Daytek F19AH

[UserName666]

Re: Daytek F19AH

From post #36 in the BENQ T905 post regarding diodes:
"Test them with your diode setting. One way should measure 0.4 to 0.7V. Reserve and the other way should measure "1" or 0L."

So would that mean that the diode giving me a reading of 1.643v is damaged??

If the diode were out of circuit then that reading would be a worry. In-circuit the reading will be affected by other componentry. Without a schematic it's hard to give a 100% guarantee but it is credible.

Out of circuit, no live power, DMM on diode setting:
Near transformer = 0 reverse .498v
Near filter cap = 0 reverse .493v

So umm I guess those are good.

[jetadm123]

Re: Daytek F19AH

PlainBill: The 10uf has already been replaced.
IC101 underneath the board is:
SG6841SZ
KZA056005340

Wrog: I dont know what the "series" of caps are but the brand was Radio shack. They were all originally 25v but now they are now 50v. The uf ratingings are exactly the same. Rated at 105 degrees. I don't know about the 10uf 50v cap as that was just in my parts bin but it was new. It is now 63v temp rating unknown. I'm gonna get a better/permanent 10uf once I see some action on the power LED.

Most people on this site will tell you that Radio Shack caps are the wrong type of caps to use. You need low-esr caps like Panasonic FM or FC series. The "shack" caps are too general purpose and will not handle the higher frequencies the power supply operates at.

IC101 is a PWM controller made by System General? Man, what's with all these oddball controllers made by unknown companies? Spec sheet below:

[UserName666]

Re: Daytek F19AH

PlainBill: The 10uf has already been replaced.
IC101 underneath the board is:
SG6841SZ
KZA056005340

Wrog: I dont know what the "series" of caps are but the brand was Radio shack. They were all originally 25v but now they are now 50v. The uf ratingings are exactly the same. Rated at 105 degrees. I don't know about the 10uf 50v cap as that was just in my parts bin but it was new. It is now 63v temp rating unknown. I'm gonna get a better/permanent 10uf once I see some action on the power LED.

[Wrog]

Re: Daytek F19AH

If it turns out to be stuff like SMPS controller, FET, SMPS transformer, output rectifier I may have to scrap this as I have no clue how to diagnose those kind of componants.

Don't scrap, it's the perfect opportunity to learn more. Don't worry, there are plenty of folks here that will give you instructions on what to try next. If I've read your responses correctly, you've already replaced all caps except for the big guy laying on its side, correct? What did you end up using in their place (brand, series, values, etc.)?

[PlainBill]

Re: Daytek F19AH

If it turns out to be stuff like SMPS controller, FET, SMPS transformer, output rectifier I may have to scrap this as I have no clue how to diagnose those kind of componants.

Upon testing that 10uf cap the 10uf 50v cap, the voltage is fluctuating between between 11 ~ 16volts.

I will retest those Diodes out of circuit in a bit. Want to wake up a little more before I start soldering.

For the time being does anyone have an opinion about the 11 ~ 16 voltage coming to the 10uf cap?

That is the startup voltage. Pulsing like that indicates a problem with the SMPS (yeah, big surprise). It could be due to a bad startup cap, or a shorted diode. I'd suggest replacing the 10uF cap first. If that doesn't help, see if you can get a set of good eyes to figure out the part number of IC101. The number you posted doesn't come up on any searches.

PlainBill

[UserName666]

Re: Daytek F19AH

If it turns out to be stuff like SMPS controller, FET, SMPS transformer, output rectifier I may have to scrap this as I have no clue how to diagnose those kind of componants.

Upon testing that 10uf cap the 10uf 50v cap, the voltage is fluctuating between between 11 ~ 16volts.

I will retest those Diodes out of circuit in a bit. Want to wake up a little more before I start soldering.

For the time being does anyone have an opinion about the 11 ~ 16 voltage coming to the 10uf cap?

[jetadm123]

Re: Daytek F19AH

Before we get too deep into this, let's get back to the 10uf cap. It is part of the startup circuit and still should be replaced. Other members have suggested that the 50V rating is used because that value is the most readily available. Try reading the voltage across the 10uf cap. If it's relatively low, for testing purposes, you might be able to use a lower voltage cap. Please observe all safety precautions, since you're working next to the high voltage cap.

[pedro]

Re: Daytek F19AH

Wondering what the significance of 1.4 is or where it comes from?? Trying to learn something as I go here and not just play musical chairs with the components lol

The line supply voltage is described in terms of its RMS value. The peak is 1.4 times the RMS value, and your incoming rectifier_bridge/filter_cap combo is a peak detector.

As for the 6 pin connector it is indeed 0 volts. - lead on middle top gnd pin and + across all others 0 volts. Same with the middle bottom gnd pin. That was tested with live power. (Transformer still clicking)

The DC at the large cap is present but no secondary voltage is derived from the SMPS. The possible candidates for this are SMPS controller, FET, SMPS transformer, output rectifier, output filter cap. The fact that the transformer is ticking suggests that the first three are still trying hard. If you get this same result with the video ("logic") board disconnected then focus your attention on the secondary rectifier(s) and filter caps.

[pedro]

Re: Daytek F19AH

From post #36 in the BENQ T905 post regarding diodes:
"Test them with your diode setting. One way should measure 0.4 to 0.7V. Reserve and the other way should measure "1" or 0L."

So would that mean that the diode giving me a reading of 1.643v is damaged??

If the diode were out of circuit then that reading would be a worry. In-circuit the reading will be affected by other componentry. Without a schematic it's hard to give a 100% guarantee but it is credible.

[UserName666]

Re: Daytek F19AH

From post #36 in the BENQ T905 post regarding diodes:
"Test them with your diode setting. One way should measure 0.4 to 0.7V. Reserve and the other way should measure "1" or 0L."

So would that mean that the diode giving me a reading of 1.643v is damaged??

[UserName666]

Re: Daytek F19AH

Wondering what the significance of 1.4 is or where it comes from?? Trying to learn something as I go here and not just play musical chairs with the components lol

As for the 6 pin connector it is indeed 0 volts. - lead on middle top gnd pin and + across all others 0 volts. Same with the middle bottom gnd pin. That was tested with live power. (Transformer still clicking)

Diode test WITHOUT live power and Diodes still in the board. DMM set to diode.
Blue (By filter cap) - .491v Reverse leads = 0v
Red (By transformer) - .491v Reverse leads = 1.643v

[jetadm123]

Re: Daytek F19AH

Sorry but Im not following that. This is the first time I have tried something like this and with doing it live. What I did was test at the secondary of the clicking transformer and thats 0 volts. Across the filter cap fluctuated from 158v to 162 volts on the DC setting. My filter cap is 120uf 400v.

Assuming your outlet voltage is 115VAC: 115x1.4= 161 Volts DC

You were asked to check for 5 and 12 volt output. Looking at your second photo, next to to the large yellow transformer and between the heatsinks looks like a 6 prong plug. Look to see if any of those prongs are labelled 5V, 12V, ground, etc. With your meter set to DC and both boards and backlights connected, power on the monitor and check for the 5V and 12V voltages. I suspect you'll read 0 volts, since the transformer secondary is putting out 0V.

[PlainBill]

Re: Daytek F19AH

Sorry but Im not following that. This is the first time I have tried something like this and with doing it live. What I did was test at the secondary of the clicking transformer and thats 0 volts. Across the filter cap fluctuated from 158v to 162 volts on the DC setting. My filter cap is 120uf 400v.

You should have seen a pulsating voltage on the DC output. Depending on the speed of your DMM, this might not be visible. The fact that the voltage across the large cap is fluctuating, I would suspect either the large cap is bad, or the diode on the output of the SMPS transformer is shorted.

PlainBill

[UserName666]

Re: Daytek F19AH

Sorry but Im not following that. This is the first time I have tried something like this and with doing it live. What I did was test at the secondary of the clicking transformer and thats 0 volts. Across the filter cap fluctuated from 158v to 162 volts on the DC setting. My filter cap is 120uf 400v.

[retiredcaps]

Re: Daytek F19AH

I only have a digital meter

If you are experienced in using a multimeter and know how to measure voltage, check to see if the secondary voltages are present. They will probably be 5V and possibly 12 or 19V DC.

If those are absent, see if you get 1.4 *main DC voltage across the main filter capacitor.

[UserName666]

Re: Daytek F19AH

I only have a digital meter and not sure how to do cap checks with it but tried the one labeled as 10u as I have never heard capacitors in anything but farads and was pretty much the same physical size/values +13 volts. Not gonna mess with the one that says u-M though.
The transformer still clicks like before any of the caps were changed. Only one left is the big filter cap which I know I do not have so will have to do some hunting now.

[jetadm123]

Re: Daytek F19AH

The "M" on the cap is +/- 20% tolerance

[PlainBill]

Re: Daytek F19AH

OK I somehow passed these before but I found two 10u-M 63 volt caps. What is 10u-M?? Will these work. The other just say 10u. Not 10u-M or 10uf.

Those are 10uF, 63 Volt.

PlainBill

[retiredcaps]

Re: Daytek F19AH

OK I somehow passed these before but I found two 10u-M 63 volt caps. What is 10u-M?? Will these work. The other just say 10u. Not 10u-M or 10uf.

I don't know about the markings because they are ambiguous. If you have a multimeter, you can measure the capacitance and make sure it is close to 10uF.

If they measure 10uF, you can use them as a test to see if the SMPS starts up, but I would use a quality cap longer term.

[UserName666]

Re: Daytek F19AH

OK I somehow passed these before but I found two 10u-M 63 volt caps. What is 10u-M?? Will these work. The other just say 10u. Not 10u-M or 10uf.