Thursday, January 31, 2013

On fixing stuff

One of my associates has taken me to task (at least it looks like it but I could be wrong-it may have been some good natured chiding) about my slightly flippant observations on a site she linked to which offers instructions in how to repair things, particularly electronic doodads and gizmos.

It may be because this person has a sneaking suspicion that we males are possessed of some secret fund of tribal knowledge passed down around the campfire that we're not sharing with the distaff side.

I am flippant by the way. It is a habit that I can't seem to shake. But nevermind.

So here goes.

Fixing stuff.....I must say that first of all, no male role models in my family shared any of the male centric secret knowledge everyone seems to think we as the (slightly) minority half of the species possess.

My father was an engineer all right but he never worked on anything at home and if he did he didn't tell me about it. My first journey to Planet Fixit was when I was 18. I had bought a 1957 Chevrolet for $25 and of course it broke down. I had a date and I asked my father if I could use his car and he took a swig of his Schaefers and a long drag on his Camel, looked over his wire rimmed glasses at me and said "Have a nice time on the bus."

Believe you me, I started learning about the drum brakes on my old Chevrolet that very afternoon. My next adventure came when I decided I had to have a 1956 Ford. I found one in a guy's back yard. dragged it out with a chain, hauled it over to Dixon's gas station and started swapping parts with a wrecked 1956 that was sitting behind the place. Eventually I had a working car, even though I left the lug nuts loose on one wheel and lost it on Vineyard Road in Edison, New Jersey.

This is how you learn-from what doesn't work, what you screw up, and what blows up in your face or bloodies your knuckles.

If there was anything I wanted to be as a kid growing up, it was a really good mechanic, because they knew all the secrets of what I was interested in, and they did not-repeat NOT-share their secrets.

Later on I worked myself into some knowledge by working for Mickey Spitzer for two dollars an hour in his garage. I could use the lift at times though and the Motors Manual was on the shelf, and there was a phone where I could talk to other equally clueless codefendants.

The entire first half of my life was bound up in shitty cars and stuff that didn't work right because I was too busted to afford new or slightly used. it is said that yankee ingenuity is born out of sheer desperation, and I tend to think that's true.

Then, I got some technical training, but it was on the other side of the country, and I had to get there in a $75 Ford Falcon. If you don't think that was a test of my nascent mechanical chops, you aren't thinking. The training morphed into a job, and that led to some tinkering with obsolete electronics like what this blog's about.

See, it's not some kind of secret lore that's passed down only to men. The knowledge is out there and you have to go and find it. There's no shortcut to it. Along the way I've learned a few things.

I've learned that unless you have some basic tactile understanding-hard to explain but you learn when something doesn't feel right (or smell or look right for that matter)-an instruction sheet is going to be just so many hieroglyphs. Unless you have a basic understanding of systems you're adrift in a sea of parts .

But these things are knowable. It takes a while to get there. Being a good technician is a matter of study and application and a quest for understanding-kinda like being a Buddhist monk on a journey.

Having said that, there are some useful published works out there. I'm not going to tell you what they are, because if you hunt them out that will get you to internalize what's in there. merely being told what to do is not a learning experience.


Monday, January 14, 2013

Handy Troubleshooting Stuff

Sometimes when you're working on an amp you get a sudden volume drop as you advance the volume past a certain point. It could be oscillation above the auditory range, but how do you sort this out?

The answer is the garden variety AM transistor radio, an example of which is depicted here. Oscillation splatters frequencies all over the place, including the AM range of 535 khz to 1700 khz more or less, and the amplitude modulation radio system is more sensitive to interference.

Simply tune the radio to a place between 600 and 700 khz where there are no stations broadcasting, turn the volume up, and then wave your magic wand over the chassis you have advanced in volume until it oscillates. You'll hear a distinct hiss, and this can also be used to track down other sources of RF noise in the house like noisy computer power supplies. Some of the boys and girls who make cheap power supplies probably figure that nobody listens to am radio anymore, which is an attitude common among people who think the world is their anime oyster and nothing else matters but their own navels and their own disorder.

After all, if you don't like truth make up your own, right? You'd be surprised at how many of these folks think that Germany won world war 2. But I digress.

You've got to be careful here because oscillation imposes crazy loads on the circuit and you can find yourself in red plate country. If you're doing this it's wise to have some method of measuring bias current connected because if it spikes that's also a clue that you're into oscillation above the audible range.

Thanks to irishsammy, where ever he may be for the image that follows.

Here's a red plated tube in case you were wondering.