Vintage electronics thread

[travelover]

Update

I found something interesting recently, re Radio Shack components. I needed a 25 watt resistor and found that Radio Shack on-line had it for $1.21, but with $6.99 shipping.

Thinking that I might order one from China cheaper, I copied and pasted the description into eBay. Up comes one from Radio Shack - $1.21 with FREE shipping.

Probably packaged by the same guy, at the same facility in either case.

I got my resistor today - delivered FedEx to MI from NJ. No way did they make a profit on that sale.

 

[ls99]

A few weeks ago found a Technics 3200 turntable at Goodwill, $10.-. Hauled it home, it worked fine. It is a direct drive turntable.

My previous acquisition was Radio Shack linear tracking record player. And was modified to work on 12VDC. The primary voltage source at the camp. This Ratshack machine is at my camp. There the temperature variations are pretty extreme. When not there inside temperature will go down to 16F or less. The Ratshack player works well but is belt driven.

I have now modified the Technics TT to work on 12VDC. Nice thing about servo controlled platter drives is the electronics, and the resulting precise speed control. Next trip will swap out the turntables. The direct drive machine will not be effected by large temperature swings. Unlike the rubber band driving the TT.

By the way this summer's project will be the solar heating which I never got around to last summer. Gotta make use of the dozens of computer cooling fans sitting in a large box..... somewhere, I know they are around here.....

 

[braumeister]

This reminded me that the other day I found this deep in the bottom of a forgotten box in the basement.

It's the motherboard from my 1987 Mac Plus. Hard to believe it was considered state of the art at the time. Individual ICs, resistors, coils, etc. all soldered on the board.

 

[NW-Bound]

Looks like the biggest chip at the center of the board is a 68K CPU chip. About that time, I did a bit of assembly language programming with the 68020 CPU (younger and bigger brother of the 68000) and the 68881 math coprocessor for an aerospace application. The hand-written assembly code was needed for a fast loop, when I saw that the code generated by a Fortran compiler truly sucked.

 

[braumeister]

You're right, it's a 68000.
That was a real learning experience for me. I did my first assembly coding with the 6502 in my 1980 Apple II+ and the difference between them was huge.

 

[NW-Bound]

The instruction sets of the 68020 and 68881 were so orthogonal that I was typing assembly code just as I was looking at the Fortran source code for that fast-loop subroutine. In other words, I was able to be a "human" compiler without much effort at all. I loved it.

But, but, but, when I later benchmarked the 68020/68881 against the Intel series, the latter won big! The instruction set of the Intel 8086 to the current Intel CPUs is anything but orthogonal, but their ad hoc machine code is shorter for more frequently used instructions and that gives them a speed advantage. Motorola later gave up further development, and fell further behind.