From nobody Mon Aug 16 07:54:24 1999 Path: news.cs.hut.fi!newsfeed3.funet.fi!news.tpu.fi!newsfeed1.funet.fi!newsfeed1.telenordia.se!algonet!isdnet!newsfeed.berkeley.edu!news.u.washington.edu!homer12.u.washington.edu!rrcc From: Raymond Carlsen Newsgroups: comp.sys.cbm Subject: Error in repair articles Date: Mon, 19 Jul 1999 19:56:59 -0700 Organization: University of Washington Lines: 529 Message-ID: NNTP-Posting-Host: homer12.u.washington.edu Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Trace: nntp6.u.washington.edu 932439423 25778 (None) 140.142.17.38 X-Complaints-To: help@cac.washington.edu NNTP-Posting-User: rrcc Xref: news.cs.hut.fi comp.sys.cbm:119471 ADDITIONS AND CORRECTIONS Many users that frequent this newsgroup are familiar with my repair articles. There are two concerning diagnosis and repair of the 1541 disk drive, and someone just brought to my attention that I made a mistake when listing the two bridge rectifiers, CR1 and CR3. I did some investigating by checking half a dozen of my own drives. Not only did I find the errors in the articles, I found two failing (but still working) bridge rectifiers in my own drives. Some guys have all the luck. ;-) CR1 and CR3 (the two bridge rectifiers) are mounted in the same place physically on the two most common versions of the 1541 disk drive, namely PC board numbers 1540050 (early) and 251830 (late). Set side by side, the layout of the two boards appears identical. However, one important difference is that CR1 in the early board is the +12 volt rectifier and CR3 is the +5V rectifier. In the later board, it is exactly reversed: CR1 is +5 and CR3 is +12. I don't have a very early (white case, long board) or a very late (1542, short board) drive, so I don't know about the rectifier locations in those drives. Since I used the early board 1541 for most of the measurements and other information in the article I wrote, I incorrectly stated the function of CR1 and CR3 for the later board. This would be confusing for someone trying to troubleshoot a faulty drive. To help in finding out which is which in your drive, there are two ways you can tell (other than from the PCB number): 1. Assuming the drive is working: the 5 volt rectifier will be warm. This also assumes the drive has been turned on for at least two minutes and the motors are not running. The reason is that the 5 volt rectifier (and 5 volt regulator) powers most of the chips in the drive all the time it is turned on. The 12 volt rectifier/regulator feeds the motors and will therefore only get warm during drive access. 2. If the drive is not working, with a DC voltmeter, measure the output of the two rectifiers. The output lead is the one marked + and the other end is marked - and is grounded. With the drive turned on but not being accessed (motors off), you should measure about 10.5 volts DC across the output of the 5 volt rectifier and about 19 volts DC out of the 12 volt rectifier. This measurement will tell you which is which if you don't know, and if one or the other voltage is low, the respective rectifier may be bad. When the 5 volt unit starts failing, it will get even hotter than normal and its voltage will drop down below 8 volts (the regulator dropout point). It is a very common failure item. Sorry for the mistakes in the articles. I'll repost the corrected copy: 1541 CHIPS VS SYMPTOMS latest additions and corrections: 07-19-99 This list represents the most common versions of the 1541 in the standard brown case, with PC board numbers 1540050 (early ALPS push-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. That drive 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 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. At the end of this article, I will give you some troubleshooting hints... things to look for when you are trying to pin down a particular fault. ***************************************************************** 1541 CHIPS VS SYMPTOMS PCB# 1540050 (early version) with ALPS drive mechanism (1982) UA1 74LS14 LOGIC 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 Drive may power up normally, but will not reset from the computer. No drive access: "DEVICE NOT PRESENT" error. 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. 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. 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... common failure in this model. ****************************************************************** 1541 CHIPS VS SYMPTOMS PCB# 251830 or 251777 with Newtronics drive mechanism (1984) UA1 74LS14 LOGIC 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 Drive powers up OK, but does not respond to computer... no reset or disk access. If drive accessed, "DEVICE NOT PRESENT" error. 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). 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. 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. ******************************************************************* DIAGNOSTICS... WHAT TO LOOK FOR When you are troubleshooting a drive, it is important to observe it closely (with the cover off) for symptoms. For example, note how the drive motors and indicator LED's function when the drive is powered up, reset, and accessed by the computer. When the drive is instructed to LOAD a program, note whether the stepper moves, how much it moves, and if it "chatters". Try various functions like Initialize and observe the results. Sometimes the clues to a malfunction are subtle. In some cases, as many as eight different chips can cause the same symptom. See article: Chips vs Symptoms. If your drive suddenly goes "dead" and you can't read disks without "FILE NOT FOUND" errors, try the Initialize command: OPEN15,8,15:PRINT#15,"I0":CLOSE15 (assuming drive is device 8). This (or formatting a disk) will return the heads to track zero and may bring it "back to life". Another cause of "dead" drive is failure of the 5 volt bridge rectifier (CR3 in early version drives, CR1 in later drives). That part normally runs hot and is a common failure in a 1541. When the 5 volt supply fails, your symptoms are dim or dark red and green LEDs and drive motor spins continuously. If the 12 volt supply fails, the motors will not work. To properly diagnose a potential problem, you have to know exactly how the drive should respond when it's working correctly... DRIVE POWER UP: Green power light comes on and stays on, red activity light comes on (and spindle motor turns) for about two seconds, then red light should go out and motor should stop. COMPUTER POWER UP (OR RESET): Drive red light should come on and go out, and motor should start and stop within two seconds. READ DIRECTORY: Insert known good disk and type: LOAD"$",8 and hit the RETURN key. The disk should spin and the head should move to track 18 and read the directory. The screen will show: SEARCHING FOR $. If it finds it, the screen will say READY. If the disk read fails for any reason (drive door open, unformatted disk, bad chips in the drive, etc.), the drive red light will flash and an error message: FILE NOT FOUND will appear. If you read the disk error channel, it will say: 74, DRIVE NOT READY,00,00. INITIALIZE: This command from the computer should move the head from wherever it was to track 18 (directory) and the disk should spin. The head will not move (but the spindle motor will turn) if it is already over track 18. If there is no disk in the drive, or you insert an unformatted disk, or if the drive door is open, it should cause the spindle motor to run and the head to seek track 18 (directory) anyway. When it tries and fails, it will pull the head back to track zero and "chatter" as it hits the head stop, then advance to where track 18 should have been. The red light will flash because of the drive read error. No error message will be shown on the screen, but if you read the disk error channel, it will say: 21,READ ERROR,18,00. FORMAT OR DISK "NEW": When you format a disk, the spindle motor will turn and the red light will come on. The drive will pull the head back to track zero and "chatter", then the stepper will advance to each track as it writes from track 1 to track 35. When it finishes the format (about 1 minute 25 seconds on a stock drive), the head will return to track 18 (directory). If the format fails, the red drive light will flash, but there will be no error message on the screen. If you read the drive error channel, it will say: 21,READ ERROR,00,00. Format failures can be caused by write protect, drive door open, bad disk, bad or clogged head, or bad chips in the drive. The format will attempt to write to track 1, then do a read, and if the read fails, the format will terminate, and the head will not move from track 1. If it advances a few tracks and stops, suspect a bad disk, or an intermittant connection to the head. If the drive will read OK but fails to format a disk, check UC1, UC2, UA1, and UD2. Swap out drive mechanics to check the head. It may test good with an ohmmeter and read OK, but if defective, will fail to format a disk. For write-protect problems, check UC1, UC2, UA1 and, of course, the sensor. As mentioned above, it is sometimes helpful to read the disk drive error channel when the drive red light is flashing. Here is a small BASIC program (for DOS V2.0) to do that. It reads the channel, displays the error message, and turns the drive light off. All of the possible drive error messages are listed in the back of the operators manual. 10 OPEN 15,8,15 20 INPUT#15,EN,EM$,ET,ES 30 PRINT EN,EM$,ET,ES 40 CLOSE 15 ******************************************************************* 1541 DIAGNOSTICS Some symptoms and solutions for a sick disk drive. last changes: 07-19-99 DRIVE DEAD... OR NEARLY Lets take it from the top. Does the drive initialize properly when first turned on? The startup sequence (drive does a self-test) should be: green power light on, red drive light comes on and goes out while spindle motor turns for a few seconds and stops. If the power light (green LED) doesn't come on, or is dim or flickers, you have a power supply problem... the 5 volt line is bad. That usually results in a spindle motor that runs continuously and red LED off. Check the bridge rectifier (CR3 in early version drives with PCB# 1540050, and CR1 in later version drives with PCB# 251830) and the 5 volt regulator VR2. Note: if the regulated 12 volt supply fails, the motor will not run at all. If the drive activity light (red LED) stays on and the motor runs continuously, it means that the drive failed to complete the startup sequence. The most common cause is a bad DOS ROM UB4 (901229-xx). Other chips to check are: UC4 (6502 MPU) and UC2 (6522 VIA). The smaller "glue" logic chips are pretty rugged, but do sometimes fail. Check UA1 (74LS14) and UD2 (7407)... they have also been known to cause those symptoms. DRIVE INITIALIZES OK, BUT WILL NOT LOAD PROGRAMS When the computer is turned on, the reset signal should cause the drive (and other periferals like the printer) to reset: the drive red LED and spindle motor should come on and go off within a few seconds. If that doesn't happen, suspect the serial cable (try a substitute) or the CIA chips in the computer or VIA chip in the drive. If the computer resets other periferals, it's probably OK. If the computer can't "see" the drive on the serial bus, you will get an error message: "DEVICE NOT PRESENT" when you try to LOAD something. The default (factory setting) for a 1541 is device #8. If your drive is hardware modified as device 9 for example, and you try to read the directory (LOAD"$",8), you will get that error message. If the VIA (UC3) 6522 interface chip in the drive is bad, the drive will likewise be "invisible" to the computer. Check also UB1 (7406) and UA1 (74LS14). These two chips carry data to and from the VIA chip. When one of them fails, if you try to load the directory (or a program), the computer will indicate: "SEARCHING FOR $" (or program name) but nothing else will happen. A "DRIVE NOT READY' message indicates that the computer can "see" the drive, but there is no disk in it (or it's not formatted), or the drive door is not closed. A dirty read/write head can do the same thing. The drive will respond by flashing the red activity LED and banging the heads (looking for track zero). If the computer can access the drive, but you can't load even the directory of a known good (formatted) disk, try the INITIALIZE command (with or without a disk inserted), then try reading the disk again. To INITIALIZE the drive: OPEN15,8,15 PRINT#15,"I" CLOSE15 One quirk of the 1541 is the "drive lost" symptom. If the head, for some reason, gets stuck past the directory track (18), INITIALIZE will return it to track zero and it should then work normally. Note: turning the drive off and back on again will -not- reset it if that's the problem! Some disk errors can do that to a drive and make it look "dead", as can exiting incorrectly from a program by just turning off the computer. I've done that myself a few times. As an alternative to Initializing, you could try formatting a disk... it takes longer, but it will also return the head to track zero. Lastly, if you insert the transit card (shipped with the drive) with the drive turned off, it will push the head back to track zero. Inserting a disk is not the same thing! The transit card has a tab on the front (or the longer of the two tabs if there are two) of it that does the job. Don't have your transit card? With the top cover off and metal shield removed, you can push it back with your finger. The drive must be turned off, of course, or the head assembly will not move. PROGRAMS FAIL TO LOAD COMPLETELY OR COMPUTER LOCKS UP: If your computer setup or components have been moved recently, take note... drive cables too close to the monitor can sometimes pick up interference from the flyback tranformer in the monitor and garble the data. Move the drive and cables at least a foot away from the monitor and try it again. If that helps, move the drive to the other side of the monitor and keep the cables as far away as possible. If you have re-initialized the drive and it still doesn't work (can't read a disk), it may be out of alignment. Try formatting a disk and see if it can read the (empty) directory of that disk. If it can't, clean the head and try it again. If it can, but can't read other disks, misalignment is a good possibility. There is one other thing you should check first: see if the head assembly rails are sticky, especially on a drive that has been unused for a time. With power off, the head assembly should slide back and forth easily. If it seems sticky (experience is necessary to know the difference), the rails should be cleaned with strong solvent (acetone, MEK, paint thinner) and either run dry or relubed with a tiny amount of graphite or silicone lube. Oil on the rails will work for a time, but eventually picks up dirt and they will get sticky again. Avoid the use of spray cans on a drive. The spray goes everywhere. DRIVE ALIGNMENT: Drive misalignment is something that doesn't happen all at once. It is a gradual process that begins with occasional errors while loading (red LED flashing), failure to work with some programs, or excessive head banging (the drive getting "lost" and having to go back to track zero to "find" it's place again.) Drives are forced out of alignment (mostly while hot from use) by copy protected programs or disk errors that cause the head to "bang" against the track zero stop repeatedly. If the alignment is far enough off, you will get "FILE NOT FOUND" and red LED flashing... the drive may try several times before "giving up". To properly realign a drive, you need special software. I use "1541/1571 Drive Alignment" by Free Spirit Software. The flipside of the program disk is the alignment disk, and as such, should not be copied (a copy is only as good as the drive that made it). The program provides a menu screen that indicates what track you're on, drive speed, etc. You make adjustments to the drive while watching the screen. The instructions even tell you how to load the program when nothing else will load. You can -check- the alignment of the drive without taking it apart, but of course realignment requires disassembly. Drive speed can drift over time, but it's rather rare to find it off far enough to cause problems. Spindle speed is reset with a small screwdriver adjustable control on a small PC board near the spindle motor. On older belt-driven spindle motors, the belt may be slipping. On all drives, the spindle or collar can get sticky and a tiny bit of lube helps. (Don't overdo it... excess oil will be thrown off and could get on the disks). Make sure the latch clamps the disk properly. Without a disk, move the lever down and see if the spring presses the collar against the spindle to clamp it tightly. You can bend the tab down -slightly- (Newtronics drives only) so it makes more firm contact if necessary. A slipping or stalling disk will produce random read and write errors, a problem that's -very- hard to track down. Some disks may work better than others. Bad (sticky) old grease on an ALPS drive can stall the spindle motor. If that is suspected, you must remove the metal bar that the hub lock is mounted on (two screws in the back) and take apart the hub lock assembly by removing the C clip. It has half a dozen assorted washers, a brass bushing and a spring along with the plastic hub. These parts need to be cleaned with solvent and put back together in the same order as before. A bit of moly lube or light oil should be used on the metal to metal surfaces. I ran through some of this rather quickly. If you have any questions, email me at: rrcc@u.washington.edu or rcarlsen@i-link-2.net Ray Carlsen CARLSEN ELECTRONICS... a leader in trailing-edge technology.