The 1 wire solution to the Wall Wart ACI issue..

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The 1 wire solution to the Wall Wart ACI issue..

Postby Corey986 » Jan Fri 04, 2013 7:02 pm

OK, I finally gave up on trying to get a consistent load with the ACI and ground instead of -12v. I got better results since I swapped out the eprom with one Vince provided that was programmed with a version of the Montior that has the correct intercept vectors that apparently Krusader messes up. But there is a workaround for that if you still want Krusader by simply pressing reset when you are done loading since the ACI software "crashes" when it tries to return to the monitor and the address isn't what is expected.

I also played around with changing out the 47k resistor for a 21k and 27k, and got better results with ground instead of -12v, but couldn't get the ipod to work and was still a little inconsistent even with cassette as I did more testing.

So I still need to test this with the stock"no-name" eprom that Vince sent for the ACI instead of the TI one...

But the solution is simple if you have a Replica-1 TE (and I swapped back the 47k resistor, but I do have 1% resistors for the voltage divider, not sure if that helps but I'm not swapping them out for 5%).

Anyway..... I was reading the Max232 data sheet for an arduino project where I was going to make a portable teletype/papertape reader for vintage computers using a set of LEDs for the "paper".

Well I had an Aha moment.... I noticed that the Max232's pump circuitry that generates the negative voltage is available at pin 6. So I measured it and sure enough there is about -8.5 to -10v available. Checking more data sheets and after some testing a simple jumper wire from pin 6 on the Max232 to Pin Z of the card edge connector and you can run your ACI on normal mode. Just make sure you never use an ATX supply with this mod or you will screw something up.

Also double check you have the correct pin when soldering from the back. I have seen too many people forget it's backwards when you solder the back.

Anyway... All fixed now, but I need to de-customize my ACI back to what Vince originally sent and confirm this will work for everyone (swap back in the old eprom)... Note: I'm pretty sure you still need to swap out the eeprom on the motherboard, but I want to test that also. I just won't be able to do more tests till late next week or the week after.

If anyone wants to check this out for themselves take note of which brand eprom you have on your ACI and let me know.

Cheers,
Corey
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Re: The 1 wire solution to the Wall Wart ACI issue..

Postby Corey986 » Jan Sun 06, 2013 7:02 am

One more thing to add is if anyone is going to try this...

I only needed a volume level on my Panasonic rq2102 of about 4.25. You don't need a ton of volume. Actually more volume is worse because you get hum and distortion. That is why I was looking for a solution that works with a low volume. These shoebox players are pretty loud. You can pretty much hook up an unamplified speaker and listen to them.

Cheers,
Corey
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Re: The 1 wire solution to the Wall Wart ACI issue..

Postby williad » Jan Tue 08, 2013 7:12 am

Hi Corey,

I have one of the ACI kits. I have not built it yet. One thing I was pondering is that the amount of hysteris will be different depending on which position JP1 is fitted. With -12V on the LM311 pin 4, then the output, pin 7, will swing to around -10V (Ithink). However with Ground on the LM311 pin 4, then the output can only swing to say +1 volt. I still need to work out what this does to the hysteresis on pin 2.

David Williams
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Re: The 1 wire solution to the Wall Wart ACI issue..

Postby Corey986 » Jan Tue 08, 2013 11:42 am

I played around a lot with hysteris and different values for the resistor. a 27k instead of the 47k did do a better job according to my Oscilliscope, but in practical terms not enough to justify changing the design.

Cheers,
Corey
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Re: The 1 wire solution to the Wall Wart ACI issue..

Postby tranter » Jan Wed 16, 2013 11:46 pm

Let me see if I can summarize the status of issues we've seen with the ACI. Not all of these are confirmed as being real problems or solutions.

The WozMon code in the Replica 1 EEPROM may not be compatible with the ACI firmware due to changes made by the Krusader assembler. There is a new firmware file available that corrects this.

Using an EEPROM for the Replica 1 firmware may generate noise that affects the ACI. The solution is to use an EPROM. You should have received one with the Briel ACI kit/board.

Some kits may have shipped with bad ACI firmware EPROMs. You should check if you reliably read the correct data using the Woz monitor.

The brand of EPROM used for the ACI firmware may be important. Some no name chips may not work well. A TI branded chip has been found to work.

Resistors R1 through R4 should ideally be 1% tolerance parts. The ACI kit shipped with 5% tolerance and may work but the original Apple ACI design called for 1%.

Better reliability may be achieved by changing R5 from 47K ohms to 27K or 22K.

When using an ATX power supply the -12V line can be noisy since there is no filtering on the Replica 1 (it may depend on the power supply used). A 100uF capacitor between the -12V line and ground (you can use the prototype area) should help clean this up. Make sure you use the correct polarity.

When using a wal wart type power supply (rather than an ATX) you may have better results by setting the jumper on the ACI to use -12V (normal) and
connecting the -12V line (pin Z on the card edge connector) to pin 6 of the MAX232 chip to provide a (close to) -12V source.

ACI reliability is generally poor even on an original Apple 1. Playback volume is critical. Best results are obtained either with the Panasonic RQ-2102 tape recorder originally specified for the Apple 1 (these are still available new) or using an iPod.
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Re: The 1 wire solution to the Wall Wart ACI issue..

Postby williad » Jan Wed 23, 2013 5:36 am

Hi Tranter,

Where can I find the updated firmware for the Replica 1 EEPROM? What version is it?
Also do you know where I can find the listing of the data which should be in the ACI EPROM?

Thank you.
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Re: The 1 wire solution to the Wall Wart ACI issue..

Postby vbriel » Jan Wed 23, 2013 11:19 am

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Re: The 1 wire solution to the Wall Wart ACI issue..

Postby williad » Jan Sat 26, 2013 5:54 am

Many thanks, Vince, for the link.
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