Visualize Better With Idea Sketch
     

Fig. 1: Idea Sketch is a handy app from NoSleep Software.
Steve Smit is the chief engineer for Salem Communications’ Twin Cities stations in Minneapolis/St. Paul. He writes in with a really neat tablet app called Idea Sketch.

How many times have you needed to draw a simple diagram but didn’t have a drawing program on your computer? Or you’re in the field with your tablet or smartphone? Idea Sketch is the answer.

You can draw a concept or flow chart and convert it to a text outline, or vice versa. The app lets you copy text in from another source such as an email or document, import it and create an idea that can be viewed as a diagram and outline.

Check out this slick YouTube video showing what it can do. The application is available for both Apple and Microsoft operating systems. The iOS version supports Box.com, Dropbox and Facebook, among other features.

Steve, this is a great suggestion; thank you for providing it.

Workbench welcomes your own ideas for handy apps. Write to me at johnpbisset@gmail.com.

* * *

Given our focus on AM maintenance items in the previous column, it is timely that Crawford Broadcasting’s Cris Alexander recently included a note in the company’s Local Oscillator newsletter reminding the chief of every AM station to make certain that the station’s occupied bandwidth measurements are up to date and in the file. Remember, AM stations must do these measurements at least once every 14 months.

And while on the subject of paperwork, it’s a good time to make certain that your quarterly tower light inspections are up to date too. Those of you with MoM (Moment of Method) licenses need to keep an eye on that two-year anniversary of the license grant. You will need to recertify the sample system before that date.

Sometimes engineers of nondirectional AMs can be lulled into a false sense of security when it comes to logging practices. Don’t forget little administrative things like this. Thanks, Cris, for the reminder.

* * *

Continuing our earlier discussion about Optimod power supplies:


Fig. 2: A typical switching power supply.
Broadcast engineer Paul Sagi has worked on a number of them over the years. He offers an alternative to a complete power supply change-out.

In Paul’s case, the issues with these switch mode power supplies were shorted 0.1 nF caps on the analog boards. (Once, an IC that converted between digital and analog was bad.)

The Artesyn SMPS pictured in Fig. 2 is the same or similar to several that Paul has repaired, most recently in Gentner telephone hybrids. In those supplies and seven or eight others, the problem was an open startup resistor. Those resistors often are something like 110k ohms at 2 W and are located near the main input filter capacitor. The 2 W size makes them easy to spot. Replacement is inexpensive and fast. Just be careful not to overheat the PCB traces when de-soldering or soldering in the new resistor; they detach easily.

Over the years, Paul has repaired at least 40 switch mode power supplies; though not an expert, he has repaired enough to spot the problem quickly. Some use a PWM control IC, number UC3842. It fails sometimes, and the 10 uF or 100 uF capacitor connected to them often fails, as does the startup resistor.

You can replace the IC with a UC3842N or UC3842AN, as the original has a nasty habit of “lockup.”

Another tip: Replacement capacitors in an SMPS must be low-ESR types. (ESR stands for equivalent series resistance.) Capacitors are not pure capacitance but have some value of resistance in series with the capacitor.

 

Fig. 3: Don’t let weeds eat your generator.

Polymer capacitors usually have a lower ESR value than “wet” electrolytic capacitors. Low ESR capacitors usually are more stable under varying temperatures. Using traditional capacitors as a replacement may cause the supply to overheat and fail. Thanks, Paul, for the information.

* * *

Generators are gaining in popularity at both the transmitter site and studio. It’s easy to forget these behemoths — until they stall or don’t start in an emergency. Eliminate the surprise factor and budget a checkup, especially when summer storm season is approaching.

Perform a visual check inside the generator housing. Look for loose or worn belts, bird (or other critter) nests at the air intake, leaking hoses or fittings, and loose hardware.

Starting up the genset is not the same as running it under load. You’re fortunate if you have a generator, but make sure it runs as it would when the utility power goes away. Routine testing and inspections are crucial. It doesn’t matter what brand generator you have; if you ignore it, the genset will fail.

Contribute to Workbench. You’ll help your fellow engineers and qualify for SBE recertification credit. Send Workbench tips to johnpbisset@gmail.com. Fax to (603) 472-4944.

John Bisset has spent 44 years in the broadcasting industry and is still learning. He handles West Coast sales for the Telos Alliance. He is SBE certified and is a past recipient of the SBE’s Educator of the Year Award.


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