Doug,

You can test the HOT like you test any other transistor. Here are some articles that might help you out:

Checking Transistors and Diodes on eHow: http://www.ehow.com/how_7600754_troubleshoot-diodes-transistors.html
Outerworld Arcade Star Castle Sound Board Repair: http://www.outerworldarcade.com/arcade/cinematronics/star_castle_sound.html

I prefer the directions on the eHow article but the Outerworld Arcade article has a nice diagram that shows you which legs are which. Follow the directions under the Testing a Transistor heading on each of these articles. If you’re still having trouble after reading these articles, our Volume 2 DVD has an exclusive video on Checking The Horizontal Output Transistor that should help you out. This video contains some good knowledge on how to test and identify different HOTs. You can order this DVD from our online store.

If you’re looking for parts, we have a list of electronic parts suppliers under the Electronic Components Distributors heading on our resources page. We really like NTE Electronics, Inc. (http://www.nteinc.com/) as they have a great cross reference tool that you can plug pretty much any part number into and it will give you the equivalent NTE part number.

Since you have a D9200, we HIGHLY recommend checking out this troubleshooting guide from Wells Gardner: http://www.wellsgardner.com/pdf/Repair/D9200_27_33_39_inch.pdf. It has some great information on what parts might be causing your issue.

Hope that helps. Thank you for your question and good luck with your repair.