Batboard

Our station has a Wheelock TPA-100-B PA amp for overhead telephone paging and monitor receiver. R 20 is burned. If you have one of these amps, will you remove top cover and give me the color bands on R 20 on the power supply board. Model TPA-60-B might have the same resistor. A copy of a schematic would really help.

1. If you can, contact the company that did the installation for help.

2. Try this site:
http://www.devicemanuals.com/guidedownl ... U56QT.html
It looks as if the book may cost a few bucks but it'll tell you what you need to know.

3. It looks like Wheelock is still in business, although their site does not have the circuit diagram shown. http://www.wedophones.com/Manuals/Wleel ... 20inst.pdf
(The misspelling of Wheelock in the URL is correct, by the way.)

A resistor in a power supply is usually one of two things. Either it's a bleeder resistor for a high-voltage supply, 500,000 ohms or so, or an equalizing resistor across each of the diodes that convert the AC power to pulsating DC. Also a remote chance it's a voltage dropping resistor used to provide some low-current auxiliary voltage. If the resistor is large I'd bet it's a bleeder.

Regards,

If its the same Wheelock that makes fire alarm equipment, they got bought out by Cooper industries and are now called Cooper Wheelock

I didn't see that amplifier listed in their "discontinued products" stuff but you might try getting ahold of them and see if they can get you a schematic.