I have a set of HP ZR2440w LED backlight monitors. One of them is having issues with the backlight. On certain backgrounds (like the one at php.net) I notice it flickering. The other zr2440w has no such flicker problem. The major issue with it is that the backlight cuts out for a fraction of a second intermittently. This happens a lot more frequently when it's first turned on after it has been off and cold overnight, so it seems to be temperature related. I suspected the capacitors in the power supply might be bad, so I opened up the monitor to have a look.
They all looked fine visually, but are Lelons which are on the "bad list." Unfortunately I don't have an ESR meter so I wasn't able to actually test them. I did test the voltages with my multimeter, however, and they were all within spec. I ordered low ESR panasonics, rubycons and nichicons to replace the Lelons. I cross referenced the Lelon datasheet and confirmed the originals I was replacing were all low esr type. I was not able to find a replacement for the 500V input filter capacitor, at that voltage rating and higher they are all snap in type.
I proceeded with replacing all the capacitors in the SMPS (except the input filter cap), however the problem persists still. There are two PCBs inside the monitor, one is the SMPS, and the other is the one which handles the inputs and connects to the panel. This other one is filled with poor quality caps as well, Capxon, Lelon, and Suscon. I looked up the datasheets and most if not all are low ESR type.
I thought I might be able to swap PCBs with the other zr2440w to at least pinpoint which board is the culprit, but the other zr2440w is a later revision with a completely different SMPS and input board, with different board to board connector types.
I've ordered an ESR meter since I'm going to need one in the future anyway, any thoughts/ideas on where I should proceed from here?
They all looked fine visually, but are Lelons which are on the "bad list." Unfortunately I don't have an ESR meter so I wasn't able to actually test them. I did test the voltages with my multimeter, however, and they were all within spec. I ordered low ESR panasonics, rubycons and nichicons to replace the Lelons. I cross referenced the Lelon datasheet and confirmed the originals I was replacing were all low esr type. I was not able to find a replacement for the 500V input filter capacitor, at that voltage rating and higher they are all snap in type.
I proceeded with replacing all the capacitors in the SMPS (except the input filter cap), however the problem persists still. There are two PCBs inside the monitor, one is the SMPS, and the other is the one which handles the inputs and connects to the panel. This other one is filled with poor quality caps as well, Capxon, Lelon, and Suscon. I looked up the datasheets and most if not all are low ESR type.
I thought I might be able to swap PCBs with the other zr2440w to at least pinpoint which board is the culprit, but the other zr2440w is a later revision with a completely different SMPS and input board, with different board to board connector types.
I've ordered an ESR meter since I'm going to need one in the future anyway, any thoughts/ideas on where I should proceed from here?
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