PSU alternative?

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Glenn
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PSU alternative?

Postby Glenn » Tue Mar 10, 2015 7:25 pm

My recently acquired QL didn't come with a power supply and finding one is proving very difficult. Is there another way of powering it? I don't mind some soldering/modding if needed.


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1024MAK
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Re: PSU alternative?

Postby 1024MAK » Tue Mar 10, 2015 7:43 pm

Will you be using Microdrives and/or the serial ports?

Mark


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)
Glenn
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Re: PSU alternative?

Postby Glenn » Tue Mar 10, 2015 9:16 pm

I'd rather not use the microdrives, but i'm still looking at alternatives for now. Serial ports, probably not.


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belg4rion67
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Re: PSU alternative?

Postby belg4rion67 » Tue Mar 10, 2015 9:29 pm

You have some alternatives: if you don't use microdrive and serial port you can plug only 9 volts and ground to power on your QL or you can try to search on ebay or on sellmyretro.com website an original power unit.
I've one spare unit but with Italian plug and a shipment to england is very expensive, so is easier to find it in your country
good luck!
Paolo


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prime
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Re: PSU alternative?

Postby prime » Wed Mar 11, 2015 1:52 am

Is the 9V used for anything other than powering the 7505?

If not then why not solve 2 problems by powering off a small regulated 5V supply?

Cheers.

Phill.


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Re: PSU alternative?

Postby RWAP » Wed Mar 11, 2015 9:25 am

I thought we found out that the MC1377P needed 12V to produce a video output - see:

viewtopic.php?f=2&t=1140&hilit=black+screen

This might help you Glenn as that user had to make up a working PSU too...


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1024MAK
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Re: PSU alternative?

Postby 1024MAK » Wed Mar 11, 2015 9:58 am

The original QL PSU has a AC output and a 9V unregulated DC output. The 9V DC supply feeds the main board 5V regulator and feeds the Microdrives (each of which has it's own 5V regulator). The AC supply is used to feed a +12V regulator and a -12V regulator. The serial ports and part of the video system use the +12V supply. The serial ports and a Microdrive improvement modification use the -12V supply.

This is the relevant part of the thread that is being referred to: see here.

However, if you are not using the Microdrives or the serial ports, you don't need a -12V supply.
You can use either a 2A regulated or unregulated 9V DC power supply and a cheap step-up DC to DC converter (to provide a 15V DC supply which connects to the AC input so that the +12V regulator powers up). Or you can by-pass the QL's internal voltage regulators and feed it directly with regulated +5V DC and +12V DC regulated supplies.

Note that the Microdrives may well work okay without the -12V supply being present. I have not tried using the Microdrives like this.

Mark


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)
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1024MAK
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Re: PSU alternative?

Postby 1024MAK » Wed Mar 11, 2015 10:04 am

QL technical information is available here, including some details of the QL power plug and the ratings of a QL PSU.

Mark


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)
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1024MAK
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Re: PSU alternative?

Postby 1024MAK » Wed Mar 11, 2015 12:47 pm

For a suitable step up DC - DC converter, search a well known auction site for "DC - DC step up converter LM2577".

Mark


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)
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schombi
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Re: PSU alternative?

Postby schombi » Wed Mar 11, 2015 2:36 pm

Maybe I got this totally wrong, since I´m not an electronics guy, but I always got told that using a DC-DC converter on an QL would be a no-go, although it works just nicely on the Spectrum. I never understood the reasons behind.



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