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Anonymous
a b B Homebuilt system
a b ) Power supply
September 9, 2005 2:51:40 PM

Archived from groups: alt.comp.hardware.homebuilt (More info?)

I picked up a stack of unwanted Compaq ( AKA duff ) 14" tft monitors
from a local computer store - all the same brand and model, but none
having power supplies.
Turns out they require dual voltage supplies ( 5 & 12v ), and it also
turns out that there's a page on the net detailing the adaption of a
computer PSU with a mouse cable to act as a power supply.
This I've done, and it works - and I've found that out of 15 or so
screens I've got 6 that work.

The question is; is it necessary to have the PSU fan running?
Granted, PSUs get hot, especially computer PSUs...but with the
relatively low load ( 2amps and 2.3 amps respectively ) is the fan
really needed?

Any opinions?

In the meantime I've rewired the fan to run on 7volts and all seems to
be well - and even after a full day running the PSU appears to be
stone cold.

Regards,



--
Stephen Howard - Woodwind repairs & period restorations
www.shwoodwind.co.uk
Emails to: showard{whoisat}shwoodwind{dot}co{dot}uk

More about : tft power supplies

Anonymous
a b B Homebuilt system
a b ) Power supply
September 9, 2005 9:49:33 PM

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Fri, 09 Sep 2005 10:51:40 +0100, Stephen Howard
<seesigfor@email.uk> wrote:

>
>I picked up a stack of unwanted Compaq ( AKA duff ) 14" tft monitors
>from a local computer store - all the same brand and model, but none
>having power supplies.
>Turns out they require dual voltage supplies ( 5 & 12v ), and it also
>turns out that there's a page on the net detailing the adaption of a
>computer PSU with a mouse cable to act as a power supply.
>This I've done, and it works - and I've found that out of 15 or so
>screens I've got 6 that work.
>
>The question is; is it necessary to have the PSU fan running?
>Granted, PSUs get hot, especially computer PSUs...but with the
>relatively low load ( 2amps and 2.3 amps respectively ) is the fan
>really needed?

"Usually" no, you could run a decent PSU without a fan with
such a low load, providing it has ample case vents, not
just a few tiny slits in the back like some generics have.
You could remove the cover and drill a lot of holes in it to
help (just be sure to remove any loose metal particles
before reinstalling it) and make sure the PSU is placed such
that it gets passive airflow (the holes are up and few
inches away from very nearby objects like walls.

However, some PSU put the output load resistors very close
to the output filter caps, they may run fairly hot in a
passive scenario even though there is little (external) load
on the supply... might depend on how many years you need it
to run.

>
>Any opinions?
>
>In the meantime I've rewired the fan to run on 7volts and all seems to
>be well - and even after a full day running the PSU appears to be
>stone cold.

If it will run at 5V, I'd try that instead of 7V.

Note that there are smaller PSU you could use. The
following is an example of the "type" or configuration I"m
thinking of but I don't know the output (current) potential
on this one in particular,
http://www.excesssolutions.com/cgi-bin/item/ES2311
Anonymous
a b B Homebuilt system
a b ) Power supply
September 10, 2005 12:34:37 PM

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Fri, 09 Sep 2005 10:51:40 +0100, Stephen Howard
<seesigfor@email.uk> put finger to keyboard and composed:

>
>I picked up a stack of unwanted Compaq ( AKA duff ) 14" tft monitors
>from a local computer store - all the same brand and model, but none
>having power supplies.
>Turns out they require dual voltage supplies ( 5 & 12v ), and it also
>turns out that there's a page on the net detailing the adaption of a
>computer PSU with a mouse cable to act as a power supply.

I wouldn't rely on a relatively flimsy data cable to supply power to
the monitor.

>This I've done, and it works - and I've found that out of 15 or so
>screens I've got 6 that work.
>
>The question is; is it necessary to have the PSU fan running?
>Granted, PSUs get hot, especially computer PSUs...but with the
>relatively low load ( 2amps and 2.3 amps respectively ) is the fan
>really needed?

If the PSU is delivering ~40W, then it will be dissipating around 10W
internally, assuming an efficiency of 80%. Natural convection *should*
handle this.

I'd be more concerned with how the PSU behaves under a no-load
condition or in the presence of a standby, power saving load.

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.
Related resources
Anonymous
a b B Homebuilt system
a b ) Power supply
September 12, 2005 1:41:23 PM

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Fri, 09 Sep 2005 17:49:33 GMT, kony <spam@spam.com> wrote:

>On Fri, 09 Sep 2005 10:51:40 +0100, Stephen Howard
><seesigfor@email.uk> wrote:
>
>>
>>I picked up a stack of unwanted Compaq ( AKA duff ) 14" tft monitors
>>from a local computer store - all the same brand and model, but none
>>having power supplies.
>>Turns out they require dual voltage supplies ( 5 & 12v ), and it also
>>turns out that there's a page on the net detailing the adaption of a
>>computer PSU with a mouse cable to act as a power supply.
>>This I've done, and it works - and I've found that out of 15 or so
>>screens I've got 6 that work.
>>
>>The question is; is it necessary to have the PSU fan running?
>>Granted, PSUs get hot, especially computer PSUs...but with the
>>relatively low load ( 2amps and 2.3 amps respectively ) is the fan
>>really needed?
>
>"Usually" no, you could run a decent PSU without a fan with
>such a low load, providing it has ample case vents, not
>just a few tiny slits in the back like some generics have.
>You could remove the cover and drill a lot of holes in it to
>help (just be sure to remove any loose metal particles
>before reinstalling it) and make sure the PSU is placed such
>that it gets passive airflow (the holes are up and few
>inches away from very nearby objects like walls.
>
>However, some PSU put the output load resistors very close
>to the output filter caps, they may run fairly hot in a
>passive scenario even though there is little (external) load
>on the supply... might depend on how many years you need it
>to run.
>
Thanks for the resistor tip, I have plenty of PSUs I can pick and
choose from - I'll bear that design constraint in mind.
>>
>>Any opinions?
>>
>>In the meantime I've rewired the fan to run on 7volts and all seems to
>>be well - and even after a full day running the PSU appears to be
>>stone cold.
>
>If it will run at 5V, I'd try that instead of 7V.

Most will 'run' on 5V..it's whether they'll start on it.
In the end I decided that trial by fire would be the best arbiter...so
I've knocked up a PSU sans the fan. After a day's running I'd say the
casing could be describe as 'luke warm'..certainly much cooler than my
laptop PSU after a couple of hours.
>
>Note that there are smaller PSU you could use. The
>following is an example of the "type" or configuration I"m
>thinking of but I don't know the output (current) potential
>on this one in particular,
>http://www.excesssolutions.com/cgi-bin/item/ES2311
>
Interesting link, thanks...I'll see if I can source something close to
home. The price seems right...and it looks rather safer from home (
aka kids ) use.

Regards,



--
Stephen Howard - Woodwind repairs & period restorations
www.shwoodwind.co.uk
Emails to: showard{whoisat}shwoodwind{dot}co{dot}uk
Anonymous
a b B Homebuilt system
a b ) Power supply
September 12, 2005 1:49:38 PM

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Sat, 10 Sep 2005 08:34:37 +1000, Franc Zabkar
<fzabkar@iinternode.on.net> wrote:

>On Fri, 09 Sep 2005 10:51:40 +0100, Stephen Howard
><seesigfor@email.uk> put finger to keyboard and composed:
>
>>
>>I picked up a stack of unwanted Compaq ( AKA duff ) 14" tft monitors
>>from a local computer store - all the same brand and model, but none
>>having power supplies.
>>Turns out they require dual voltage supplies ( 5 & 12v ), and it also
>>turns out that there's a page on the net detailing the adaption of a
>>computer PSU with a mouse cable to act as a power supply.
>
>I wouldn't rely on a relatively flimsy data cable to supply power to
>the monitor.

I did wonder about that.. but then if you consider how thin a 5amp
car fuse is, then consider that your average mouse cable is made from
stranded cable with at least half a dozen strands per wire, I doubt
there'll be any problems.
All the same, in terms of mechanical reliability I've found a couple
of PS2 extension cables that use slightly more substantial strands.

>
>>This I've done, and it works - and I've found that out of 15 or so
>>screens I've got 6 that work.
>>
>>The question is; is it necessary to have the PSU fan running?
>>Granted, PSUs get hot, especially computer PSUs...but with the
>>relatively low load ( 2amps and 2.3 amps respectively ) is the fan
>>really needed?
>
>If the PSU is delivering ~40W, then it will be dissipating around 10W
>internally, assuming an efficiency of 80%. Natural convection *should*
>handle this.
>
>I'd be more concerned with how the PSU behaves under a no-load
>condition or in the presence of a standby, power saving load.

It shuts down. Runs for about two minutes when disconnected from the
monitor, then turns itself off. Needs about a minute before it will
restart on powering up.
I'm assuming this is a 'feature' rather than an overload symptom...?
Haven't noticed the same behavior when the PSU is connected to the
monitor in power saving mode, or when switched off.


Regards,



--
Stephen Howard - Woodwind repairs & period restorations
www.shwoodwind.co.uk
Emails to: showard{whoisat}shwoodwind{dot}co{dot}uk
Anonymous
a b B Homebuilt system
a b ) Power supply
September 12, 2005 11:07:40 PM

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Mon, 12 Sep 2005 09:49:38 +0100, Stephen Howard
<seesigfor@email.uk> wrote:


>>I wouldn't rely on a relatively flimsy data cable to supply power to
>>the monitor.
>
>I did wonder about that.. but then if you consider how thin a 5amp
>car fuse is,

That suggests the opposite though, the whole point of it
being thin is so it's finely tuned to fail in an unexpected
curent condition.

> then consider that your average mouse cable is made from
>stranded cable with at least half a dozen strands per wire, I doubt
>there'll be any problems.

?? What's the significance of a mouse cable being thin when
it's only expected to use about 100mA, maybe less?



>>I'd be more concerned with how the PSU behaves under a no-load
>>condition or in the presence of a standby, power saving load.
>
>It shuts down. Runs for about two minutes when disconnected from the
>monitor, then turns itself off. Needs about a minute before it will
>restart on powering up.
>I'm assuming this is a 'feature' rather than an overload symptom...?
>Haven't noticed the same behavior when the PSU is connected to the
>monitor in power saving mode, or when switched off.

Well it is a "feature" per se, it's the over or undervoltage
safety shutdown, a "feature" in the same respect as an
overload feature would be. I don't think they plan for the
PSU to be continually operating in that state and can't
guess about reliability over the long term with it. If you
find it isn't really loading all power rails it uses,
enough, it could be prudent to put a small load on those
rails.
Anonymous
a b B Homebuilt system
a b ) Power supply
September 13, 2005 12:57:30 PM

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Mon, 12 Sep 2005 19:07:40 GMT, kony <spam@spam.com> wrote:

>On Mon, 12 Sep 2005 09:49:38 +0100, Stephen Howard
><seesigfor@email.uk> wrote:
>
>
>>>I wouldn't rely on a relatively flimsy data cable to supply power to
>>>the monitor.
>>
>>I did wonder about that.. but then if you consider how thin a 5amp
>>car fuse is,
>
>That suggests the opposite though, the whole point of it
>being thin is so it's finely tuned to fail in an unexpected
>curent condition.

Precisely...and if you made the fuse from a thicker strand of wire it
would carry more current before it failed. Essentially then, the
relatively flimsy cores of the mouse cable are six times thicker than
the typical 5 amp fuse - and taking all things into account it would
be reasonable to assume that such cable can sustain a greater
amperage. As it is, the maximum current is given as 12v @ 2.3 amps.
>
>> then consider that your average mouse cable is made from
>>stranded cable with at least half a dozen strands per wire, I doubt
>>there'll be any problems.
>
>?? What's the significance of a mouse cable being thin when
>it's only expected to use about 100mA, maybe less?
>
It's expected to carry rather more current in the use to which I've
put it.
>
>>>I'd be more concerned with how the PSU behaves under a no-load
>>>condition or in the presence of a standby, power saving load.
>>
>>It shuts down. Runs for about two minutes when disconnected from the
>>monitor, then turns itself off. Needs about a minute before it will
>>restart on powering up.
>>I'm assuming this is a 'feature' rather than an overload symptom...?
>>Haven't noticed the same behavior when the PSU is connected to the
>>monitor in power saving mode, or when switched off.
>
>Well it is a "feature" per se, it's the over or undervoltage
>safety shutdown, a "feature" in the same respect as an
>overload feature would be. I don't think they plan for the
>PSU to be continually operating in that state and can't
>guess about reliability over the long term with it. If you
>find it isn't really loading all power rails it uses,
>enough, it could be prudent to put a small load on those
>rails.

OK, thanks for that.
I've made a "MK II" power supply that uses an adaptor that plugs
straight into a hard drive power plug ( as opposed to hard wiring the
monitor power lead into the PSU ). That, and a bridge pin for the ATX
connector, means that swapping out a PSU in the event of a failure is
a mere minute's work.
I ran the PSU under load all through the night, and this morning its
still working fine with the casing barely warm to the touch.

It occurs to me that the adaptor would allow the use of the computer's
own PSU to power the monitor - but I'd imagine that the total load
would become an issue on all but the most powerful PSU.
Having said that, with the monitor requiring 5v @ 2amps and 12v @ 2.3
amps, I wouldn't have thought the draw would be much more than 40
watts...

Regards,



--
Stephen Howard - Woodwind repairs & period restorations
www.shwoodwind.co.uk
Emails to: showard{whoisat}shwoodwind{dot}co{dot}uk
Anonymous
a b B Homebuilt system
a b ) Power supply
September 13, 2005 12:57:31 PM

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Stephen Howard wrote:
> On Mon, 12 Sep 2005 19:07:40 GMT, kony <spam@spam.com> wrote:
>
>
>>On Mon, 12 Sep 2005 09:49:38 +0100, Stephen Howard
>><seesigfor@email.uk> wrote:
>>
>>
>>
>>>>I wouldn't rely on a relatively flimsy data cable to supply power to
>>>>the monitor.
>>>
>>>I did wonder about that.. but then if you consider how thin a 5amp
>>>car fuse is,
>>
>>That suggests the opposite though, the whole point of it
>>being thin is so it's finely tuned to fail in an unexpected
>>curent condition.
>
>
> Precisely...and if you made the fuse from a thicker strand of wire it
> would carry more current before it failed. Essentially then, the
> relatively flimsy cores of the mouse cable are six times thicker than
> the typical 5 amp fuse - and taking all things into account it would
> be reasonable to assume that such cable can sustain a greater
> amperage. As it is, the maximum current is given as 12v @ 2.3 amps.

No offense but your logic is seriously flawed as you seem to be measuring
'suitability' solely on whether the wire self destructs in 10 seconds like
a fast acting fuse and there's a bit more to it than that.

But if you're happy then so be it.


>>>then consider that your average mouse cable is made from
>>>stranded cable with at least half a dozen strands per wire, I doubt
>>>there'll be any problems.
>>
>>?? What's the significance of a mouse cable being thin when
>>it's only expected to use about 100mA, maybe less?
>>
>
> It's expected to carry rather more current in the use to which I've
> put it.
>
>>>>I'd be more concerned with how the PSU behaves under a no-load
>>>>condition or in the presence of a standby, power saving load.
>>>
>>>It shuts down. Runs for about two minutes when disconnected from the
>>>monitor, then turns itself off. Needs about a minute before it will
>>>restart on powering up.
>>>I'm assuming this is a 'feature' rather than an overload symptom...?
>>>Haven't noticed the same behavior when the PSU is connected to the
>>>monitor in power saving mode, or when switched off.
>>
>>Well it is a "feature" per se, it's the over or undervoltage
>>safety shutdown, a "feature" in the same respect as an
>>overload feature would be. I don't think they plan for the
>>PSU to be continually operating in that state and can't
>>guess about reliability over the long term with it. If you
>>find it isn't really loading all power rails it uses,
>>enough, it could be prudent to put a small load on those
>>rails.
>
>
> OK, thanks for that.
> I've made a "MK II" power supply that uses an adaptor that plugs
> straight into a hard drive power plug ( as opposed to hard wiring the
> monitor power lead into the PSU ). That, and a bridge pin for the ATX
> connector, means that swapping out a PSU in the event of a failure is
> a mere minute's work.
> I ran the PSU under load all through the night, and this morning its
> still working fine with the casing barely warm to the touch.
>
> It occurs to me that the adaptor would allow the use of the computer's
> own PSU to power the monitor - but I'd imagine that the total load
> would become an issue on all but the most powerful PSU.
> Having said that, with the monitor requiring 5v @ 2amps and 12v @ 2.3
> amps, I wouldn't have thought the draw would be much more than 40
> watts...
>
> Regards,
>
>
>
Anonymous
a b B Homebuilt system
a b ) Power supply
September 13, 2005 1:43:29 PM

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Tue, 13 Sep 2005 08:57:30 +0100, Stephen Howard
<seesigfor@email.uk> wrote:

>On Mon, 12 Sep 2005 19:07:40 GMT, kony <spam@spam.com> wrote:
>
>>On Mon, 12 Sep 2005 09:49:38 +0100, Stephen Howard
>><seesigfor@email.uk> wrote:
>>
>>
>>>>I wouldn't rely on a relatively flimsy data cable to supply power to
>>>>the monitor.
>>>
>>>I did wonder about that.. but then if you consider how thin a 5amp
>>>car fuse is,
>>
>>That suggests the opposite though, the whole point of it
>>being thin is so it's finely tuned to fail in an unexpected
>>curent condition.
>
>Precisely...and if you made the fuse from a thicker strand of wire it
>would carry more current before it failed. Essentially then, the
>relatively flimsy cores of the mouse cable are six times thicker than
>the typical 5 amp fuse - and taking all things into account it would
>be reasonable to assume that such cable can sustain a greater
>amperage. As it is, the maximum current is given as 12v @ 2.3 amps.

You may be lucky and get away with what you're doing, but
your argument for why ti should work is flawed. These are
rather common engineering concepts and it would be best to
simply use them rather than trying to think about the
thickness of a fuse's filament. The spec for the cable will
dictate what it can carry.


>>
>>> then consider that your average mouse cable is made from
>>>stranded cable with at least half a dozen strands per wire, I doubt
>>>there'll be any problems.
>>
>>?? What's the significance of a mouse cable being thin when
>>it's only expected to use about 100mA, maybe less?
>>
>It's expected to carry rather more current in the use to which I've
>put it.

Yes, exactly... it could be concluded that it's safe to
carry LESS than 100mA, rather than more.


>It occurs to me that the adaptor would allow the use of the computer's
>own PSU to power the monitor - but I'd imagine that the total load
>would become an issue on all but the most powerful PSU.

That depends quite a bit on what you have and what it's
powering already. Generally speaking, it would be good to
expect a system to have a spare couple amps reserve power.


>Having said that, with the monitor requiring 5v @ 2amps and 12v @ 2.3
>amps, I wouldn't have thought the draw would be much more than 40
>watts...

Even less if your cable is dropping voltage due to being
under-spec'd.
Anonymous
a b B Homebuilt system
a b ) Power supply
September 13, 2005 8:47:23 PM

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Tue, 13 Sep 2005 09:43:29 GMT, kony <spam@spam.com> wrote:

>On Tue, 13 Sep 2005 08:57:30 +0100, Stephen Howard
><seesigfor@email.uk> wrote:
>
>>On Mon, 12 Sep 2005 19:07:40 GMT, kony <spam@spam.com> wrote:
>>
>>>On Mon, 12 Sep 2005 09:49:38 +0100, Stephen Howard
>>><seesigfor@email.uk> wrote:
>>>
>>>
>>>>>I wouldn't rely on a relatively flimsy data cable to supply power to
>>>>>the monitor.
>>>>
>>>>I did wonder about that.. but then if you consider how thin a 5amp
>>>>car fuse is,
>>>
>>>That suggests the opposite though, the whole point of it
>>>being thin is so it's finely tuned to fail in an unexpected
>>>curent condition.
>>
>>Precisely...and if you made the fuse from a thicker strand of wire it
>>would carry more current before it failed. Essentially then, the
>>relatively flimsy cores of the mouse cable are six times thicker than
>>the typical 5 amp fuse - and taking all things into account it would
>>be reasonable to assume that such cable can sustain a greater
>>amperage. As it is, the maximum current is given as 12v @ 2.3 amps.
>
>You may be lucky and get away with what you're doing, but
>your argument for why ti should work is flawed. These are
>rather common engineering concepts and it would be best to
>simply use them rather than trying to think about the
>thickness of a fuse's filament. The spec for the cable will
>dictate what it can carry.

I think it'll be just fine. There's no discernable voltage drop over
the length, and no sign of the cable showing any signs of stress after
two days or so hours under load.
>
>
>>>
>>>> then consider that your average mouse cable is made from
>>>>stranded cable with at least half a dozen strands per wire, I doubt
>>>>there'll be any problems.
>>>
>>>?? What's the significance of a mouse cable being thin when
>>>it's only expected to use about 100mA, maybe less?
>>>
>>It's expected to carry rather more current in the use to which I've
>>put it.
>
>Yes, exactly... it could be concluded that it's safe to
>carry LESS than 100mA, rather than more.

I have no idea what the official rating of the cable is, but I suspect
that rather than build the cable to spec, it was chosen through a
combination of flexibility, mechanical practicality and with a view to
not costing more than the mouse to which it was attached.
All the same, just out of interest, I dropped a line the Belkin to ask
the boffins what the max rating might be at 12 and 5 volts.

>
>>It occurs to me that the adaptor would allow the use of the computer's
>>own PSU to power the monitor - but I'd imagine that the total load
>>would become an issue on all but the most powerful PSU.
>
>That depends quite a bit on what you have and what it's
>powering already. Generally speaking, it would be good to
>expect a system to have a spare couple amps reserve power.

I could work it out I guess...or I could make the practical assumption
that if a system works fine with a 250W supply, then a 350W supply of
similar quality ought to have enough grunt to handle the extra. I'm
shin deep in PSU's, so there's certainly no harm in having a bash!

Regards,



--
Stephen Howard - Woodwind repairs & period restorations
www.shwoodwind.co.uk
Emails to: showard{whoisat}shwoodwind{dot}co{dot}uk
Anonymous
a b B Homebuilt system
a b ) Power supply
September 13, 2005 8:59:17 PM

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Tue, 13 Sep 2005 05:21:33 -0500, David Maynard <nospam@private.net>
wrote:

>Stephen Howard wrote:
>> On Mon, 12 Sep 2005 19:07:40 GMT, kony <spam@spam.com> wrote:
>>
>>
>>>On Mon, 12 Sep 2005 09:49:38 +0100, Stephen Howard
>>><seesigfor@email.uk> wrote:
>>>
>>>
>>>
>>>>>I wouldn't rely on a relatively flimsy data cable to supply power to
>>>>>the monitor.
>>>>
>>>>I did wonder about that.. but then if you consider how thin a 5amp
>>>>car fuse is,
>>>
>>>That suggests the opposite though, the whole point of it
>>>being thin is so it's finely tuned to fail in an unexpected
>>>curent condition.
>>
>>
>> Precisely...and if you made the fuse from a thicker strand of wire it
>> would carry more current before it failed. Essentially then, the
>> relatively flimsy cores of the mouse cable are six times thicker than
>> the typical 5 amp fuse - and taking all things into account it would
>> be reasonable to assume that such cable can sustain a greater
>> amperage. As it is, the maximum current is given as 12v @ 2.3 amps.
>
>No offense but your logic is seriously flawed as you seem to be measuring
>'suitability' solely on whether the wire self destructs in 10 seconds like
>a fast acting fuse and there's a bit more to it than that.
>
>But if you're happy then so be it.

No offence taken, for sure. I'm probably a couple of notches up the
scale inasmuch as a guess based on practical experience tells me the
cable would probably complain at around 3-4 amps per strand.
Certainly, the cable is no thinner than that old an IBM laptop PSU -
and that's rated at 2.2A @ 16V.
Time will tell, all seems to be running tickety-boo at the
moment....and I've got six working TFTs with power supplies at
precisely zero pence. Happy? I'm as chuffed as a chuffed up chuffy
thing!

Regards,



--
Stephen Howard - Woodwind repairs & period restorations
www.shwoodwind.co.uk
Emails to: showard{whoisat}shwoodwind{dot}co{dot}uk
Anonymous
a b B Homebuilt system
a b ) Power supply
September 13, 2005 8:59:18 PM

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Stephen Howard wrote:
> On Tue, 13 Sep 2005 05:21:33 -0500, David Maynard <nospam@private.net>
> wrote:
>
>
>>Stephen Howard wrote:
>>
>>>On Mon, 12 Sep 2005 19:07:40 GMT, kony <spam@spam.com> wrote:
>>>
>>>
>>>
>>>>On Mon, 12 Sep 2005 09:49:38 +0100, Stephen Howard
>>>><seesigfor@email.uk> wrote:
>>>>
>>>>
>>>>
>>>>
>>>>>>I wouldn't rely on a relatively flimsy data cable to supply power to
>>>>>>the monitor.
>>>>>
>>>>>I did wonder about that.. but then if you consider how thin a 5amp
>>>>>car fuse is,
>>>>
>>>>That suggests the opposite though, the whole point of it
>>>>being thin is so it's finely tuned to fail in an unexpected
>>>>curent condition.
>>>
>>>
>>>Precisely...and if you made the fuse from a thicker strand of wire it
>>>would carry more current before it failed. Essentially then, the
>>>relatively flimsy cores of the mouse cable are six times thicker than
>>>the typical 5 amp fuse - and taking all things into account it would
>>>be reasonable to assume that such cable can sustain a greater
>>>amperage. As it is, the maximum current is given as 12v @ 2.3 amps.
>>
>>No offense but your logic is seriously flawed as you seem to be measuring
>>'suitability' solely on whether the wire self destructs in 10 seconds like
>>a fast acting fuse and there's a bit more to it than that.
>>
>>But if you're happy then so be it.
>
>
> No offence taken, for sure. I'm probably a couple of notches up the
> scale inasmuch as a guess based on practical experience tells me the
> cable would probably complain at around 3-4 amps per strand.

Like I said, you're happy, fine. But just in case someone else is reading,
your method of determining what's ok by 'fuse strand size' makes no sense
whatsoever. Current capacity in a cable isn't based on "good till she blows."

> Certainly, the cable is no thinner than that old an IBM laptop PSU -
> and that's rated at 2.2A @ 16V.

I wouldn't know but I'd bet it also fed straight into a regulator and
wasn't powering circuitry directly.

> Time will tell, all seems to be running tickety-boo at the
> moment....and I've got six working TFTs with power supplies at
> precisely zero pence. Happy? I'm as chuffed as a chuffed up chuffy
> thing!
>
> Regards,
>
>
>
Anonymous
a b B Homebuilt system
a b ) Power supply
September 14, 2005 11:10:30 AM

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Mon, 12 Sep 2005 19:07:40 GMT, kony <spam@spam.com> put finger to
keyboard and composed:

>On Mon, 12 Sep 2005 09:49:38 +0100, Stephen Howard
><seesigfor@email.uk> wrote:
>
>
>>>I'd be more concerned with how the PSU behaves under a no-load
>>>condition or in the presence of a standby, power saving load.
>>
>>It shuts down. Runs for about two minutes when disconnected from the
>>monitor, then turns itself off. Needs about a minute before it will
>>restart on powering up.
>>I'm assuming this is a 'feature' rather than an overload symptom...?
>>Haven't noticed the same behavior when the PSU is connected to the
>>monitor in power saving mode, or when switched off.
>
>Well it is a "feature" per se, it's the over or undervoltage
>safety shutdown, a "feature" in the same respect as an
>overload feature would be. I don't think they plan for the
>PSU to be continually operating in that state and can't
>guess about reliability over the long term with it. If you
>find it isn't really loading all power rails it uses,
>enough, it could be prudent to put a small load on those
>rails.

I install aluminium clad load resistors inside the PSU. I bolt them to
the case and locate them in the air stream.

Something like these should do the trick:
http://www.nikkohm.com/nikkohmpdfs/RH25RH50_e20050212.p...

I'd try a 10 ohm 25W/50W resistor across the +12V rail and a 4.7 ohm
10W/25W resistor across +5V.

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.
Anonymous
a b B Homebuilt system
a b ) Power supply
September 14, 2005 11:10:30 AM

Archived from groups: alt.comp.hardware.homebuilt (More info?)

On Mon, 12 Sep 2005 09:49:38 +0100, Stephen Howard
<seesigfor@email.uk> put finger to keyboard and composed:

>On Sat, 10 Sep 2005 08:34:37 +1000, Franc Zabkar
><fzabkar@iinternode.on.net> wrote:
>
>>On Fri, 09 Sep 2005 10:51:40 +0100, Stephen Howard
>><seesigfor@email.uk> put finger to keyboard and composed:
>>
>>>
>>>I picked up a stack of unwanted Compaq ( AKA duff ) 14" tft monitors
>>>from a local computer store - all the same brand and model, but none
>>>having power supplies.
>>>Turns out they require dual voltage supplies ( 5 & 12v ), and it also
>>>turns out that there's a page on the net detailing the adaption of a
>>>computer PSU with a mouse cable to act as a power supply.
>>
>>I wouldn't rely on a relatively flimsy data cable to supply power to
>>the monitor.
>
>I did wonder about that.. but then if you consider how thin a 5amp
>car fuse is, then consider that your average mouse cable is made from
>stranded cable with at least half a dozen strands per wire, I doubt
>there'll be any problems.

A fuse is designed to heat up before it ruptures. You're not comparing
the same things.

>All the same, in terms of mechanical reliability I've found a couple
>of PS2 extension cables that use slightly more substantial strands.

Pick your wire size and go through the voltage drop calculation:
http://www.powerstream.com/Wire_Size.htm

BTW, the "1-way circuit length" is the length of your cable divided by
two.

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.
Anonymous
a b B Homebuilt system
a b ) Power supply
September 16, 2005 1:52:51 AM

Archived from groups: alt.comp.hardware.homebuilt (More info?)

Stephen Howard wrote:
> I picked up a stack of unwanted Compaq ( AKA duff ) 14" tft monitors
> from a local computer store - all the same brand and model, but none
> having power supplies.
> Turns out they require dual voltage supplies ( 5 & 12v ), and it also
> turns out that there's a page on the net detailing the adaption of a
> computer PSU with a mouse cable to act as a power supply.
> This I've done, and it works - and I've found that out of 15 or so
> screens I've got 6 that work.

I'd use one of those card-edge connectors
("http://store.yahoo.com/svcompucycle/pcimolex-17.html") and run the
monitor from the system's power supply. That's what I do now, though the
monitor I have (Tatung/HP) is 12 volts only.
!