Atari SLM804 Troubleshooting Guide
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Fault-finding for the Atari SLM804 laser printer and its SLMC804 controller, from the specification pages of TEC's Service Manual Model SLM-804 (E0-16172A, 1987), Atari's The Atari Page Printer Interface (April 1988) and the engine, power supply and controller schematics.[1][2] The hosted scan has no fault-finding chapter or parts list, so the checks below come from the signal and status definitions.
The engine has a mains power supply and a heat roll fixing unit.[3][4] Unplug the printer before working inside it.
Panel indicators
[edit | edit source]| Indicator | Lights when |
|---|---|
| READY | The printer is in standby. It goes out while the heater warms up and when an error occurs. |
| WAIT | The heater is warming up, or an error has occurred. |
| ADD PAPER | The paper cassette is empty, or the printer is in manual feed mode. |
| CHECK PAPER PATH | Paper has jammed. |
| REPLACE TONER | The engine reports toner empty (TE). |
Warm-up takes less than 2 minutes and the first page less than 22 seconds.[3] At power-on the engine holds its reset line (RES) low for at least 10 ms and raises the warm-up line (WUT) within 2 minutes, when the heater is ready.[5]
What the engine reports
[edit | edit source]The engine tells the controller about faults on separate lines of its 37-way video interface.[6]
- ERR (pin 9) goes low on any error: polygon motor sync error, memory error, control error, heat fixing control error, paper jam or paper empty.[6]
- PJ (pin 12) goes low on a paper jam, and also whenever the cover is open.[7]
- PE (pin 10) goes low when the cassette is out of paper, and also when no cassette is fitted.[7]
- TE (pin 11) reports toner empty.[6]
- CAS1 and CAS2 (pins 6 and 8) tell the controller which cassette is fitted: A4 is low/low, B5 low/high, Letter high/low and Legal high/high.[7]
The error timing charts show two kinds of stop. After the first paper jam error or paper empty, the paper feed motor runs on until the sheet has left the printer and then stops, and the heater is switched off. After the second or third jam error, or when the cover is opened, the motor and heater stop at once.[8]
Printing sequence
[edit | edit source]The scan also holds a single page numbered 4-23, a flowchart of the printing sequence (Fig. 4-20), in a different typeface from the specification pages. Its jam numbering, JAM1 to JAM3, matches the SLM-804 timing charts.[9] In that flowchart:
- After initialisation the engine checks for an error and, if there is one, shows it before going further.
- It switches the heater on and waits for the set temperature. If the temperature is not reached in time, it shows an error.
- JAM1 is checked after a sheet has been fed and before printing. JAM2 and JAM3 are checked during printing and until the post-rotation has finished.
- On any jam error the heater is switched off and the jam is displayed until the error is cleared.[9]
SLMC804 status codes
[edit | edit source]The SLMC804 returns a status byte after each command, and at the end of every page during printing. A driver reads it with the Request Sense command (0x03).[10][2] Atari lists the codes in order of rising priority.[2]
| Group | Code | Status | Atari's description |
|---|---|---|---|
| 0x00 | No Error | Command completed without error. | |
| Printer | 0x02 | Ornery Printer | Catch-all for a printer error that has no code of its own. |
| 0x03 | Toner Empty | Toner supply exhausted (not fatal). | |
| 0x04 | Warm Up | Fuser unit warming up. | |
| 0x05 | Paper Empty | Paper exhausted in the selected automatic feed (not returned in manual feed). | |
| 0x06 | Drum Empty | Drum surface exhausted (not fatal). | |
| 0x07 | Input Jam | Paper jam at entry. | |
| 0x08 | Through Jam | Paper jam during printing. | |
| 0x09 | Output Jam | Paper jam at exit. | |
| 0x0a | Cover Open | Printer cover open. | |
| 0x0b | Fuser Malfunction | Error in the fuser unit, which fixes the toner to the paper by heat. | |
| 0x0c | Imager Malfunction | Error in the imager unit, which generates the image and scans it onto the drum. | |
| 0x0d | Motor Malfunction | Error in the motor unit, which drives the paper feed, drum, toner hopper and fuser pulleys. | |
| 0x0e | Video Malfunction | Error in the video unit, which provides the external video interface and controls the printer's housekeeping. | |
| Controller | 0x10 | System Timeout | The controller timed out waiting for something, such as manual feed input. |
| Command | 0x12 | Invalid Operation Code | Command not implemented. |
| 0x15 | Invalid Device Number | Device does not exist. | |
| 0x1a | Invalid Parameter List | A parameter is out of bounds. |
Points from the same document that explain some puzzling behaviour:
- The controller checks the printer before and after a Print command. Toner Empty and Drum Empty do not stop the job; the page is printed and the error reported afterwards.[2]
- By default the controller tries the manual feed whenever it sees Paper Empty. It waits for paper for the System Timeout set in its parameter list and then returns code 0x10.[11][12]
- The page size follows the cassette fitted, read from CAS1 and CAS2. With the paper empty the controller assumes Letter.[11][7]
- A Stop Print command is only accepted in a 100 ms window after a page's status byte. Outside a multi-page print it returns Invalid Operation Code.[13]
Controller, cable and supply checks
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On the SLMC804 schematic, the controller's VCC comes from the printer through pins 16, 17, 35 and 36 of its 37-way connector J3, with C32 (470 µF) and C33 (0.1 µF) across it.[14] The engine provides these supplies on its interface connector, a Fujitsu FCN-774J037-G/C:[6][7]
| Pins | Supply | Rating |
|---|---|---|
| 16, 17, 35, 36 | +5 V | ±10 %, 3 A |
| 1 | +12 V | ±10 %, 0.15 A |
| 20 | −12 V | ±10 %, 0.15 A |
| 22 to 30 | Signal ground | |
| 21 | Frame ground (signal ground in the pin table) |
If the controller shows no sign of life with the printer switched on, measure the +5 V between those pins and a signal ground pin at the printer's connector. Then check the cable. The engine's outputs are open-collector (7406 or 7407 type) and its inputs are 74LS14 Schmitt triggers with pull-ups to +5 V.[6]
On the controller board, the 6801 microcontroller U1 runs from a 4.0 MHz crystal, Y1. Sheet 1 also shows a 4.7 µF electrolytic, C42.[15] Sheet 2, marked "TEC", shows the 74LS14 and 7408 buffers between the 6801's ports and the TEC engine's signals (VCK, VSY, ST, REQ, CONT, ERR, WUT, PE, TE, CAS1, CAS2).[16] PDF page 9 of the scan holds a second version of this interface, marked with an arrow labelled "Canno" where the scan cuts the word off, with differently named signals, 75113 line drivers and a 29.821 MHz oscillator.[17]
Atari's example driver addresses the controller as device number 7 on the DMA bus.[18] Each device on the chain needs its own number, so a hard disk set to 7 would clash with it.[19]
Engine power supply (200 V version)
[edit | edit source]TEC's drawing SLE52-00301 covers the 200 V power supply board, SLE61-0081. It gives no component values or fuse ratings.[4]
| Output | Path on the drawing |
|---|---|
| +12 V | Fuse F203, diode D204, regulator Q204, capacitors C209, C211, C213 |
| −12 V | Fuse F202, diode D203, regulator Q203, capacitors C208, C210, C212 |
| +24 V | Diodes D201, capacitors C205, C206, fuse F204, Q202 and R208, filter L201 and C207, then switch S201 (with SP201) |
| +5 V | Switching transistor Q205 with chokes L202 and L203 and fuse F201, controlled by Q206 |
| Reset (RES) | Q207 |
On the mains side, the supply enters at CN15 and passes through a filter of L101, L102 and capacitors C101 to C110, then SM101, to the bridge rectifier D101. Fuse F101 follows the rectifier. A triac, Q101, driven through optocoupler HC101, switches mains to the two-pin connector CN16. CN19 carries +5 V (pins 1 and 2), signal ground (3 and 4), +12 V (5) and −12 V (6).[4]
The drawing does not cover the 100 to 120 V version. TEC's specification lists the two mains ranges, 90 to 132 V and 198 to 264 V.[3]
Not covered here
[edit | edit source]The hosted scan holds only the specification chapter of TEC's manual, with no adjustment procedures beyond the two variohms (see Atari SLM804 General Maintenance#Adjustments). The Atari Document Archive lists a separate SLM804 parts list and recommended spare parts list (E5-16168, May 1987), which is not hosted here.[20] For general electrolytic capacitor faults see Capacitor Failure Symptoms.
References
[edit | edit source]- ↑ 1.0 1.1 TEC, Service Manual Model SLM-804, section 4, Operation Panel, p. 5 (PDF p. 21).
- ↑ 2.0 2.1 2.2 2.3 2.4 The Atari Page Printer Interface, section 3, Status Definitions, pp. 13-14 (PDF pp. 15-16).
- ↑ 3.0 3.1 3.2 Tokyo Electric Co., Ltd., Service Manual Model SLM-804, document E0-16172A, 1987, section 3, Basic Specification, pp. 3-4 (PDF pp. 19-20). File:Atari SLM804 Service Manual and SLMC804 Schematics (1987).pdf.
- ↑ 4.0 4.1 4.2 4.3 TEC, "Laser Printer Power Supply 200V", drawing SLE52-00301, for board SLE61-0081, April 1987 (PDF pp. 2-3 of the same file).
- ↑ TEC, Service Manual Model SLM-804, section 6-1, Timing Chart, Power On, p. 10 (PDF p. 26).
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 TEC, Service Manual Model SLM-804, section 6-1, Video Interface: pin assignment and signal descriptions, pp. 6-7 (PDF pp. 22-23).
- ↑ 7.0 7.1 7.2 7.3 7.4 7.5 TEC, Service Manual Model SLM-804, section 6-1, signal descriptions continued, p. 8 (PDF p. 24).
- ↑ TEC, Service Manual Model SLM-804, section 6-1, Timing Chart, Error, p. 13 (PDF p. 29).
- ↑ 9.0 9.1 TEC, "Flowchart of printing sequence", Fig. 4-20, p. 4-23 (PDF p. 30 of the same file). A single page numbered 4-23; no other page of that chapter is in the scan.
- ↑ Atari Corp., The Atari Page Printer Interface, 13 April 1988, sections 2 and 2.1, Command Definitions and Request Sense, pp. 3-4 (PDF pp. 5-6). File:The Atari Page Printer Interface (April 1988).pdf.
- ↑ 11.0 11.1 The Atari Page Printer Interface, section 2.5, Mode Sense, parameter list notes, p. 10 (PDF p. 12).
- ↑ The Atari Page Printer Interface, section 2.5, System Timeout, p. 11, and section 3, System Timeout, p. 15 (PDF pp. 13 and 17).
- ↑ The Atari Page Printer Interface, section 2.6, Stop Print, p. 12 (PDF p. 14).
- ↑ "Schematic Diagram SLMC 804", drawing C026455 Rev. 2, sheet 3 (PDF pp. 11-12 of the same file).
- ↑ Atari (Japan) Corporation, "Schematic Diagram SLMC 804", drawing C026455 Rev. 2, sheet 1 (PDF p. 8 of the same file).
- ↑ "Schematic Diagram SLMC 804", drawing C026455 Rev. 2, sheet 2 (PDF p. 10 of the same file).
- ↑ Atari (Japan) Corporation, SLMC804 schematic, interface page without a title block (PDF p. 9 of the same file).
- ↑ The Atari Page Printer Interface, Appendix, Driver Example, p. 19 (PDF p. 21).
- ↑ Atari Corp., SH Hard Disk Drive Owner's Manual, C026263 Rev. B, 1986, chapter 3, Setting the DIP Switches, pp. 19-21 (PDF pp. 25-27). File:Atari SH Hard Disk Drive Owner's Manual C026263 Rev B.pdf.
- ↑ Atari Document Archive, search results for "slm804" (catalogue listing). https://docs.dev-docs.org/htm/search.php?find=slm804 (retrieved 2026-10-06).