Octigen MA9CKA - dead

[tmcw]

Got this monitor today, just seeing if I can revive it.

Have attached photos of the powerboard, both sides.

There are 2 connections off it going to the videoboard and to the display buttons board. The expected voltages there are +5V, but I'm getting only a couple of mV.

Working through the powerboard from the mains-in, I'm typically seeing +/-100-150V all the way to the right-hand side of T1. On the left-hand side of T1, just a couple of mV.

Is this transformer likely to be the culprit, or do I need to check anything else?

[retiredcaps]

Re: Octigen MA9CKA - dead

1) What is the DC voltage across the big cap?

2) What is the DC voltage across the small startup cap just to the left of the big cap? Is this voltage stable?

3) Great pics.

[tmcw]

Re: Octigen MA9CKA - dead

1) 323V

2) Do you mean PC4? If yes, no, it's not stable, seems to max at about 10V, then decreases to 0V, increasing again to 10V, etc.

3) Cheers, nice day here today, the natural light makes a huge difference to getting good pics.

[retiredcaps]

Re: Octigen MA9CKA - dead

2) Do you mean PC4? If yes, no, it's not stable, seems to max at about 10V, then decreases to 0V, increasing again to 10V, etc.

This little cap plays an important role to the proper startup of the SMPS. A fluctuating voltage suggests the cap is bad even though it is not bloated. Change this cap out with a quality one like a Panasonic FC or equivalent.

3) Cheers, nice day here today, the natural light makes a huge difference to getting good pics.

It is raining here. :-(

[retiredcaps]

Re: Octigen MA9CKA - dead

In addition to changing the little one, you may want to change the other 5 electrolytic caps. This board was made in 2006 so the caps are 5 years old and could also be bad.

Capacitors die from age, heat, and shoddy build quality. Capacitors DO NOT have to be visibly bloated in order to bad. They can be out of tolerance uF (a 1000uF measures 20uF) and/or have high ESR (ohm). A multimeter will be insufficient to test for ESR. For that you need an ESR tester which costs between $50 and $300.

Most members here will recommend that you replace ALL capacitors with reputable brands from reputable sellers. Brands like Rubycon, Panasonic, and United Chemicon are suggested. A list of recommended caps can be found at

https://www.badcaps.net/forum/showthread.php?t=2280

[tmcw]

Re: Octigen MA9CKA - dead

This little cap plays an important role to the proper startup of the SMPS. A fluctuating voltage suggests the cap is bad even though it is not bloated. Change this cap out with a quality one like a Panasonic FC or equivalent.

Thanks for the help.

I think I measured the wrong cap, the one I measured was the light-blue ceramic one.

The measured the dark-blue one, near the leads of the big capacitor, and it was fluctuating between 15V and 20V.

Is it still an issue? When you say that if it's fluctuating it suggests it's bad, should the voltage be rock steady?

[retiredcaps]

Re: Octigen MA9CKA - dead

The measured the dark-blue one, near the leads of the big capacitor, and it was fluctuating between 15V and 20V.

Is it still an issue? When you say that if it's fluctuating it suggests it's bad, should the voltage be rock steady?

The startup cap is the 47uF 50V electrolytic cap. The PCB designation is obscured by the angle of the pic. If it is fluctating between 15V and 20V DC, replace it. The voltage should be steady.

[Rtech]

Re: Octigen MA9CKA - dead

It may help to advise the part number on the SMPS chip...this is the 8 pin one placed centrally on the bottom of the board,as referring to its datasheet may well be helpful.

[retiredcaps]

Re: Octigen MA9CKA - dead

It may help to advise the part number on the SMPS chip

Good point that I forgot to mention. That is PU1 on the backside.

The datasheet will help us understand the circuit a bit better and see what the voltage across the startup cap should be.

I estimate about 50% of the problems are bad startup caps and the other 50% are bad SMPS chips.

[sabre504]

Re: Octigen MA9CKA - dead

I have seen these boards used in suyama monitors and have repaired a couple .
As Retiredcaps has said replace all caps but also resolder all transformers
in fact resolder most components then try your board .
Doing this sorted the ones i have worked on ,if it does'nt then you have
narrowed down the possible problems

[tmcw]

Re: Octigen MA9CKA - dead

The startup cap is the 47uF 50V electrolytic cap. The PCB designation is obscured by the angle of the pic. If it is fluctating between 15V and 20V DC, replace it. The voltage should be steady.

It's actually a 4.7uF (PC13), impossible to see the decimal point in the pic, it's off the edge, but I can see it ok further down the body. Don't have any to hand, but will get some, and report the results.

PU1 is "LT 633" on top line, "OB2269CP" on the bottom line, was tough to get a good pic, but under the magnifying glass, I'm fairly certain the number is correct. I initally thought the first character was a zero, but changing to an "O" turns up the datasheet. I've attached the datasheet I think is correct for the chip.

[tmcw]

Re: Octigen MA9CKA - dead

Replaced the small 4.7uF 50V cap, but I'm getting more or less the same, fluctuating between about 14V and 19V this time. Resoldered all the other major components.

Does this suggest a problem somewhere between the power connector and the big cap? PU1 at fault?

[PlainBill]

Re: Octigen MA9CKA - dead

Replaced the small 4.7uF 50V cap, but I'm getting more or less the same, fluctuating between about 14V and 19V this time. Resoldered all the other major components.

Does this suggest a problem somewhere between the power connector and the big cap? PU1 at fault?

No, it doesn't. Let's measure a voltage to make sure we are on the same page. Use either the - lead of the large cap, or pin 1 of the SMPS controller as ground. Don't use the chassis as ground. What is the voltage on pin 7 of the SMPS controller (PU1). If this is fluctuating between 15 and 20 volts, we need to make a few more measurements.

These will be easiest to make with the power supply right side up on a non-conductive surface. Use pins 7 or 8 of CN1 as ground. What is the voltage on the banded end of PD20 or PD21? What is the voltage on the banded end of PD22 or PD23?

PlainBill

[tmcw]

Re: Octigen MA9CKA - dead

No, it doesn't. Let's measure a voltage to make sure we are on the same page. Use either the - lead of the large cap, or pin 1 of the SMPS controller as ground. Don't use the chassis as ground. What is the voltage on pin 7 of the SMPS controller (PU1). If this is fluctuating between 15 and 20 volts, we need to make a few more measurements.

Yes, fluctuating between 15 and 20 volts.

These will be easiest to make with the power supply right side up on a non-conductive surface. Use pins 7 or 8 of CN1 as ground. What is the voltage on the banded end of PD20 or PD21? What is the voltage on the banded end of PD22 or PD23?

PlainBill

Voltage on PD20/21: 0.570V to 0.600V
Voltage on PD22/23: under 1 mV

[PlainBill]

Re: Octigen MA9CKA - dead

Yes, fluctuating between 15 and 20 volts.



Voltage on PD20/21: 0.570V to 0.600V
Voltage on PD22/23: under 1 mV

Interesting. Let's see, we're getting at least 1 volt pulses out of the 5V secondary; we aren't getting anything out of the 12V secondary; we're getting approximately full voltage out of the tertiary winding that provides run power for the SMPS.

I see several troubleshooting approaches; I'm going to take the most direct. Unsolder one end of both PD22 and PD23 and lift them clear of the board, then repeat the above test, checking only PD20 and PD21. That will completely eliminate the 12 volt portion of the board.

PlainBill

[tmcw]

Re: Octigen MA9CKA - dead

Thanks Bill, have done that, and get 6.13V on PD20/PD21.

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?

Have a bit of a problem for later on when desoldering one end of PD22. Looks like there was some heat fatigue there from before I got it (you can see some discoloration in the pics in the first post). Anyway, I desoldered the leg, and was pulling it out, the pressure on the other leg has caused the pad to lift off the board, the legs on those diodes are pretty stiff, so it was either them or the board that were going to give. There's still continuity there, but I'll probably need to solder some heavy wire between the two diodes there later on.

[PlainBill]

Re: Octigen MA9CKA - dead

Thanks Bill, have done that, and get 6.13V on PD20/PD21.

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?

Have a bit of a problem for later on when desoldering one end of PD22. Looks like there was some heat fatigue there from before I got it (you can see some discoloration in the pics in the first post). Anyway, I desoldered the leg, and was pulling it out, the pressure on the other leg has caused the pad to lift off the board, the legs on those diodes are pretty stiff, so it was either them or the board that were going to give. There's still continuity there, but I'll probably need to solder some heavy wire between the two diodes there later on.

First of all, congratulations; you have found the problem; PD23 was shorted. I'd replace both. I had noticed the discoloration there.

Go ahead with your plan of adding some wire to reinforce the connection. If you can't read the part number on the diodes, you are going to need high speed Schottky diodes.

If retiredcaps hasn't addressed the caps, I'd suggest replacing every electrolytic except the large one with name brand low ESR caps. The only exception to that rule is if they are already a known good brand / series. My personal preference is Panasonic FMs.

PlainBill

[tmcw]

Re: Octigen MA9CKA - dead

Thanks Bill, and to the others with the help and pointers.

I'll order the diodes from eBay, seems I can get a pack of 10 sent from Hong Kong for about half the cost than it would for me to drive 20-30kms to the nearest store. They're SB5100, these will probably do? You mention that they should be high-speed - should I be looking for a different one? I saw another one listed with "FS" which I understand is fast-switching or fast recovery.

Will probably take a week or two to get them, but I'm in no rush. I'll update when I get them in.

I'll replace the caps too as advised, 4 are Fuhiyyu, the other 3 are Hermei, names I don't see on the recommended list.

[PlainBill]

Re: Octigen MA9CKA - dead

Thanks Bill, and to the others with the help and pointers.

I'll order the diodes from eBay, seems I can get a pack of 10 sent from Hong Kong for about half the cost than it would for me to drive 20-30kms to the nearest store. They're SB5100, these will probably do? You mention that they should be high-speed - should I be looking for a different one? I saw another one listed with "FS" which I understand is fast-switching or fast recovery.

Will probably take a week or two to get them, but I'm in no rush. I'll update when I get them in.

I'll replace the caps too as advised, 4 are Fuhiyyu, the other 3 are Hermei, names I don't see on the recommended list.

Fuhiyyu and Hermei are both in the 'Replace on Sight' category. There may be poorer caps available; I'm not aware of any.

PlainBill

[tmcw]

Re: Octigen MA9CKA - dead

Just to update the thread, I got the Schottky diodes, and once they were put in, the monitor came to life without replacing any of the other capacitors. I changed them all anyway with Panasonic FC's, except the big cap and the one at the far bottom left, because I had the correct value cap, except the width/height was different. Is this ok, or am I better off with the correct size/dimensions of cap as well?

Monitor is really nice, the built-in speakers are atrocious though, they're like the speakers you'd get on portable cassette player headphones 30 years ago! Using this monitor to replace my old 19" Dell/Sony Trinitron CRT, prefer the 4:3 ratio over widescreen too, so it's worked out well.

Thanks again to everyone for the help and pointers.