Question for the techies

[merc-blue]

hey i got a old AT PSU and it needs modding so i can run my charger from it basicaly there is a lead that needs to be put to sumthing all the molex have been takes out und just the 12V and ground are in place.. there is a motherboard signal wire that needs to be modded….. any one got any help full links or such?

[jamiekulhanek]

merc whats “molex”

[micro_Amps]

The motherboard wire will probably have to be tied ‘low’ to 0 volts, or to a 5v ‘high’.
Ph2t will proably know, or else I am sure there is a comp tech somewhere on these forums.
:)uA

Jamie, “molex” connectors are those white nylon connectors you see everywhere in computers and auto wiring looms.

Edited by – micro_Amps on 22 August 2004 22:57:33

[PandaBear]

Honestly, unless you’re a qualified Power Electrical Engineer & a paid-up member of the IEEE, I’d avoid any mucking about with PC PSUs.

Especially if you value your charger… and Life. blackeye:

[jamiekulhanek]

I’ve got a tv to fix, and just worry that the capacitor might still be charged…

[merc-blue]

yeh microamps i fiquered that i just wonder which one .. il try low because less likely to kill i then a higher V.. panda its not that hard.. any all you do in take out the molex cables and replace them with he leads that you are going to run

[trash]

The circuit protection circuit sounds like what your trying to stuff around with. Switch modes require a load to work properly. Computer PSU’s really aren’t the thing to be using when you have such small loads like charging batteries.
(unless of course you have a rather huge bank of them).

There are lots of better options out there.

[PandaBear]

Old “AT” PSUs usually don’t need anything to trigger them ‘on’, but they might need some load balancing across the various taps. Usually done (quik-n-dirty method) by whacking on a bank of ceramics which dissipate 100-odd watts or so.

But the main problem is voltage… most of them supply only about 11.5V under load. Chargers like a clean 12V+, preferably 13.8V.

Quote:

I’ve got a tv to fix, and just worry that the capacitor might still be charged…

Heh… leave them off for 30mins and all the caps should be pretty drained, even the flyback ones.

Unless its a simple job like dry joints or an dessicated capacitors, old TVs are hard to fix. Can’t get parts, can’t get schematics…:evil:

[jamiekulhanek]

it’s an intermittant proble wills, so i’m gonna resolder everything, and check for any obvios problems….

[merc-blue]

hmm yeh its just i dont wanna pay 100 bux for a 6 amp PSU and even more for anything better ..

[Aaron]

Merc, price up a real basic transofrmer from tricky dickies/jaycar and then get a big diode bridge and a couple of caps and knock one up yourself. Becuase you’re only using it to runn a charger you may find that it’s mucho cheaper.

Other option: 8A car battery charger, usually puts out enough voltage and current to act as a cheapo supply.

Both these presume you don’t want some mega clean nice stable 12v but rather something slightly over 12v (13.8ish) and with the kick of a mule.

A.

--
Site Owner Guy.

[trash]

Yep, that’s what I was building up too.
Work out how much current you need. If it’s only milliamps, then just use one of those plugpack thingies. If you need about 1 amp, then a cheapy transformer and bridge rectifier, a handful of caps and a 7812.

If you want a few more herbs, then a slightly bigger transformer and a transistor in a common base arangement for your regulator and the 7812 as the voltage reference.

How many amps do you need ?

I prefer the older TV’s. I think they’re much easier to fix than the new ones. But in most cases they have common PSU capacitor problems, De-gausing thermistor failure, or flyback transistor.

It’s amazing how many TV’s I’ve found on cleanup days that just have a busted thermistor.
I only look for the big screen tv’s these days.
You can’t give the others away even if they’re working.

On a side note I used to fix microwave ovens as a kid, made a lot of money out of them. Again, these days I’m lucky to get $20 for a working one in good condition. I get more value out of entertainment in blowing them up. 🙂

Recently I needed a dryer, and the cleanup day provided me with 5 of them, after I discovered how simple they were inside.

Our old washing machine broke down… didn’t take long to learn what makes them tick either.
Water and electricity need a little bit of special attention.

But then again, microwaves and TV’s can bite those stupid enough to venture inside even when the power is turned off 🙂

[merc-blue]

i need 6 amps.. which makes it hard

[trash]

… and you said this was for charging batteries ??

[merc-blue]

yeh for charging 1:10 packs which get charger at 3-4 amps.. and to play it safe i want a 6 amp PSU

[trash]

Can you explain a 1:10 pack a little for me ?
It just sounds like a hell of a lot of power to be charging anything with. Other than a big capacitor. 🙂

[merc-blue]

battery packs for 1:10 racing. there 7.4V 3300 mAh nad there designed to be charged at about 3 amps

[trash]

You mean fast charged at 3 amps ? what about slow charging ? They sound like NiCd’s ?

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