| reply to TheMG
Re: Looking for a desktop power backup said by TheMG:I have a 15 year old (MFR date June 18, 1998) SmartUPS 1400. It was actually a trash find from 4 years ago. Hasn't skipped a beat. Of course, it needed a fresh set of batteries.
Have you ever opened it up? the "SU" prefix era units have design defect (current loop) which tends to cook two resistors over time. |
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| said by Thane_Bitter:Have you ever opened it up? the "SU" prefix era units have design defect (current loop) which tends to cook two resistors over time. Oh? Do tell. I have an older SU2200NET (unsure of exact age) that lets you know the batteries are bad by randomly shutting off the load for a few seconds...
/M |
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| If yours is a 48V DC unit (battery voltage) then this will apply to you.
Standard warnings about playing with electricity, you don't want to work on one of these things plugged in, or with the batteries attached, and there are exposed parts (namely the cooling fins for power transistors) which are live even after line and batter power is removed thanks to some very large capacitors.
Next time you have it apart have a look at the PCB board reversion (I think yours will be "K") and look for R38 and R43, you may find them looking a tad cooked. The issue is that due to an oversight more current is pushed through them then what they are rated for, the fix is to replace them with the same value using a higher power resistor (2 W or better). You will have to mod the new resistors to fit, the pads and holes on the board are design for 1/4 resistors.
Not sure if it will fix your issue, there could be other problems which are causing your UPS to act funny. |
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TheMGPremium
join:2007-09-04
Canada
kudos:2 | reply to Thane_Bitter
Nope, never had a reason to.
said by Thane_Bitter:If yours is a 48V DC unit (battery voltage) then this will apply to you. Mine is 24V. |
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| Thanks, ok then it should not be an issue in your UPS, the current through those resistors will be 1/4 of what it is on the 48volt model.  |
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| One thing that could be better about the new "Smart UPS" line is that the charge rate on the batteries is aggressive, and the batteries only last 3.5 years now. The older RM1200 that I used to have would go 7 years on a set of batteries and it ran cool. I have a 3000 VA Smart UPS now, but every 3.5 years, like clockwork, the batteries fail. And they run hot. Would love to lower the charge current to make it run cooler and get the battery life I enjoyed with my RM1200 years ago. |
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