Sampo 70FA2 series LCD..... briefly works.

**stevo1210** · 07-28-2007, 07:22 AM

Re: Sampo 70FA2 series LCD..... briefly works.

Here are some images that I took of the internal parts of the LCD. When I was fiddling around with the internal parts of the LCD, I also checked for loose wire connections and bad solder joints and there aren't any as far as I can see.

When I am really really lucky, I can see an image with a very feint whitish colour background in the far rght corners and that's about it.
Other times, I usually see the Windows Desktop or a message saying "Cable not connected" for about 5 seconds and that's about it.

I can take some more photos if that helps. Feel free to ask me if anyone needs more images.

Thanks.

**stevo1210** · 07-28-2007, 07:51 AM

Re: Sampo 70FA2 series LCD..... briefly works.

I just tested the LCD monitor again, but this time with my MP3 player plugged into the Line-in port of the LCD monitor.
I noticed that when the monitor blanks out, the audio/ music also turns off.... So now it's not only the panel that has power issues, but also the audio on the LCD.
This probably means that there is a power problem somewhere in the LCD and not just a faulty screen.

Thanks.

**Harvey** · 07-28-2007, 03:11 PM

Re: Sampo 70FA2 series LCD..... briefly works.

Hmmm, interesting construction inside that monitor - looks almost home made :>

When you say it fades out, do you mean the actual image goes to black or the CFL lights stop working? You can generally see if the CFLs are alight in a darkend room as they shine out the back somewhere.

**stevo1210** · 07-29-2007, 03:51 AM

Re: Sampo 70FA2 series LCD..... briefly works.

Originally posted by Harvey

When you say it fades out, do you mean the actual image goes to black or the CFL lights stop working? You can generally see if the CFLs are alight in a darkend room as they shine out the back somewhere.

The whole display goes black, not just the CFL lights. In other words, the image fades out until it turns completely black.

**starfury1** · 07-30-2007, 04:46 AM

Re: Sampo 70FA2 series LCD..... briefly works.

Well no idea on the monitor

But were's the PSU? is it a external box?

It sounds to me as if the PSU might be your problem or something taking out the psu

But you would have to identify the supply rails and measure them in fault condition to be sure.

Stop press I found it LOL from you first post

The original power supply with the proper plug connection died a while back and my friend, being a licensed electronics technician, wired in an external power supply, which also supplys 12V, 2A like the original one.

So humm have to think on that a bit more but still the same thing do you have full Voltage from supply in fault mode?

Seems whats most likely to die with LCD TFT is the inverter...weather this could cause the PSU to shut down is another question

The inverter is on the left hand side (looking at picture above)
The 3 boards vertically next to that are
top touch screen panel interface
middle Audio amplifier and
bottom audio touch screen i/o whatever

From what I can tell

The big board is the video etc board, it may have some type of power circut or PSU filter on board judging by those coils and caps...I dont know
There is a 3 terminal voltage regulator near there. The LM 2937ES

National link here

I would check psu and possibly see what voltages are showing on that regulator as well
If they are ok you fault will probably lay elsewhere.

you could try another PSU if you have one to hand

Being in mind not the guru here and this may not be a good idea if a smpsu is left unloaded...if anyone knows of a reason why not please pipe up!

Working on the assumption that inverters are most likely to go faulty
(bad caps shorted turns on the transformers)

Id try disconnecting the inverter (the grey cable at the middle of the pcb)
Then power it up and see if you can see the image with a torch.
(this will depend on the psu measurements above, if they were low or none)

anyway a few suggestions at this point

But there are other possibilities and I may totally be barking up the wrong tree again here with regard to the mains senerio as out lined

I once had a power supply that used to do this

It would work ok if unplugged from the mains but shut it down and leave it plugged in, it would not fire up
it turns out the was an open circuit resistor (dry joint) that was causing this.

I assume it was some part of the startup circuit and possibly a cap was discharging through it but when it went open the cap held its charge while plugged into the mains so it wouldn't start up till the charge had been dissipated by unplugging it from the mains...
(probably part of the STB 5 Volt supply)

thats the theory although I am not sure how close to the truth it is as I never looked into it further.

Anyway hope its of some help...Be careful as always

Cheers

**stevo1210** · 07-30-2007, 05:23 AM

Re: Sampo 70FA2 series LCD..... briefly works.

Originally posted by starfury1

I would check psu and possibly see what voltages are showing on that regulator as well
If they are ok you fault will probably lay elsewhere.

I just check the output voltage of the PSU without any load and it supplies 13.77 -14.0V !!!!.
It's supposed to be rated at 12V, not 14V.... could that be where the problem lies??.... overvoltage to the LCD monitor, then LCD monitor automatically switches off??

Originally posted by starfury1

you could try another PSU if you have one to hand

I don't have another PSU that I could try. I'll have to ask a few friends for one. I have another one here also 12V, but supplies only 1A.... which probably won't work with this LCD.

I also looked online for a 12V 2A DC adaptor, and I can't find any. The electronics store here sells only 12V 5A AC, not a DC one....

Thanks.

**starfury1** · 07-30-2007, 05:33 AM

Re: Sampo 70FA2 series LCD..... briefly works.

with load it would probably pull down a bit and 2 volts shouldn't make much diff
The circuits are probably run from a regulator(s) anyway but it a bit hard for me to judge that...there is one for sure but the current seems a bit small 500 ma
although I didn't check it out totally from the above doc's link

As I said possibly the inverter may be loading it down due to a fault but its not the only possibly.

**stevo1210** · 07-30-2007, 06:31 AM

Re: Sampo 70FA2 series LCD..... briefly works.

I just measured the voltage of the power supply with the LCD monitor attached and turned on.

The two volt meter probes are attached to the red and black wires where the power cable from the power supply meets up with the cables coming out of the back of the LCD.... hopefully I've done this correctly.

When I first turn on the external power supply, I get an nice image on the screen.
The voltage at that moment measures 12.00V exact.

After half a second, the voltage falls to 10V, by this stage I can see the monitor starting to fade very slightly.

Then after another half second, the voltage drops to 7 or 8V, the image fades out alot now, it is also very dark by now too.

The next second or so, the monitor goes out completely, with the LED on the front of the LCD still green.
The voltage at that moment is about 4 or 5V.

The voltage then slowly drops to about 3 or 4V, by this time, it stabilises it self around 3 or 4V and stays like that.

I then decided to turn off the power supply, wait a minute or two and turn it back on, the exact same happens, but the figures aren't quite the same, it starts at 11.80 then it first drops to 11V and then goes down straight to 6V or so. It then stabilises itself at 3V.... there is no image on the LCD either.

Is my power supply telling me there's something wrong because the voltage is dropping so much?? If I remember correclty, shouldn't the power from the power supply always be a continous 12V supply??

Can a weak power supply cause issues with the screen fading out and completely going blank??

Thanks.

**stevo1210** · 07-30-2007, 06:47 AM

Re: Sampo 70FA2 series LCD..... briefly works.

Originally posted by stevo1210

I then decided to turn off the power supply, wait a minute or two and turn it back on, the exact same happens, but the figures aren't quite the same, it starts at 11.80 then it first drops to 11V and then goes down straight to 6V or so. It then stabilises itself at 3V.... there is no image on the LCD either.

I need to rewrite this section. It sounds a bit confusing....

I turn off the power supply after the first testing and wait a minute or two. I then turn it back on.
The exact thing happens like before.... I get a nice image on the screen, but this time it only lasts for 2 or 3 seconds because I haven't unplugged it for very long.
The voltage readings aren't the same as before though. The voltage starts off at 11.80V, and drops to 11V in an instant.
After a second or so, the voltage drops down to 6 or 7 volts. By this time, the image also fades out completely and I see nothing but a blank screen.
The voltage then stabilises at 3 or 4V just like the test before.

Thanks.

**kc8adu** · 07-30-2007, 06:51 PM

Re: Sampo 70FA2 series LCD..... briefly works.

i would open up the psu and have a look.
i would also try to run it from a +12 line on a pc psu with a 5a fuse in series.
i service lcd units in industrial robots used to load barrels and crates of beer.
the psu in the main unit goes bad and acts exactly like this.
i have a ups battery i wired up for my icom w2 ht.same plug.5 second test.
i run units under test with it too.

**starfury1** · 07-30-2007, 11:52 PM

Re: Sampo 70FA2 series LCD..... briefly works.

Thanks KC8...hoping you would add your comments as I know you have a fair amount of experience with these.

The psu was my first guess and thats why its important to check the supply rails (of anything you service first.)

Is my power supply telling me there's something wrong because the voltage is dropping so much?? If I remember correclty, shouldn't the power from the power supply always be a continous 12V supply??

To answer your question

Yes your psu if stated @ 12V should be close to it always
this is what is meant by "regulated"...if its 12 volts it maintains that regardless of current drawn (100 mA or 1A5 it should remain close to 12 Volts)

So thats probably your best bet try another psu to confirm it is the psu thats gone

As KC8 said above , stuffed psu causes these type of symptoms

On my first look at the post
I couldn't see the PSU...(but know some have external psu)....ok solved that one it did have one but it went belly up so was replaced with a similar spec device (external).
(from your posts)

since you dont have one you could get this item from Jaycar for testing stuff

CAT. NO. MP3036

3, 5, 6, 9, 12, 13.8 VDC 2.5A- Switchmode Switchable Power Supply $50
(2A2 @13V8)

The only thing is watch the polarity!, make sure + is + and - is - when you connect it up.

Side point here

There are a few ways you can safe guard against reverse polarity (inside the monitor) and maybe it has this....doubt it thought if it originally used a internal SMPSU

They also carry a 12 Volt (only) 4 Amp version CAT. NO. MP3240 $60
Here

Again watch the polarity!

This would be my choice.
(2 amps max sound like its cutting it a bit fine, more work on the psu)

Another alternative is flea markets and Ebay maybe you will get one cheap.

It is possible you could repair the old one
(depending on whats wrong I suppose)

If you are going to test stuff its handy to have some type of Bench psu for this.....there are even ways to mod a ATX computer supply to be a bench testing supply.
(KC8 was talking about using this as a test psu for the monitor)

Anyway get another PSU and test it, sounds like, from KC8 experience its gone belly up too....

Cheers

**stevo1210** · 07-31-2007, 02:14 AM

Re: Sampo 70FA2 series LCD..... briefly works.

Originally posted by starfury1

To answer your question

Yes your psu if stated @ 12V should be close to it always
this is what is meant by "regulated"...if its 12 volts it maintains that regardless of current drawn (100 mA or 1A5 it should remain close to 12 Volts)

So thats probably your best bet try another psu to confirm it is the psu thats gone

As KC8 said above , stuffed psu causes these type of symptoms

Well, I found the problem after opening up the external power supply and having a closer look....

Look into the picture and see what I mean.

I don't know who wired it up to the "Battery" section, but after I wired it back into the section that's labelled "DC output", the LCD monitor turned on right away and stayed like that too.
The voltage is now a continuous 13V DC. Just a bit higher than the 12V, but at least the LCD works now....

Thank you everyone for the help and advice on the problems with this LCD monitor.

Now I have a decent LCD monitor to use as a TV set in my room......

just have to buy a TV tuner card to allow that to happen though.....

Thanks.

**kc8adu** · 07-31-2007, 02:41 AM

Re: Sampo 70FA2 series LCD..... briefly works.

get the 3m/microtouch drivers and you have a touchscreen!
just noticed the board and the ribbon cable the the calibration sticker.

**starfury1** · 07-31-2007, 03:16 AM

Re: Sampo 70FA2 series LCD..... briefly works.

well that says it all...now how did that happen ??????

I would haven't picked that

Still good to know its going.....yeah it is a touch screen

I was thinking it was using a one like the above as a replacement BTW
(and they are buggers to get open if rf sealed (whatever) and not screwed

Cheers

**stevo1210** · 07-31-2007, 03:29 AM

Re: Sampo 70FA2 series LCD..... briefly works.

Originally posted by starfury1

well that says it all...now how did that happen ??????

I have no idea how someone could connect the wires up wrongly, but I think this power supply may have been used for some other purpose before it was handed to me.
I have no idea why there's a battery terminal.... maybe it's to power battery run circuits??

Originally posted by starfury1

Still good to know its going.....yeah it is a touch screen

It's a touch screen, but there's no touch screen cable....

I think the touch screen cable is a serial/ COM cable. The connection port on the LCD looks exactly like a serial port.

The drivers are going to be the big problem though. From an image I took of the LCD, the touch screen module says Micro- something.
Microtouch maybe??

I am not going to open up the LCD again either because it's going to be very hard to pull apart and put back together again...... This monitor uses a range of plastic clips and screws to hold it together....

Thanks.

**starfury1** · 07-31-2007, 04:10 AM

Re: Sampo 70FA2 series LCD..... briefly works.

sounds like the usual nightmare to open.

most likely it does use a com port serial....I wouldn't worry about it unless you have a real need of touch screen input
(leaves wear marks after time anyway, depending)

I thought that was the psu you were using with it and yes it is not what I was expecting but if its works why not

anyway hope it serves you well mate

Cheers

**Maxxarcade** · 08-02-2007, 08:06 PM

Re: Sampo 70FA2 series LCD..... briefly works.

That is a Microtouch controller. You can get the drivers from their website, and it is a normal RS-232 serial port.

The power supply appears to be for a security/burglar alarm system. You connect a battery to it and it functions as a UPS. The reason the voltage was dropping off at the battery terminals is because of the charging circuit. When a battery is fully charged it draws less current, so the charger shuts down.

So when the monitor is connected, it will draw more power when it is cold. After it warms up and the current goes down, the charging circuit thinks a fully charged battery is attached and goes into trickle mode. At least that's how I see it

**starfury1** · 08-02-2007, 10:19 PM

Re: Sampo 70FA2 series LCD..... briefly works.

Yeah that was my thought on the psu since it had battery terminals probably an alarm system psu

No thats very interesting maxxacade

your analysis of "why and how" it did then didn't work from the Batt terminals

I didn't think about that later and was thinking at the time the psu he had was stuffed and drifting all over the place
(at that point didn't know what the psu was, only that it was a ring in and not the monitors original...I thought it may have been one like I posted links to)

Cheers

**kc8adu** · 08-03-2007, 02:35 AM

Re: Sampo 70FA2 series LCD..... briefly works.

http://solutions.3m.com/wps/portal/3.../TouchDrivers/
i work with these units every day.

Sampo 70FA2 series LCD..... briefly works.

Sampo 70FA2 series LCD..... briefly works.

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