Electron Plus 3, some questions.

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emeu1
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Electron Plus 3, some questions.

Post by emeu1 » Tue Jun 05, 2018 5:24 pm

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

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CMcDougall
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Re: Electron Plus 3, some questions.

Post by CMcDougall » Tue Jun 05, 2018 5:41 pm

1, pic below:
pls3 right.jpg
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.
ImageImageImage

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Re: Electron Plus 3, some questions.

Post by emeu1 » Tue Jun 05, 2018 7:32 pm

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

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daveejhitchins
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Re: Electron Plus 3, some questions.

Post by daveejhitchins » Tue Jun 05, 2018 8:19 pm

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

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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Re: Electron Plus 3, some questions.

Post by CMcDougall » Tue Jun 05, 2018 8:29 pm

^ no problem Erik 8)

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
pins3.jpg
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! :D
image below : ACP 1770 DFS Rom v2.00
http://www.stairwaytohell.com/roms/Elec ... 0-2.00.zip

cheers, Col.
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Slo
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Re: Electron Plus 3, some questions.

Post by Slo » Tue Jun 05, 2018 9:01 pm

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

34454243_10157552023167222_1300066040490754048_n.jpg
34506540_10157552023607222_2298720166730530816_n.jpg

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Re: Electron Plus 3, some questions.

Post by DutchAcorn » Tue Jun 05, 2018 9:13 pm

emeu1 wrote:
Tue Jun 05, 2018 5:24 pm

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. 8)


8EA1C827-6D3F-45AA-848C-1FE85437BD7D.jpeg
Paul

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Slo
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Re: Electron Plus 3, some questions.

Post by Slo » Tue Jun 05, 2018 9:23 pm

They had to be taking the p155 when they did that surely, what good will that do? The entire case is plastic :lol: 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.

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danielj
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Re: Electron Plus 3, some questions.

Post by danielj » Wed Jun 06, 2018 5:06 am

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.

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Re: Electron Plus 3, some questions.

Post by daveejhitchins » Wed Jun 06, 2018 6:25 am

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 :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ABR, ATI, AP6, MGC, AP5 . . .
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Re: Electron Plus 3, some questions.

Post by rharper » Wed Jun 06, 2018 9:22 am

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
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Re: Electron Plus 3, some questions.

Post by myelin » Wed Jun 06, 2018 9:56 am

emeu1 wrote:
Tue Jun 05, 2018 5:24 pm
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.
SW/EE from New Zealand, now in San Francisco, making BBC/Electron hardware projects for fun.
Most popular: fast serial port, FX2+PiTubeDirect Tube/Cartridge adapter, USB cart interface.

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Re: Electron Plus 3, some questions.

Post by 1024MAK » Wed Jun 06, 2018 10:05 am

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
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Re: Electron Plus 3, some questions.

Post by emeu1 » Thu Jun 07, 2018 3:18 pm

@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

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1024MAK
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Re: Electron Plus 3, some questions.

Post by 1024MAK » Thu Jun 07, 2018 3:38 pm

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
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Re: Electron Plus 3, some questions.

Post by emeu1 » Thu Jun 07, 2018 8:11 pm

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! :D

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

Best regards,

Erik

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