Jaycar MKII Silicon Chip Article and CCT Diagram

**sandery** · 08-01-08, 07:20 AM

Hi All

I am searching for the silicon chip article for the Jaycar MKII. If you have a copy of the article (cct diagram and write up) I would appreciate it. Cheers

**LeroyPatrol** · 08-01-08, 08:00 AM

Originally Posted by sandery

Hi All

I am searching for the silicon chip article for the Jaycar MKII. If you have a copy of the article (cct diagram and write up) I would appreciate it. Cheers

If no one posts it I'll scan it at work tomorrow.

Leroy

**MrElectricity** · 08-01-08, 08:34 AM

It is from an artical in Silicon Chip Magazine
If you are not a subscriber the artical is $8.80. I'm sorry I don't have a scanner any more but I could fax to you.

**sandery** · 08-01-08, 08:48 AM

Originally Posted by LeroyPatrol

If no one posts it I'll scan it at work tomorrow.

Leroy

That would be great. Thanks

**MrElectricity** · 08-01-08, 08:49 AM

Do you want a fax?

**LeroyPatrol** · 08-01-08, 09:15 AM

Originally Posted by MrElectricity

Do you want a fax?

that's very 70's of you Mr. E

Leroy

**MrElectricity** · 08-01-08, 09:26 AM

But I never ever needed the bloody scaner so I tossed it.

**Farmsky** · 08-01-08, 09:32 AM

If you're stuck I can do

**MrElectricity** · 08-01-08, 09:36 AM

3 cheers Farmsky is back.

On ya mate

**Farmsky** · 08-01-08, 09:54 AM

I'll do it in the morn.

**LeroyPatrol** · 08-01-08, 10:07 AM

Originally Posted by Farmsky

I'll do it in the morn.

Welcome back. I can't compete with that. I would of only done it mid morning

Leroy

**nathj** · 08-01-08, 11:08 AM

if you want the cct diagram to build the mkII it will be cheaper to buy one it even comes with the detailed article....... or the local libary...

**LeroyPatrol** · 08-01-08, 08:28 PM

Here is a link to a pdf.

Leroy

**Farmsky** · 08-01-08, 08:37 PM

Nice work LP.

I thought a cup of coffee before I started the scanning job would be handy

**sandery** · 08-01-08, 09:06 PM

Thanks everyone, Cheers.

**z80** · 10-01-08, 03:36 AM

there are some critical mods for that unit to be capable of doing what we like to do with it....

a couple of track cuts/links and a schottky 1n5819 diode replacing a resistor as i recall...

**Farmsky** · 10-01-08, 05:09 AM

These mods and circuit diagram (to better support the white card) were superbly offered by GW1.

I can add some more pics and further info if anyone really wants them.

**fandtm666** · 10-01-08, 05:23 AM

these ones

**Farmsky** · 10-01-08, 05:34 AM

I've tested a couple of Gammas with Jaycar Mk II Phoenix and found they do work if you apply a few mods and don't overclock. At minimum I suggest:
• SCHOTTKY MOD (replace 4K7 with a schottky diode)
• GAMMA MOD: add 27K between schottky anode and IC2 pin 14
• OVERCLOCKING: Don't go above 6MHz; use 3.58MHz to be safe.
• DECOUPLING: Add a small decoupling capacitor (ideally a tantalum) directly across the card socket's VCC and GND pins, ie on the solder side of the board. Use heat shrink or electrical tape to prevent shorts with other tracks.
Be sure to observe correct polarity. The Gamma code I've seen runs faster than ACS 4 & 5, reducing the need for over clocking. For best stability, stay with 3.58MHz, if you can.

I've had a couple of email requests for photos of the Jaycar Mk II modifications, so here's what I've been doing.

None of the values here are critical and I usually substitute whatever suitable parts I find on the day. Here I fitted a single 2.2uF 35V tantalum across the card socket. Ensure your cap has at least a 10V rating and double check the polarity - tantalums tend to explode if you make a mistake. For best stability I recommend a tantalum but if all you have is a ceramic, say between 0.01uF and 1uF, that's better than nothing. The smartcard's high frequency current spikes are the main concern and modern ceramics are generally better for that than electrolytics. As you can see from the photo you need to insulate the capacitor leads from PCB tracks. I've used heatshrink but a couple of bits of electrical tape on the PCB would work just as well.

A smaller schottky such as BAT85 would be easier to fit than a 1N5819 but many people will be stuck with the latter since that's the only one Jaycar stocks. In that situation I suggest you solder a couple of offcuts from a resistor or LED in place of the 4K7, lay the 1N5819 against the protruding leads on the component side and solder in place. Be sure to observe correct polarity or it won't work.

The interface will probably work fine without the 27K pullup, but it won't hurt and may help with some cards. Any value around 6K8-33K should be alright.

My note about upgrading the 78L05 to a 7805 is just a safeguard in case the Gamma (whose specs I haven't seen) ever exceeds the 78L05's current limit. It's not likely to happen and I haven't bothered making the change myself but it's a potential issue to be aware of. A shitty underrated 150mA plugpack would be a bigger stability risk than the 78L05.

Tks again GW1