ACI workaround for Replica 1 Plus?

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resurgam's picture
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Joined: Apr 5 2015
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Hi all,

I'm new to the forums, so please be gentle. Smile I'll soon be building a Replica 1 Plus, and was considering an ACI replica from Mike Willegal (or something similar) as a period-accurate mass-storage solution, especially since I already have a Panasonic RQ2102 that I've been using with my TRS-80 Model 100, and would rather not resort to a menu-driven system like the CFFA. However, I know that the (non-ATX) Replica 1's lack of -12V has been a problem in the past, though a problem that seems to have been at least partially solved on earlier revisions of Vince's R1 board. So I guess my question is this: will earlier workarounds still function on the Plus, even though the Plus (and Tenth Anniversary Edition) have completely done away with the ATX and wall wart power options in favour of USB? Has anybody tested an ACI on the Plus?

I have to admit that the hardware side of the things has always been pretty intimidating to me, so I'd definitely appreciate any input/suggestions!

Thanks in advance. Mac

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Re: ACI workaround for Replica 1 Plus?

There are two problems. First is the EEPROM puts too much noise on the lines. Vince has an EPROM that is a drop in replacement or you can burn your own.

Second is the -12V. I cheated on mine. I used a spare MAX232 to generate the -12v. I tried at first using the onboard one, but it pulls enough current to drop the voltage down too low with the existing stuff on the system. You could simply create your own voltage pump/inverter as well or there are chips specifically for this use.

I also added extra power supply caps including a big blue in the process of figuring our why the ACI doesn't work, but they weren't necessary.

Another option is to use a 12v wall wart, a voltage regulator to drop it down a bit and route it into the regulator for the Replica-1 to avoid overheating/damaging the onboard regulator. Then use a voltage inverter on the 12V from the wall wart, which should actually be higher that 12V since it's from a wall wart. That route is actually best since the Apple-1 ACI uses unregulated -12V anyway. Still don't forget the EEPROM.

Cheers,
Corey

resurgam's picture
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Re: ACI workaround for Replica 1 Plus?

Thanks very much for that, Corey. I remember reading about the EEPROM noise issue, but somehow it had slipped my mind! Good to know. As for your recommended solution, my problem is that the Replica 1 Plus doesn't *have* the option to use a wall wart out of the box; it's USB only. Unfortunately, nobody seems to have done much testing with the R1 Plus/TEN, so I'm very much shooting in the dark (or at least stumbling about in a dimly lit cave). Also, I've never dealt with USB power supplies before, except for using them on my phone and such in a very surface-level way, so I'm not really sure what I'm doing there. I guess I can cross that bridge once I've received and successfully built my kit. I'm just getting antsy.

In all honesty, I need to brush up on my electronics fundamentals before attempting to build something like a voltage pump. I haven't done any hardware design since high-school, and years of linguistics study has made those skills as sharp as the tip of a soggy carrot.

Thanks again,

-Dave

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Posts: 1046
Re: ACI workaround for Replica 1 Plus?

Well USB is regulated supply, so I'm guessing there isn't a regulator on the board anymore. You should be able to use a voltage doubler and inverter chip. If you use a spare MAX232, you can steal the negative voltage from the some of the pins. The problem is tapping off a regulated 5v you will get around -9v which means the ACI will require a bit more signal. Your iPhone/iPod may need a pre-amp. A cassette player won't, just run a higher volume. I have noticed modern audio isn't as strong as a real cassette player.

Cheers,
Corey

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Re: ACI workaround for Replica 1 Plus?

First, as Corey notes, make sure you have the correct PROM in your replica-1.

As an experiment, you can simply try connecting -12 volts of the voltage comparitor to ground. -12 volts is pin 4 and ground is pin 1 of the LM311. I'm not sure what Vince put on the -12 volt pin of the edge connector, but you can avoid any conflicts by lifting pin 4 out of the socket, and jumpering it to pin 1.

This isn't as robust a solution as using a true -12 volt power source, but it might be good enough. I think I did this experiment on a Mimeo at one point and it worked well enough in that environment.

regards,
Mike Willegal

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Re: ACI workaround for Replica 1 Plus?

I had trouble with the ground instead of negative voltage on the Replica-1. If be curious to hear if that works for others.

resurgam's picture
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Re: ACI workaround for Replica 1 Plus?

Thanks for the thorough words of wisdom, guys. It looks like I have quite a lot of testing to do once my kit comes in.

I'll likely have more questions as the adventure unfolds, so thanks in advance for humouring a hardware newbie.

All the best,

-Dave

gsmcten's picture
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Re: ACI workaround for Replica 1 Plus?

resurgam,

Welcome to the forum!
Don't forget your toga.

Steven Smile

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Steven (gsmcten)

"Apple ][.....It's ALIVE!!!!!"

resurgam's picture
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Re: ACI workaround for Replica 1 Plus?

Thanks, Steven. I always keep my toga handy (and a tunic for those rowdy Germanic mead-parties). Smile I just received my kit today, and was nearly finished soldering it together when--horrible to relate--I discovered there were no 0.1uf caps in the box. Oops. So, I plan to head out tomorrow and buy some. Once assembly is completed, I'll start doing some more thorough testing. The ACI problem doesn't seem as hopeless as I had thought, though we'll see if I'm still singing the same tune after brushing up on my electronics fundamentals. A little knowledge can be intoxicating; a lot of knowledge can be sobering.

Best,

-Dave