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Re: The joys of ONAN power supplies in Motorola Quantar repeaters
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One of the primary causes of switcher failures is line transients.? Linear PSUs have built-in isolation (transformer) which switchers do not have.? While degraded components, excessive load, environmental issues, and tin whiskers can also cause failures transients and static probably cause more failures than anything else.? Motorola R56 calls for a Type 2A SPD (MOV/SAD Surge Protective Device) at the electrical panel and a Type 3 SPD (MOV) at the device location.? One of the best things that can be done to prevent this kind of thing is to use an on-line UPS in-line with the equipment - not a bypass type UPS that connects the equipment to the line and float-charges the batteries - but a UPS that has a full-current charger and inverter running at all times - so the current used is from the UPS at all times- not directly from the utility.? The MOV/SAD combination in the SPDs will take care of most transients and if it can't it should sacrifice itself and save the equipment.?? High (or low) temperatures and adverse conditions (fumes, carbon dust from elevator motors, dirt, etc), along with age can also increase the odds of a failure - but sometimes failures are just due to poorly designed supplies or cheap or old components failing.? I suspect we are going to see a lot more failures of this kind in consumer electronics as the switchers that have become so prevalent over the last 10-15 years age to the point of failure - many of which likely do not have proper safety features.? Fires are going to become much more common due to these which rarely happened with the old linear wall-wart supplies.?? Additionally it is very important to bond all of your equipment (not to be confused with grounding - though the bonded equipment should also be properly grounded) so that all equipment is at the same electrical potential.? This lessens the chance of damage and failures due to static and lightning while also decreasing chances of electrocution hazards due to wiring faults.? If you ever want to see something interesting and have Cable TV just throw an AC VOM on the shield of your cable TV coax and measure to your electrical ground.? I have seen upwards of 100V on these at times - and most TVs are not grounded to avoid ground loops so it is a serious hazard.? The cable companies are SUPPOSED to bond the cable to your electrical safety ground at the entrance point but very few bother or do it properly.? Another reason I have FTTH. In regards to fire suppression systems roughly equivalent to Halon the most common that is in use today is FM-200.? While it is not illegal to have or maintain Halon systems no new systems can be installed and no more Halon gas can be produced - so if you need a system FM-200 is likely your best option.? While these can be expensive they can also save a lot of $ depending on the scenario and application.? I still see lots of Halon extinguishers and suppression systems at sites though they are steadily being replaced with FM-200 systems and CO2/ABC extinguishers.? Motorola R56 calls for having a minimum of one ABC and one CO2 extinguisher at any site. If any of you have not had the pleasure of reading Motorola R56 it is a good read and might open your eyes to some potential problems with your installs that could save some serious $.? It is not easy or cheap to implement all of the recommendations but it can be worth it and generally if you follow that standard site owners will be happy with you and not complain about your install.? The current R56 is the 2017 revision - 68P81089E50-C which is 736 pages of enjoyable reading covering far more than just bonding and grounding. Thanks, Dan Woodie, CETsr KC8ZUM? On Fri, Jan 15, 2021 at 4:34 PM RFI-EMI-GUY <rhyolite@...> wrote: In General, is there any theory on failure modes on switchers? |
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