Compaq 1520 just standby light on

[sam67]

Just got this monitor off of a friend ..power light is on but cannot see any pic in back ground ..Fuses are all ok on both boards when checked even though i knew these were not the case else i would not get standby light on ..

Cannot see any burn marks and all caps look good ...i do have a blue ring tester ,analogue meter,esr meter and dvm .. oh and i have just bought a scope but waiting on it's arrival..

Not really sure where i should start testing for voltages on this as it's a little different on some of the monitors i have played about with ,plus i am a newbie trying to learn so thought it would make it easier to buy some helpful tools to help me along and with the right guidance from good folks on here...

Any help and guidance appreciated .

Thanks p.s Thanks to plainBill's hint on using macro mode i now can post pics

[smason]

Re: Compaq 1520 just standby light on

Where's the power supply? Is it external? If so, I'd check the output of it first.

[sam67]

Re: Compaq 1520 just standby light on

Hi, yes it is lol i forgot to mention ..the psu is fine , that was the first thing i checked ...not sure where to start probing next..

[PlainBill]

Re: Compaq 1520 just standby light on

Hi, yes it is lol i forgot to mention ..the psu is fine , that was the first thing i checked ...not sure where to start probing next..

Well, this is the same inverter design that Benq has been using all along. So the first point to check was PF751. Since you already did that, we'll have to get more creative.

I'm a little confused by your description. Does the power light ever go from 'standby' (usually orange) to 'on' (green or blue)? Have you tried applying a signal?

Looking at the back of the power supply / inverter, it appears they generate the voltages for the processor there. Check the voltages on CN701. Too bad they didn't indicate what they are.

PlainBill

[sam67]

Re: Compaq 1520 just standby light on

Hi plainBill,

Thanks for the reply..The power light goes to orange when switched on then it blinks but does not change color ,it stays orange.

I tried it hooked up to a pc but nothing happens apart from no signal.

I have hooked the boards to the panel but not sure how i can test the voltages correctly from CN701 while it is facing this way as there is a connector under the board that the board joins to..Sorry if i sound a bit dumb but not to sure where to probe at..I have attached a pic so that you can see how it is now hooked up with the power cord attached ..Can i still check it this way ?

Thanks once again for your time. p.s just realized i took the photo with the board upside down

[smason]

Re: Compaq 1520 just standby light on

Hi, yes it is lol i forgot to mention ..the psu is fine , that was the first thing i checked ...not sure where to start probing next..

Well just to be sure we cover all the bases, please define "Fine"
What is the voltage under load, when the monitor is connected?

One man's fine could be another man's low, ripply output

[PlainBill]

Re: Compaq 1520 just standby light on

Hi plainBill,

Thanks for the reply..The power light goes to orange when switched on then it blinks but does not change color ,it stays orange.

I tried it hooked up to a pc but nothing happens apart from no signal.

I have hooked the boards to the panel but not sure how i can test the voltages correctly from CN701 while it is facing this way as there is a connector under the board that the board joins to..Sorry if i sound a bit dumb but not to sure where to probe at..I have attached a pic so that you can see how it is now hooked up with the power cord attached ..Can i still check it this way ?

Thanks once again for your time. p.s just realized i took the photo with the board upside down

Take a look at the top view of the connector. The pins are numbered 1-12 with the even numbered pins on the 'outside'. Clearly you can measure the voltage on the even numbered pins. Now look at the bottom of the boards.

What do you see? Some of the odd numbered pins are connected to even numbered pins!!!! 3 & 4; 5 & 6; 7 & 8; 11 & 12 are connected pairs. So by measuring the voltage on 4 you also measure the voltage an 3; by measuring 6 you also measure 5; and so forth. "BUT," you observe, "some are NOT connected together." True, pins 1 and 2 are not connected together but pin 1 is at the end of the connector so you can probe in from the end. That leaves pin 9. And looking at the pictures, pin 9 is connected to J13 on the power supply board.

PlainBill

[seanc]

Re: Compaq 1520 just standby light on

Have you tested the ESR of the small caps on the inverter? I've had one of those fail and take down an LCD with an external power brick completely.

[sam67]

Re: Compaq 1520 just standby light on

Hi plainBill,

Hope you are not got gonna be mad at me if i did not test in the right place

I have added a pic (the right way around lol) i have circled in red the pin that i call pin 1.

I measured using the 2v setting as i could only get one reading in the 20v dc setting on pin 1 from ground to each pin.

I also measured at the pico fuse and it was- 11.80v




pin 1- 1.362
pin 2 - 0.001
pin 3 - 000
pin 4 - .001
pin 5 - .008
pin 6 - .001

Thanks again for your time.

[sam67]

Re: Compaq 1520 just standby light on

Forget the numbers above ,silly me had probe in wrong socket ...here is what i got

Pin 1- 1.291
pin 2- .000
pin 3- .000
pin 4 - .000
pin 5 - .026
pin 6 -.000

Voltage at fuse 12.10v


sorry for the above mistake.

[PlainBill]

Re: Compaq 1520 just standby light on

Forget the numbers above ,silly me had probe in wrong socket ...here is what i got

Pin 1- 1.291
pin 2- .000
pin 3- .000
pin 4 - .000
pin 5 - .026
pin 6 -.000

Voltage at fuse 12.10v


sorry for the above mistake.

OK, brace yourself. You are going to have FUN!!! This is a very interesting design. According to the numbers you gave me, the standby LED can't be on. Whoops!! I missed a pin.

Here we go again. The 'exposed' pins are numbered 2, 4, 6, 8, 10, 12. Pin 12 is ground. The 'hidden' pins are numbered 1, 3, 5, 7, 9, 11. I want the voltage on pins 1, 2, 4, 5, 6, 8, 9, and 10. I have numbered arrows pointing to the jumpers which are at the same potential as pins 5 and 9.

NOW, just for luck, hit the power button as you make each measurement and see if the voltage jumps.

Note that this board takes the voltage from the external 'brick' and uses it to generate the voltages the processor requires. For what it's worth, I think one (or more) of these is dead.

PlainBill

[sam67]

Re: Compaq 1520 just standby light on

Hi plainBill,

I will do the measurements later as i have to go out now ,but before i do them later what is the best setting to use on my vol meter as it is not auto ranging ..The settings are 200m ,2v, 20, 200v, 1000v

I seem to get readings on the j4 jumper wire using 20v setting ..so should i use the 20v setting for all the tests ?

Thanks.

[PlainBill]

Re: Compaq 1520 just standby light on

Hi plainBill,

I will do the measurements later as i have to go out now ,but before i do them later what is the best setting to use on my vol meter as it is not auto ranging ..The settings are 200m ,2v, 20, 200v, 1000v

I seem to get readings on the j4 jumper wire using 20v setting ..so should i use the 20v setting for all the tests ?

Thanks.

The 20 volt setting is a good compromise. The usual recommendation is to start at the highest range and then work downward until you get maximum resolution. The 20 volt range will be appropriate for anything between 2 volts and 20 volts. At this point there is no need for the higher resolution the 2 volt range would give on any lower voltages.

PlainBill

[sam67]

Re: Compaq 1520 just standby light on

Hi plainBill sorry for late response..voltages at setting 20v first reading without power button pressed and next reading was with power button pressed -

pin 1 0.01 - 4.88

pin 2 1.27 - 1.85

pin 4 0.00 - 0.00

pin 5 5.0 7 fluctuated between 5.07 and 5.08

pin 6 0.00 - 5.07

pin 8 0.00 - 0.00

pin 9 0.01 - 3.23

pin 10 0.01 - 3.23

Thanks again for your help..

p.s hope the cataract surgery goes well for you , my mother in-law has had it done twice and said it worked well for her.

[PlainBill]

Re: Compaq 1520 just standby light on

Hi plainBill sorry for late response..voltages at setting 20v first reading without power button pressed and next reading was with power button pressed -

pin 1 0.01 - 4.88

pin 2 1.27 - 1.85

pin 4 0.00 - 0.00

pin 5 5.0 7 fluctuated between 5.07 and 5.08

pin 6 0.00 - 5.07

pin 8 0.00 - 0.00

pin 9 0.01 - 3.23

pin 10 0.01 - 3.23

Thanks again for your help..

p.s hope the cataract surgery goes well for you , my mother in-law has had it done twice and said it worked well for her.

It'll be tomorrow (your time) before I can really look at these. I've just used up my energy for the day running an irrigation line for a rose bush. Everything was going smoothly until I opened the wrong valve and flooded the trench I had just dug (6" deep) with water - which turned into gooey, sticky mud.

PlainBill

[sam67]

Re: Compaq 1520 just standby light on

No problem PlainBill i am in no rush.. Don't you just hate it when things end up going wrong.hope you get it sorted.

Best

sam67

[PlainBill]

Re: Compaq 1520 just standby light on

I can't believe I missed this. On the back of the logic board - check out U2. What is the part number?

This is a two processor design. The one mounted diagonally handles the video processing. The other one handles the control functions.

PlainBill

[sam67]

Re: Compaq 1520 just standby light on

Hi plainBill,

Sorry for late reply only i was out all weekend..The part number for U2 is -

ST CHN K 319 M317M

I have searched for this but have not found it yet.

Thanks

sam

[Bobdee]

Re: Compaq 1520 just standby light on

Hi plainBill,

Sorry for late reply only i was out all weekend..The part number for U2 is -

ST CHN K 319 M317M

I have searched for this but have not found it yet.

Thanks

sam

Hello
Check these out on this link
http://www.alldatasheet.com/view.jsp?Searchword=317M
Page 3 number 110 lm317mdt
Page 6 number 25 lm317ms
Page 6 number 11 lm317mx
...

[sam67]

Re: Compaq 1520 just standby light on

Managed to get this monitor to stay on..Power light is orange then stays green but lines all over screen ..first pic is how it starts then gets more lines the longer it is on..is this a panel problem ..connector is seated right and i could see no physical damage to TCP when i removed panel..any ideas anyone ?