Post
by e3steve » Wed Sep 12, 2007 4:11 pm
Sorry guys, I've been away to UK (little girl got married); and my laptop was stolen, so other priorities....
For reference, take a look at the diagram again: positive output lug is normally adjacent to the bevelled corner, negative output is diagonally opposite. AC input is fed into the remaining two lugs, either way around. This is 99.99% the case with the type of bridge rectifiers we're dealing with here. If there's a different diode layout in this type of package I've never seen it in my 36 yrs in electronics (but that doesn't mean to say that it may not exist!). Ergo, as long as you can locate either the pos or neg lug, then you'll have no trouble locating the remainder. All a diode really is? An electrical non-return valve! So it's quite easy to test with a continuity tester or a meter. See also my post "Let's test a rectifier", which will show how to locate the lugs if there are no markings,
13.25V sounds like a big improvement over the old celenium rec, DD! The heat sink is indispensible, as the rec will get hot, so dissipation is the key. If you look back thru my previous idle chit-chat, you'll find reference to some recs with their current-handling figures; the higher the Amps it will handle, the less heat it will produce. One problem, of course, is that it's not in much of an airflow, so the biggest, fattest (and finned) h/s you can get in, the better. Make sure the rec sits on the h/s absolutely flat (de-burr the mounting hole) and it's always a good idea to bed it down on some heat-conducting paste (cheap as chips from Radio Shack) and bolt it good & tight. The charging system probably produces a maximum of 10 Amps and, as the system is fused at 15, so a 15-Amp rec will suffice; but if you want it to run cooler, go for a 25-Amp. Please look at my previous posts here, as there are different types of diode with less attenuation (reduction), but a silicon-diode bridge rectifier should be the favourite. For best heat-handling results get a rec that's potted in a metal package too.
Get back here if you need any more info.
Regards, Steve
