Philips P2000T Troubleshooting Guide
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Philips serviced the Philips P2000T by isolating a fault to a module and exchanging it. Its Field Service Manual of 1982 gives the fault isolation procedure for the T-version step by step, with a check of the supply voltages at the board sockets and a maintenance program on cartridge that tests the memory, keyboard, screen, tape drive and interfaces.[1][2] The Field Support manual adds the circuit diagrams and parts lists that let the fault be taken down to a component.[3] Opening the cabinet is described on Philips P2000T General Maintenance.
Philips's fault isolation procedure
[edit | edit source]Remove all cartridges and the cassette before starting.[1]
| Step | Reaction | Action |
|---|---|---|
| 1. Switch on the basic cabinet | Power-on indicator lit | Go to step 3 |
| No power-on indicator | Check the mains connection; go to step 2 | |
| 2. Insert any cassette and press the reset button | Cassette moves | Check the keyboard connection; replace the keyboard (Philips notes "indicator defect") |
| No reaction | Check the fuses (figure 1.8, callout 1), the power supply connections (callout 3) and the cassette connection; check the supply at step 7 | |
| 3. Switch on the television | Screen shows "Philips/P2000 Microcomputer" | Go to step 4 |
| No correct screen | Check the TV interface (callout 2); select the right band and adjust the channel; check that the modulator is seated (callout 4); check the fuses; check the CPU board connections; try another television; replace the CPU board | |
| 4. Insert the maintenance program in the first slot and press reset | "Test Menue" | Run the maintenance program |
| "Philips/P2000 Microcomputer" | Go to step 5 | |
| 5. Switch off, wait 10 seconds, switch on | "Test Menue" | Check the reset button wiring; replace the reset key; replace the CPU board |
| "Philips/P2000 Microcomputer" | Clean the cartridge socket; replace the CPU board; replace the maintenance cartridge |
Supply checks
[edit | edit source]For the supply, the T-version procedure sends the engineer to steps 7 and 8 of the M-version procedure (section 1.2.4.2), which check the voltages at the power supply sockets with the cables unplugged from the CPU, video and extension boards.[1][4]
| Check | Where | If it fails |
|---|---|---|
| +5 V for each board | Between the right-hand pin and the second pin from the left of the CPU, video and extension board sockets | No 5 V anywhere: replace the power supply. No 5 V on the CPU socket only: replace the top regulator. Video socket only: the second regulator from the top. Extension socket only: the second from the bottom. |
| +12 V | Between the left-hand pin and the second pin from the left of the CPU board socket | Replace the bottom regulator |
The schematic numbers the regulators 1 to 3 (7805, for the CPU, video and extension boards) and 4 (7812), and they are mounted on the aluminium backplate that serves as their heat sink.[5][6] On the T-version regulators 1 and 2 are connected together to give more +5 V current.[7]
Two points from Philips's circuit description help when the supplies look wrong:
- TS1 and TS2 short-circuit the +12 V line for as long as +5 V is missing. A dead +5 V supply therefore takes +12 V with it; find the +5 V fault first.[7]
- A second winding of the transformer gives an unregulated negative supply of about -20 V across C4, which goes to every logic board and is regulated to -5 V and -12 V on each board. The CPU board carries LM79L12 and LM79L05 regulators for this.[7][8]
For capacitor faults in the supply see Philips P2000T Capacitor Replacement Guide and Capacitor Failure Symptoms.
Maintenance program
[edit | edit source]Philips's maintenance program runs from a cartridge in the first slot. After choosing the national version, the menu offers: 1 RAM, 2 V24, 3 keyboard, 4 screen, 5 tape drive, 6 beeper, 7 floppy drive and 8 summary.[2]
| Test | What it does | Action on failure |
|---|---|---|
| RAM | Fills and reads back the memory; after some minutes it lists the address ranges tested | A fault in 6000 to 9FFF is in the CPU board's system RAM; A000 to DFFF is the extension board |
| V24 | Printer character test, serial interface test at a chosen baud rate, viewdata interface test, static test of the socket pins | Fit the module connector in the printer socket; replace the serial or viewdata interface; replace the CPU board for a printer interface fault |
| Keyboard | Shows the keys on screen; each key must be pressed in turn | Replace keys that do not respond; replace the keyboard interface or CPU board |
| Screen | Character test, graphics test, national version test, screen adjustment pattern, special screen test | Replace the character generator (on the CPU board in the T-version) |
| Tape drive | Read master tape; write, skip back and read; continuous status test | |
| Beeper | Sounds the beeper |
The 1984 service lecture notes describe the same tests on a test module: the RAM test exercises the eight 4116 chips of 16384 × 1 bit that make up the user memory and shows any errors on screen, and the video test shows every symbol and colour.[11]
Memory map and ports
[edit | edit source]| Address or port | Use |
|---|---|
| 0000–0FFF | Monitor program (4K) |
| 1000–4FFF | Interpreter (cartridge, 16K) |
| 5000–5FFF | Video RAM |
| 6000–9FFF | User RAM, standard |
| A000–DFFF | User RAM, optional |
| E000–FFFF | Not used on the P2000T |
| Ports 00–09 | Keyboard |
| Ports 10–1F | Output to recorder and printer |
| Ports 20–2F | Input from recorder and printer |
| Ports 30–3F | Video scroll register |
| Ports 50–5F | Beeper |
With the BASIC cartridge fitted, PEEK, POKE, INP and OUT reach these addresses and ports directly, which is enough to test parts of the machine without the maintenance cartridge.[10]
Printer socket
[edit | edit source]The 25-pin printer socket on the back carries serial data in on pin 2, data out on pin 3, ground on pin 7 and the printer ready (DTR) input on pin 20. The service notes also list +10 V on pins 5 and 6.[12][11]
Related pages
[edit | edit source]- Philips P2000T
- Philips P2000T General Maintenance
- Philips P2000T Capacitor Replacement Guide
- Philips P2000 Documentation
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 Philips Data Systems, Field Service Manual P2000, publication 5122 991 30703, October 1982, pp. 1-19 to 1-21: troubleshooting at module level; figure 1.8 (basic cabinet) and section 1.2.4.1, T-version procedure steps 1 to 5. Hosted as File:Philips P2000 Field Service Manual 5122 991 30703.pdf.
- ↑ 2.0 2.1 2.2 Philips Data Systems, Field Service Manual P2000, October 1982, pp. 1-25 to 1-29, section 1.2.4.3: maintenance program (national version selection; RAM, V24, keyboard, screen, tape drive, beeper, floppy drive tests and summary). Hosted as File:Philips P2000 Field Service Manual 5122 991 30703.pdf.
- ↑ Philips, Documentatie P 2000 (Field Support manual, 8111), p. 0-1: chapters 4 (diagrams) and 6 (parts). Hosted as File:Philips P2000 Field Support Manual 8111.pdf.
- ↑ 4.0 4.1 4.2 Philips Data Systems, Field Service Manual P2000, October 1982, p. 1-24: steps 5 to 8 of the M-version procedure (section 1.2.4.2), referred to by step 2 of the T-version procedure, including the 5 V checks at the CPU, video and extension board sockets, the 12 V check at the CPU board socket and the regulator to replace for each failure. Hosted as File:Philips P2000 Field Service Manual 5122 991 30703.pdf.
- ↑ Philips, Documentatie P 2000 (Field Support manual, 8111), p. 4-33, figure 4.14: power supply basic cabinet. Hosted as File:Philips P2000 Field Support Manual 8111.pdf.
- ↑ Philips Data Systems, Field Service Manual P2000, October 1982, p. 1-9: the aluminium backplate as the heat sink for the power supply regulators. Hosted as File:Philips P2000 Field Service Manual 5122 991 30703.pdf.
- ↑ 7.0 7.1 7.2 Philips, Documentatie P 2000 (Field Support manual, 8111), p. 3-23, section 3.4.1: power supply basic cabinet (regulators, the positive voltage over C3 and negative voltage over C4, the unregulated -20 V to all logic boards regulated to -5 V and -12 V on each board, and the TS1 and TS2 protection that short-circuits +12 V while +5 V fails). Hosted as File:Philips P2000 Field Support Manual 8111.pdf.
- ↑ Philips, Documentatie P 2000 (Field Support manual, 8111), p. 6-19: PCB Economy CPU parts list, with the LM79L12 and LM79L05 negative regulators. Hosted as File:Philips P2000 Field Support Manual 8111.pdf.
- ↑ Philips Data Systems, Field Service Manual P2000, October 1982, pp. 1-30 to 1-35, section 1.2.5: replacements, with the memory circuits on the CPU board (6000 to 9FFF) and the extension board (A000 to DFFF) and the T-version character generator SAA505X on the CPU board. Hosted as File:Philips P2000 Field Service Manual 5122 991 30703.pdf.
- ↑ 10.0 10.1 10.2 Philips Nederland, Technische Service, Notities bij de servicelezing: De Philips P2000T thuiscomputer, February 1984, p. 4: memory map, input/output ports, and testing with OUT, INP, POKE and PEEK from BASIC. Hosted as File:Philips P2000T Servicelezing Notities 1984.pdf.
- ↑ 11.0 11.1 Philips Nederland, Technische Service, Notities bij de servicelezing, February 1984, pp. 14 and 15: fault finding with the test module in the first slot (RAM test on the 4116 chips, V24 connector pins 2, 3, 5 and 6, 7 and 20, keyboard, video and tape drive tests). Hosted as File:Philips P2000T Servicelezing Notities 1984.pdf.
- ↑ Philips Data Systems, Field Service Manual P2000, October 1982, p. 1-15, section 1.1.5.2: printer interface, 25-pin connector, pin 3 data out, pin 2 received data, pin 7 logic ground, pin 20 printer ready. Hosted as File:Philips P2000 Field Service Manual 5122 991 30703.pdf.