INTRODUCTION The Model 520 Transistor Tester is designed for in-circuit transistor testing, with special features for making additional tests on devices out-of-circuit. It uses a high current, low duty-cycle pulse technique to test transistors in the presence of shunting circuitry, and a system which eliminates the need to identify the terminals of the device. The instrument is designed for a minimum amount of control manipulation, making for rapid testing of most devices. SPECIAL FEATURES 1. Patented limited-energy pulse circuit permits highly successful use of in-circuit testing in the presence of low shunt impedances with complete safety for the device under test. 2. A human-engineered panel design which eliminates the need to refer to manuals — only two switches, no panel adjustments. 3. Six-position TEST switch sequentially connects the device being tested in all possible configurations making it unnecessary to know the device terminal identification. Can be left in GOOD position so that additional tests can be made without memorizing test position. 4. Base or gâté lead indicated by color as test switch is operated. 5. Audible tone tells when device under test is good - no need to take eyes off circuit board while testing hard-to-get-at devices. 6. A logarithmic leakage meter which displays a wide leakage current range on a single meter scale. 7. Automatic polarity indication to identify NPN or PNP type devices. 8. Identification of SILICON and GERMANIUM device types for proper evaluation of leakage current with color-keyed LED indicators for positive test interpretation. 9. Locking test leads that make positive connections to devices in difficult locations. Frees operator’s hands to make further tests. 10. Choice of test leads or front panel socket for out-of-circuit tests.gned for a minimum amount of control manipulation, making for rapid testing of most devices.