PSU alternative?

Nagging hardware related question? Post here!
User avatar
1024MAK
Super Gold Card
Posts: 592
Joined: Sun Dec 11, 2011 1:16 am
Location: Looking forward to summer in Somerset, UK...

Re: PSU alternative?

Post by 1024MAK »

As I said above, you would need two transformers.
One with a 15V secondary - feed one wire to the QL via a fuse
The other wire connects to the 0V pin on the QL

The second transformer should have an output of 9V. This should then be full wave rectified. Then go to a simple "pre-regulator". Followed by a large electrolytic capacitor (smoothing) and then the output goes to the QL. Include a fuse.

The "pre-regulator" can be a power transistor (mounted on a heatsink) controlled by a resistor and Zener diode.

If you use a single 15V transformer and try to use this to feed the 9V DC supply, you will need a big transformer and an even bigger heatsink to get rid of the excessive voltage (power).

However you could use a "simple switcher" switch mode DC to DC converter to drop the rectified and smoothed 21V (that you would get from the 15V transformer) to 7.5V DC. See here for one of many available.

Mark


:!: Standby alert :!:
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer in Somerset later in the year :)

QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)
User avatar
Lurch666
ROM Dongle
Posts: 14
Joined: Sun May 10, 2015 3:54 pm

Re: PSU alternative?

Post by Lurch666 »

Now that doesn't look too difficult.
In reference to the DC to DC converter would this be better?

http://www.ebay.com/itm/DC-DC-Buck-Step ... 43dc1dcfb6

As it is a converter and voltage regulator?

I'm thinking I use a full rectifier bridge to convert the ac into dc,run it through this regulator and drop it down to 9v giving me the 15v ac and 9v dc?


Thanks for all the help dude.


You rang......
User avatar
1024MAK
Super Gold Card
Posts: 592
Joined: Sun Dec 11, 2011 1:16 am
Location: Looking forward to summer in Somerset, UK...

Re: PSU alternative?

Post by 1024MAK »

The one you linked to uses a LM2596 like the one I linked to. This chip does all the hard work, it is a switch mode regulator chip.
Up to you if you want a voltmeter. There are lots of these DC-DC converters on eBay. It does need to be a step down type though. Oh and remember to adjust the output before connecting to the QL!

I was thinking of a circuit like this:-
Replacement QL PSU e1.png
Because we are feeding the output of the secondary of the transformer to the QL and the QL uses the DC 0V / GND line as a common for the 15V ac as well, you cannot use a four diode full bridge rectifier.

Mark


:!: Standby alert :!:
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer in Somerset later in the year :)

QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)
Derek_Stewart
Font of All Knowledge
Posts: 3929
Joined: Mon Dec 20, 2010 11:40 am
Location: Sunny Runcorn, Cheshire, UK

Re: PSU alternative?

Post by Derek_Stewart »

Hi,

I have fitted a TSR 1-2450 in place of the 7805 regulator. There is no heat from the TSR 1-2450, so no heat sink.

All work with QL-SD and Qubide Clone.


Regards,

Derek
User avatar
Lurch666
ROM Dongle
Posts: 14
Joined: Sun May 10, 2015 3:54 pm

Re: PSU alternative?

Post by Lurch666 »

So being a collector of old computers I suddenly remebered having a simalar problem with my TRS-80.
I had a PSU for it but needed another for the expansion unit I got for it.I ened up using a USA one with a stop down transformer before I managed to get myself a U.K. one.
I still have the USA psu and its outputs might be usful for powering my Q.L.

http://www.trs-80.com/images/zaps-Model ... Pinout.png

Could I use the AC output as is and use a DC to DC converter to drop the 19v dc to 9v dc?


You rang......
User avatar
1024MAK
Super Gold Card
Posts: 592
Joined: Sun Dec 11, 2011 1:16 am
Location: Looking forward to summer in Somerset, UK...

Re: PSU alternative?

Post by 1024MAK »

Yes, but only if the AC and the DC outputs are not internally connected in the PSU. And if the DC output can safely supply the required current / power.

Mark


:!: Standby alert :!:
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer in Somerset later in the year :)

QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)
User avatar
Lurch666
ROM Dongle
Posts: 14
Joined: Sun May 10, 2015 3:54 pm

Re: PSU alternative?

Post by Lurch666 »

OK so I've copped out.

Managed to get a spares and repairs Q.L. with a working PSU so now I have my Q.L. running.
Just got to sort the microdrives out now.Will have a look and will maybe use some parts from the non-working Q.L. microdrive mechs to get a fully working one.

Thanks for all you help dudes.


You rang......
User avatar
vanpeebles
Commissario Pebbli
Posts: 2816
Joined: Sat Nov 20, 2010 7:13 pm
Location: North East UK

Re: PSU alternative?

Post by vanpeebles »

What are your plans for the QL? :)


User avatar
Lurch666
ROM Dongle
Posts: 14
Joined: Sun May 10, 2015 3:54 pm

Re: PSU alternative?

Post by Lurch666 »

Open it up.clean the heads on the microdrives to see if that fixes them.If that doesn't work look around on here and the 'net to find other solutions and if that doesn't work swap the microdrives from the spares Q.L. into the working one to see if they work.


You rang......
User avatar
vanpeebles
Commissario Pebbli
Posts: 2816
Joined: Sat Nov 20, 2010 7:13 pm
Location: North East UK

Re: PSU alternative?

Post by vanpeebles »

What will you be using it for? :)


Post Reply