NeXT Cube - powers on briefly then off again

[Ian Finder]

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)
>