VX 724 black screen green light flashing

[Jasgriff]

Re: VX 724 black screen green light flashing

Hi Nocta,

Just a few bits...

To give you an idea of what the regulars are finding confusing I will show you what you are getting on 2 of the regulators compared with what you should be betting....

U1

Pin 1 (left): 4.96v Should be ( 5V so this is close enough )
Pin 2: 3.94v Should be ( 3V 25% out of spec )
Pin 3: 2.70v

U3

Pin 1: 4.96v Should be ( 5V so this is close enough )
Pin 2: 3.94v Should be ( 2.5v This is massively out )
Pin 3: 2.25v

Something is very strange about the fact that both of the output readings that you have given are exactly the same.

I have attached a diagram which shows you where each pin number is. Can you look at this diagram and use that as a reference when giving us readings from pin numbers as i'm sure they are the wrong way around.

I know you have said that you have replaced some caps and you removed some caps to get to the Voltage regulators. Can you you confirm if you have changed the following? if so can you tell us what you replaced them with? EC1, EC2, EC3, EC4, EC5 and EC6

Can you also check that EC5 is definitely in the the correct way around and all of the others too please. ( Its hard to tell from the pictures but it looks like I get can see more white under that EC5 cap on the + side of it ).

[budm]

Re: VX 724 black screen green light flashing

Nothing close to the diagram I supplied.

[retiredcaps]

Re: VX 724 black screen green light flashing

U1

Pin 1 (left): 4.96v
Pin 2: 3.94v
Pin 3: 2.70v

U3

Pin 1: 4.96v
Pin 2: 3.94v
Pin 3: 2.25v

Hmm, those still look incorrect to me, but trying test the new regulators to see if they are shorted or not.

[Nocta]

Re: VX 724 black screen green light flashing

Hmm, those voltages look a bit low too me, but they could be right depending on the VR on the other board. See below.



What is the reading for this VR with the two new ones installed? If it is shorted, we can recommend a replacement.



For cold ground, either use the chassis or a ground screw on the logic board. Using the heatsink for ground is quite dangerous as it may be live with high voltage.

On the other, you get one bonus point for showing a picture of your multimeter.

U1

Pin 1 (left): 4.96v
Pin 2: 3.94v
Pin 3: 2.70v

U3

Pin 1: 4.96v
Pin 2: 3.94v
Pin 3: 2.25v

1084

Pin 1: 4.77v
Pin 2 (cutted): 3.30v
Pin 3: 2.05v

Voltages are quite different now. I used the ground screw of the power board.

I don't know what the exact voltages were before because I replaced the VR.

[budm]

Re: VX 724 black screen green light flashing

I have a feeling that heatsink for MOSFET on the hot side is not tied to the chassis ground, which may explain the reading of the voltages in the early posts did not look right.

[selldoor]

Re: VX 724 black screen green light flashing

I laughed as well, actually when I saw the pic I knew there would be a comment
about the probe and the meter. Just proves I spend too much time on here.

[Jasgriff]

Re: VX 724 black screen green light flashing

On the other, you get one bonus point for showing a picture of your multimeter.

I LOLLED at that.... It should be compulsory....

I definitely agree with Retired caps on the skill full balancing of the negative probe. If that head sink was live you might have some real issues if it touched.

[retiredcaps]

Re: VX 724 black screen green light flashing

From left to right, VR (U1 & U3) read 1,18-1,22v.

Hmm, those voltages look a bit low too me, but they could be right depending on the VR on the other board. See below.

I didn't replaced the VR next to VTI03601 because I can't find its datasheet. I don't know if AS1117 should work too. The name is 1084 - 0527CL (I can't find the datasheet).

What is the reading for this VR with the two new ones installed? If it is shorted, we can recommend a replacement.

Black lead on ground (mosfet dissipator) and red lead on each pin.

For cold ground, either use the chassis or a ground screw on the logic board. Using the heatsink for ground is quite dangerous as it may be live with high voltage.

On the other, you get one bonus point for showing a picture of your multimeter.

[selldoor]

Re: VX 724 black screen green light flashing

Pretty sure it will be an as1084

[Nocta]

Re: VX 724 black screen green light flashing

From left to right, VR (U1 & U3) read 1,18-1,22v.

I didn't replaced the VR next to VTI03601 because I can't find its datasheet. I don't know if AS1117 should work too. The name is 1084 - 0527CL (I can't find the datasheet).

Black lead on ground (mosfet dissipator) and red lead on each pin.

[selldoor]

Re: VX 724 black screen green light flashing

Post some pics front and back of the damage zone.

[Jasgriff]

Re: VX 724 black screen green light flashing

Something is definately not right with those readings. If you test them again can you write down the exact readings so we can see what's going on.

[retiredcaps]

Re: VX 724 black screen green light flashing

you may want to check your works real close again.

Yes. In particular see if the new regulators are shorted or not.

[Nocta]

Re: VX 724 black screen green light flashing

It looks just like before changing the VR.

I'm gonna try later. I'll also buy a couple of new caps and replace the ones I burnt.

[budm]

Re: VX 724 black screen green light flashing

Something does not sound right, you may want to check your works real close again. By the way, what does the picture on the screen look like now?

[Nocta]

Re: VX 724 black screen green light flashing

Now less than 2v but I think that I burned some caps using the soldering iron. I burned the plastic of a couple of them (even though I took them off for soldering the VR).
A couple of minutes ago, I got more than 9v more or less.

[budm]

Re: VX 724 black screen green light flashing

What voltage reading are you getting now?

[Nocta]

Re: VX 724 black screen green light flashing

I changed the VR and still no joy :/ I replaced them with AS1117.

[budm]

Re: VX 724 black screen green light flashing

I use Weller PTC7 (1/8", 3mm) for de-soldering works and PTA7 for soldering work on my old faithful Weller soldering station.
http://compare.ebay.com/like/2510385..._lwgsi=y&cbt=y

[retiredcaps]

Re: VX 724 black screen green light flashing

I cut the legs and add more solder to the tab, the trick is to use wide tip soldering iron with at least 40watts.

Is your definition of wide at least 3.2mm? I have one of these tips on order as my current one is 1.6mm.