark plug and reinstall it.

- - -

A Needless Retaining Clip To Watch Out For

Tecumseh likes to install a barb-fastened retaining clip on a cooling fin of the cylinder head to keep the spark plug wire in place. On this engine, the clip has come part way off. (The clip is right at the centre of the following photograph.)


Delete the clip entirely; it's not needed, and it can come loose and get into the engine's flywheel/starter-gear area. I've had that happen on an MTD snow thrower with much the same engine. The little gone-astray clip had the engine jammed solid until I found and removed it. Here's a view of the clip from this engine, alongside the one that I had once retrieved from a similar Tecumseh engine.


Again, the clip is not needed, and can cause nasty trouble if it comes loose.

- - -

It Starts!

At room temperature here in the workshop, it started on the first pull with only choking -- no priming. I know from experience with this engine that it is very easily flooded by needless priming. I wonder if that might have been a factor in the original owner's decision to let the machine go -- perhaps he'd been inadvertently flooding the engine. There's a chart decal[1] on the dashboard, though, that gives good guidance for use of the primer bulb. What all went on with the machine before my son got it, I'll never know.

- - -

Rear/Underside Accessibility

Rear/underside service accessibility on this machine is dreadful. There's a single rear/underside cover that incorporates the dashboard. Gaining access to the carburetor to remove and service it looks like a daunting task. Here are two views.




Note that someone has cut away the grillwork under the carburetor to lend accessibility to the carburetor's float bowl. I'll remove the float bowl and take a look-see for contamination.

- - -

There's some particulate matter in the float bowl, but no evidence of water. The float level appears to be set very high.

Be that as it may, for the time being I'll go with the adage, "If it ain't broke, don't fix it.", clean the float bowl and put it back on. There are some improvements I want to make to a couple of cover attachment points.

- - -

Two Cover Attachment Brackets Riveted So They Can't Swivel

The Tinnerman nut brackets for attaching the top cover at its upper rear corners tended to swivel a bit, so the nuts would fail to align with the screw holes in the cover. I gave each bracket a 1/8" hollow rivet, and that's the end of that little problem.




Electric Starter Switch

Dismounting the electric starter switch is the key to removing the rear/underside cover. (Along with removing the wheels.) With the switch off its mounting block, and the mounting block off the cover, the switch can be passed up through a big opening, out of the way of cover removal. Here's a view of that.


Wheel and axle removal is straightforward -- there are external snap rings holding the wheels on.


And here we are with the rear/underside cover out of the way of carburetor removal.


In addition to getting the starter switch and its mounting block and the wheels out of the way, the following items must be dealt with:
  • The discharge chute's positioning crank must be unpinned and removed from its shaft.
  • The kill switch's wiring must be disconnected from the kill switch.
  • The choke handle must be forced through its grille opening.
  • The primer tube must be removed from its nipple at the carburetor.
With all that done, the starter cord can be eased out a bit, and the cover moved well aside.

- - -

Carburetor Removal

Here's the carburetor accessible for removal.


And here's the carburetor off the engine.


Note the following:
  • A spring-type hose clamp secures the 1/4" I.D. fuel line to its nipple. Have a suitable container handy to drain the fuel tank, or a stopper for the end of the fuel line.
  • Two 3/8" A/F hex nuts fasten the carburetor to the engine.
  • There's a gasket, and then a spacer/insulator block between the carburetor and the engine. The gasket is likely to be welded to the carburetor. Just leave it be. Leave the spacer/insulator block on the engine.
  • There are no extraneous mystery holes for the governor spring and link. Governor spring and link installation is straightforward.
  • The carburetor is as simple as carburetors ever get. There is no idle circuit -- the carburetor is designed to operate only at the engine's 4,000 rpm governed speed via the main jet. There is no mixture adjustment.
  • The choke detenting on my carburetor is imperfect; the choke butterfly's lever doesn't want to engage the fully wide open detent. The choke butterfly's wide open position is a little askew from fully wide open. I can see no way to correct the flaw.
- - -

Fuel Tank Removal

I chose to remove the fuel tank so I could thoroughly drain it and dry it out. The tank is attached at two points, with one 1/4"-20 fastener and one 10-24 fastener. The nuts used are prevailing-torque types, so they're a bit stiff to get off and on.
- - -

A Brief Trial -- MONDAY, FEBRUARY 4, 2019

I buttoned up the machine sufficiently to try it out, mixed up a half litre of 32:1 fuel and took it outside. It started on the first pull. It's been mild lately, and the snow has compacted and gained density, so it wasn't much of a trial. But the machine does work. 'Time to finish up 'perfecting' it.

- - -

Remounting The Electric Start Switch Mounting Block And Switch

The original fasteners were discrete screws and nuts. I prefer not having to deal with discrete nuts, so I'll install threaded inserts. We'll see how that works out.

- - -

And here we are with two 6-32 inserts in the mounting block.


And three 10-24 inserts in the underside cover.


I add a bead of runny CA adhesive around the flanges of threaded inserts, just for good measure.

I'll reinstall the mounting block and switch with anti-seize compound on the screw threads, and I can get on with an examination of the snow thrower's drive train.

- - -

Drive Train Cover Trouble

The two lowermost screws for attaching the cover are not original -- they're 10-24 screw-and-nut arrangements that have rusted to near seizure. I managed to get them apart and out. Here's a view of the cover fastener complemement.


The best I'll be able to do will be to come up with hex head replacements for the 10-24 screws. New nuts and anti-seize compound should make for an assembly that can be opened up again readily if and when the time comes.

- - -

The V-Belt Drive Train

It appears to be in remarkably good condition.


The belt looks ok. The tension idler runs on a big sleeve bearing that's in fine condition. I can button that up, and put the machine outside to see how well it starts at low temperatures.

- - -

Whoops! -- THURSDAY, FEBRUARY 7, 2019

There's nothing like old machinery to keep one occupied. I was trying out the machine this afternoon, and it started to run poorly after a bit. It turned out that the choke handle's stud had popped loose from the choke lever. The engine must have remained choked after I thought I'd opened the choke.


Not one of Tecumseh's finer moments.There are three possible ways to go to repair this:

a) Swage the stud back in place in its lever with a centre punch. That might work, but if the stud worked loose once, it may work loose again. The design is evidently not trustworthy.

b) Cut away the grillwork in the cover immediately behind the carburetor, so one can reach in and operate the choke lever directly, without the aid of a handle. That would do away with the possibility of another choke handle failure, but it's an inelegant solution -- the sort of thing a bush mechanic would do in a pinch. I'll leave that for a last-ditch solution.

c) Fabricate a new stud from a 2-56 screw and hex nuts and red threadlocker. I have some stainless steel 2-56 screws on hand that I got from Amazon a while ago. The screws are very nice, and one of them ought to be strong enough to serve as a stud. I think I'll go with that.

- - -

Fixed

Here's my replacement choke handle stud.


That's a 2-56 x 3/8" stainless steel hex socket head screw and three hex nuts assembled with red threadlocker. That should work and last. And here it is with the choke lever's handle clipped on.


Now I can button up the works again and try it out in the morning.

- - -

Choke Position Detenting

Earlier on, I mentioned that there was a defect in the choke's detenting -- the choke couldn't be quite fully opened. While I had the carburetor off the engine again, I tried modifying the detent profile with a diamond burr in a rotary tool. That worked out ok, and the choke now detents correctly. Here's a view of the modified detents.

- - -

A Proper Trial -- WEDNESDAY, FEBRUARY 13, 2019

We had some real snow here, so I got a chance to try out the snowthrower. It started easily, and it chewed its way through snow as deep as the height of the snowthrower's intake maw. I cleared a walkway all across the back of the house with it.

I'm actually quite impressed by these small machines. They save the user a lot of heavy lifting, and they're far more maneuverable than the big, two-stage snowthrowers. For dealing with relatively light snowfalls, they can't be beat.

I'll put this machine up for sale on Kijiji, but I'll hang onto my MTD SnowFlite.


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Note:

[1] Here's the primer usage data from the decal. (Temperatures were Fahrenheit. My approximate Celsius equivalents are given in square brackets.)

FUEL PRIMER

BELOW 15° - FIVE PRIMES [Below approx. -9.5° Celsius]
15° TO 30° - TWO PRIMES [Approx. -9.5° to -1° Celsius]
ABOVE 30° - NO PRIMES [Above approx. -1° Celsius]


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