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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Philips PM3335/40 scope startup problems
We have a Philips PM3335 combiscope which has begun to get startup
problems, the LCD shows all characters, and CRT is blank (seems like a uController not initialized) When the scope is switched off and in fast sequence switched on again, it most often comes up. I have looked at several signals to the uP (8032AH) especially the RESET line, but I can't see anything obvious. We don't have a service manual for the scope Any tips are welcome. Stein-Olav Lund Trondheim, Norway Service engineer |
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Philips PM3335/40 scope startup problems
"Stein-Olav Lund" bravely wrote to "All" (06 Oct 03 12:23:43)
--- on the heady topic of "Philips PM3335/40 scope startup problems" It may be a problem with the LCD display communicating with the uP and nothing wrong with the reset. But the idea may just be a case of killing the messenger. If you strongly suspect the reset line then trace it and replace any dry or leaky electro used for timing you may find. Perhaps a switching diode is associated with the reset cap and diodes sometimes do go intermittant open circuit. Does mechanical force seem to affect the failure to start up? Perhaps a cold solder joint in an area that gets a lot of heat cycling like in the power supply? SL From: Stein-Olav Lund SL We have a Philips PM3335 combiscope which has begun to get startup SL problems, the LCD shows all characters, and CRT is blank (seems like a SL uController not initialized) SL When the scope is switched off and in fast sequence switched on again, SL it most often comes up. I have looked at several signals to the uP SL (8032AH) especially the RESET line, but I can't see anything obvious. SL We don't have a service manual for the scope SL Any tips are welcome. SL Stein-Olav Lund SL Trondheim, Norway SL Service engineer .... High voltage can give a dangerously uncomfortable discharge. |
#3
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Philips PM3335/40 scope startup problems
"Stein-Olav Lund" bravely wrote to "All" (06 Oct 03 12:23:43)
--- on the heady topic of "Philips PM3335/40 scope startup problems" It may be a problem with the LCD display communicating with the uP and nothing wrong with the reset. But the idea may just be a case of killing the messenger. If you strongly suspect the reset line then trace it and replace any dry or leaky electro used for timing you may find. Perhaps a switching diode is associated with the reset cap and diodes sometimes do go intermittant open circuit. Does mechanical force seem to affect the failure to start up? Perhaps a cold solder joint in an area that gets a lot of heat cycling like in the power supply? SL From: Stein-Olav Lund SL We have a Philips PM3335 combiscope which has begun to get startup SL problems, the LCD shows all characters, and CRT is blank (seems like a SL uController not initialized) SL When the scope is switched off and in fast sequence switched on again, SL it most often comes up. I have looked at several signals to the uP SL (8032AH) especially the RESET line, but I can't see anything obvious. SL We don't have a service manual for the scope SL Any tips are welcome. SL Stein-Olav Lund SL Trondheim, Norway SL Service engineer .... High voltage can give a dangerously uncomfortable discharge. |
#4
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Philips PM3335/40 scope startup problems
Asimov wrote: "Stein-Olav Lund" bravely wrote to "All" (06 Oct 03 12:23:43) --- on the heady topic of "Philips PM3335/40 scope startup problems" It may be a problem with the LCD display communicating with the uP and nothing wrong with the reset. But the idea may just be a case of killing the messenger. If you strongly suspect the reset line then trace it and replace any dry or leaky electro used for timing you may find. Perhaps a switching diode is associated with the reset cap and diodes sometimes do go intermittant open circuit. Does mechanical force seem to affect the failure to start up? Perhaps a cold solder joint in an area that gets a lot of heat cycling like in the power supply? SL From: Stein-Olav Lund SL We have a Philips PM3335 combiscope which has begun to get startup SL problems, the LCD shows all characters, and CRT is blank (seems like a SL uController not initialized) SL When the scope is switched off and in fast sequence switched on again, SL it most often comes up. I have looked at several signals to the uP SL (8032AH) especially the RESET line, but I can't see anything obvious. SL We don't have a service manual for the scope SL Any tips are welcome. SL Stein-Olav Lund SL Trondheim, Norway SL Service engineer ... High voltage can give a dangerously uncomfortable discharge. The problem was burnt RS232 drivers _AND_ the UART in the scope. The 5V was a little low due to this (around4.6V) Stein |
#5
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Philips PM3335/40 scope startup problems
Asimov wrote: "Stein-Olav Lund" bravely wrote to "All" (06 Oct 03 12:23:43) --- on the heady topic of "Philips PM3335/40 scope startup problems" It may be a problem with the LCD display communicating with the uP and nothing wrong with the reset. But the idea may just be a case of killing the messenger. If you strongly suspect the reset line then trace it and replace any dry or leaky electro used for timing you may find. Perhaps a switching diode is associated with the reset cap and diodes sometimes do go intermittant open circuit. Does mechanical force seem to affect the failure to start up? Perhaps a cold solder joint in an area that gets a lot of heat cycling like in the power supply? SL From: Stein-Olav Lund SL We have a Philips PM3335 combiscope which has begun to get startup SL problems, the LCD shows all characters, and CRT is blank (seems like a SL uController not initialized) SL When the scope is switched off and in fast sequence switched on again, SL it most often comes up. I have looked at several signals to the uP SL (8032AH) especially the RESET line, but I can't see anything obvious. SL We don't have a service manual for the scope SL Any tips are welcome. SL Stein-Olav Lund SL Trondheim, Norway SL Service engineer ... High voltage can give a dangerously uncomfortable discharge. The problem was burnt RS232 drivers _AND_ the UART in the scope. The 5V was a little low due to this (around4.6V) Stein |
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