| Manufacturer: | Wang |
| Model: | 520 |
| Year: | 1972 |
| Form: | Desktop |
| Functions: | Scientific, programmable, tape storage, printer. |
| Number of Digits: | 11, 11E2 |
| Display Type: | NIX |
| Display: | Wang 340-0011 | | Display: | Wang 340-0010 | | Logic Technology: | SSI,MSI |
| Memory Technology: | LSI |
| Diodes: | 2469 |
| Transistors: | 98 |
| Principal ICs: | 7400 TTL Series (219 total) |
| Tech. Data Level: | 2 |
| Tech. Data Source: | MF |
| Tech. Data Pages: | 21 |
| Tech. Data: | offline |
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No, this model did not originally come in a solid wood case.
This was another unit, like the Casio AL-1000, received in an incomplete state.
The case, printer and cassette deck were missing.
Fortunately, what remained - the keyboard, main chassis and core-rope ROM board - were enough to make a functioning calculator.
The wooden case was constructed to hold it all together and protect the delicate core-rope ROM.
This model and other related 500,600,700-series Wang models use a microcoded design to deal with the level of complexity and features.
They were developed just before the introduction of LSI ROM, the microcode store is instead a form of core-rope ROM.
A technical description of the ROM is presented in an article about core rope ROM.
| Notes: |
- Store/Recall Register-N function keys operate by pressing a numeral-pad key
(not a register 0-15 key) after the Store/Recall key.
Decimal-point, Clear-display, Set-exp keys, etc., are used for registers >9.
|
Keyboard, main chassis, and core-rope ROM (propped up at the rear) modules operating sans case.
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The keyboard module.
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The main chassis, with logic boards, NIXIE display and power supply.
|
The core-rope ROM board containing the microcode.
This is a 2048-word-by-42-bit ROM (86,016 bits or the equivalent of 10,152 bytes).
As such, there are 2048 wires weaving the 42-bit words.
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IC decoders and diode decoding matrix on the flip side of the core-rope ROM board.
|
A detail view of the core-rope ROM.
A group of 4 bits has been opened by removing the top holding 3 of the 4 sides of 4 transformer cores.
The word-wires variously weave around the plastic pegs so as to either go through a core or stay outside
the core to determine the value (0/1) of that bit of the word at a given address.
|
- Unit Log -
| Serial Number: | BB 1046 |
| Year of Manufacture: | 1972 (Board stamped with 31 January 1972) |
| Date of Receipt: | 21 Sep 2003 |
| Source: | SPARC contact. |
| State upon Receipt: | Received as 3 parts, main chassis, ROM board and keyboard.
Missing case, printer and tape drive.
-12V regulator transistor dented.
ROM has at least one broken wire.
Complete model number is 520-14-T-P.
Also marked with Canada Agriculture 128516. |
| Current State: | Fully functional, except tape and printer operations cannot be tested (03 Apr 2015). |
| Date: | 29 Sep 2003 |
| Procedure: | Dusted off, parts connected together to test basic functionality. |
| Date: | 29 Sep 2003 |
| Procedure: | Power supply tested with all logic boards removed, all seems OK.
Dented -12V regulator transistor (2N1540) replaced with ES21 (PNP-Ge).
Upon power-up with everything connected, multiplexed display was active,
but unresponsive to keyboard. After a minute, with switches set properly,
unit was functional as regards basic operations. |
| Date: | 05 Mar 2005 |
| Procedure: | Keyboard panel cleaned. Peeling sticker on keyboard removed
("Ensure Printer is OFF before switching Wang ON or OFF"). |
| Date: | 05 Mar 2005 |
| Procedure: | Redrawing of diagrams from Wang schematic largely complete.
Exercises performed to figure out functioning. |
| Date: | 11 Mar 2005 |
| Symptoms: | Program storage from locations 952 to 1463 (inclusive) have "4" bit stuck on. |
| Analysis: | MK4008 memory chips for bit 4 moved around to confirm bad chip and to map memory.
Chip in location 213 has 4 pins (16,15,14,11) rotted off. |
| Solution: | New pins soldered on to IC (ceramic package). |
| Date: | 25 Mar 2005 |
| Procedure: | Core-rope ROM interface constructed and program written to examine ROM via SWTP M6800 computer.
Contents of ROM read successfully, except for a few locations which present inconsistent data. |
| Date: | 26 Mar 2005 |
| Symptoms: | Search function and f(x) (which presumably uses search) do not function. |
| Solution: | Broken wire on core ROM board at address 1260 (octal) spliced. Functional. |
| Date: | 03 Apr 2015 |
| Symptoms: | Reassembled and powered up. Numbers can be entered, but arithmetic operations result in display such as "+1.00000 +10". |
| Solution: | Boards reseated and six MK4008 memory chips wiggled in sockets but problem occasionally reoccurs. |
| Date: | 13 Apr 2015 |
| Symptoms: | Numeral entry results in display such as 3217.9764326. |
| Solution: | Spliced wire in core ROM had broken at splice. Respliced. Lead from solder post replaced with 40-gauge. |
| Date: | Apr 2015 |
| Procedure: | Case constructed. |
