Octigen MA9CKA - dead

[PlainBill]

Re: Octigen MA9CKA - dead

Caps with different form factor, but identical series often have slight differences in ESR and surge current ratings the differences are small and would not affect operation. The general rule of thumb is match the capacitance, use the same or higher voltage, and make sure the replacement will fit the space available.

Glad to see you got it working.

PlainBill

[tmcw]

Re: Octigen MA9CKA - dead

....Also, I did a diode test on PD22 and PD23 whilst they are disconnected. PD22 shows a value of 0.216, and PD23 gives 0. PD23 also has continuity through it. Are they toasted?....

Just to revisit this thread, I got another one of these monitors, same symptoms, same two diodes gone faulty, again, one of them shorted and the other with a low reading (approx. 0.180). So far, I've just replaced the two diodes, and the monitor has come back to life; I'll replace the Hermai capacitors at a later date when I put in another order for parts.

So I'm wondering what's more likely to be the cause of the failures; board design, or diodes not being the best perhaps? Or is it possible that using capacitors (or other components) of questionable quality in the original design, has caused the diodes to fail relatively early?

The monitor we fixed in June has been in more-or-less daily service, and is still working great.

[PlainBill]

Re: Octigen MA9CKA - dead

Just to revisit this thread, I got another one of these monitors, same symptoms, same two diodes gone faulty, again, one of them shorted and the other with a low reading (approx. 0.180). So far, I've just replaced the two diodes, and the monitor has come back to life; I'll replace the Hermai capacitors at a later date when I put in another order for parts.

So I'm wondering what's more likely to be the cause of the failures; board design, or diodes not being the best perhaps? Or is it possible that using capacitors (or other components) of questionable quality in the original design, has caused the diodes to fail relatively early?

The monitor we fixed in June has been in more-or-less daily service, and is still working great.

The most likely cause is under-rated parts. Most power supplies found in monitors will have the output diodes mounted on heat sinks. While the monitors have become more energy efficient, it still hasn't reached the point where the heat sink can be eliminated. Basically, the poor little diodes cooked themselves to death.

PlainBill

[tmcw]

Re: Octigen MA9CKA - dead

Thanks Bill,

So not much I can really do about it then. I do have the power saving set up to shut down the monitor after a couple of minutes, and switch it off if I'm leaving for an extended period, so I guess that might help them live a bit longer.

Thankfully the diodes are cheap, so if I had to change them out every couple of years, it's not too bad. If the rest of the panel lasts that long of course...