Nuts & Volts - July 2005

Tech Forum

for a piece of 40-year-old electronics!

The preference of tubes vs. transistors is highly personal, there's no clear "right" choice for everyone, and each has its advantages. Tubes are often cited as being prone to failure. Yet a well-known tube amp designer has stated that a properly designed tube amp can be every bit as reliable as a solid-state device. While solid-state products have controlled the market for years, there have been more tube devices manufactured lately than at any time in the last 25 years. Who'd have guessed that would happen?

Jim Addie La Grange Park, IL

the diode does and recommend a replacement. It is quite certain that it was not used as a rectifier in the high voltage circuit. Using a diode as a fuse would not be reliable because the failure mode is almost always as shorted. Using a diode as a switch is a common application. If the broken diode is a small glass type, a 1N34A will no doubt replace it.

Russell Kincaid Milford, NH

Starting with calendar year 2004, we are archiving a years’ worth of issues on a CD that can be searched, printed, and easily stored.

[#05054 - May 2005]

I need an inexpensive I/O card that has about 12 digital input/ outputs and six analog input points. It needs to fit into a standard slot in a PC.

#2 That is probally a Tunnel Diode made from germanium. They can switch in less than a nanosecond but the voltage range is about 0.1 to 0.5 volts and are usually followed by amplification. Your best bet is to find a Tek website and try to get a replacement from a similiar model scope. Or at least the same part number. TDs are no longer made and if so, are very rare.

Ken Roibbins Reading, MA

You can purchase said disk from us for your own personal use and dispose of your old paper copies that are collecting dust in the garage. (Your spouse will love you for it!)

We will also be archiving earlier years as well, so stay tuned for their availability.

Omega.com sells a board for $479.00 www.omega.com/ppt/ pptsc.asp?ref=CIO-DAS16JR

Have you considered using a microcontroller such as Atmel's ATMega8, connected to your PC's RS-232 port? This MCU has enough onboard I/O to meet your requirements and the RS232 interface is easy to program. I can help you with this if you are interested.

Daryl Rictor circuithelp@yahoo.com

[#06054 - June 2005]

There is an Internet provider in Calypso, NC which provides broadband Internet service with microwave radio:

www.nboxwireless.net

We need someone to put something like this in our community, as the phone company will not install DSL lines because there is not enough revenue to pay for new fiber optic cables.

F o r

E l e c t r o n i c s

NUTS & VOLTS E v e r y t h i n g

[#05055 - May 2005]

I was troubleshooting a Tektronix scope's high voltage circuit and I broke a germanium diode. It looks like it functions as a switch in this application. Why would a germanium diode be used in any circuit other than a crystal radio? Are they sometimes used as fusing devices because of their lower current rating?

Will any germanium diode work?

#1 If you gave the scope model, someone could tell you exactly what

102

#1 I know Curt WB4WAA personally, and am in the exact same situation. The local phone provider here is Sprint, and the cable company is also Adelphia.