A1200 LEDs schematics

[Hodgkinson]

Agreed. I seem to remember seeing the resistors on a LED board.

Im puzzled about the 100R there on the _LED output...Maybe the idea is, rather than toggling the LED off and on, toggling the _LED line would cause the LED brightness to fluctuate between partial and full brightness. Am I mistaken or can this be seen on a warm-reset on the pwr LED?

Anyone know what that optional circuit would be used to indicate?

Hodgkinson.

[Hodgkinson]

Oooooh. I've got an idea. :-D

[Hodgkinson]

@Doobrey

Bugger. Someones already done what I was thinking of  :-D

Im having a look at your page now. Thanks for the info.

Hodgkinson.

[Hodgkinson]

I've got an idea im working on with regards to the floppy LED (Since this is the least used of the three...).

I'd like to maintain the exact same colour scheme as the A1200 in terms of LED's and avoid adding additional LED's all over the place, so what im going to do is replace the dual-LED floppy indicator with a pair of rectangular yellow LED's, fill the gap between them with some special white plastic spacers which I should have made tomorrow, cut a track on the underside of the LED board, reroute ground a little, tweak the existing FDD led resistor, and get it so that the right most yellow LED (Which im going to have to add a extra wire for) will indicate PCMCIA access - And the left most LED will still indicate FDD activity.

I thought about adding a dual colour LED, but the problem is i’ve never seen them in rectangular LED packages, and getting the light output from a standard round LED to illuminate the slot properly is virtually impossible.

I’m still undecided whether to attempt to find and solder some SMD parts to the motherboard (The resistors should be easy enough to find as SMD, the 2N3904 will probably have to be discrete though...); or bring two wires off from either end of the pads for R637 to a little veroboard board with the discrete parts mounted on it.

Hodgkinson.

[Hodgkinson]

"Don't forget to adjust the Floppy LED's resistor - only one instead of two LEDs in line."

Already done that, but cheers anyway. 270R Seems to give a nice even brightness from the new rectangular yellow LED's compared to the existing yellow LED's.

Re trace re-routing, all that’s necessary is to cut the track in between the two LED’s, ground the side of this cut track that connects to the LED that goes directly to the on-board resistor, and solder a limiting resistor to the other side on which the tail lead will connect to (And secure the wire properly so tracks don't get torn off...)
Unfortunately, cutting tracks with a old hacksaw blade is tricky, and I caught a track nearby (Not enough to break the track, just took the top surface off) so its now covered, along with the split track, with a blob of superglue to prevent corrosion.
Also, the original ground pad for the series LED chain has begun to lift off of the board, so I’ve scratched back some of the coating on the track just before the pad so the whole area can be reinforced with solder.

Fortunately, I’ve found a wire with the correct crimp for the LED PCB header plug, so it looks like im going to try and find all the correct SMD's and make a good job of this little project.

You might have noticed by now that im paranoid about even the tiniest of mistakes... :-)

The plastic fill will be a piece of white 2mm thick acrylic, composed of a 7mm by 7mm square section at the top, followed by a 5mm long symmetrical taper down to 3mm width at the bottm to act as a stand-off to ensure the correct height of the LED's. I'll *make use of* the local schools laser cutter tomorrow and churn 9 off at once (Just in case I want to mod 9 A1200's...)

Hodgkinson.

[Hodgkinson]

A dim LED when it should be off doesn't sound good. Are you sure that everything’s wired in properly? It sounds like the kind of fault that you might get if a resistor was in the wrong place or a ground rail was disconnected somewhere.

@Eriond: Should be interesting. Keep us posted :-D

EDIT: Oh, I uploaded a photo of how mine turned out ages ago. Must of forgot to mention it. It's here anyway.