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Tellab TL801

Posted: Sun Feb 24, 2019 7:17 am
by nollkolltroll
Yesterday I bought an unbuilt ZX80/81 kit Tellab TL801, which was available via https://web.archive.org/web/20060507212 ... exeng.html
It is apparently possible to use a switch to configure it for ZX80- or ZX81-mode, but it is designed more like the ZX80.
The PCB is not a bad one, but the instructions are Italian only :)
It is not featured on the internet very much.
Anyone has any experiences with this?

Re: Tellab TL801

Posted: Sun Feb 24, 2019 1:41 pm
by Dim_75
Hello, had you some contact with them by mail before ordering the kit ? As the initial site is not online currently and the mirror site you mentioned if from 2006, i wonder if there is someone to sell the kit anymore ?

Re: Tellab TL801

Posted: Sun Feb 24, 2019 2:55 pm
by nollkolltroll
The kit I bought was second hand, but still not built.

Re: Tellab TL801

Posted: Sun Feb 24, 2019 4:04 pm
by zx81jens
Hey there.

I also have the TL801 - you can change the Mode (ZX80/ZX81) with a Jumper!

Greetings
Jens (German ZX-TEAM)

Re: Tellab TL801

Posted: Sun Feb 24, 2019 5:03 pm
by nollkolltroll
Great to hear that you have one Jens! I have all the original docs and pieces, it's just not built yet.
Do you have any comments on the compatibility of the ready-built computer? Any other opinions about it?
I am really tempted to build it and try it out!

Re: Tellab TL801

Posted: Mon Feb 25, 2019 9:24 am
by neazoi
nollkolltroll wrote:
Sun Feb 24, 2019 5:03 pm
Great to hear that you have one Jens! I have all the original docs and pieces, it's just not built yet.
Do you have any comments on the compatibility of the ready-built computer? Any other opinions about it?
I am really tempted to build it and try it out!
Without seeing a closer photo, I believe it should be compatible because I guess it has the classic mods, i.e. one big ram chip instead of two small, composite video output instead of RF, bigger ROM with the 4k and 8k basic burned into it and selected with a switch and maybe a black recover circuit. These are all classic mods that are described mostly in old magazines.
Perhaps a closer photo of yours would help.

Re: Tellab TL801

Posted: Mon Feb 25, 2019 11:08 am
by nollkolltroll
Neazoi: I was thinking about the ZX81-compatibility mainly. I'm sure the ZX80-parts are just plain copied from the original, but the NMI-circuitry has a few different implementation variants. Also, the switching between the ZX80- and ZX81-mode can possibly differ too. For example, a ZX81 in FAST mode still produce HSYNCs, which the ZX80 does not. I have a new(ish) scope that I will test with, if/when I have a built kit.
Nut you are correct, one 16k SRAM-chip, dual-mode EPROM, composite video output. Back porch circuitry is something I have no idea about on this one.
I can supply photos, but only as naked PCB :)

Re: Tellab TL801

Posted: Mon Feb 25, 2019 11:12 am
by neazoi
nollkolltroll wrote:
Mon Feb 25, 2019 11:08 am
Neazoi: I was thinking about the ZX81-compatibility mainly. I'm sure the ZX80-parts are just plain copied from the original, but the NMI-circuitry has a few different implementation variants. Also, the switching between the ZX80- and ZX81-mode can possibly differ too. For example, a ZX81 in FAST mode still produce HSYNCs, which the ZX80 does not. I have a new(ish) scope that I will test with, if/when I have a built kit.
Nut you are correct, one 16k SRAM-chip, dual-mode EPROM, composite video output. Back porch circuitry is something I have no idea about on this one.
I can supply photos, but only as naked PCB :)
Naked PCBs would be very fine, and useful if someone wants to take his chance to copy it. Just make sure they are good quality scans, these will be very valuable.
I guess you have seen Searle's NMI generator page?
I do not think your clone includes an nmi generator at all, the NMI requires 6 more chips or so. So your only chance with this would be the 8K rom in fast mode.

Re: Tellab TL801

Posted: Mon Feb 25, 2019 12:39 pm
by nollkolltroll
Neazoi: hm, you are probably right. I first imagined that it really WAS a true ZX80/81, but they probably mean it is possible to switch ROM from 4k to 8k. So silly and dishonest to claim ZX81-compatibility :)
Oh well, then I really MUST build an NMI-solution for the Minstrel I already have. Might sell this one, only need one ZX80-clone.

Re: Tellab TL801

Posted: Mon Feb 25, 2019 12:58 pm
by neazoi
nollkolltroll wrote:
Mon Feb 25, 2019 12:39 pm
Neazoi: hm, you are probably right. I first imagined that it really WAS a true ZX80/81, but they probably mean it is possible to switch ROM from 4k to 8k. So silly and dishonest to claim ZX81-compatibility :)
Oh well, then I really MUST build an NMI-solution for the Minstrel I already have. Might sell this one, only need one ZX80-clone.
The 8K is compatible with the ZX81 but in fast mode only. So do not expect flicker-free graphics. But the BASIC is identical to the zx81 as far as I am aware of, so you should be able to run zx81 programs that do not have moving graphics without problems. But I guess you like games so... :)