Among the multitude of sources of information available on Atari 8-bit computers, I make a clear distinction between two categories: information made public, and Atari's internal information.

The information made public is flyers and brochures, advertisements, user manuals, articles in specialised magazines, and books. Today, what is admirable is that everything is available to us on the Internet. Back then, European fans had almost no access to what was published in the USA and vice versa. Even in Europe, the information available to fans was often limited to one country. You either had to visit the specialist "import" shops or be a journalist to get access to wider information. And in the end, you only had the flyers handed out in the local shops, the manuals for the software you bought, and a few specialised books, not hundreds like today.

The fascinating thing about Atari's internal information is that it wasn't supposed to be accessible to fans like us. The ultra-technical notes and brainstorming of the engineers, the studies, the proposals, the internal documents about never released prototypes, the technical documents and descriptions for the developers, the documents for the wholesalers & dealers or the authorized repairers... all this was completely inaccessible to us at the time. Today everything has changed. The wonderful thing is that we have privileged access to unpublished and exclusive information, access to the backstage, to better understand the history of Atari 8-bit computers, from the inside.

Atari Field Service Manuals (FSM)

These FSM — highly technical documents — were intended for use by Atari's authorized repairers (service centres) nationwide to help them diagnose and perform simple repairs. Help was also available by telephone with a specialist in California. Very specific step-by-step guides explained how to determine the source of problems and then how to disassemble computers and peripherals and where exactly to find the defective parts to be replaced.

In addition — and this is the subject of this article — the FSM were often supplemented by other technical documents, offered as appendices:

These are those appendices that I propose to you below. I have corrected some obvious mistakes and made some editorial changes to facilitate understanding.

This section is currently still in "Work in Progress" status: scanning, reading and retyping all these documents takes time.

Tech tip #1 (2 Apr 1982)

Subject: Atari 810 disk drive, rear board Molex connectors.

New Atari 810 disk drives rear boards are assembled with the two 3-pin Molex Connectors (J104 and J105) removed. The 5 volts Regulator (A108) and the Pass Transistor (Q113) are now soldered directly to the Rear Board (see Silk Screen).
Parts Removed: Atari Part No. CO14716-03 (2)
Part Location: Atari 810 disk drive — rear board location J104 and J105

Troubleshooting and Maintenance procedures:
For troubleshooting, maintenance, and testing, observe warnings and cautions in the Atari 810 Field Service Manual.
Note that the voltage regulator (A108) and the pass transistor (Q113) are fastened to the base plate. In order to remove the rear board, you must remove the mounting screws from each. Remember to use heat sink compound when replacing the rear board, before securing the mounting screws.

Tech tip #2 (28 May 1982)

Subject: Atari 400/800 Operating System ROMs, Revision B.

New Atari 400/800 computers contain Revision B ROMs — a refined version of an Operating System ROM, which has a different checksum from Revision A ROMs. When replacing components, do not mix revision levels. System will not operate if Revision A is paired with Revision B.

Parts affected:

  • Old (Revision A) ROMs: CO12499A and CO14599A
  • New (Revision B) ROMs: CO12499B and CO14599B

Part locations:

  • 400 computer system — Motherboard location — A103 (CO14599) and A104 (CO12499)
  • 800 computer system — Personality Board location — A401 (CO14599) and A403 (CO12499)

You can recognize the new parts in this manner: Top is imprinted with a copyright © symbol followed by 1981 Atari.

Troubleshooting and Maintenance procedures:
For troubleshooting, maintenance, and testing, observe warnings and cautions stated in Atari 400/800 Home Computer system Field Service Manual. Before a component or board is added or removed from the system, power the system down.
If ROM chips are defective or if printer overprints (hiccups), replace ROM chips.

400 Computer

  • Follow 400 computer disassembly instructions in Atari 400/800 Home Computer system Field Service Manual to access motherboard.
  • Remove ROM chips located at A103 (CO14599A) and A104 (CO12499A).
  • Replace CO14599A and CO12499A with A103 (CO14599B) and A104 (CO12499B).
  • Follow reassembly instructions in Atari 400/800 Home Computer system Field Service Manual.

800 Computer

  • Follow 800 computer disassembly instructions in Atari 400/800 Home Computer system Field Service Manual to access ROM module.
  • Remove ROM chips located at A401 (CO14599A) and A403 (CO12499A) on ROM module.
  • Replace CO14599A and CO12499A with A401 (CO14599B) and A403 (CO12499B).
  • Follow reassembly instructions in Atari 400/800 Home Computer system Field Service Manual under ROM Module Installation.

Testing procedures:
Follow standard test procedures using Atari Stand Alone Test (Diagnostic) as outlined in Atari 400/800 Home Computer system Field Service Manual.

Tech tip #3 (Missing)

Believe me, I have many, many copies of Tech Tips, but Tech Tip #3 has never appeared anywhere. Do you have it? Please contact me! (see bottom of page)

Tech tip #4 (17 Nov 1982)

Subject: Atari 810 disk drive units containing the following:

  • Data separator board added to sideboard
  • Sideboard stepper motor circuit voltage increase to regulated 12 volts DC
  • New power adaptor to provide increased current required by the above modifications

New Atari 810 disk drives units manufactured by Atari contain a data separator board added to the sideboard, modifications to the stepper motor circuit to increase voltage, and a new power adaptor. This Tech Tip instructs those who are repairing Atari 810 disk drives containing these modifications.

Parts affected:

  • Data Separator Board — Atari Part No. CAO17231
  • Sideboard — Atari Part No. CAO14834
  • Power Supply — Atari Part No. CO16804

Part Location — P103 on data separator board, Atari Part No. CAO17231, plugs into the sideboard location A105 on Atari sideboard Part No. CAO14834, where FDC 1771 (Floppy Disk Controller) is usually installed.

Troubleshooting and Maintenance procedures:

For troubleshooting, maintenance, and testing, observe warnings and cautions stated in Atari 810 disk drive Field Service Manual. Before a board is added to or remove from the unit, power the system down.

In a board is suspected, follow the standard troubleshooting procedure outlined in Atari 810 disk drive Field Service Manual, to check circuitry and alignment. If circuitry and alignment check out but board has many 144 errors or many intermittent errors, swap the data separator board in the unit with a known good one. This procedure isolates the problem to a faulty data separator board or faulty side board.

Use procedure outlined in Atari 810 disk drive Field Service Manual.

Note: These boards cannot be installed in the existing socket in sideboards not designed for data separator. Doing so may result in shorts or intermittent failures.

Testing procedures:
Use standard test procedures outlined in the Atari 810 disk drive Field Service Manual. Diagnostic testing — Use flawtest III and align 3K Disk Alignment Program.

Tech tip #5 (17 Nov 1982)

Subject: 138, 140, and 143 Errors with Atari 410 program recorder.

Description: It is a common occurrence for a customer to experience problems while trying to load cassette tapes with the Atari 410 program recorder.

Troubleshooting: We have separated troubleshooting into two sections: one for the servicer and one for the user. The user section has purposely been put on a separate page to allow copies to be made for distribution to users.

Tech tip #5 > Troubleshooting for Servicer

Servicer #1 Periodic maintenance

Problem: Failure to perform periodic maintenance. Dirty pinch roller or capstan can cause uneven tape speed and damage media. Buildup of oxide residue on the read/write head can interfere with proper operation.

Solution: Perform periodic maintenance as outlined in the Atari 410 Operator's Manual.

Servicer #2 Peripheral Connection

Problem: The Atari 410 is connected through a peripheral (Atari 810, 850, 820, 822) that does not properly pass on the signal to the computer.

Solution: Connect the Atari 410 directly to the computer and repair the defective peripheral.

Servicer #3 OS Revision B Incompatibility

Problem: The software is not compatible with Revision B of the OS. All Atari software is fully compatible with Revisions A or B but some third party titles are not compatible.

Solution: The third party vendors usually are able to replace the software with an updated version. It is possible to determine what version of the OS is installed by checking memory location 58383. From BASIC: PRINT PEEK(58383) (RETURN). A value of 56 indicates Revision A whereas 0 indicates Revision B.

Servicer #4 PAL Operating System

Problem: An international PAL version of the OS is installed instead of domestic NTSC version.

Solution: Install a domestic 10K ROM. It is possible to determine what version of the OS is installed by checking memory location 58383. From BASIC: PRINT PEEK(58383) (RETURN). A value of 56 or 0 indicates NTSC whereas 249 indicates PAL.

Servicer #5 Atari 410 Motor Control

Problem: The computer does not properly control the Atari 410 motor. After a cold start in BASIC, merely pushing PLAY on the Atari 410 should not cause the tape to begin moving. POKE 54018,52 should start the motor and POKE 54018,60 should stop the motor.

Solution: Check to see if transistor Q107 on the Atari 800 or Q102 on the Atari 400 motor control line is improperly shorted to ground.

Servicer #6 Atari 410

Problem: Faulty I/O cable, drive mechanism, or electronics, necessitates repair or replacement of the 410.

Solution: Follow the procedures in the Atari 410 Field Service Manual.

Tech tip #5 > Troubleshooting for Users

Users #1 New Atari 410

Problem: Many Atari cassette-based products have loading problems on the newer model of the 410 (with PAUSE and no carrying handle) but not on the older 410. The newer 410 has a more powerful amplifier which raises previously insignificant background noise to significant levels and causes error conditions when interpreted as data. All Atari cassette-based products have been remastered and the finished goods stock was replaced as of March 1, 1982.

Solution: Replace the media with inventory acquired after March 1, 1982.

Users #2 System Reset (on Atari 400/800)

Problem: Pressing SYSTEM RESET does not reset the data I/O line in the POKEY. Subsequent use of CSAVE is unreliable because the data I/O line is not clear, POKEY sends garbage, and the data stored is unrecoverable.

Solution: Avoid pressing SYSTEM RESET. Before using CSAVE or CLOAD, always execute a LPRINT command.

Note: Executing a serial bus command properly resets POKEY and clears the data I/O line. The simplest bus command to execute is LPRINT. If a printer is not attached when the LPRINT is executed, an error 138 occurs. The occurrence is normal and does not interfere with the reset of POKEY.

Users #3 Pre-recorded Tape Positioning

Problem: Tape is improperly positioned.

Solution: Pre-recorded tapes should load properly if rewound completely. If not, manually wind the leader onto the take-up reel before attempting to load.

Users #4 User-Recorded Tape Positioning

Problem: Tape is improperly positioned relying on the counter.

Solution: Store only one program per side of tape positioned manually at the end of the tape leader.

Users #5 Faulty Pre-recorded Media

Problem: Tapes produced in mass quantity are not individually verified to load successfully because of sampling techniques.

Solution: Replace the tape.

Users #6 Faulty User-Recorded Media

Problem: The oxide coating on audio cassette tape is subject to momentary dropouts that does not record data.

Solution: Replace the tape.

Users #7 Worn Media

Problem: Tapes stretch and warp after prolonged normal usage.

Solution: Replace the tape. Avoid leaving the PLAY, ADVANCE and REWIND button engaged after tape movement is completed.

Users #8 Magnetic Field

Problem: Data is altered during transmission because of the Atari 410 I/O cable's close proximity to a magnetic field.

Solution: Do not set the Atari 410 on or close to a TV or power transformer.

Users #9 Vibrations

Problem: Data is altered during transmission because the Atari 410 was bumped, moved or jarred.

Solution: Keep the Atari 410 stationary during data transmission.

Users #10 Chrome (CRO²) Tape

Problem: The bias of CRO² tape is incompatible with the Atari 410

Solution: Use normal ferrite audio tape.

Tech tip #6 (17 Nov 1982)

Subject: Data reliability on the Atari 810 analog disk drive.

Description: Atari 810 analog disk drives (those manufactured after August 1981) that exhibit diskette compatibility problems, and/or troubles in formatting new diskettes, should have the write current resistor (R218) replaced with a 1.4K ohm resistor.

Troubleshooting and Maintenance procedures:

Part removed: 2K ohm 1/4 W 5% Resistor — Atari Part No. 14-5202

Replace with: 1.4K ohm 1/4 W 2% Resistor — Atari Part No. 14-2142

Part location: Atari 810 analog board location R218

Testing procedures: Follow the diagnostic flowchart and troubleshooting guide for the analog disk drive in the Atari 810 Field Service Manual.

Tech tip #7 (17 Nov 1982)

Subject: Atari 810, reformatting preformatted diskettes.


Because the format on preformatted diskettes in effect becomes the standard for in-the-field disk drive testing, they must be created on master duplicating machines. These diskettes must never be reformatted. If a diskette is reformatted by another source, it becomes useless for the test intended.

Unfortunately, there is no way to know if a "Preformatted diskette" has been reformatted. The possible results of reformatting a "Preformatted diskette" or nor using a preformatted diskette are:

  1. You may replace a drive mechanism when no problem exists.
  2. You may misalign the heads, thus making your customer's diskette library unusable on the "fixed" disk drive.

Do not use a reformatted preformatted diskette to align or troubleshoot an Atari 810 disk drive.

Tech tip #8 (17 Nov 1982)

Subject: Reset problem on Atari 820 printer.


When the printer is cycled (powered OFF then ON) quickly, the printer's 6507 fails to RESET properly. Thus, if the next operation for it to perform is advance paper one space, the printer continuously advances paper until the printer is turned OFF. Or, if the computer issues a PRINT command, printing errors occur because the printer is not "set" to receive data.

The reset problem occurs when the customer cycles the printer in less than 2 seconds.

Troubleshooting and Maintenance procedures:

When a customer's complaint centers around the Atari 820 not resetting properly, ask if the customer waits a full five seconds between turning the printer OFF and then ON again. If the answer is NO, advise the customer that it takes a full five seconds to allow the voltage circuitry to be at or near the 0 (zero) volts required for a valid system RESET.

We are not aware of any service problem related to this RESET problem.

Knowledge base article: kb-technical-0001-atari-field-change-orders-tech-tips-and-upgrade-bulletins
REV. 002.

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