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Texas Instruments SR-51-II ... a more complex calculator than you think 
Friday, November 8, 2013, 12:00 AM
Posted by Administrator
This was a mixture between an older SR-51A and the later TI-55, it's inner electronics is more complex than comparable other TI models of the same decade.
My own one is working, but in a less desirable condition, around the power switch, painting is already gone. Also, I had to open it because the display was not fitted correctly (see second picture how to open).

How to open... somewhat tricky, also because the plastic material is a bit brittle.

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New toy: Texas Instruments LED/VFD Display Calculators (1972 - 1980) 
Sunday, October 27, 2013, 05:14 PM
Posted by Administrator
Do you remember the time a scientific calculator was (very) expensive ?
I am not really a collector of these vintage calculators, but some are very interesting and also unique. The first mass production LED display based calculator was the Texas Instruments Datamath 2500, and luckily I own also one (which I bought at Ebay a few years ago, still not too expensive).
Later, many real famous models (also from HP) were sold, e.g. the TI-57, TI-58C and the Rolls Royce of these all, the TI-59 with magnetic stripe reader.
In the next time, I will introduce some here, starting with the TI-45, which was not too common also because it has a green VFD (Vacuum Fluorescent Display),

This one has basically a set of common scientific functions, but can't be programmed.
The calculator case is comparable to the cases of the TI-57/58/59 series.
For me, it's a very beautiful one (due to the green display).
Unfortunately most of the time you buy nowadays such a vintage calculator, the battery pack is destroyed by battery acid (from the NiCD cells).
For these who are looking for a replacement, take a look >here<.

A real interesting page is also ><.
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Successor of Kryoflux - the new SuperCard Pro from Jim Drew ? 
Tuesday, October 1, 2013, 11:00 PM
Posted by Administrator
There will be something new I didn't expected... a new device was developed from Jim Drew (he already developed a lot of cool gadgets for the Commodores), which may supersede the Kryoflux device (you know it - the magic pcb/box which could read almost every floppy disk format).

It's much better than the Kryoflux:
It uses a 25ns capture resolution, where Kryoflux uses a 41.66ns resolution.
So, copies and images made with SuperCard Pro will be much more exact.

Take a look at his website to follow his news about it !

This is it what the new pcb looks like:

If it costs less than $100, it will be a success for sure.

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Notebook floppy disk drive repair - an impossible mission... 
Saturday, September 7, 2013, 12:00 PM
Posted by Administrator
I own an old but beautiful Intel 486 based notebook, a Siemens PCD-4ND with a build-in floppy drive (a Citizen W1D). This drive is removable.

Unfortunately the floppy drive is not working reliable enough anymore.
So I had the idea to repair it, and I had to open it:

You have to remove the plasic case (fixed with 2 screws), then a metal sheet (fixed with 4 very small screws)...

... and you can recognize now a missing tension for the belt:

To get the belt out of the drive, you have to lift the motor also (2 screws).
The dimensions of the belt are: 220mm circumference (110mm x2, as shown in the picture below, that means a diameter of 70mm), 1mm width and far less then 1mm thickness.

As you can see, I marked a red dot in the third picture, may be I can place there a small bumper to increase the tension of the (old) belt.

I have NO IDEA where to get such a belt. Seems to be very difficult.
If someone has an idea where to get such a plastic belt, let me know, thanks in advance.
Others already looked for some and had no success (see related link)...
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Interesting Z80 project using a real Z80 but for all I/O using an MCU 
Tuesday, August 6, 2013, 09:19 AM
Posted by Administrator
Very nice project, the Mini80. A real Z80 CPU is used (this is important for speed and compatibility), but all I/O is done by a Parallax Propeller chip.

Very small footprint, simple logic board design ... what else (except a build in VGA interface) do you want ?
This is a picture from the prototype board:

And this is the related CP/M boot screen:

It can run CP/M 2.2, using disk images from a larger "pack" file.
Hopefully his transfer utilities (for single files) will be implemented soon.

Just take a look at the Micro Vibe Site and that Mini80 article ... o-overview
for an introduction.

I recommend visiting his site (see also "related link") !
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