Samsung 2693HM - Doesn't turn on (no standby)

[twist3r]

Re: Samsung 2693HM - Doesn't turn on (no standby)

RAM sticks you can do with a cheap hot air with no bottom heater because the size of the PCB is small.

With desktop PC video cards, you may or may not be able to do them just with a cheap hot air. That said, I have a cheapo station, and I have removed RAM and GPU chips even from bigger video cards. But I used a bottom heater (gas stove and on one occasion, also electric stove), which made this a lot easier.

When you did it with gas stove, ...did the 'flame' touched the board from the bottom, or you held the bottom of the board even above the flame of gas stove? Could the flame (if 'licks' the board) damage the board or its components?

If one chip on the RAM stick (module) is faulty, will the RAM module be 'fixed' when I solder the good chip from another ram module (of the same tipe), or... these memmory modules has some 'control' IC that wont allow 'alien' chips to be used on a RAM module? I don't know if I explaind this good. I'm asking if the RAM module needs to be 'programmed' (in a way) to accept new 'brother' (new memmory chip) among other memmory chips which were already on the RAM module?

If you're doing memory chip swaps, the new chip must have the same exact part number as the old chip. That means, not only the same memory size, but also same speed and timings. The last 2 digits in the part number typically indicate the chip speed. For example, for a Samsung memory chip with part # K4J52324QC-BC14, the "14" part indicates a 1.4 ns chip. This corresponds to (1 / 1.4 ns ) x 1000 = ~714 MHz. The same chip with "BC16" at the end would be a 1.6 ns chip and clock at ~625 MHz max.

But apart from that, no these chips are not programmed inside, so you can swap them as you please.

Ok, thanks. I think I understood. Just 2 extra questions:

1. Does that means, that even if I find the chip with the same 'speed' like 1.4ns or same frequency, it MUST be made by the same chip manufacturer (in this example Samsung) or it can be from other manufacurer, just needs to be of the same specific (response and frequency)?

2. If I solder the wrong chip, what will happen? RAM wont work or somethign else would brake? Will the RAM module get tosted for good, or I could still remove the wrong chip andd after putting correct one, make the RAM work as it should?

Then again, there were 'protection' diodes, so... I really don't know if they failed by lettiner higher current flow, which means 'line' was not broken, ...OR they let the current flow and then failed by braking the line. I'm on the edge of misery here.

The "protection" diodes in your monitor have a very simple function: the way they are connected, if a voltage "signal" goes over 4V on the HDMI or DVI signal lines (due to voltage spike or whatever other reason), it will get passed through the protection diode(s) on that line to the 3.3V_LIVE rail, so the voltage signal will be capped to 4V MAX. On the other hand, if a voltage "signal" goes less than -0.7V on the signal line, then ground will conduct through the protection diode(s) on that line and keep the signal capped at -0.7V max. This essentially means any signals going to the ICs will be limited between the range of 4V and -0.7V so as to protect the ICs.

The MAIN PROBLEM behind the above implementation of the protection diodes in your monitor is that the 3.3V_LIVE rails feeds into the ICs and there is no over-voltage protection (OVP) on the 3.3V_LIVE to stop it from going above 3.3V. Thus, with no OVP on the 3.3V line, a signal on the HDMI or DVI line that has sufficient current and voltage over 4V can force the 3.3V_LIVE to go much higher than 3.3V... and that's what likely happened in your case when the cable box was connected. So once the 3.3V_LIVE went much higher than 3.3V, it then comes down to which IC is the weakest and breaks down the first from the over-voltage. In your case, that happened to be some of the power lines connected to L300-L307 on IC300. Basically, they took a hit and that's all there was to it - IC300 damaged.

What Samsung SHOULD have done is put something like a Zener diode rated for 3.5 to 3.7V on the 3.3V_LIVE rail. Then, any voltage spike on the DVI or HDMI signal lines higher than 4V will pass through the protection diodes and get shunted to ground through that Zener diode. If that voltage spike has sufficient current, it would blow the Zener diode short-circuit... which will still "break" the logic board (i.e. it will need repair). But the repair would be much easier - just replace the shorted Zener and the monitor will work again. Instead, Samsung didn't do this and now you have IC300 dead. In other words, the addition of a $0.10 component (or less) could have saved your monitor.

Thanks for explanation!

Its really bad fact that just becuase Samsung wanted to spare $0.10 for that Zener diode, I got my main/logic board chip fried.
Your idea got me thinking.... is it possible to solder such Zener diode on the board (somewhere) and make that 'custom' over-voltage protection that Samsung 'forgot' to implement?

Ok, one 'quick' question here: How you guys always calculate what voltage will be measured across that BIG FAT filter capacitor? What is the calculation formula?
...
If 230v AC comes at primary tranformer side, what voltage comes out as DC at its secondary side after bridge rectifier? I was trying to guess that 230v AC was multiplied by 1.41 (square root (of 2), I don't know how it is properly said in english).

Yup, that's correct.
AC input * Sq_root (2) is indeed how it's done.

I don't usually even bother with that, though. I just know that for 110-120V AC mains, expected DC voltage is usually around 160-170V and for 220-240V AC mains, the expected DC voltage is around twice that (i.e. 320-340V.)

Ok, thank you.
Just, thats before the power board is connected to anything else, correct? I mean, once the monitor power up, that FAT filter cap end up with much higher voltage, right?




Ok, that was it for now. I hope you didn't missed my long posts (ofcorse you didn't, I'm just joking).

Thanks again momaka, for all the patience you showed during long 2 (or is it 3?) months of dealing with me, while helping me to fix my monitor.

If there are no further responds to this topic, I may revive it again, once I get ahold of some hotair station so I can change those firmware chips on my monitor.

cheers!