The Sorcerer's Progress (Page 14 of 62)

I know your pain njc - we've only managed to find the last few things a final spot this weekend and I think what you're doing is worse than just moving to a new place in some regards.

Our collection of books that will never work in a digital format ranges from wildlife photo books to Asterix books before we had kids. The trick is not to buy more ... sounds easy, but it's really hard. But good luck, I hope you find the space you need for the ones you want to keep!

I still owe you a review as well - amy has a deadline, so she's top of the list later this week, but your latest chapter is blinking brightly like 500 LEDs on my radar. Lucky for me, at the rate I'm writing these days, I'm able to keep up with reviews! (it's actually not a good thing at all, I'd still take more time to write any day even if it means falling further behind with reviews). This is just a long way of saying I'll get to it soon-ish.

What's this head-amp thing? Is this something you need for the telephone gadget or does this mean the telephone gadget is done or does this mean the electronics "laboratory" (with questionable fire safety as deemed by pencil pushers in a city office somewhere) is being/has been moved and is working again or is not working at all or has been fixed to be deemed adequately safe by the esteemed council officers? Worst case is that you've just added another thing that needs to be built to your list before you have to dismantle your work-bench. Or did I miss something important again? 

And when I have the head-amp done, I'll need to go through my resistor stocks and see what I need to order.  There are 24 "preferred number" values per decade (see Wiki-P, E24), and eleven plus decades of interest, with some values missing on the ends.  (Plus different sizes for 1/8, 1/4, 1/2, 1, and 2 watt dissipation.)  Most resistors are cheap in quantity 10 or 25, but the sheer number to stock adds up the cost.

(I also need to order some 100uF tantalums.  I thought sure I had some around here.)

Your stories are worth it.  Your weakness  match at least some of my strengths, and vice versa.  I know you're trying to nurture some of those skills in me.  I'm happy to return the favor.

Well, I have tinkered with the head amp to make it more resistant to changes in battery voltage.  (The output drops about 2 dB when the voltage drops by 1.6 volts.)  I'm going to have to play fast and loose with the circuit board to fit it all.

And then I have to -try- it to see how much noise the thing introduces.

Wednesday I try to find someone to take books with a hope of selling them.

I'll try to get your photos today.

I've been working on changing the bias network to keep the base bias currents steady as the supply voltage changes.  Unfortunately, my digital meter only gives me two figures at the currents in question, and when the upper digit is '1', you don't get the full benefit of the two figures.

Now, I found a configuration that combines a voltage regulation mechanism that's not good enough with a crossover-counterbalance.  They hold the current in the collector circuits (governed by the base currents) to within 10 microamps out of 120 from 4.4 to 9.4 volts.  I'll have to set it up with an analog meter to see just how stable it really  is, but it looks more than good enough.

Why is this important?  Because the amplification of small signals in the common-base circuit is quite sensitive to the DC operating point, which is set by the bias circuits and the currents they produce.

If those readings look good, the next step is to build the AC small-signal circuit on top of this stabilized-bias amp.  I don't know how much extra noise the voltage-regulating transistor may allow in, but I'll probably add a cap to help bypass it.  I need two more resistors, four signal caps, and two high-frequency bypass caps.

We'll see if I still have the factor-of-20 voltage gain.  If not, I can try tweaking up the collector current a bit.

Then I need to worry if I have enough resistors in the values I need.  They are not values available at Radio Snack (which is being wolfed down by Sprint).

Start writing, dude. Shove that circuit board back under your bed and give us more of Merran's story! We miss her!

And I think I see a clearer way for me to approach the rapid changes in attitude he experiences.  While I'm at it, I would like to drop in a little backstory (there is no such thing as a little backstory) and flip a fillip at some of my reviewers.

And I just had a talk with my brother.  I need to find a way to visit my mother soon and regularly.  The doctors say that they don't have anything more to help her weak heart.   They are guessing weeks to months.

Okay, the problem with the head amp is that I'm only getting a gain of 2 instead of 20.  I'm feeding the thing through an attenuator cable so I can turn the input down far enough, and it's easy to forget that the attenuator is 1/100, not 1/1000.

That's why I didn't see the problem.  Now, what's causing it?  Maybe my voltage stabilizing network.  If so, I think I know how to fix it ... but I'll have to find room on the circuit boards.  I need to test it on the breadboard.

First sleep, then the first set of shelf mods.  The second set I can do or hold, but I'll need to see if I need the third set.  If so, it's a trip to Lowes or Home Depot to get some melamine-covered board cut -- and get some 8d common nails, hoping they're the right diameter to cut for pegs on those shelves.

Oh no njc. All the best and my thoughts are with you too.

The nails were the right diameter.

The inspection axe fell promptly and I wasn't ready.  All of management's worries were unfounded.  The inspector did chat about the electronics, maybe to satisfy himself that I do know what I'm doing.  I have to finish cleaning up before I leave tomorrow.

And I have to change my no-inline-review request.  The X-line format is usable.

The blanket prohibition on '-ing' verbs does not recognize the difference between passive, gerund, participle, and present continuing tense. If you don't recognize each of those and the role it plays, you can't validly criticize, unles you can assert that one rule will cover all. No one rule will.

This has been rubbing about my ankles for so long that I'm going to name it 'Peeve'.