Cassette Interface now works!!

What have you built or do you want to design to go with your replica 1

Postby vbriel » Feb Mon 12, 2007 8:00 pm

Ok, after some time I finally have a final prototype that I'm testing out. After I am sure this version is working good, I'll start taking preorders.

Vince

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Schematics

Postby scelbi8h » Mar Sun 18, 2007 12:15 pm

hum I have a question! Did you change original schematics? I was thinking about building it for myself. Do I need to do something special, or just follow schematics as they are? I have Replica 1 Revision C

Thanks

Luis
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Postby vbriel » Mar Sun 18, 2007 2:33 pm

The only change I did was to mod the 256x4 byte proms to a 27C64. When I used a 28C64 there was too much noise from the EEPROM (they ring really bad) and the circuit didn't work.

There is an error in the original schematic (ahh, not Woz's fault, it was a error in translation). Pin 8 in the LM311 is actually pin 5.

Also, I have issues with stability, it is difficult to get the cassette to work consistantly with different replica's.

Still a thorn in my side.

Vince
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Postby franz » Mar Mon 19, 2007 5:16 am

Hi Vince,

i asked Steve Wozniak last month about this problem.

Here his answer:

----------------------
I would suggest a low-pass filter, cutoff around 5 kHz., on the signal from the tape recorder. Such a filter would be beneficial for the data to the tape as well. I may have myself included a filter or I may have assumed that the cheap cassette decks of the day did enough filtering along those lines. Oddly enough, it implies that a lower quality voice quality recorder might work better with the Apple I than a better cassette might.
----------------------

br
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Postby mcphja2 » May Fri 04, 2007 9:08 pm

Vince,

Any word on these? I know you have been busy with other projects (grats on the KIM, BTW), but I am anxiously awaiting the cassette interface (even if it is a little buggy)!
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Postby vbriel » May Fri 04, 2007 10:13 pm

Actually, it's more than just other projects, but I have a theory as to what is going on. I'm going to try some things this weekend and see if I can make progress.

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Two years later....

Postby choasruler5151 » May Sat 12, 2007 1:14 am

Where is it it has been forever!
I thought you said you had it working...
TWO YEARS AGO!!!!
you just stop on the idea or what?
the 3 poort expansion card does no good withouot a tape interface or sound ect...
just finish it and start the orders up already
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Postby vbriel » May Sun 13, 2007 10:10 am

Yes, I know. I think I found the problem, minor that will require a new prototype to verify that I found the problem. Keep in mind that I'm using the original schematics to make this only changing the 2 256X4 byte proms for an EPROM.

The delay is, well real life. While I would love to do this full time, the market doesn't justify this. So, until 50-100K replica 1's ship a year, I'll have to keep my day job.

To be honest I think this part of the project is cursed. Everytime I think I've solved the issues, it comes back again.

I've made real progress with this and I will get it finished. I have over $1000 invested just in the cassette project and don't want to quit but I'm also not going to sell something that people are going to have problems getting to work.

Vince
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Postby vbriel » May Mon 14, 2007 12:56 pm

Just an update. I did some work yesterday and found some things out which is helping to debug the board. Grounding is super critical on the cassette interface and the replica 1 expansion connector has only a single tiny ground connection. When I attach a ground strap to the expansion board this really helped. Also, 65C02's aren't friendly to the cassette but standard 6502's work great.

I need to respin the board one last time to fix an error and to verify that it works. Keep in mind that this technology is oldschool and very unreliable. It is very hit or miss, but if you want the full tilt boogie of vintage experience, I'll finish this project soon. Right now I have 4 prototypes working but I want to be 100% sure.

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nice

Postby choasruler5151 » May Mon 14, 2007 8:36 pm

vbriel wrote:I'll finish this project soon. Right now I have 4 prototypes working but I want to be 100% sure.


yea 5 is the lucky number
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Bitte!, Bitte, Herr choasruler5151

Postby Aaron Teeling » May Wed 16, 2007 12:19 pm

.... Of course we are all familiar with your contributions to the Replica 1 hobby. As for the rest of us, we are in various positions on his coat tails.

Please keep it civil, Vince does not answer to you.
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Postby Mojoseph_12 » Jul Sat 21, 2007 2:33 am

Just wondering if there is any new news about the interface :D
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Postby vbriel » Jul Tue 24, 2007 11:15 pm

Nothing yet to report. Until I can get the boards to work with some reliability, I can't produce kits. It is too frustrating to get the programs to load every time. It could be the cassette player I'm using so I'll have to see about a different one.

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Postby mcphja2 » Jul Wed 25, 2007 7:55 pm

What kind of player are you using? I may have an old Radio Shack "portable" cassette player in storage. I may also have a VIC 20 cassette player, but that will take some digging. It's yours if you think you can use it.
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Postby vbriel » Jul Thu 26, 2007 8:08 am

Right now I have a TRS-80 CCR-81. I need to find something new that will work good. I have read that the original cassette interface was difficult to work also. From what I read, the cheaper the recorder, the better.

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