[cctalk] Re: Diablo Model 40 Series - Disturbed head positioning
Yes the oscilloscope are your eyes and ears for electrons… Marc > On May 1, 2024, at 11:44 PM, Dominique Carlier wrote: > > Hi Marc ! > > It should be so great if it was just the PSU, everything else is hyper > overkill in terms of complexity but on the multimeter all the voltages show > the correct values, including +15V and -15V (generated from the +24V and -24V > of the power supply). > But is it possible that one of these currents, for example the stabalized +5V > is 'parasitized' ? How can it be diagnosed? With an oscilloscope I suppose? > > The interesting thing now is the lack of emergency retraction of the heads if > the power is cut during RUN mode. There is an unfuse +24V provided for this > purpose but it is present in the power supply. If that problem is common to > the others issues, this leads me to think that there is an issue at the > logical level, in this case the breakdown hypotheses are unfortunately > infinite (summing junction on SO board, servo positioner, SR board, sensors, > ...). If it's not common, it should be a dead capacitor concerning the > emergency retraction of the heads, and a dead amplifier transistor on the > heat sink board dedicated to the plus/minus (forward/reverse) servo > positioner, who knows ? > > Dominique > > >> On 2/05/2024 01:38, Curious Marc wrote: >> Power supply problem? >> Marc >> On Apr 30, 2024, at 8:58 AM, Dominique Carlier via cctalk wrote: >>> >>> Hello everyone >>> >>> I need your help to identify an issue on my Diablo Model 40 Series. I don't >>> know where to look, it's so vast ! >>> >>> Here's the problem: >>> When RUN is activated, the drive begins its spin up and simultaneously >>> deploys the heads (normal) but instead of stabilizing them, the Head >>> Positioner receives a burst of reverse/forward micro signals. The heads >>> "vibrate", this creates an audible frequency "BRR", and it >>> is infinite, the heads are never loaded and the drive never reaches READY. >>> >>> At first I thought that perhaps the track zero sensor was defective or >>> something of the same order but when I disengage RUN mode, the drive >>> unloads the heads and they should be in a fixed position, here they >>> continue to reverse/forward but more slowly than in RUN mode. >>> Because the heads continues to mess around even in unload mode, this a >>> priori excludes alignment problems. >>> >>> Here is a video of that issue: >>> >>> https://youtu.be/HzzxLnSdEOg >>> >>> Other information, if I cut the power while the drive is in RUN mode, it >>> does not do an emergency retraction of the heads, related problem? >>> I was hoping for a power supply problem but all the voltages and even on >>> the main board cage seem ok (with a multimeter). >>> >>> If one of you had already encountered this problem of lack of head >>> stabilization and continuous reverse/forward on this type of drive? >>> >>> Thanks ! >>> >>> Dominique >>>
[cctalk] Re: Diablo Model 40 Series - Disturbed head positioning
Hi Marc ! It should be so great if it was just the PSU, everything else is hyper overkill in terms of complexity but on the multimeter all the voltages show the correct values, including +15V and -15V (generated from the +24V and -24V of the power supply). But is it possible that one of these currents, for example the stabalized +5V is 'parasitized' ? How can it be diagnosed? With an oscilloscope I suppose? The interesting thing now is the lack of emergency retraction of the heads if the power is cut during RUN mode. There is an unfuse +24V provided for this purpose but it is present in the power supply. If that problem is common to the others issues, this leads me to think that there is an issue at the logical level, in this case the breakdown hypotheses are unfortunately infinite (summing junction on SO board, servo positioner, SR board, sensors, ...). If it's not common, it should be a dead capacitor concerning the emergency retraction of the heads, and a dead amplifier transistor on the heat sink board dedicated to the plus/minus (forward/reverse) servo positioner, who knows ? Dominique On 2/05/2024 01:38, Curious Marc wrote: Power supply problem? Marc On Apr 30, 2024, at 8:58 AM, Dominique Carlier via cctalk wrote: Hello everyone I need your help to identify an issue on my Diablo Model 40 Series. I don't know where to look, it's so vast ! Here's the problem: When RUN is activated, the drive begins its spin up and simultaneously deploys the heads (normal) but instead of stabilizing them, the Head Positioner receives a burst of reverse/forward micro signals. The heads "vibrate", this creates an audible frequency "BRR", and it is infinite, the heads are never loaded and the drive never reaches READY. At first I thought that perhaps the track zero sensor was defective or something of the same order but when I disengage RUN mode, the drive unloads the heads and they should be in a fixed position, here they continue to reverse/forward but more slowly than in RUN mode. Because the heads continues to mess around even in unload mode, this a priori excludes alignment problems. Here is a video of that issue: https://youtu.be/HzzxLnSdEOg Other information, if I cut the power while the drive is in RUN mode, it does not do an emergency retraction of the heads, related problem? I was hoping for a power supply problem but all the voltages and even on the main board cage seem ok (with a multimeter). If one of you had already encountered this problem of lack of head stabilization and continuous reverse/forward on this type of drive? Thanks ! Dominique
[cctalk] Re: Diablo Model 40 Series - Disturbed head positioning
Power supply problem? Marc > On Apr 30, 2024, at 8:58 AM, Dominique Carlier via cctalk > wrote: > > Hello everyone > > I need your help to identify an issue on my Diablo Model 40 Series. I don't > know where to look, it's so vast ! > > Here's the problem: > When RUN is activated, the drive begins its spin up and simultaneously > deploys the heads (normal) but instead of stabilizing them, the Head > Positioner receives a burst of reverse/forward micro signals. The heads > "vibrate", this creates an audible frequency "BRR", and it is > infinite, the heads are never loaded and the drive never reaches READY. > > At first I thought that perhaps the track zero sensor was defective or > something of the same order but when I disengage RUN mode, the drive unloads > the heads and they should be in a fixed position, here they continue to > reverse/forward but more slowly than in RUN mode. > Because the heads continues to mess around even in unload mode, this a priori > excludes alignment problems. > > Here is a video of that issue: > > https://youtu.be/HzzxLnSdEOg > > Other information, if I cut the power while the drive is in RUN mode, it does > not do an emergency retraction of the heads, related problem? > I was hoping for a power supply problem but all the voltages and even on the > main board cage seem ok (with a multimeter). > > If one of you had already encountered this problem of lack of head > stabilization and continuous reverse/forward on this type of drive? > > Thanks ! > > Dominique >
[cctalk] Re: Diablo Model 40 Series - Disturbed head positioning
I also thought about it first, but in the documentation it is clearly explained that during the startup sequence, the deployment of the heads is done at the same time as the spin up, during this deployment the heads are raised, they are normally loaded on disc only after one minute +- after the brush cycle, after the nominal speed is reached. On 30/04/2024 21:38, Jon Elson via cctalk wrote: On 4/30/24 12:37, Dominique Carlier via cctalk wrote: Thanks for your response Jon :! The technical documentation is available on Bitsavers here: http://www.bitsavers.org/pdf/diablo/disk/model_40/81603_Diablo4xMaint_Apr75.pdf But also here: https://www.wang2200.org/docs/external/DiabloSeries40DiskDriveFieldLevelMaintenanceGuide.03-0057.pdf I thought like you about the sensors, but here the reverse/forward movements even after unloading the heads lead me to think that the issue is at the level of the circuitry involved in the control of the head positionner linear motor. I would like to be able to follow the diagrams easily, but it is incredibly complex. The only good news is that it is perhaps easily identifiable for those who specifically know the Diablo model 40 series disc drives, in the video we can observe very briefly that these reverse/forward movements start as soon as I press RUN, even before the machine begins to deploy the heads. Precisely here: https://youtu.be/HzzxLnSdEOg?t=4 We could deduce that this is a problem at the very base of what balances the voltages for controlling the linear motor.But even in this case, my limited skills do not allow me to direct my research, which is why I need some advice ;) On 30/04/2024 19:05, Jon Elson via cctalk wrote: On 4/30/24 10:46, Dominique Carlier via cctalk wrote: Hello everyone I need your help to identify an issue on my Diablo Model 40 Series. I don't know where to look, it's so vast ! Here's the problem: When RUN is activated, the drive begins its spin up and simultaneously deploys the heads (normal) but instead of stabilizing them, the Head Positioner receives a burst of reverse/forward micro signals. The heads "vibrate", this creates an audible frequency "BRR", and it is infinite, the heads are never loaded and the drive never reaches READY. At first I thought that perhaps the track zero sensor was defective or something of the same order but when I disengage RUN mode, the drive unloads the heads and they should be in a fixed position, here they continue to reverse/forward but more slowly than in RUN mode. Because the heads continues to mess around even in unload mode, this a priori excludes alignment problems. Well, I don't know this particular drive, but I can think of a few things to check. Presumably, this drive has some sort of velocity sensor, either part of the voice coil assembly or the head motion motor. It is possible that the velocity sensor has gone bad, or that a wire to the sensor has broken. OK, without looking at the docs, generally these types of drives have a linear amplifier that takes a velocity command from some control logic and a velocity feedback signal from a sensor. When the run switch is turned on, the servo amp might be enabled, and then the amp gets a zero velocity command. When the disc is up to speed, the velocity command is set so that the heads load onto the pack, and then track counting logic moves the heads to the desired track. With the heads advancing as SOON as the run switch is flipped on, then it seems like the command to the amp is happening at the wrong time. It seems pretty clear the velocity servo is working properly, as the motion looks very smooth. But, the heads move toward the pack, and then some kind of safety circuit must be tripping as the pack is not up to speed yet. This will take some careful debugging. Jon
[cctalk] Re: Diablo Model 40 Series - Disturbed head positioning
On 4/30/24 12:37, Dominique Carlier via cctalk wrote: Thanks for your response Jon :! The technical documentation is available on Bitsavers here: http://www.bitsavers.org/pdf/diablo/disk/model_40/81603_Diablo4xMaint_Apr75.pdf But also here: https://www.wang2200.org/docs/external/DiabloSeries40DiskDriveFieldLevelMaintenanceGuide.03-0057.pdf I thought like you about the sensors, but here the reverse/forward movements even after unloading the heads lead me to think that the issue is at the level of the circuitry involved in the control of the head positionner linear motor. I would like to be able to follow the diagrams easily, but it is incredibly complex. The only good news is that it is perhaps easily identifiable for those who specifically know the Diablo model 40 series disc drives, in the video we can observe very briefly that these reverse/forward movements start as soon as I press RUN, even before the machine begins to deploy the heads. Precisely here: https://youtu.be/HzzxLnSdEOg?t=4 We could deduce that this is a problem at the very base of what balances the voltages for controlling the linear motor.But even in this case, my limited skills do not allow me to direct my research, which is why I need some advice ;) On 30/04/2024 19:05, Jon Elson via cctalk wrote: On 4/30/24 10:46, Dominique Carlier via cctalk wrote: Hello everyone I need your help to identify an issue on my Diablo Model 40 Series. I don't know where to look, it's so vast ! Here's the problem: When RUN is activated, the drive begins its spin up and simultaneously deploys the heads (normal) but instead of stabilizing them, the Head Positioner receives a burst of reverse/forward micro signals. The heads "vibrate", this creates an audible frequency "BRR", and it is infinite, the heads are never loaded and the drive never reaches READY. At first I thought that perhaps the track zero sensor was defective or something of the same order but when I disengage RUN mode, the drive unloads the heads and they should be in a fixed position, here they continue to reverse/forward but more slowly than in RUN mode. Because the heads continues to mess around even in unload mode, this a priori excludes alignment problems. Well, I don't know this particular drive, but I can think of a few things to check. Presumably, this drive has some sort of velocity sensor, either part of the voice coil assembly or the head motion motor. It is possible that the velocity sensor has gone bad, or that a wire to the sensor has broken. OK, without looking at the docs, generally these types of drives have a linear amplifier that takes a velocity command from some control logic and a velocity feedback signal from a sensor. When the run switch is turned on, the servo amp might be enabled, and then the amp gets a zero velocity command. When the disc is up to speed, the velocity command is set so that the heads load onto the pack, and then track counting logic moves the heads to the desired track. With the heads advancing as SOON as the run switch is flipped on, then it seems like the command to the amp is happening at the wrong time. It seems pretty clear the velocity servo is working properly, as the motion looks very smooth. But, the heads move toward the pack, and then some kind of safety circuit must be tripping as the pack is not up to speed yet. This will take some careful debugging. Jon
[cctalk] Re: Diablo Model 40 Series - Disturbed head positioning
Hi Don ! Good suggestion, these microswitches are used to indicate that the heads are completely retracted. Unfortunately, that would have been too simple, both microswitches work perfectly :-/ On 30/04/2024 19:43, D. Resor wrote: What is the purpose of the two microswitches seen in the upper right of the video view? Could one or both of those be intermittent? Have they been tested for continuity/intermittence with an analog VOM? Don Resor -Original Message- From: Dominique Carlier via cctalk Sent: Tuesday, April 30, 2024 8:47 AM To: General Discussion: On-Topic and Off-Topic Posts Cc: Dominique Carlier Subject: [cctalk] Diablo Model 40 Series - Disturbed head positioning Hello everyone I need your help to identify an issue on my Diablo Model 40 Series. I don't know where to look, it's so vast ! Here's the problem: When RUN is activated, the drive begins its spin up and simultaneously deploys the heads (normal) but instead of stabilizing them, the Head Positioner receives a burst of reverse/forward micro signals. The heads "vibrate", this creates an audible frequency "BRR", and it is infinite, the heads are never loaded and the drive never reaches READY. At first I thought that perhaps the track zero sensor was defective or something of the same order but when I disengage RUN mode, the drive unloads the heads and they should be in a fixed position, here they continue to reverse/forward but more slowly than in RUN mode. Because the heads continues to mess around even in unload mode, this a priori excludes alignment problems. Here is a video of that issue: https://youtu.be/HzzxLnSdEOg Other information, if I cut the power while the drive is in RUN mode, it does not do an emergency retraction of the heads, related problem? I was hoping for a power supply problem but all the voltages and even on the main board cage seem ok (with a multimeter). If one of you had already encountered this problem of lack of head stabilization and continuous reverse/forward on this type of drive? Thanks ! Dominique
[cctalk] Re: Diablo Model 40 Series - Disturbed head positioning
What is the purpose of the two microswitches seen in the upper right of the video view? Could one or both of those be intermittent? Have they been tested for continuity/intermittence with an analog VOM? Don Resor -Original Message- From: Dominique Carlier via cctalk Sent: Tuesday, April 30, 2024 8:47 AM To: General Discussion: On-Topic and Off-Topic Posts Cc: Dominique Carlier Subject: [cctalk] Diablo Model 40 Series - Disturbed head positioning Hello everyone I need your help to identify an issue on my Diablo Model 40 Series. I don't know where to look, it's so vast ! Here's the problem: When RUN is activated, the drive begins its spin up and simultaneously deploys the heads (normal) but instead of stabilizing them, the Head Positioner receives a burst of reverse/forward micro signals. The heads "vibrate", this creates an audible frequency "BRR", and it is infinite, the heads are never loaded and the drive never reaches READY. At first I thought that perhaps the track zero sensor was defective or something of the same order but when I disengage RUN mode, the drive unloads the heads and they should be in a fixed position, here they continue to reverse/forward but more slowly than in RUN mode. Because the heads continues to mess around even in unload mode, this a priori excludes alignment problems. Here is a video of that issue: https://youtu.be/HzzxLnSdEOg Other information, if I cut the power while the drive is in RUN mode, it does not do an emergency retraction of the heads, related problem? I was hoping for a power supply problem but all the voltages and even on the main board cage seem ok (with a multimeter). If one of you had already encountered this problem of lack of head stabilization and continuous reverse/forward on this type of drive? Thanks ! Dominique
[cctalk] Re: Diablo Model 40 Series - Disturbed head positioning
Thanks for your response Jon :! The technical documentation is available on Bitsavers here: http://www.bitsavers.org/pdf/diablo/disk/model_40/81603_Diablo4xMaint_Apr75.pdf But also here: https://www.wang2200.org/docs/external/DiabloSeries40DiskDriveFieldLevelMaintenanceGuide.03-0057.pdf I thought like you about the sensors, but here the reverse/forward movements even after unloading the heads lead me to think that the issue is at the level of the circuitry involved in the control of the head positionner linear motor. I would like to be able to follow the diagrams easily, but it is incredibly complex. The only good news is that it is perhaps easily identifiable for those who specifically know the Diablo model 40 series disc drives, in the video we can observe very briefly that these reverse/forward movements start as soon as I press RUN, even before the machine begins to deploy the heads. Precisely here: https://youtu.be/HzzxLnSdEOg?t=4 We could deduce that this is a problem at the very base of what balances the voltages for controlling the linear motor.But even in this case, my limited skills do not allow me to direct my research, which is why I need some advice ;) On 30/04/2024 19:05, Jon Elson via cctalk wrote: On 4/30/24 10:46, Dominique Carlier via cctalk wrote: Hello everyone I need your help to identify an issue on my Diablo Model 40 Series. I don't know where to look, it's so vast ! Here's the problem: When RUN is activated, the drive begins its spin up and simultaneously deploys the heads (normal) but instead of stabilizing them, the Head Positioner receives a burst of reverse/forward micro signals. The heads "vibrate", this creates an audible frequency "BRR", and it is infinite, the heads are never loaded and the drive never reaches READY. At first I thought that perhaps the track zero sensor was defective or something of the same order but when I disengage RUN mode, the drive unloads the heads and they should be in a fixed position, here they continue to reverse/forward but more slowly than in RUN mode. Because the heads continues to mess around even in unload mode, this a priori excludes alignment problems. Well, I don't know this particular drive, but I can think of a few things to check. Presumably, this drive has some sort of velocity sensor, either part of the voice coil assembly or the head motion motor. It is possible that the velocity sensor has gone bad, or that a wire to the sensor has broken. Another possibility is that the track position encoder has gone bad. They often are quadrature optical encoders, and possibly a light bulb has failed or a photodiode has gone bad or has a broken wire or bad sensor conditioning circuit. If you have drawings for this drive, it should be easy to follow this circuit. If not, then you will have to find drawings and tech info. Hopefully, bitsavers has what you need. Jon
[cctalk] Re: Diablo Model 40 Series - Disturbed head positioning
On 4/30/24 10:46, Dominique Carlier via cctalk wrote: Hello everyone I need your help to identify an issue on my Diablo Model 40 Series. I don't know where to look, it's so vast ! Here's the problem: When RUN is activated, the drive begins its spin up and simultaneously deploys the heads (normal) but instead of stabilizing them, the Head Positioner receives a burst of reverse/forward micro signals. The heads "vibrate", this creates an audible frequency "BRR", and it is infinite, the heads are never loaded and the drive never reaches READY. At first I thought that perhaps the track zero sensor was defective or something of the same order but when I disengage RUN mode, the drive unloads the heads and they should be in a fixed position, here they continue to reverse/forward but more slowly than in RUN mode. Because the heads continues to mess around even in unload mode, this a priori excludes alignment problems. Well, I don't know this particular drive, but I can think of a few things to check. Presumably, this drive has some sort of velocity sensor, either part of the voice coil assembly or the head motion motor. It is possible that the velocity sensor has gone bad, or that a wire to the sensor has broken. Another possibility is that the track position encoder has gone bad. They often are quadrature optical encoders, and possibly a light bulb has failed or a photodiode has gone bad or has a broken wire or bad sensor conditioning circuit. If you have drawings for this drive, it should be easy to follow this circuit. If not, then you will have to find drawings and tech info. Hopefully, bitsavers has what you need. Jon
