PSU alternative?

[Glenn]

Cheers folks. Lots of info to go on. I'll probably sacrifice the Microdrives and serial ports for the time being and just make sure it's alive.
I've been looking at the schematics and a PSU project could be on the cards soon.

[Mr_Navigator]

This is totally theoretical, and comes with a major health warning, you did originally say you don't mind a bit of soldering, so here goes.

A PC power supply normally gives out +5V +12V & -12v amongst others. So you could get hold of one and wire it up via a purpose made plug and socket arrangement and replace the existing power connector on the QL. From the new socket you could connect the +5V +12V & -12v and 0V directly to the QL main board the other side of the three regulators. This will invalidate your warranty btw.

Full QL circuit diagram here http://www.dilwyn.me.uk/docs/hardware/index.html

Converting PC power supply here http://www.wikihow.com/Convert-a-Comput ... wer-Supply

Old PC power supply here http://www.ebay.co.uk/sch/i.html?_from= ... =&_sacat=0

New Power Supply for possible converting here http://www.ebuyer.com/169215-casecom-35 ... su-350watx

A nice solid 4-pin connector could be something like this http://www.ebay.co.uk/itm/5X-Aviation-P ... 2684&rt=nc

[1024MAK]

If you going to feed in separate +5V, +12V and -12V feeds, either remove the existing voltage regulators, or install reverse connected 1N4001 diodes with the anode connected to the regulator output terminal side and the cathode connected to the regulator input connector side. Otherwise the regulator chips may die due to reverse bias. It's not good to have a slowly self destructing regulator, as it may fail short circuit at a later date.

Also the Microdrives run off the +9V supply, so as shown above, they would not work.

Mark

[Lurch666]

So I've just got a Q.L. with no PSU and am trying to get it powered up.
Just putting 9V into the computer (Leftmost pins on the power input looking from the back) lights the power LED but I'm getting no signal.I'm using an LCD TV and tuning it to channel 36.
I have a scart adapter coming for my Q.L. so at least my tuning problems will go away.
Reading another thread it seems that I still need the +12 to run part of the video circuit so I tried wiring up the power connecter from a Molex hard drive power cable (+5,0,0,+12) to see if that would work.


No luck-the Q.L. power light was dim so it looks like a PC power supply doesn't output enough to run a Q.L.

Any suggestions?

(I already have a post in wanted for a Q.L. PSU)

[Derek_Stewart]

If you going to feed in separate +5V, +12V and -12V feeds, either remove the existing voltage regulators, or install reverse connected 1N4001 diodes with the anode connected to the regulator output terminal side and the cathode connected to the regulator input connector side. Otherwise the regulator chips may die due to reverse bias. It's not good to have a slowly self destructing regulator, as it may fail short circuit at a later date.

Also the Microdrives run off the +9V supply, so as shown above, they would not work.

Mark

It might be a an idea to build a new QL PSU, should not be too difficult.

Maybe the only problem would be the casing, as I think the original case could be hard to make, assuming we do not have a laser scanner and 3D Printer availble.

However, there could be a existing case suitable.

[dilwyn]

So I've just got a Q.L. with no PSU and am trying to get it powered up.
Just putting 9V into the computer (Leftmost pins on the power input looking from the back) lights the power LED but I'm getting no signal.I'm using an LCD TV and tuning it to channel 36.
I have a scart adapter coming for my Q.L. so at least my tuning problems will go away.
Reading another thread it seems that I still need the +12 to run part of the video circuit so I tried wiring up the power connecter from a Molex hard drive power cable (+5,0,0,+12) to see if that would work.
No luck-the Q.L. power light was dim so it looks like a PC power supply doesn't output enough to run a Q.L.
Any suggestions?
(I already have a post in wanted for a Q.L. PSU)

Have a look at http://www.dilwyn.me.uk/docs/hardware/qlpsu.png which shows the QL PSU pinout, voltages and current.

[Lurch666]

Well I've got a 3d printer (rigidbot) so making a PSU case would be easy for me.

I have looked at making a PSU but can't find anything simple that would give me an output of 15V ac AND 9V dc
I used to mess around with electronics about 35 years ago but then found out about computers so I'm a bit rusty now.

[1024MAK]

If you remove the existing three voltage regulators, you could use a old style ATX PC power supply (you need the type that has a main +5V output, not a 3.3V main output).
Then in addition to feeding the +5V, +12V and -12V to the relevant points on the QL circuit board, feed +12V from the ATX to a 7809 voltage regulator (can mount on the QL's existing heatsink). That then gives you a 9V line to feed to the main board to power up the microdrives.

If you don't want to modify the QL, any external PSU will have to have two transformers unless you ask a transformer winding company to make you a custom one.

There are other work arounds, but it starts getting more complex

Mark

[1024MAK]

Reading another thread it seems that I still need the +12 to run part of the video circuit so I tried wiring up the power connecter from a Molex hard drive power cable (+5,0,0,+12) to see if that would work.


No luck-the Q.L. power light was dim so it looks like a PC power supply doesn't output enough to run a Q.L.

How did you connect it up ?

And yes, the video section needs a +12V supply. If you are not using the serial ports and don't care about the Sinclair Microdrive reliability modification, you can (should be able to) feed a regulated 15V DC into the 15V AC input. This should power up the +12V regulator. But as far as I know,no one has tried this...

The 9V needs to be a DC supply of at least 7.5V regulated, or if unregulated 9V DC.

[Lurch666]

First try was with a spare 9V mains adapter plugged into the leftmost pins of the Q.L.'s 3 pin power socket.This got the power light to shine but I couldn't tune in the picture (black screen or otherwise-this is on an small lcd T.V. though that's why I ordered the scart)

After that failed I used a P.C. PSU and connected to the hardrive power molex socket to get +12 and +5 volts that I fed to the 15v ac and 9v dc pins respectively.But reading more about the Q.L. I needed at least 9V and 15V to power the regulators in the Q.L. itself for this to work.

Looking around I could get a transformer that converts to 15v ac but I don't know how to then get a +9v supply off that for the other pin.I know I could use a simple rectifying bridge to get dc but how do I drop the voltage to 9v from 15v?