Jump to content

Sharp MZ-80K2 General Maintenance

From RetroTechCollection
Sharp MZ-80K
The MZ-80K, of which the MZ-80K2 is the factory-assembled version (Wolfgang Stief, CC0). No freely licensed photograph of an MZ-80K2 has been found.

The Sharp MZ-80K2 is a Japanese 100 V machine, sold assembled from 1980, with 32 KB of RAM and the MZ-80K's keyboard, monitor and cassette recorder in one case.[1] SharpMZ.net, which hosts the MZ-80K service manual, lists only a Japanese owner's manual for the K2.[2] The nearest service document is Sharp's Sharp MZ-80K Service Manual for the European MZ-80K; check a K2 against it before following an MZ-80K procedure.

Mains supply

[edit | edit source]

Warning: the power switch, fuse and transformer are inside the case at mains voltage. Unplug the machine before opening it.

The Japanese MZ-80K series runs from 100 V AC at 50 or 60 Hz.[1] Run a K2 from a 100 V supply; in a 230 V country that means a step-down transformer. Japanese Wikipedia gives the series' consumption as 20 W, while Sharp's manual gives about 45 W for the European MZ-80K.[1][3] Size the transformer for the higher figure until the K2's own rating plate has been read.

Opening the case

[edit | edit source]

SharpMZ.net's procedure for the MZ-80K is to remove the four screws in the base plate, lift the top half with the keyboard, tube and cassette deck, and lock the support hinge.[4] The procedure is described in full in Sharp MZ-80K General Maintenance#Opening the case. SharpMZ.net describes the MZ-80K only, so check the K2's base for the same four screws before lifting. The display's anode runs at about 11 kV on the MZ-80K; follow the CRT Discharge Procedure before working near the tube.[3]

Power supply

[edit | edit source]

The 100 V supply in the K2 is not the one drawn in the MZ-80K manual, which covers the European 220 V and 240 V units only.[3][1] If the K2's CPU board matches the MZ-80K's, it needs +12 V, +5 V and −5 V; the MZ-80K takes these on a four-pin connector, with the 100 µF capacitors C36, C37 and C38 beside it.[5] Measure those rails with the machine running. The European MZ-80K's supply uses four 10 µF tantalum capacitors that owners report shorting.[6] Look for tantalum capacitors on the K2's supply and test them before powering a machine of unknown history.

Memory

[edit | edit source]

The K2 came with 32 KB of RAM.[1] On the MZ-80K the memory size is set by links on the headers CS1 and CS2, and SharpMZ.net's table of settings covers 20, 24, 36 and 48 KB, with no 32 KB arrangement.[4] Record the K2's links and the type of RAM in each bank before changing any chips. The MZ-80K uses 4116 and 4027 dynamic RAMs in sockets, and the 4116s are a known failure.[7][8]

Cassette recorder

[edit | edit source]

The K2 has a built-in cassette recorder, like the MZ-80K.[1] Sharp's cleaning and azimuth instructions for the MZ-80K deck are in Sharp MZ-80K General Maintenance#Cassette recorder: clean the heads, capstan and pinch roller with alcohol, and set the azimuth with a 3 kHz test tape.[9]

Keyboard

[edit | edit source]

The K2 keeps the MZ-80K's grid of keys, with matt-finished key caps. Sharp offered the MZ-80TK typewriter-layout keyboard as an option, so a K2 may have been converted.[1]

MZ-80K2E

[edit | edit source]

The cheaper MZ-80K2E has its CPU soldered directly to the board, with no socket, and two single-colour LEDs in place of the K2's two-colour LED.[1] Treat the CPU as a soldered part when diagnosing an MZ-80K2E.

Maintenance checklist

[edit | edit source]
  1. Confirm the mains supply is 100 V before switching on.
  2. Inspect the power supply for burnt or shorted tantalum capacitors.
  3. Measure +12 V, +5 V and −5 V at the CPU board.
  4. Record the RAM links and chip types before changing memory.
  5. Clean the cassette heads, capstan and pinch roller.
[edit | edit source]

References

[edit | edit source]
  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 MZ-80, Wikipedia (Japanese)—link(accessed 2026-10-21) MZ-80K2 (1980): assembled, 32 KB RAM, nearly equivalent to the MZ-80K in software, paler colour around the CRT, redesigned keyboard surround, matt key caps; MZ-80TK typewriter keyboard offered as an option. MZ-80K2E (1981): 32 KB, green around the CRT, white key tops, two single-colour LEDs, CPU soldered without a socket. MZ-80K series in Japan: AC 100 V ±10 % 50/60 Hz, 20 W; built-in data recorder.
  2. ↑ MZ-80K Manuals, SharpMZ.net—link(accessed 2026-10-21) Lists the "Japanese Manual MZ-80K2" and the MZ-80K Service Manual.
  3. ↑ 3.0 3.1 3.2 Sharp Corporation, Service Manual, Personal Computer MZ-80K (File:Sharp MZ-80K Service Manual.pdf), specifications, printed pages 1 and 2 (PDF pages 3 and 4): AC 220 V or 240 V 50 Hz, about 45 W; RAM 20 KB, extension to 48 KB; power supply outputs 12 V 1.6 A, 5 V 1.6 A, −5 V 0.2 A; display 12 V 1.1 A, 11 kV anode voltage. Hosted with a description at Sharp MZ-80K Service Manual.
  4. ↑ 4.0 4.1 MZ-80K Hints and Tips, SharpMZ.net—link(accessed 2026-10-21) MZ-80K: remove the four screws that secure the bottom plate, lift the top and lock the support hinge; RAM banks RAM1 to RAM3 set by links on CS1 and CS2, with settings for 20, 24, 36 and 48 KB.
  5. ↑ Sharp, MZ-80K service manual (File:Sharp MZ-80K Service Manual.pdf), circuit diagram (10) of the CPU board section, printed page 35 (PDF page 37): +12 V, +5 V, GND and −5 V at the power connector, with C36, C37 and C38 (100 µF 25 V); parts list, printed page 44: CN6 4-pin terminal for the power supply.
  6. ↑ Sharp MZ-80K Power Supply repair– xAD / nIGHTFALL, nIGHTFALL Blog, 2013-01-13—link(accessed 2026-10-21) Four short-circuited tantalum capacitors in an MZ-80K power supply; owners report smoke and the F101 fuse blowing.
  7. ↑ Sharp, MZ-80K service manual (File:Sharp MZ-80K Service Manual.pdf), parts list, printed page 43 (PDF page 45): 16K RAM ITT4116 or MB8116, 4K RAM ITT4027 or MB8227.
  8. ↑ 1980 Sharp MZ-80K Repair & Restoration– Adam Wilson, Adam's Vintage Computer Restorations, 2026-01-31—link(accessed 2026-10-21) Nine of the MZ-80K's socketed 4116 DRAMs failed on a DRAM tester.
  9. ↑ Sharp, MZ-80K service manual (File:Sharp MZ-80K Service Manual.pdf), azimuth adjustment and head cleaning, printed page 23 (PDF page 25).


Retrieved from "https://retrotechwiki.com/index.php?title=Sharp_MZ-80K2_General_Maintenance&oldid=28659"