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
