Electron Plus 3, some questions.

[emeu1]

Hello all,

I recently required an Electron Plus 3 in good and original condition and have a few questions:

1. The secondary floppy drive connector on the back of the Plus 3, has no indication on which side (left or right) pin 1 is. The manual also doesn't tell this. So on which side is pin 1 (when looking from the back of the Plus 3 to the connector)?
2. The Plus 3 came with the original User Guide which included a separate, single, double sided sheet titled: "Electron Plus 3 User Guide Errata". On this sheet, under "Installation", it says (I quote):
   

   You should have a cream-coloured self adhesive label, which must be fixed to the Electron before attaching the Plus 3.
   This label is made from a metallic substance, and its purpose is to provide an electromagnetic field between the Electron and the Plus 3.
   This will improve the performance of your Plus 3.

   Really (improve performance)? Can't be true, can it?
3. Does anyone have a picture of that cream-coloured self adhesive label? Have never seen one, just being curious.
4. Is the power supply powerful enough to power two more modern (PC) floppy drives (assuming the internal drive is disconnected)?

Best regards,

Erik

[CMcDougall]

1, pic below:

on the header pin1 is on left, and gold finger drive2 connector is pin1 on bottom right, use an old 51/4" PC drive connector for this
2, never seen one either, will make no diff
3, same
4, the 2x drives could run off the plus3 IF you have the black brick PSU, & extend the cable out to feed them 5v & Gnd
I power my external drives from a 5V 1AMP USB mobile phone charger, so less stress on the elk.

[emeu1]

Hi CMcDougall,

thanks for the answers.
One last question, you wrote:

... and gold finger drive2 connector is pin1 on bottom right ...

that is as seen "from above" (as in the picture you showed) or as seen when looking to the connector from the back of the Plus 3 (as I wrote)?

I have the large PSU, but hadn't thought about using a simple USB charger.
Thanks for the tip, will try that first.

Best regards,

Erik

[daveejhitchins]

I have Acorn Plus 3 second drive adaptors, if you need one? £4.59 + Post

Dave H

[CMcDougall]

^ no problem Erik

as per my pic, being from above
here is new photo showing the numbers, as the ribbon cable hid the numbers 1 & 2 on my older pic

plus3 drive 1/2 gold, 0/2 header

you can also take out the ADFS1.00 rom (as it's buggy as hell, to say the least..)
& just put in DFS in it's place, so PAGE is set to &1900 (can go as low as &1100) not &1D00, so more games work!
image below : ACP 1770 DFS Rom v2.00
http://www.stairwaytohell.com/roms/Elec ... 0-2.00.zip

cheers, Col.

[Slo]

As an alternative you can hack a modern double sided drive to replace the single side drive and make it fit blue peter style

I just run it from the 19v original psu and its been fine in all the years ive had it although sometimes have to ctrl/break it when i first turn it on

[DutchAcorn]

The Plus 3 came with the original User Guide which included a separate, single, double sided sheet titled: "Electron Plus 3 User Guide Errata". On this sheet, under "Installation", it says (I quote):

You should have a cream-coloured self adhesive label, which must be fixed to the Electron before attaching the Plus 3.
This label is made from a metallic substance, and its purpose is to provide an electromagnetic field between the Electron and the Plus 3.
This will improve the performance of your Plus 3.

Really (improve performance)? Can't be true, can it?
[*]
Does anyone have a picture of that cream-coloured self adhesive label? Have never seen one, just being curious.
[*]

Yes, mine has it. It improves performance phenomenally.

[Slo]

They had to be taking the p155 when they did that surely, what good will that do? The entire case is plastic not only that the original psu inside the elk, which is right next to the drive, isn't in use when the plus 3 is attached either, that some strange wtf'ness right there.

[danielj]

It is, I think, still providing power to the elk/peripherals AFAIK. The plus 3 psu is only powering the drive. That's if I remember correctly... Which I might not.

d.

[daveejhitchins]

You're correct, Daniel. With the Acorn Plus 3 attached the power to the Electron power-supply is through those grey wires that everyone wondered what they were for.

One thing I've not got around to checking is where the expansion connector, on the back of the Acorn Plus 3, gets it +5V from! The Schematic doesn't give you any clue as the net names, for the 5V, are all the same e.g. +5V. I'll trace these out when I get home at the weekend. I suspect it will still be fed from the Electron - which is fine, of course.

As for the stick-on-aluminium-screen making a difference . . . . I've not noticed any issues, when using systems without it! Maybe some experimentation is needed here?

Dave H

[rharper]

My original Plus 3 came with the stick-on strip for the Electron (long gone) which I duly applied as instructed, as did one I bought recently. I took it off as I always look at the internals to check for corrosion, 'bugs', etc.
I thought the idea of the alloy stick-on strip was to shield the electron components from electromagnetic interference from the drive. I guess the probability of that is as near zero as it doesn't matter.
Ray

[myelin]

You should have a cream-coloured self adhesive label, which must be fixed to the Electron before attaching the Plus 3.
This label is made from a metallic substance, and its purpose is to provide an electromagnetic field between the Electron and the Plus 3.
This will improve the performance of your Plus 3.

Really (improve performance)? Can't be true, can it?

Does anyone have a picture of that cream-coloured self adhesive label? Have never seen one, just being curious.

I remember that label! (I must have been 7 years old at the time... funny what you remember as a kid.) It's probably for EM shielding, to help with some kind of interference, maybe to make the Electron + Plus 3 combo pass EMC testing.

[1024MAK]

What EMC testing? In the U.K. the regulations at the time were not very strict at all.

A piece of metal foil on it's own will have fairly limited benefits, as it is not connected to anything else and there are breaks/gaps around the sides and between the two case halfs. So the noise can get around the "shield". Furthermore, at a particular frequency, noise at the resonance frequency (of the foil) would actually be reradiated from the foil.

Secondly, there is so much electrical noise inside a computer and ALL the connected expansions, that a bit more noise (or a bit less noise) is not going to make much difference... And the Plus 3 is electrically connected to the Electron...

So maybe it was not intended as a screen/shield, but instead was a halfhearted attempt to help with the heat dissipation from the Electrons internal PSU. Not that I can see it having much effect on the outside of a plastic case...

Mark

[emeu1]

@All,

thanks for all your answers and tips.

@Col:
My Plus 3 still has the original ADFS 1.00 ROM. Will program an EPROM with ACP DFS 2.00. Thanks for the hint and the ROM image.

@Daveejhitchins:
My local electronics store still had the connector on stock, so I already found one. Nevertheless, thanks for the offer.
You wrote:

One thing I've not got around to checking is where the expansion connector, on the back of the Acorn Plus 3, gets it +5V from! The Schematic doesn't give you any clue as the net names, for the 5V, are all the same e.g. +5V.

I've been searching for a copy of the Plus 3's schematic. Is it digitally available? If so, can you tell me where I can find it?

@DutchAcorn:
Thanks for the picture! Never seen that before. I'm stunned ... Still wondering why Acorn sold that along with the Plus 3.

@slo:
That's exactly what I'm aiming to do (replace the internal single-sided drive and replace it with a more modern double sided drive and attach a second, identical one as external drive).

Yesterday I connected a PC floppy drive as secondary drive with a straight cable (internally still the original single sided drive fitted and the original ADFS 1.00).
If I do an *MOUNT 0, the internal drive is accessed and I can do a *CAT.
However, if I issue a *MOUNT 1, the external drive's light turns on but a subsequent *CAT 1 doesn't display anything. I have to press the Escape key to get the Basic prompt back.
Connecting the external drive with a twisted cable (10,11,12 twisted thus 10=12, 11 stays 11, 12=10) makes things worse.
A *MOUNT 0 in this case turns on the drive lights of both drives simultaneously.
So is my conclusion correct that the external drive should be connected with a straight cable?
And that the problem I then see comes from the fact that the PC floppy drive and internal drive have been set at different drive address (DS0..3)?

Best regards,

Erik

[1024MAK]

I can't remember how Acorn wired the device/drive select (DS) but as you have found, a twisted cable, as designed for use in IBM compatibles does not work. Acorns use the earlier Shugart floppy drive interface, with two DS lines and only one group motor on (MO) control.

Unmodified, IBM compactabe floppy disk drives always come with them internally configured as the second device/drive (so DS1 if counting from zero, or DS2 if counting from 1). Often this is a zero ohm SMD resistor (link).

Mark

[emeu1]

Hello Mark,

now you mentioned the difference between the way IBM wired the floppy's, I took a look at the original floppy drive.
It was configured as DS0 ...
And, as you already mentioned, IBM always set the PC drives on DS1 (one can't even change this anymore on most modern floppy drives).
So by twisting wire 10 and 12 for the internal drive, the PC floppy drive becomes drive 0/2 and with a flat cable for the external drive, the external drive becomes 1/3. Done!

Next step is to make a mounting bracket so that I can install the PC floppy drive in the Plus 3.

Best regards,

Erik

[CJE-4D]

I'm trying to help someone power their Electron with Plus 1 and Plus 3, I'm confused by:

It is, I think, still providing power to the elk/peripherals AFAIK. The plus 3 psu is only powering the drive. That's if I remember correctly... Which I might not.

You're correct, Daniel. With the Acorn Plus 3 attached the power to the Electron power-supply is through those grey wires that everyone wondered what they were for.

One thing I've not got around to checking is where the expansion connector, on the back of the Acorn Plus 3, gets it +5V from! The Schematic doesn't give you any clue as the net names, for the 5V, are all the same e.g. +5V. I'll trace these out when I get home at the weekend. I suspect it will still be fed from the Electron - which is fine, of course.
Dave H

Also

Also in viewtopic.php?t=5030

I've had no issue running the Plus 3 (with ROMbox and other stuff as well) off the standard 19V supply. It's likely the internal drive is broken.

http://chrisacorns.computinghistory.org ... Plus3.html says Acorn expected users to use two PSUs, a 19V AC into the Electron and a 21V AC into the Plus3?
Can anyone confirm this?

I've also read on Stardot (and been able to confirm myself) that using a modern higher rated 19V DC 1.5A PSU will power an Electron with Plus1
So what is now considered a good solution for Electron with Plus1 and Plus3?
One or two PSUs?
Voltage/s?
AC or DC?

Chris

[danielj]

Chris's Acorns would be incorrect on that front. Just 21VAC into the plus 3.

[DutchAcorn]

I'm trying to help someone power their Electron with Plus 1 and Plus 3, I'm confused by:

It is, I think, still providing power to the elk/peripherals AFAIK. The plus 3 psu is only powering the drive. That's if I remember correctly... Which I might not.

You're correct, Daniel. With the Acorn Plus 3 attached the power to the Electron power-supply is through those grey wires that everyone wondered what they were for.

One thing I've not got around to checking is where the expansion connector, on the back of the Acorn Plus 3, gets it +5V from! The Schematic doesn't give you any clue as the net names, for the 5V, are all the same e.g. +5V. I'll trace these out when I get home at the weekend. I suspect it will still be fed from the Electron - which is fine, of course.
Dave H

Also

Also in viewtopic.php?t=5030

I've had no issue running the Plus 3 (with ROMbox and other stuff as well) off the standard 19V supply. It's likely the internal drive is broken.

http://chrisacorns.computinghistory.org ... Plus3.html says Acorn expected users to use two PSUs, a 19V AC into the Electron and a 21V AC into the Plus3?
Can anyone confirm this?

If you connect the Plus3 the normal power socket is obscured; you can only use one PSU and that plugs into the Plus 3. The 21V AC is converted to the various DC voltages used in the Elk. Apparently this is partly done in the Plus 3 itself (for powering the disc drive) and partly in the Elk for powering the computer.

What makes it confusing is that the part of the power supply electronics (the part that brings it down and to DC) is built into the Elk. Some sources refer to that as the (built-in) PSU.

If Acorn expected users to use 2 PSUs that would probably be for the 2 configurations; with or without the Plus3 connected.

I've also read on Stardot (and been able to confirm myself) that using a modern higher rated 19V DC 1.5A PSU will power an Electron with Plus1
So what is now considered a good solution for Electron with Plus1 and Plus3?
One or two PSUs?
Voltage/s?
AC or DC?

Chris

The Elk is not fussy about PSUs. It should provide enough power. There have been some discussions on the extra stress that a DC power supply puts on the diodes in the Elk. See this thread. But many users simply go for something they can find <=21 and has enough power for the Elk and the drive.

[daveejhitchins]

I'm trying to help someone power their Electron with Plus 1 and Plus 3, I'm confused by:

Without the Acorn Plus 3 attached the Electron power supply supplies ALL power to any added peripheral.

With the Acorn Plus 3 attached the Plus 3 wall unit supplies AC power to the Plus 3 AND the Electron. The Plus 3 then powers everything IN the Plus 3. The Electron then powers itself and anything plugged into the BACK of the Plus 3 e.g. Plus 1 etc.

Hope this helps - Sorry it's late . . .

Dave H.

[CJE-4D]

Thanks for all the very quick info lads.
I must apologise to Chris Whitehead on re-reading it he doesn't say on chrisacorns.computinghistory.org.uk two PSUs are used. He says: "The left view of the Plus 3 shows the socket for the 21 V AC power supply. When a Plus 3 is fitted the Electron runs of the more powerful Plus 3 psu rather than the Electron psu. " I can't see how I managed to misread that earlier. I do also, now I've been prompted, recall that "If you connect the Plus3 the normal power socket is obscured"

The users Electron, Plus1 & Plus3 will when using a 19VDC 1.58Amp PSU not power up, the PSU will power the Electron with Plus1 o.k. I'm suspecting therefore the Plus3 and probably the drive.

[danielj]

Doubt there's anything wrong with the +3, just not enough power.

[CJE-4D]

Doubt there's anything wrong with the +3, just not enough power.

We've tried a new 20V 3.25A DC PSU on it. It will power the electron o.k. Powering the plus 3 without the electron the disc drive powered up and spins, light comes on etc. Connecting the electron and trying again and the light on the disc drive flickers for a second and then stays out, drive doesn’t spin and you here a click from the electron but it won’t turn the electron on.
Can it really need more than 65W?
Unfortunately I don't have the unit here and the user doesn't have a meter.

[danielj]

That doesn't sound right. It probably needs rather more looking at then. Perhaps the drive is duff or the PSU in the Plus 3 is not doing what it should :/

d.

[Marvin]

We've tried a new 20V 3.25A DC PSU on it. It will power the electron o.k. Powering the plus 3 without the electron the disc drive powered up and spins, light comes on etc. Connecting the electron and trying again and the light on the disc drive flickers for a second and then stays out, drive doesn’t spin and you here a click from the electron but it won’t turn the electron on.
Can it really need more than 65W?

The original supply as spec'd by Acorn is 21 volts AC 1.75 amps 50 watts.

So the PSU you're trying to use could be considered a little low on voltage but as it's DC you should get away with it being lower however it's DC, which although both the Plus3 and the Elk are going to rectify into DC isn't ideal as half of the bridge rectifiers will be working constantly rather than 50% duty cycle.

Having said all that I've read reports of other users getting away with using a DC supply on their Plus3 so YMMV.

I suspect you have problems elsewhere. Can you measure the DC voltages coming out of the Elk and Plus3 supplies ?

If I remember correctly the Elk wants +5v, 0v and -5v. While the Plus3 needs 12v, 5v and 0v.

[Slo]

You might have a poorly +3 then, i can power my electrons (got two) with +3 and +1 connected using the original 19v psu, its got a slight delay when switching on vs nothing connected and instant beep but other than that it seems to run perfect and ive spent many hours soak testing it too. Not saying its ideal because it isnt but it at least works

[mr-macrisc]

While we are talking about plus 3 I am sure the rom/ram upgrade available from Dave H (canny remember which of our members makes it but was one of usual suspects).

It gives you access to ADFS and DFS at &E00