I would replace the electrolytic capacitors in the power supply before going further.

Sent from my iPhone

On Oct 25, 2015, at 17:42, Ian Finder <ian.finder at gmail.com> 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. Cheers, - Ian Sent from my iPhone >> On Oct 25, 2015, at 16:37, Toby Thain <toby at telegraphics.com.au> wrote: >> >> On 2015-10-25 7:21 PM, Ian Finder wrote: >> I would replace the electrolytic capacitors in the power supply before going further. > > Well, the problem disappears with the standard setup. You still think caps could be at issue with the splitter setup? What's your detailed thinking? > > --Toby > >> Sent from my iPhone >> >>>> On Oct 25, 2015, at 15:38, Toby Thain <toby at telegraphics.com.au> wrote: >>>> >>>> On 2015-10-25 5:28 PM, Toby Thain wrote: >>>> Hi, >>>> >>>> After a few years I wanted to try my Cube with the soundbox/VGA splitter >>>> configuration for the first time. (I have the fading phosphor N4000A so >>>> have been keen to have an alternate video solution.) >>>> >>>> However, all is not well. Using the keyboard power button, the machine >>>> powers on for a couple of seconds, just long enough to see a NeXT logo >>>> and grey desktop on the VGA (yay!) but then powers itself off again. >>> >>> >>> I did the obvious thing and tested it with a standard monitor and cable and everything is okay. So the problem must exist with the splitter/soundbox setup. Soft power signals? >>> >>> Any suggestions welcome. >>> >>> --Toby >>> >>>> Any clues? >>>> >>>> Thanks in advance >>>> >>>> --Toby >>>> (not having a good classic computing week) >

On 2015-10-25 8:42 PM, Ian Finder wrote: 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=80e5f0626e… Is 20W the right rating? Thanks! --Toby

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 Oct 26, 2015, at 9:27 AM, Paul Koning <paulkoning at comcast.net> wrote: My favorite low tech dummy load is the one my father came up with: a couple of resistors (carbon composite is best, carbon film or metal film will do), 1-2 watt size, in a jar filled with water. Works just fine for 100 watts or so, and is useable not just for power supplies but for HF transmitter testing. paul

On Oct 26, 2015, at 10:56 AM, Paul Koning <paulkoning at comcast.net> wrote: ... But for low voltage dummy loads, or for medium power ham transmitters, the voltages involved are not that high. Plain tap water is slightly conductive, but nowhere near as much as the resistors you're using.

On Oct 26, 2015, at 11:02 AM, Dale H. Cook <radiotest at juno.com> wrote: At 10:45 AM 10/26/2015, Jerry Weiss wrote: I concur. Tap water may have contaminants (such as chlorine) that will cause electrical leakage.

On Oct 26, 2015, at 11:21 AM, Tapley, Mark <mtapley at swri.edu> wrote: On Oct 26, 2015, at 10:09 AM, Paul Koning <paulkoning at comcast.net> wrote: OK, so a couple years back, I wanted to have some chemistry fun with the kids. So, I got out the jump cables, clamped them onto some aluminum foil, stuffed the foil into test tubes, filled the tubes with water, inverted both of them in the same basin and sprinkled in a little salt, cranked up the car, and sure enough ? bubbles started evolving off the foil and collecting in the test tubes. Just as expected, one tube was filling with gas twice as fast as the other. Just as expected, when we held that tube over a candle, it went ?WHEEP? and got hot (the flame was barely visible). Um? the OP had a 12V supply, right? How *do* you keep from electrolyzing your coolant in this apparatus?

On Oct 26, 2015, at 09:24, simon <simski at dds.nl> wrote: please skip this ridicule and grab yourself a couple of headlights from a car. -- Met vriendelijke Groet, Simon Claessen drukknop.nl

On 2015-10-26 1:23 PM, Ian Finder wrote: Damn, I already ordered a pile of HVAC gear. j/k - yeah that was what I was basically planning, Ian ... just as a noob, I'm not totally confident with what a single air cooled part can dissipate. (The thread was kind of interesting anyway!) --Toby Sent from my iPhone

Not sure how much of a noob you are, although you repeatedly claim to be one so just on the safe side we'll cover some Engineering for Poets (or Programmers) to reassure you ;) -- V = I * R Power (watts) = I * V You know the voltage of the monitor. You know the resistance of your resistor. So, you also know the maximum power the resistor needs to be rated to dissipate. If the spec says the single air-cooled resistor you're buying is good to dissipate X watts into ambient temperature Y, I'd just go ahead and believe it. Make sure the numbers work out and you're fine, no heavy duty HVAC needed. :-P

Cheers, - Ian On Mon, Oct 26, 2015 at 10:52 AM, Toby Thain <toby at telegraphics.com.au> wrote:

The talk about dummy loads brought back a memory of the Heath Cantenna--an RF dummy load consisting of a Globar (noninductive) resistor in a gallon paint can filled with mineral oil with an attachment to a SO-239 "UHF" connector on top. IIRC, it was literally capable of dissipating a full "gallon".

... but tap water even in NYC?

My favorite low tech dummy load is the one my father came up with: a couple of resistors (carbon composite is best, carbon film or metal film will do), 1-2 watt size, in a jar filled with water. Works just fine for 100 watts or so, and is useable not just for power supplies but for HF transmitter testing.