Re: APC Back-ups RS 1500 Dead
Back-UPS XS 1500 was repaired by replacing all 22uF SMD electrolytic caps. There are five of them and they were reading anywhere from tens of ohms to infinite ESR. Symptom was failure to charge battery and eventually failure to power on at all emitting only a chirp on attempt.
Thank you to the guys at HEGE supporting Badcaps [ HEGE ] [ HEGE DEX Chart ]
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Re: APC RS 800 Completely Dead
Hey Behemot, not sure if this is related to your problem or if you will see this reply but when testing a Back-UPS XS 1500 repair (also all bad 22uF 16V SMD caps, which I replaced with normal 105deg caps soldered to the SMD pads), I noticed this fault condition also (a short time after power up, all leds flashing except Power on solid). I noticed that when I removed the battery the fault went away immediately. I checked charging voltage (good, 27V) and battery voltage (good, 13.8V), then realized I needed two 12V batteries in series for a valid test....
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Re: Sony MBX-197 power circuit, help me think it through
You guys are great. I gave up on the motherboard because I could not determine the source of a short near the southbridge and, due to burned looking southbridge chip and zero ohms after removing all nearby SMD components, assumed southbridge was shorted. I could not spend any more time on it. With the schematic I probably would have had more luck finding the problem but I had to give up on it due to time constraints. Thanks for participating and hopefully this thread will help the next guy. This seems to be a very common problem...
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Re: Sony MBX-197 power circuit, help me think it through
Got back to this tonight.
Found bad AO D452 n-channel FET. <10 ohms gate/source/drain all directions. There are a total of 3 of these fets on the board, I will replace all of them.
Datasheet here:
Replacement component is D452A but so far I can't find for purchase.
Fairchild FDD6796A seems like suitable replacement.
Somehow spilled flux pen contents all over myself.Last edited by runderwo; 11-20-2011, 09:48 PM.
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Re: Sony MBX-197 power circuit, help me think it through
I found the MOSFET 4433 ( ) only reads 99K ohm from source to gate and has 19V present at both source and gate with a near zero voltage at drain. Something is wrong here. I will desolder this suspect and test it out of circuit.
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Re: Sony MBX-197 power circuit, help me think it through
Maybe not overload protection after all. When power is applied, I read transient ~200V at gate driver output (pin 12) of the SC411 that remains powered. I checked gate driver voltage input of that SC411 and there is no spike there. This driver output would drive the MOSFETS that power the second SC411. Seems to be overvoltage shutdown, but gate driver output is the cause or effect?
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Re: Sony MBX-197 power circuit, help me think it through
As far as suspected mosfets go (I'm not too familiar with the numbering used), I have two 4468, 4433, F7904, F8707, F8714. Other 8-pin chips nearby power circuit were eeprom, flash, etc. Any of the above part numbers usual troublemakers?Last edited by runderwo; 10-09-2011, 09:56 PM.
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Re: Sony MBX-197 power circuit, help me think it through
Ok, I fiddled a little more with it. I was able to see 3.3VSB at the switch as well as 5V at the second SC411 briefly at startup, then they go to zero volts. Combined with the "tweet" noise, this must be an overload protection kicking in. As a bonus, one time (out of maybe 100 times unplugging/replugging the power) I was able to get the more typical repeated tweeting of an overload protection.
I enlisted a helper to repeatedly unplug/replug the power (one tweet per replug). When doing this repeated...
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Sony MBX-197 power circuit, help me think it through
This Sony MBX-197 comes out of an all-in-one PC. When plugged into a known and tested good power supply, a small noise from circuits can be heard while fans start and immediately stop. There is no 3.3V at the power button and no LED activity.
I verified the fuse is good and poked around for bad solder joints and pressed on BGA chips. Checked for crossed pins in external jacks and all removeable hardware is removed and unplugged. All large capacitors verified for ESR and non-shorted.
There is 2.25V at the USB jacks instead of the usual 5V.
I can find...
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Re: Gateway MA7 laptop won't charge or run off of A/C
By the way, when you add a jumper wire, pay attention to the conductive surfaces (one copper foil, one braid type) that rest between the power jack and the plastic case when the board is installed. Insulate with something in between. Otherwise you'll get a neat fireworks show and probably hate yourself for a little while...
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Re: Gateway 900G frustration
I saw a post where someone had mentioned getting the backlight connections messed up. It is easy to do because the connectors aren't keyed. The correct wire order from the top down is white, pink, black, grey, on both sets. Note that unexpectedly the black and grey wires will connect to a white and pink harness.
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