Even a 10W resistor will get really hot. I embed two 5W resistors into a pentium class CPU cooler for a good compromise on space/thermal concerns. You can see a pic on my site here: http://asterontech.com/Asterontech/next_adb_conversion.html
Internal to the cube, I've found using a 5W appliance bulb to be the easiest. -- Brian Archer On Sun, Oct 25, 2015 at 7:46 PM, Toby Thain <t...@telegraphics.com.au> wrote: > On 2015-10-25 8:56 PM, Toby Thain wrote: > >> On 2015-10-25 8:42 PM, Ian Finder wrote: >> >>> No- if it works with the standard display, the supply is fine. >>> >>> Now that that's clear, I recall some cube supplies would do this >>> without a load for a display- I used to test them by triggering the >>> power-on pin, and seem to remember this behavior occurring if I didn't >>> have a big-ass resistor attached across the pins that normally >>> supplied power to the CRT. >>> >>> Try getting a dummy load on there, the circuitry you have may not be >>> putting enough load on the lines that usually run the CRT to keep the >>> supply in a steady state. >>> >>> >> >> Even though I'm an electronics noob, that seems pretty logical. Can you >> spell out what kind of resistor I'd need? >> >> Is it the 20 Ohm 20W between pin 12 (-12V) and GND that is mentioned here: >> >> >> http://www.nextcomputers.org/forums/viewtopic.php?t=1374&sid=80e5f0626eeb6a10eed066e21b61808d >> >> >> Is 20W the right rating? >> >> Thanks! >> --Toby >> >> > I got a really helpful response from Rob Blessin, from whom I bought the > splitter cable, along the same lines. My supply must be the 152 type that > requires a load. > > Boiling down all the info so far, it seems that a 20 Ohm resistor across > -12V and GND (maybe 12V and GND would work equally well?) would dissipate > 7.2W, which seems enough to keep the supply running (that other link talked > about a 5W load, so this seems a good margin). > > Now, 7.2W is more than one resistor in say a DB-19 shell could safely > dissipate, so I'm maybe looking at some kind of ambiently cooled board. Rob > provided these links: > > > Here: http://www.nextcomputers.org/forums/viewtopic.php?t=3736 and > version 1.0 megaload here: > http://www.nextcomputers.org/forums/viewtopic.php?t=3616&highlight=load+board > > > So I'm wondering what kind of thermal design is both easy and safe. A > single 10W resistor exposed to the air? Or should I spread it over a few > resistors on a little board that might have a DB-19 male at the Cube end. > > Just noob brainstorming here. > > --Toby > > >
