Hi All, I've aquired a Bugtrap 2074A all boxed with manuals condition unknown and was trying to do a comparison against my HP comparator to ascertain it's condition. My problem is this: The HP identified a faulty o/p on a 74ls20 chip so I dropped the bugtrap on and it says it's fine, or rather I should say no leds came on after I pressed the reset button (some where on before). I'm using the same 'known good' comparison chip and I've buzzed the ribbon cables out and there are no breaks. And I did have the power clips connected :o) I cracked the bugtrap open and there doesn't seem to be anything obviously blown though I note that someones replaced one of the power supply protection diodes in it at some point. So I suppose my quesion is, from the manual it appears that you only need to switch in the VCC and GND signals and not worry about setting I/P and O/P like the HP am I reading this correctly or just being dumb? Cheers Chris If you ever want to (un)subscribe yourself with TTL, you can send mail to: <Majordomo@flippers.com> with the following command in the body of your email message: (un)subscribe techtoolslist or from another email account, besides xxx@yyy.com: (un)subscribe techtoolslist xxx@yyy.com