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C64 Diagnose: Blank Screen

Ray Carlsen CARLSEN ELECTRONICS… a leader in trailing-edge technology.

Blank screen is the most common symptom, and a failing PLA chip is the most common reason. However, quite a few other failures can cause it as well, such as a bad power supply (check with a known good substitute), bad RAM chip(s), and in general, just about any other chip in there because many chips share multiple data lines. If any one of those lines is loaded down or missing a signal for whatever reason, it can produce that symptom. To narrow it down a bit:

Turn the computer off and back on rapidly about five times. If the screen ever comes up with flashing colors or all one color, the PLA is suspect. Replace it to check. Try a cartridge, such as a game. It essentially „replaces“ some of the chips in the computer when it runs. If a cart works, check the ROMs. The screen may have a normal border even if the CHARacter or BASIC ROMs are bad. A bad Kernal ROM will produce no border.

The internal RF unit outputs a signal that goes to the antenna input of your TV. If the picture is snowy, suspect the RF modulator, assuming the direct video output of the 64 is normal. If the computer is „dead“ but is getting power (red LED on), the modulator will produce a black screen… darker than the blank screen of a failing chip in the computer. A missing 9VAC (power supply problem) is a possiblility. Note that the later C64C will still work without the 9VAC or if the internal fuse opens. However, you will have no sound, the cassette will not work, and the TOD clocks will not work.

See if any of the RAM chips (there are eight of them) get warm or hot… feel each one with the back of your finger after the computer has run for about 5 minutes. Shorted chips will get hotter than the others. Note: bad RAM doesn’t always get hot. See if the computer resets the other components in the system like the drive and/or printer. If so, try a „blind“ disk command and see if the drive responds.. try formatting a disk. If that works, you may have a bad VIC chip (no screen display). Sometimes a bad SID chip will produce a blank screen… pull it out and try the computer. It will run without it, although you will have no sound, and a proportional mouse will not work. The few large chips that normally run hot have a high failure rate: in rough order… the PLA, SID, MPU and the VIC. Static zaps usually take out chips like the CIAs. A shorted CIA can produce a blank screen. Note that you will get the startup screen with the CIA’s removed. You can use that as a diagnostic. The smaller so-called „glue logic“ chips (TTL) run cool and are pretty rugged. Although they rarely fail, I’ve had a few that drove me crazy by making me unsolder a dozen IC’s until I found the bad one. With the above noted exceptions, removing a chip will not allow the computer to produce the startup screen. Removing a chip will in most cases produce a blank screen.

The only practical way to check chips is by substitution. The easiest way to do that is by inserting each suspected chip into a working computer that already has all chips socketed. (You can chase your tail doing it the other way around if you have more than one bad one.) I made a test board for just that purpose. Suspected chip(s) can be tested one at a time and only the bad ones need be replaced. At the very least, you need a source of known good chips for test purposes. Be careful… they are static sensitive. If you don’t want to go to that much trouble to diagnose the problem, you will probably be better off hunting up another C64. Chips are hard to find and expensive. Keep a spare „breadbox“ or two, even if only for parts.

C64 BLANK SCREEN 02-22-99

C64 Diagnose: 1540 und 1541

1540 / 1541 Service Manual

From: Ray Carlsen CET

1541 CHIPS VS SYMPTOMS latest additions or corrections: 2-15-08
This list represents the most common versions of the 1541 in the standard brown case with PC board numbers 1540050 (early ALPSpush-down door mechanism) and the 251830 and 251777 (Newtronics twist door mechanism). Although the very early „long board“ (white case) 1541 is not represented here, major chip functions are of course similar. Thatdrive used more TTL (so-called „glue logic“) chips that were later „integrated“ into a single motor control IC. Although functionally identical, newer drives such as the 1541C and 1541-II integrate more functions into fewer more specialized IC’s, making some repair parts even harder to find. Although most of the chips in the different versions of the standard brown case 1541 are the same, board layout and some chip ID numbers may be different. To eliminate confusion, I will list the two major versions of the drive separately. In another article (fix1541.txt) I will give you some troubleshooting tips. Included is how the drive should behave during normal operation and what is likely to cause a particular fault. Before suspecting any IC chips, don’t overlook more common causes of problems such as a dirty read/write head. Always check the „easy stuff“ first.

1541 CHIPS VS SYMPTOMS PCB# 1540050 (early version) with ALPS drive mechanism (1982)

UA1 74LS14 LOGIC

Partial failure common cause of „FILE NOT FOUND“ error. Total failure: when drive powered up, red LED stays on and spindle motor runs continuously (check also UB4, UC2, UC4, UC5, UC6, UD3, and UD5).

UB1 7406 (M53206P) LOGIC

Partial failure most common causing „SEARCHING FOR“ (also check UC3), or „DEVICE NOT PRESENT“. Total failure: drive may power up normally, but will not reset when the computer is turned on.

UB2 TMM2016AP-10 16K RAM TMM2116AP-15 or MB8128-15

When drive powered up, motor runs continuously and red LED flashes slowly (about 1 flash every 2 seconds).

UB3 325302-01 DOS ROM

When drive powered up, red LED flashes 3 times repeatedly.

UB4 901229-03 or -05 DOS ROM

When drive powered up, red LED stays on and spindle motor runs continuously. DOS ROM is a common failure. Check also UA1, UC2, UC4, UC5, UC6, UD3, and UD5.

UC1 325572-01 MOTOR CONTROLLER

When drive powered up, red LED comes on and goes out, but spindle motor does not turn. When LOAD attempted, spindle does not turn, red LED flickers, screen displays „FILE NOT FOUND“ and red LED flashes.

UC2 6522 VIA (MOTOR CONTROL INTERFACE)

When drive powered up, red LED stays on and spindle motor runs continuously. Check also UA1, UB4, UC4, UC5, UC6, UD3, and UD5.

UC3 6522 VIA (SERIAL INTERFACE)

Drive powers up and resets normally. When LOAD attempted, screen indicates „SEARCHING FOR …“, but no motors run and red LED does not light.

UC4 6502 MPU

When drive powered up, red LED stays on and spindle motor runs continuously. Check also UA1, UB4, UC2, UC5, UC6, UD3, and UD5.

UC5 74LS04 (74LS14) LOGIC

When drive powered up, red LED stays on and spindle motor runs continuously. Check also UA1, UB4, UC2, UC4, UC6, UD3, and UD5.

UC6 74LS00 LOGIC

When drive powered up, red LED stays on and spindle motor runs continuously. Check also UA1, UB4, UC2, UC4, UC5, UD3, and UD5.

UC7 74LS42P LOGIC (DECODER)

When drive powered up, motor runs continuously and red LED flashes slowly (about 1 flash every 2 seconds). Red LED may stay on and/or motor may stop.

UD1 7406 (M53206P) LOGIC

When drive powered up or reset, spindle motor runs momentarily, but red LED doesn’t come on. When LOAD attempted, screen indicates „SEARCHING FOR …“ but red LED does not light, spindle runs continuously, and screen shows „FILE NOT FOUND“ error.

UD2 7417 LOGIC (R/W CONTROL BUFFER)

When drive powered up or reset, red LED comes on and goes out, but spindle motor does not turn. If LOAD is attempted, red LED comes on, stepper moves slightly, spindle doesn’t turn, screen shows „FILE NOT FOUND“ and red LED flashes.

UD3 74LS86 LOGIC

When drive powered up, red LED stays on and spindle motor runs continuously. Check also UA1, UB4, UC2, UC4, UC5, UC6, and UD5.

UD4 9602 (8602) LOGIC (MMV)

Drive powers up and resets normally, but if LOAD is attempted, spindle motor runs with red LED out. Screen displays „SEARCHING FOR …“ and stepper does not move. Check also UE6.

UD5 74LS197 (74177) LOGIC (TIMER)

When drive powered up, red LED stays on and spindle motor runs continuously. Check also UA1, UB4, UC2, UC4, UC5, UC6, and UD3.

UE4 LM311 COMPARITOR (READ LOGIC)

Powers up normally. When LOAD attempted, spindle turns and red LED comes on, but „FILE NOT FOUND“ and red LED flashes. Check also UF3 and UF4.

UE6 74LS193 (7417) LOGIC (BIN COUNTER)

Drive powers up and resets normally, but if LOAD is attempted, spindle motor runs with red LED out. Screen displays „SEARCHING FOR …“ and stepper does not move. Check also UD4.

UF3 NE592N READ PREAMPLIFIER

Powers up normally. When LOAD attempted, spindle runs and red LED comes on, but „FILE NOT FOUND“ and red LED flashes. Check also UE4 and UF4.

UF4 NE592N READ AMPLIFIER

Powers up normally. When LOAD attempted, spindle runs and red LED comes on, but „FILE NOT FOUND“ and red LED flashes. Check also UE4 and UF3.

VR1 UA7812KC (LM340KC-12) +12 VOLT REGULATOR

Drive powers up „normally“, but motors run slowly or not at all. If that happens, drive access will produce a flashing red activity LED and errors „file not found“ or „drive not ready“ on the error channel.

VR2 UA7805KC (LM340KC-5.0) +5 VOLT REGULATOR

Green (power) LED dim, flickers, or does not come on at all, but spindle may run continuously and red LED may be dark.

CR1 2 AMP 200V BRIDGE RECTIFIER (FOR +12V)

Drive appears to power up normally, but motors do not run. Should get warm only if the drive is being accessed (motors running).

CR3 2 AMP 200V BRIDGE RECTIFIER (FOR +5V)

On power up, green and red LED’s are dim or dark and spindle motor runs continuously. May be intermittant and „die“ after warmup. Part runs very hot normally and is a common failure in this model.

1541 CHIPS VS SYMPTOMS PCB# 251830 or 251777 with Newtronics drive mechanism (1984)

UA1 74LS14 LOGIC

Partial failure common cause of „FILE NOT FOUND“ error. Total failure: when drive powered up, red LED stays on and spindle motor runs continuously (check also UB4, UC2, UC4, UC6, UC7, UD3, and UD5).

UB1 7406 (M53206P or 7707) LOGIC

Partial failure common cause of „SEARCHING FOR“ (check also UC3) and „DEVICE NOT PRESENT“ errors. Total failure: drive powers up OK, but does not respond to computer… no reset or disk access.

UB2 TMM2016AP-10 16K RAM TMM2116AP-15 or MB8128-15

When drive powered up, spindle motor runs continuously and red LED flashes about once every two seconds.

UB3 325302-01 DOS ROM

When drive powered up, red LED flashes 3 times repeatedly.

UB4 901229-03 or -05 DOS ROM

When drive powered up, red LED stays on and spindle motor runs continuously. DOS ROM is a common failure. Check also UA1, UC2, UC4, UC6, UC7, UD3, and UD5.

UC1 325572-01 MOTOR CONTROLLER

When drive powered up or reset, red LED comes on and goes out, but spindle motor does not turn. When LOAD attempted, spindle does not turn, red LED flickers, screen displays „FILE NOT FOUND“ and red LED flashes.

UC2 6522 VIA (MOTOR CONTROL INTERFACE)

When drive powered up, red LED stays on and spindle motor runs continuously. Check also UA1, UB4, UC4, UC6, UC7, UD3, and UD5.

UC3 6522 VIA (SERIAL INTERFACE)

Drive powers up and resets normally. When LOAD is attempted, screen indicates „SEARCHING FOR …“, but no motors run and red LED does not light.

UC4 6502 MPU

When drive powered up, red LED stays on and spindle motor runs continuously. Check also UA1, UB4, UC2, UC6, UC7, UD3, and UD5.

UC6 74LS04 (7713) LOGIC

When drive powered up, red LED stays on and spindle motor runs continuously. Check also UA1, UB4, UC2, UC4, UC7, UD3, and UD5.

UC7 74LS00 LOGIC

When drive powered up, red LED stays on and spindle motor runs continuously. Check also UA1, UB4, UC2, UC4, UC6, UD3, and UD5.

UC8 74LS42 LOGIC

When drive powered up, spindle motor runs continuously. Red LED may stay on, or flash three times and go out.

UD1 7406 (M53206P) LOGIC

When powered up, spindle motor runs momentarily, but red LED doesn’t come on. When LOAD attempted, screen indicates „SEARCHING FOR …“ but red LED does not light and spindle runs continuously.

UD2 7407 (7417) LOGIC (R/W CONTROL BUFFER)

When drive is powered up or reset from computer, red LED comes on and goes out, but spindle motor does not turn. When LOAD is attempted, stepper moves slightly, spindle doesn’t turn, and error message on screen is „FILE NOT FOUND“ with flashing red LED.

UD3 74LS86 LOGIC

When drive powered up, red LED stays on and spindle motor runs continuously. Check also UA1, UB4, UC2, UC4, UC6, UC7, and UD5.

UD4 9602 (74123) LOGIC (MMV)

Drive powers up and resets normally, but when LOAD is attempted, screen indicates „SEARCHING FOR …“ red LED does not light and spindle runs continuously. Check also UE6.

UD5 74LS197 (74177) LOGIC (TIMER)

When drive powered up, red LED stays on and spindle motor runs continuously. Check also UA1, UB4, UC2, UC4, UC6, UC7, and UD3.

UE4 LM311 COMPARITOR (READ)

Drive powers up and resets normally. Spindle motor runs, stepper moves slightly, but „FILE NOT FOUND“ error, and red LED flashes. Check also UF3 and UF4.

UE6 74LS193 (7417 or 7407) LOGIC (COUNTER)

Drive powers up and resets normally, but when LOAD is attempted, screen indicates „SEARCHING FOR …“ red LED does not light and spindle runs continuously. Check also UD4.

UF3 NE592N (LM592) READ PREAMP

Drive powers up and resets normally. Spindle motor runs, stepper moves slightly, but „FILE NOT FOUND“ error and red LED flashes. Check also UF4 and UE4.

UF4 NE592N (LM592) READ AMPLIFIER

Drive powers up and resets normally. Spindle motor runs, stepper moves slightly, but „FILE NOT FOUND“ error and red LED flashes. Check also UF3 and UE4.

VR1 UA7812KC (LM340KC-12) +12 VOLT REGULATOR

When powered up, green power LED comes on and red LED comes on and goes out normally, but motors do not run (or move slowly). Drive access will produce a flashing red activity LED and error messages „file not found“ or „drive not ready“ on the error channel.

VR2 UA7805KC (LM340KC-5.0) +5 VOLT REGULATOR

Green (power) LED dim, flickers, or does not come on at all. Drive appears dead, but spindle motor runs continuously.

CR1 2 AMP 200V BRIDGE RECTIFIER (FOR +5V)

Drive appears dead, but spindle motor runs continuously with both green and red LEDs dim or dark. May be intermittant and fail after warmup. This part normally runs hot and is a common failure item.

CR3 2 AMP 200V BRIDGE RECTIFIER (FOR +12V)

Drive appears to power up normally, but motors do not run. Should get warm only if drive is accessed (motors running).

Notes: UC2, UC3, UB4, and regulators VR1 and VR2 run warm normally and bridge rectifiers CR1 and CR3 run very hot if drive is being accessed. Otherwise, only CR3 will get hot.

Newtronics drives (twist type door latch) normally run a bit noiser (stepper chatter) than earlier ALPS (push down door) types.

Ray Carlsen CET CARLSEN ELECTRONICS… a leader in trailing-edge technology. Questions and comments are welcome, especially if you spot a mistake here. Thanks!

Classic Computing 2011 in Holzminden

Die Classic Computing 2011 fand am 01.10 und 02.10.2011 in Holzminden statt.

30 Jahre Retrocomputing

Die nur einmal im Jahr stattfindende, überegionale Ausstellung und Treffen stand im Jahr 2011 unter dem Motto „30 Jahre Retrocomputing“. Es waren Exponate aus den vergangenen Jahrzehnten der Computergeschichte zu sehen. Neben Klassikern wie dem C64 und dem Amiga 500 gab es Atari 8-bit, Atari ST Reihe, weitere Amiga Systeme (1200/4000/etc), aber auch Computer der Fa. Sinclair und Schneider sowie weitere Commodore Systeme nicht nur zu bestaunen, sondern auch zum ausprobieren. Zu den klassischen Rechnern wurde auch aktuell entwickelte Zusatzhardware vorgeführt. Klassischen Spiele wie z.B. Great Giana Sisters, Donkey Kong oder Arkanoid wurden mit Begeisterung gespielt.

Es trafen sie Gleichgesinnte und Interressierte zum Gedankenaustausch, Fachsimpeln und einfach zum Spaß an der
Sache. Viele zeigten ihren Kindern, wie ihre ‚Playstation‘ damals aussah und wieviel Spaß damit möglich war.

Pressespiegel

Bilder von der CC 2011

Classic Computing 2010 in Altensteig-Walddorf

Die Classic Computing 2010 fand am, 2. und 3. Oktober 2010 in der Festhalle in Altensteig-Walddorf statt.

10 Jahre Classic Computing

Mehr als 25 Mitglieder des Vereins zum Erhalt klassischer Computer e. V. und viele weitere Aussteller hatten zu der Präsentation ihrer schönsten Computer aus vergangenen Zeiten herzlich eingeladen. Für Jung und Alt – also für Jedermann – war Interessantes dabei. Alle Exponate konnten angefasst und intensiv charakterisiert werden.

 
Wer früher einmal einen Commodore 64, Atari oder einen Amiga hatte, wurde wieder ins Retro Feeling versetzt. Für alte und defekte Computer war die Reparaturecke geöffnet, die einige Rechner wieder in Betrieb setzen konnte.

Pressespiegel

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Classic Computing von 2000 bis 2009

Die Classic Computing wurde erstmalig im Jahr 2000 veranstaltet.

Veranstaltungsorte waren:

  • 2009: Hachenburg
  • 2008: Moers
  • 2007: Stuttgart-Degerloch
  • 2006: Nordhorn
  • 2005: Neubulach
  • 2004: Oberhaugstett
  • 2003: Eberstadt
  • 2002: Möckmühl
  • 2000: Neukirchen-Vluyn

Über diese Veranstaltungsreihe wurde in der Presse oft berichtet und es exisitiert vielfältiges Bildmaterial zu diesen Veranstaltungen. Hier finden Sie eine Auswahl dieser Erinnerungen.

Pressespiegel

Bilder von der Classic Computing

Retrobörse 2009

Die Retrobörse findet an wechselnden Orten statt und ist Handelsplatz für Video- und Computerspiele. Hier sind Fotos unserer Teilnahme zu finden.

Alle Bildergalerien der Classic Computing

Hier finden sich viele Bilder von den Classic Computing Veranstaltungen seit dem Jahr 2000.

Classic Computing 2000

Bilder von der CC 2000 in Neukirchen-Vluyn.

Classic Computing 2002

Classic Computing 2002 in Möckmühl

Classic Computing 2003

Classic Computing 2003 in Eberstadt

Classic Computing 2004

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Bilder von der Classic Computing 2005 in Neubulach

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Bilder von der Classic Computing 2007 in Stuttgart-Degerloch

Classic Computing 2008

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