Electron Power Supply

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bleeper
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Re: Electron Power Supply

Postby bleeper » Sat Apr 09, 2016 2:58 pm

Wiffleplop wrote:Dredging this one back up again again, but am I correct in the inference that the Elk can accept an 18v DC supply as well as AC? Someone made a comment about it rectifying it. I have a couple of old laptop PSUs knocking about, which I think are DC out, and could do without the expense of a new PSU off eBay (about £15) or the components, once I've found a suitable transformer of course. :)


Yes Laptop PSUs of the correct voltage and barrel work fine with Electrons. With the added bonus that polarity doesn't matter :D

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RetroMike
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Re: Electron Power Supply

Postby RetroMike » Sat Apr 09, 2016 3:10 pm

Superb, thanks. I seriously didn't expect a reply that quickly! =D>
Not quite all there...

bleeper
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Re: Electron Power Supply

Postby bleeper » Sat Apr 09, 2016 6:46 pm

Wiffleplop wrote:Superb, thanks. I seriously didn't expect a reply that quickly! =D>


Easy - I have no life :lol: :lol: :lol:

You're welcome! :)

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RetroMike
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Re: Electron Power Supply

Postby RetroMike » Sun Apr 10, 2016 8:03 pm

I've heard of these lives and always fancied one, but never got round to acquiring one myself :roll:
Not quite all there...

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dhg2
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Re: Electron Power Supply

Postby dhg2 » Fri Jan 06, 2017 3:26 pm

Hello,
I'm bumping this thread because I thought it would be more appropriate than starting a new one, since I only have a quick question. Sorry if this was inappropriate.

I have a laptop power adapter, and it only seems to have a choice between 18.5v and 19.5v, and not exactly 19v which the electron seems to want. Although the label on the adapter suggests that 19.5 is practically the same as 19, I thought I should ask here before trying it, in case it might cause damage.
Is it safe to use a 19.5v adapter instead of a 19v one?
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Regards,
- Patrick

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sydney
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Re: Electron Power Supply

Postby sydney » Fri Jan 06, 2017 4:12 pm

I reckon all of those voltages would be fine except for 22v + 24v. I'd just leave it on 18.5 and it'll be fine.

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dhg2
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Re: Electron Power Supply

Postby dhg2 » Fri Jan 06, 2017 4:42 pm

Cheers, I've plugged it in at 18.5 and it's working with no problems.
Regards,
- Patrick

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1024MAK
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Re: Electron Power Supply

Postby 1024MAK » Fri Jan 06, 2017 7:30 pm

Yes, I Would recommend setting it to 18.5V.

Mark
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chinnyhill10
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Re: Electron Power Supply

Postby chinnyhill10 » Mon Jan 30, 2017 12:37 am

Running my Elk on a 9v DC 2 amp supply and it's fine. According to someone I spoke to last year, 9V is the idea voltage if you are looking to run a DC supply instead of an AC supply. The rectifier won't get any warmer than if using 18v AC so I was told.

May all be rubbish but the Elk is stable, fine and doesn't get hot. No point sticking extra voltage through elderly equipment IMO if 9v DC works fine. And it's the same regulated PSU I use for my Speccy +2 which kills two birds with one stone.

The gotcha of course is the pass through to the expansion port but does anything even use that? If it does then you need the 18v AC.

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1024MAK
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Re: Electron Power Supply

Postby 1024MAK » Mon Jan 30, 2017 5:47 am

chinnyhill10 wrote:Running my Elk on a 9v DC 2 amp supply and it's fine. According to someone I spoke to last year, 9V is the idea voltage if you are looking to run a DC supply instead of an AC supply. The rectifier won't get any warmer than if using 18v AC so I was told.

May all be rubbish but the Elk is stable, fine and doesn't get hot. No point sticking extra voltage through elderly equipment IMO if 9v DC works fine. And it's the same regulated PSU I use for my Speccy +2 which kills two birds with one stone.

The gotcha of course is the pass through to the expansion port but does anything even use that? If it does then you need the 18v AC.

Err, whoever you spoke to is incorrect. The internal PSU in an Elk is a switched mode type. Excluding power supply losses, the amount of power needed by the Elk main board is the same regardless of the voltage from an external PSU.

So if the power needed is the same, at lower input voltages, a higher current is drawn.

Power = Voltage X Current

or Current = Power / Voltage

More current means the diode losses increase. These losses are in the form of heat, so the diodes get hotter as the input voltage falls...

If the input is DC rather than AC, all the current will now only flow through two out of the four diodes.

If your Elk works fine, then don't worry about it. But I just wanted to clear up the electrical theory and practice :wink:

The 18V AC lines on the expansion port are normally only used when a Plus 3 is attached, because the Plus 3 then supplies the Elk with power, with a higher current (higher power) PSU supplying the Plus 3.

Mark
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chinnyhill10
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Re: Electron Power Supply

Postby chinnyhill10 » Mon Jan 30, 2017 10:06 am

1024MAK wrote:
If your Elk works fine, then don't worry about it. But I just wanted to clear up the electrical theory and practice :wink:

The 18V AC lines on the expansion port are normally only used when a Plus 3 is attached, because the Plus 3 then supplies the Elk with power, with a higher current (higher power) PSU supplying the Plus 3.

Mark


Thanks for clearing that up. I'm no electronics expert so just trusted what I was told.

So would it be better to give it a higher voltage then? 12v?

A assume Acorn did it this way to keep the heavy transformer outside of the main unit. Trying to think of other machines that need AC. The Super Nintendo seems to for some bizarre reason.

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1024MAK
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Re: Electron Power Supply

Postby 1024MAK » Mon Jan 30, 2017 10:32 am

Memotech used an external PSU that is just a transformer, but that one has multiple tappings (outputs).
Sinclair used a hybrid (for want of a better word) for the QL, it had one "9V" DC output plus one AC output.

There are many variations of DC supplies. What was used depends on the designers preferences, what the final voltage(s) to the chips are, and which was lowest cost.

By putting the transformer in a separate box, it had a number of advantages:
  • No mains voltage in the computer, makes the design easier in respect of safety,
  • No large and heavy transformer in the computer case,
  • The external PSU manufacture can be sub-contracted to other companies (Sinclair ZX81 PSUs were made by at least four different companies),
  • The heat from the transformer (and other components if a DC supply) is kept separate from the computer.
There may be other reasons.
Of course, there are some disadvantages as well.

Mark
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Richard Russell
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Re: Electron Power Supply

Postby Richard Russell » Mon Jan 30, 2017 12:22 pm

1024MAK wrote:But I just wanted to clear up the electrical theory and practice

Where's the Like button when you want it?! =D>

Richard.

chinnyhill10
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Re: Electron Power Supply

Postby chinnyhill10 » Fri Feb 03, 2017 1:21 am

1024MAK wrote:Memotech used an external PSU that is just a transformer, but that one has multiple tappings (outputs).

There may be other reasons.
Of course, there are some disadvantages as well.

Mark


Picked up a Tandy Colour 2 this week on Ebay for next to nothing. Listed as having no power supply.

Turned up, only only does it have a built in power supply, but has a permanent cable out of the back with a modern style moulded plug.

Made me laugh. Wonder how many people were put off by the "no power supply" in the listing!

gebes
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Re: Electron Power Supply

Postby gebes » Thu Mar 02, 2017 10:49 pm

As a replacement power supply for my Electron, Is this one considered suitable please?

https://www.amazon.co.uk/Selectec-Unive ... wer+supply

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MartinB
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Re: Electron Power Supply

Postby MartinB » Thu Mar 02, 2017 11:59 pm

This one is closer to the original being AC-AC which the Electron is actually designed to use.

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1024MAK
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Re: Electron Power Supply

Postby 1024MAK » Fri Mar 03, 2017 8:28 am

See also this thread...

Mark
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daveejhitchins
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Re: Electron Power Supply

Postby daveejhitchins » Mon May 22, 2017 8:14 pm

I've been doing some measurements on the Electron, with various peripherals attached . . . It's interesting, from my perspective, as I'm building/ planning to build lots of Electron accessories!!

Let's start by saying that the Electron Service Manual states the rated output current, for the Electron Power Supply, is 1.5A , remember that number!

Code: Select all

Electron Currents:

(1) Electron (Issue 6 board)                           0.55
(2) Electron + Plus 1 (standard)                       0.64
(3) Electron +  MRB                                    1.07A
(4) As (3) + Plus 1 + AP6 (almost fully loaded)        1.45A
(5) As (4) + AP5 (2 ROM fitted)                        1.72A
(6) As (5) + De0-Nano                                  1.9A
(7) As (5) + Matchbox                                  1.8A
(8) As (7) + DataCentre                                1.8A
(9) AS (8) + AP3/4 (fully loaded)                      1.88A < That was a surprise! (No GALs!!)

Voltage change over this range of currents is: 0.3V < This shows how good this little Electron Power Supply is.


As you see, in some cases we are exceeding the 1.5A limit by some considerable margin! And it's down to the use of GALs. Now the interesting thing is that the power supply still works - it does get VERY hot after a while, though :?

Now, If you're using a Plus 3 the situation should be a lot better, as you're using the Plus 3's Power Supply - which is much beefer. Although I don't think there is a spec for it (I'll see if it can be worked out from the Schematic).

BUT . . . There aren't that many Plus 3s out there! So, I think one of my up and coming projects will be a replacement Power Supply for the electron!

Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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CMcDougall
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Re: Electron Power Supply

Postby CMcDougall » Mon May 22, 2017 9:00 pm

^ :shock: 8) interesting! :D
daveejhitchins wrote:There aren't that many Plus 3s out there as they have ADFS1.00 which is pants

^yes, we know =D>

weird how for years my original cream adaptor runs the Plus1+3 happily, its a great sound pressing CTRL-Shift-D-Brk :lol:

also runs happy with just a 12v DC 1.5amp bband hub box adaptor too :mrgreen:
think one of my up and coming projects will be a replacement Power Supply

good, but, where Dave is the time to play games....
has anyone actually found the internal fuse for it :?: I've got two on naughty step already :cry: :x
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