IBM 3270 PC/GX Maintenance Guide
.jpg)
The IBM 3270 PC/GX shares its PC XT-based 5371 system unit with the PC/G, so the IBM 3270 PC Maintenance Guide covers the chassis. The parts specific to the PC/GX are the IBM 5378 Display Attachment Unit and the 19-inch IBM 5379 Display. Both are covered to card level by IBM's AT/GX maintenance manual, which is hosted here and applies to the same units on the XT-based machine.[1]
Safety
[edit | edit source]A PC/GX has two mains cords: the system unit's and the 5378's. The 5379 takes its mains from the 5378, and the On/Off switch on the front of the 5378 controls it. IBM's set-up instruction is to "ensure that the power cable of the 5379 display is plugged into the 5378 DAU and NOT into the system unit".[1][2]
IBM's hazard labels for these units are 25,000 V on the 5379 and 800 V on the 5378.[1] Treat both as high-voltage equipment.
IBM's power sequences for the work station:[1]
- To switch off: the system unit first, then the 5378, then unplug both.
- To switch on: plug in both, switch on the 5378, then the system unit last.
Before working on the 5379, follow the CRT Discharge Procedure. IBM's CRT instructions warn that some tubes build up a second charge after the first discharge, so discharge again immediately before removing the tube, and wear safety glasses and long sleeves when handling it.[1] The 5379 weighs 32 to 35 kg depending on the IBM document.[2][3]
The 5378 logic cards are static-sensitive; follow IBM's ESD handling notes.[1]
See also Recommended Tools.
Documentation
[edit | edit source]- IBM 3270 PC AT/GX Maintenance Information (SY33-0125-1): problem isolation charts, locations, removal procedures and parts catalogue for the 5378 and 5379.[1]
- IBM Personal Computer Family Service Information Manual (SA38-0037-00), chapter 10.[2]
- Introducing the IBM 3270 Personal Computer/G and /GX Work Stations (GA33-3141-0, May 1984).[3]
- IBM's PC/GX maintenance manual for the XT-based work station was SY33-0111.[3]
Opening the system unit
[edit | edit source]The 5371 is opened as described in the PC/G maintenance guide. Its slot layout and adapters are the same as the PC/G's.[2]
IBM 5378 Display Attachment Unit
[edit | edit source]The 5378 measures 495 × 406 × 130 mm and weighs 14 kg (31 lb); it can sit above or below the 5371, 5373 or 5161.[2] All its power and signal connections are on the rear input/output panel. It connects to the system unit by a 62-way bus extender cable.[1]
Inside are a power supply producing +5 V, −5.2 V, +12 V and −12 V, two 12 V fans (P/N 4421916), and a logic gate holding up to eight cards: display bus receiver, graphics processor, system control, update control, clock and video driver, and up to three bit-plane cards.[1] The graphics processor is a Motorola 68000 with 128 KB of memory shared with the system unit.[2] The mains fuse is 6 A slow-blow 250 V (P/N 5214456).[1] Model C01 drives the colour 5379 and Model M01 the monochrome one.[3]
Refitting logic boards
[edit | edit source]IBM warns that the 5378 logic boards can be inserted the wrong way round, which damages the cards. When fitting a board, find the angled corner of its land pattern and install it with that corner farthest from the fan and towards the top of the housing; the A1 board has the corner towards the bottom.[2] IBM's service manual gives the full procedure for removing the gate A and B logic boards.
Card pins in each row are lettered D, J, P, U, B, G, M and S. IBM's mnemonic for them is "Dow Jones Prices Up Buy General Motors Stock".[2]
Power supply checks
[edit | edit source]The supply has four LEDs on its top; all four should be lit.[1]
| Rail | Where to measure | Limits |
|---|---|---|
| +5 V | Logic board pins A1-D2D03 (ground A1-D2D08) and B1-A2D03 (ground B1-A2D08) | 4.8 to 5.2 V |
| −5.2 V | Logic board pin B1-A2D06 (ground B1-A2D08) | −4.9 to −5.5 V |
| +12 V | Fan connector pin C (ground pin A) | 10.8 to 13.2 V |
If all four LEDs are lit and a fan has stopped, IBM checks +12 V at the fan connector: within limits, replace the fan; outside them, check continuity through the interconnect card (P3 pin 6 to fan pin C, P3 pins 7, 8, 11 and 12 to fan pin A), then replace the supply or the interconnect card. If none of the LEDs light, check the outlet, the 5378 mains fuse and the power cable before replacing the supply. A fuse that blows again may be the 5379's fault: IBM unplugs the 5379's mains cable from J2 on the rear of the 5378 and fits another fuse, and if that one holds, suspects the cable or the 5379's primary power supply assembly.[1] If the power light stays off, also check the voltage selector switch at the upper right of the rear of the 5378 supply.[2]
IBM 5379 Display
[edit | edit source]The 5379 is broken down in IBM's parts catalogue into a power supply card, primary power supply assembly, video amplifier card, deflection amplifier card, CRT socket card, manual controls card, CRT and bezel assembly, EHT cable and, on the colour model, a fan and degauss coil. Colour and monochrome versions have different part numbers.[1] The colour model has a degauss control.[2]
Clean the screen with the power off, using a soft cloth dampened with IBM's screen cleaner, water, water and detergent (then plain water), or an ammonia-based glass cleaner, and dry it before switching on. Do not use acid solutions or abrasives: they damage the non-reflective coating.[1]
Keep printers and plotters at least 305 mm from the display, and do not place a second-screen 5151 too close to the 5379; IBM notes that they interfere.[2]
Known service notes
[edit | edit source]IBM's diagnostic tips for these units:[2]
- Out-of-focus or unstable pictures can come from high-voltage arcing between the two capacitors on the side of the 5379 CRT card that faces away from the tube. IBM's temporary fix was to separate the two as far as possible.
- Deflection card P/N 4421622 does not mate with the old green XY connector from the yoke. Units from serial number 2585 have the brown connector; IBM's CRT/adapter kit P/N 59X6942 (ECA037) corrects mismatched pairs.
Keyboard, mouse and tablet
[edit | edit source]As on the PC/G: the 122-key 3270 PC keyboard, and one 5277 optical mouse or one 5083 tablet at a time.[2]
Related pages
[edit | edit source]- IBM 3270 PC/GX
- IBM 3270 PC/GX Troubleshooting Guide
- IBM 3270 PC/GX Capacitor Replacement Guide
- IBM 3270 PC/G Maintenance Guide
- IBM 3270 PC Maintenance Guide
References
[edit | edit source]- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 IBM, IBM 3270 Personal Computer AT/GX Maintenance Information, SY33-0125-1, June 1986, hosted as IBM 3270 PC AT/GX Maintenance Information. CRT handling p. xliv; 5379 and 5378 descriptions and screen cleaning pp. 1-11 to 1-13; power-off and power-on sequences pp. 1-17 and 1-18; display set-up p. 3-10; 5378 power supply charts pp. 3-4400-39 and 3-4400-40; ESD handling p. 5-9; parts catalogue pp. 7-6, 7-10 and 7-12.
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 IBM, IBM Personal Computer Family Service Information Manual, SA38-0037-00, 1989, hosted as IBM Personal Computer Family Service Information Manual. Chapter 10, pp. 10-9 to 10-13: 5378 and 5379 specifications and power, 5378 card plugging chart and pin locator, and diagnostic tips for the 5378 and 5379.
- ↑ 3.0 3.1 3.2 3.3 IBM, Introducing the IBM 3270 Personal Computer/G and /GX Work Stations, GA33-3141-0, May 1984, hosted as File:Introducing the IBM 3270 PC G and GX Work Stations GA33-3141-0.pdf. Dimensions and weights p. 81; related publications p. v.