Need Zener markings/info from Gateway 900w 700g 900g 860-ALZ-GJ712D please!

[AWD_Guy]

In addition to bad caps, I have a gateway 900w or FPD1975W Rev. J that fried the zener right under the caps labeled ZD201 on the board. No markings are legible on it since it got so hot it cracked.

Power supply is the 860-ALZ-GJ712D which is common on a bunch of gateway 17-19" LCDs including some 700g and 900g models.

ZD201 is located right above the pin header to the other board. Attached pic is not my board but has a clear picture of where the zener is and I have highlighted it in red.

Any info would help, either the markings on yours or checking the voltage across yours would work too.

Thanks in advance.

[PlainBill]

Re: Need Zener markings/info from Gateway 900w 700g 900g 860-ALZ-GJ712D please!

In addition to bad caps, I have a gateway 900w or FPD1975W Rev. J that fried the zener right under the caps labeled ZD201 on the board. No markings are legible on it since it got so hot it cracked.

Power supply is the 860-ALZ-GJ712D which is common on a bunch of gateway 17-19" LCDs including some 700g and 900g models.

ZD201 is located right above the pin header to the other board. Attached pic is not my board but has a clear picture of where the zener is and I have highlighted it in red.

Any info would help, either the markings on yours or checking the voltage across yours would work too.

Thanks in advance.

Check where that zener is connected. By any chance is it from the 12V output to the 5V output?

PlainBill

[AWD_Guy]

Re: Need Zener markings/info from Gateway 900w 700g 900g 860-ALZ-GJ712D please!

Check where that zener is connected. By any chance is it from the 12V output to the 5V output?
PlainBill

I am going by pictures since I do not have the board in front of me.

One side appears to go straight down to the header and 5v and the other appears to go back to the top of the Cap stack and into one of the heat synced 3 legged power transistors(regulator?) the other side of which appears to come back down to 12v. It is not directly connected 5v-12v as far as I can tell.

And obviously other components are tied to those paths as well, but that is the most direct path I can find 5v-12v relative to it.

[AWD_Guy]

Re: Need Zener markings/info from Gateway 900w 700g 900g 860-ALZ-GJ712D please!

Check where that zener is connected. By any chance is it from the 12V output to the 5V output?
PlainBill

I am going by pictures since I do not have the board in front of me. One side appears to go straight down to the header and 5v and the other appears to go back to the top of the Cap stack and into one of the heat synced 3 legged power transistors(Regulator maybe?) the other side of which appears to come back down to 12v. It is not directly connected 5v-12v as far as I can tell.

In the pic, it is the trans on the middle of the Z bend facing the camera above the cap forest.

And obviously other components are tied to those paths as well, but that is the most direct path I can find 5v-12v relative to it.

[PlainBill]

Re: Need Zener markings/info from Gateway 900w 700g 900g 860-ALZ-GJ712D please!

Those three legged devices are schottky diodes used to rectify the outputs of the 5V and 12V windings on the transformer. One design I've seen links the 12V output to the 5V output through a 8-10 volt Zener diode. If you can confirm the hookup (or post pictures) I'll dig through my collection of schematics and se if I can come up with something better than a wild guess.

PlainBill

[AWD_Guy]

Re: Need Zener markings/info from Gateway 900w 700g 900g 860-ALZ-GJ712D please!

Oops, sorry for the double post earlier. I edited it, but apparently it reposted for some reason.

There are a ton of pictures of the PS from different angles in this thread. Every picture on page 1 is of the same model and they are in much less "Tanned" condition than mine.

I marked up one of them on the trace side for the location of ZD201.

[PlainBill]

Re: Need Zener markings/info from Gateway 900w 700g 900g 860-ALZ-GJ712D please!

Oops, sorry for the double post earlier. I edited it, but apparently it reposted for some reason.

There are a ton of pictures of the PS from different angles in this thread. Every picture on page 1 is of the same model and they are in much less "Tanned" condition than mine.

I marked up one of them on the trace side for the location of ZD201.

As you noted - it's hard to tell from the picture. When you get your hands on the board, simply use a DMM set on the 200 ohm range to make some simple checks.
1. Is the resistance across the zener > 20 ohms?
2. Does one end of the zener show less than 1 ohm resistance to 5V?
3. Does one end of the zener show less than 1 ohm resistance to 12V?

If the answer to all three is 'yes' I can suggest a zener I am confident is equivalent to the original. I COULD suggest a 1N5344 or 1N5345, but I'm not sure that wouldn't smoke and glow bright red.

PlainBill

[AWD_Guy]

Re: Need Zener markings/info from Gateway 900w 700g 900g 860-ALZ-GJ712D please!

As you noted - it's hard to tell from the picture. When you get your hands on the board, simply use a DMM set on the 200 ohm range to make some simple checks.
1. Is the resistance across the zener > 20 ohms?
2. Does one end of the zener show less than 1 ohm resistance to 5V?
3. Does one end of the zener show less than 1 ohm resistance to 12V?

If the answer to all three is 'yes' I can suggest a zener I am confident is equivalent to the original. I COULD suggest a 1N5344 or 1N5345, but I'm not sure that wouldn't smoke and glow bright red.

PlainBill

Sorry, for the delay getting the info to you. I really appreciate the help.

The Zener is very badly damaged and cracked through but still just brely in one piece, so take its resistance numbers with a grain of salt. These are when isolated/removed from the board.
1.6 M ohm forward
36 M ohm reverse

Anode is directly connected to +5V output header on the board.

Cathode is M Ohm+ resistance to +12 and gnd.

Does that help?

Thanks in advance.

[AWD_Guy]

Re: Need Zener markings/info from Gateway 900w 700g 900g 860-ALZ-GJ712D please!

Just for yucks, I tested the zener in series with a 3.3KOhm resistor on a variable power supply and got a threshold of right around 11.7V

Again, the thing is fried, but apparently working enough to test at low loads I guess?

I am clearly showing my power supply design ignorance, but why would a 12V(assuming 11.7V DVM reading=12V Spec???) zener be attached to the +5v output?

It looks significantly bigger than a 1W 1N4742 and smaller than a 1N5349 at my local electronics store, so that has me a bit confused too.

Will it hurt anything if I just throw a 5W in there and it was a 1W?

[PlainBill]

Re: Need Zener markings/info from Gateway 900w 700g 900g 860-ALZ-GJ712D please!

Just for yucks, I tested the zener in series with a 3.3KOhm resistor on a variable power supply and got a threshold of right around 11.7V

Again, the thing is fried, but apparently working enough to test at low loads I guess?

I am clearly showing my power supply design ignorance, but why would a 12V(assuming 11.7V DVM reading=12V Spec???) zener be attached to the +5v output?

It looks significantly bigger than a 1W 1N4742 and smaller than a 1N5349 at my local electronics store, so that has me a bit confused too.

Will it hurt anything if I just throw a 5W in there and it was a 1W?

1. Good job of investigating.

2. One design I saw had a zener running from the 12V supply to the 5V supply. I suspect the intent was to limit the voltage on the 12V supply when the inverter was off. I'd say the zener you are looking at is there for a
similar reason.

3. Yes, you can go to a 5 Watt zener. As a matter of fact, I'd recommend it.

PlainBill

[AWD_Guy]

Re: Need Zener markings/info from Gateway 900w 700g 900g 860-ALZ-GJ712D please!

lcdman over in This thread had a matching board and found that ZD201 is a Motorola P6KE12A 12V 5W Zener confirming my investigation.

I'll be replacing it with a 1N5349

Maybe this thread will help somebody else some day.

Thanks PlainBill and lcdman.

[montecarlo5]

Re: Need Zener markings/info from Gateway 900w 700g 900g 860-ALZ-GJ712D please!

I also need some help with a zener. I have the same board and the only thing i can see to be bad is ZD103. All caps test good and so do many other parts I've tested. My problem started with the monitors osd showing up by itself and not going away, turned power off and screen never came back on. Took apart and saw that ZD103 is all i can see bad. Any help I would thank you for.