Model 152 PSU dummy loads - Re: NeXT Cube - powers on briefly then off again

[Toby Thain]

On 2015-10-26 2:32 PM, Ian Finder wrote:
> 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

Yes, I got that far, and I got the same figure Mike did: 7.2W. Should I 
put that on one (say 10W) part, or copy Brian's technique and spread 
over multiple resistors?

Now to see about building the board... Thanks for everyone's inputs.

--Toby

>
> Cheers,
>
> - Ian
>
> On Mon, Oct 26, 2015 at 10:52 AM, Toby Thain <toby at telegraphics.com.au>
> wrote:
>
>> On 2015-10-26 1:23 PM, Ian Finder wrote:
>>
>>> This thread took a turn for the absurd. Oil? Water? What a practical
>>> bunch of people. /s
>>>
>>> They make resistors with adequate cooling... Almost as if they're
>>> rated for a certain number of watts of dissipation and you can buy
>>> them based on that. They are resistors after all.
>>>
>>> And if they overheat-- oh wait, they're heavy duty resistors, not
>>> ICs. Get a couple, put them in a metal project box, put it inline
>>> with the cable, and call it a day.
>>>
>>
>> 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
>>>
>>> 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.
>>>>
>>>>
>>>>
>>>> On 26-10-15 17:16, Dale H. Cook wrote:
>>>>> My recommendation of oil is based upon my decades of experience with
>>>>> broadband dummy loads from 60 watts to 2.5 kilowatts. The dummy loads that
>>>>> I have worked with for medium wave and below and from 5 kilowatts down have
>>>>> all been convection air cooled. Broadband dummy loads that I have used for
>>>>> higher powers (up to 25 kilowatts) have been forced air cooled.
>>>>>
>>>>> I prefer to stick with what I have experience with. As for water, YMMV.
>>>>>
>>>>> Dale H. Cook, Radio Contract Engineer, Roanoke/Lynchburg, VA
>>>>> http://plymouthcolony.net/starcityeng/index.html
>>>>>
>>>>
>>>> --
>>>> Met vriendelijke Groet,
>>>>
>>>> Simon Claessen
>>>> drukknop.nl
>>>>
>>>
>>>
>>
>
>