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HP3586A 5V supply overheating

Raymond Boute All Messages By This Member #92895 My HP3586A suddenly lost its 5 V, with neither red nor green 5 V led on the A80 board. I traced the?problem to overheating pins in the connector between the transformer and the A99 motherboard (burn marks around the pins). Wiggling the connector reestablished 5 V, but the overheating is nearly immediate and severe . It does not occur in standby, nor do the connector pins on the A80 board show any overheating when the unit is on.? One would expect the current limiter to cut in if there were a short on the bus.?The rectifier diodes also get very hot. Evidently?troubleshooting cannot last more than a few seconds at a time lest the connector is destroyed. Questions: (a) is this a known issue, (b) what is the normal current drawn from the 5 V supply, (c) might the rectifier diodes be switching improperly (e.g., causing shorts at switchover), (c) would replacing them by Schottky diodes be indicated?
[email protected] All Messages By This Member #92896 开云体育 Bad Molex. Multiple Ground Paths or on Hot Side thru’ Molex. Some Paths thru Molex Higher Resistance than others. Burns up the Connectors. This has been seen before. ? Regards Bill Lauchlan ? toggle quoted message Show quoted text From: [email protected] [mailto:[email protected]] On Behalf Of Raymond Boute Sent: Monday, November 26, 2018 12:32 AM To: [email protected] Subject: [HP-Agilent-Keysight-equipment] HP3586A 5V supply overheating ? My HP3586A suddenly lost its 5 V, with neither red nor green 5 V led on the A80 board. I traced the?problem to overheating pins in the connector between the transformer and the A99 motherboard (burn marks around the pins). Wiggling the connector reestablished 5 V, but the overheating is nearly immediate and severe . It does not occur in standby, nor do the connector pins on the A80 board show any overheating when the unit is on.? One would expect the current limiter to cut in if there were a short on the bus.?The rectifier diodes also get very hot. Evidently?troubleshooting cannot last more than a few seconds at a time lest the connector is destroyed. Questions: (a) is this a known issue, (b) what is the normal current drawn from the 5 V supply, (c) might the rectifier diodes be switching improperly (e.g., causing shorts at switchover), (c) would replacing them by Schottky diodes be indicated?
Chuck Harris All Messages By This Member #92902 Most likely you have a rectifier diode that is burned to short, or a filter capacitor that has created a short. When a shorted rectifier diode puts AC onto the electrolytic capacitor filter, it shows as a dead short, and can burn the molex connector up. The electrolyte from electrolytic capacitors is very low resistance, if it leaks out of the bottom of a capacitor to a circuit board, it can short out the circuit board to very high current. -Chuck Harris Raymond Boute wrote: toggle quoted message Show quoted text My HP3586A suddenly lost its 5 V, with neither red nor green 5 V led on the A80 board. I traced the problem to overheating pins in the connector between the transformer and the A99 motherboard (burn marks around the pins). Wiggling the connector reestablished 5 V, but the overheating is nearly immediate and severe . It does not occur in standby, nor do the connector pins on the A80 board show any overheating when the unit is on. One would expect the current limiter to cut in if there were a short on the bus. The rectifier diodes also get very hot. Evidently troubleshooting cannot last more than a few seconds at a time lest the connector is destroyed. Questions: (a) is this a known issue, (b) what is the normal current drawn from the 5 V supply, (c) might the rectifier diodes be switching improperly (e.g., causing shorts at switchover), (c) would replacing them by Schottky diodes be indicated?
Peter Gottlieb All Messages By This Member #92906 开云体育 Moles connector problem, they do not last at the currents they were being used at in this application. Replace both the PCB header and the one on the cable.? Peter toggle quoted message Show quoted text On Nov 26, 2018, at 12:31 AM, Raymond Boute <Raymond.Boute@...> wrote: My HP3586A suddenly lost its 5 V, with neither red nor green 5 V led on the A80 board. I traced the?problem to overheating pins in the connector between the transformer and the A99 motherboard (burn marks around the pins). Wiggling the connector reestablished 5 V, but the overheating is nearly immediate and severe . It does not occur in standby, nor do the connector pins on the A80 board show any overheating when the unit is on.? One would expect the current limiter to cut in if there were a short on the bus.?The rectifier diodes also get very hot. Evidently?troubleshooting cannot last more than a few seconds at a time lest the connector is destroyed. Questions: (a) is this a known issue, (b) what is the normal current drawn from the 5 V supply, (c) might the rectifier diodes be switching improperly (e.g., causing shorts at switchover), (c) would replacing them by Schottky diodes be indicated?

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