Cosmic Quandaries with Dr. Neil deGrasse Tyson

[HysteryDiagnosis]

http://www.youtube.com/watch?v=CAD25s53wmE

[MineralMan]

1. I like your animated gif of the bridge rectifier.

It's a great explanatory illustration. I've saved it to my PC to use when needed.

[HysteryDiagnosis]

2. A Wheatstone bridge if memory serves, they use these on gas/diesel powered welders

to convert the 110 ac to dc, then the fields are excited with it. Perhaps we could hook it up to the seats in the congressional building and get them excited about doing what it was that we sent them there to do.

[MineralMan]

3. Actually, a Wheatstone bridge is something completely

different, although the circuit diagram is a similar shape. A Wheatstone bridge is used to determine the value of an unknown resistor or capacity. The four components are resistors or capacitors, rather than solid state diodes. Completely different function.

Your image is a full-wave bridge rectifier, which uses four semiconductors to convert AC current to DC. It creates an output that contains the voltage from both halves of the AC waveform, therefore it is more efficient than a single rectifier circuit which only passes half of the AC waveform.

Bridge rectifiers are used in all sorts of power supplies, and have been around for a very long time, including the vacuum tube days.

Here's a page that explains the Wheatstone bridge: http://www.efunda.com/designstandards/sensors/methods/wheatstone_bridge.cfm

[HysteryDiagnosis]

4. How could I have messed that up? It's been almost 35 years since I built circuits on

breadboard, built a digital VOM, Heathkit 20 mghz scope, (still works) tv and a power supply, signal generator breadboard combo.

Thanks for the correction muh old brain ain't what it used to be.

http://en.wikipedia.org/wiki/Wheatstone_bridge

[MineralMan]

5. Yah, that stuff slips away if you don't use it.

I'm still monkeying around with electronics. These days, it's mostly restoring old vacuum tube stuff. Right now, I'm working on a 1946 television set. 7" CRT, in a box the size of a large microwave. Restoring that old stuff is getting expensive, and many parts are not available in their original forms. Many of the vacuum tubes used in that receiver are scarce, and weren't used in many things, since TVs were rare that early. So, a defective tube can cost a pile.

The worst thing, though, is the difficulty of getting electrolytic capacitors with a high enough working voltage. This set operates the plates of some of the vacuum tubes at 450 volts. You can no longer get usable electrolytic capacitors with the same form factors as the original metal can types used in that equipment. So, to maintain the appearance of the chassis, you have to dismantle those old capacitors, deal with the strong base used as an electrolyte and use the can as a housing for more modern capacitors. It's tedious work, and it's always tempting just to wire in the caps under the chassis. But that's not a nice thing to do for purists.

I did, however find a NOS 7DP4 CRT to replace the dim and weak original. You do not want to know how much that thing cost.

And, when I'm done, I'll run VHS tapes of old television shows on the set, just for grins, and to show today's kids what a TV started out looking like. Fun times.

[HysteryDiagnosis]

6. Oh my gosh, you are hardcore. You will definitely have to get the honeymooners to

play on it.

http://www.amazon.com/Honeymooners-Classic-39-Collection-VHS/dp/6304179103/ref=sr_1_1?ie=UTF8&qid=1312591225&sr=8-1

[MineralMan]

8. Way too late a show for that set.

The reality is that there is nothing available from 1946, but I do have some recordings from kinoscope from 1949, and some more from 1951 and 1952. You wouldn't recognize the programming. There's actually quite a large collector community out there for early television. I used to have a 5" set from 1939, but prewar stuff is wonky if you want to see it in operation. Different standards. I sold it to another collector, in perfect working order with no restoration required. That paid for a lot of the stuff for my usable set.

[HysteryDiagnosis]

7. One other thing, things have changed a tad since we played with our radio shack

electronic kits.

[MineralMan]

9. Indeed. My interest is only really in early stuff.

I'm working on a line of catwhisker galena radio detectors right now. There are none being made currently, so there should be a ready market for them. I'm doing a very close replica of an actual detector and should be into small-scale production this winter. They work great, and there's a new interest in building crystal receivers these days for hobbyists. The problem is the unavailability of the detectors. Wish me luck. There's no money in this, BTW. It's a labor of love. The low melting temperature alloy used to imbed the galena in is expensive. I don't want to use Babbitt metal, like the originals, due to the lead content, and an equivalent uses some expensive stuff.

[HysteryDiagnosis]

10. I have to deal with digital stuff most every day..... it's amazing how some software

tries to inform you of a problem such as "missing input function". Cryptic to be sure, good luck with your projects, I imagine you a fan of Nikola Tesla as well.