visio vx37l resistor indentity help

[budm]

Re: visio vx37l resistor indentity help

Thanks for the follow-up on the repair.

[sdinelli]

Re: visio vx37l resistor indentity help

well finally had time to get the part and replace the 16pin IC.
and guess what it works!
Feels good.

thank you everyone for your assistance

[sdinelli]

Re: visio vx37l resistor indentity help

UGH I'm pissed I got all the parts and installed everything. when I got to the IC it turned out I ordered the 16-DIP and not the surface mount. gerr

Should have just bought the board for 35$

[budm]

Re: visio vx37l resistor indentity help

I would replace both MOSFETs since they work together.

[sdinelli]

Re: visio vx37l resistor indentity help

Welp, The one mosfet is bad. doesn't turn on. the other I was able to turn off and on.
Will order:
x2 .22ohm resistor
x1 4.7ohm smc resistor
x1 IC L6598
x1 MOSFET (STP12NM50FP)

Will report back when installed and tested

[sdinelli]

Re: visio vx37l resistor indentity help

I asked about how you test the IC in post 36, and you reply "LOL oops i already tested it. nothing blew up." in post 37.
Bottom line: replace the IC beside the MOSFETs +any damaged Gate drive network.

I shouldn't have used the word tested.
I just meant I turned it on and nothing blew up.
All I really know about the IC is that I have 10.66V on pin 12(Vs) I think that's above the threshold to turn it on.
I didn't have the schematic when I was poking around.

So ill should pull the mosfets to Test them and see if I need some or not right?

[budm]

Re: visio vx37l resistor indentity help

I asked about how you test the IC in post 36, and you reply "LOL oops i already tested it. nothing blew up." in post 37.
Bottom line: replace the IC beside the MOSFETs +any damaged Gate drive network.

[sdinelli]

Re: visio vx37l resistor indentity help

How did you test the IC? If one of the output stuck high then one of the MOSFET will be fully on and when the other out put goes hing then you will have two MOSFETs conduct at the same time which will be bad news for the new MOSFETs. You do not want half- bridge drive circuit to have two MOSFETs on at the same time. The resistor/diode network will be damaged when the 400VDC from the Drain pin is dumped through the GATE and the output Gate drive of the IC. When you find bad GATE resistor that is a sure sign of damaged Gate drive output.

"measuring the voltage drop from Gate to source in circuit i get .056V. On the other mosfet i get OL." That means the Voltage was too high for the meter to display the Voltage reading.

I tested the mosfets in circuit, black lead on source red lead on gate, then switched them. got .56V both directions. I also measured it in ohms and got around 60ohms.
Ialso tested with black lead on source and red lead on drain and got ~.500V
reverse biased I got OL.

The other one, I got OL in all directions other than drain to source, which I got ~.500V drop.

Do I need to test these out of circuit to be sure?

obviously I need to replace 4.7ohm resistior, two .22ohm resistors and ic601

[budm]

Re: visio vx37l resistor indentity help

LOL oops i already tested it. nothing blew up.

I found another blown resistor on the gate.. R622 4.7ohm.
its reading OL
The one right by it is a 22r1(R619) and that's good

The 4.7ohm resistor(R623) on the other gate is still good.

it seems the only trace leading directly to the IC with out passing through another component is pin 14. labeled "OUT- high side driver reference"

How did you test the IC? If one of the output stuck high then one of the MOSFET will be fully on and when the other out put goes hing then you will have two MOSFETs conduct at the same time which will be bad news for the new MOSFETs. You do not want half- bridge drive circuit to have two MOSFETs on at the same time. The resistor/diode network will be damaged when the 400VDC from the Drain pin is dumped through the GATE and the output Gate drive of the IC. When you find bad GATE resistor that is a sure sign of damaged Gate drive output.

"measuring the voltage drop from Gate to source in circuit i get .056V. On the other mosfet i get OL." That means the Voltage was too high for the meter to display the Voltage reading.

[sdinelli]

Re: visio vx37l resistor indentity help

actually.. when i first replaced the mosfets and powered up the unit. i did here a buz coming from that area.
I never heard it again other times when powering up.

measuring the voltage drop from Gate to source in circuit i get .056V
On the other mosfet i get OL.

[sdinelli]

Re: visio vx37l resistor indentity help

That IC601 is probably has blown Gate drive outputs when MOSFET's went out. I would not take a chance on a new pair of MOSFET's without replacing the IC at the same time.

LOL oops i already tested it. nothing blew up.

I found another blown resistor on the gate.. R622 4.7ohm.
its reading OL
The one right by it is a 22r1(R619) and that's good

The 4.7ohm resistor(R623) on the other gate is still good.

it seems the only trace leading directly to the IC with out passing through another component is pin 14. labeled "OUT- high side driver reference"

[budm]

Re: visio vx37l resistor indentity help

That IC601 is probably has blown Gate drive outputs when MOSFET's went out. I would not take a chance on a new pair of MOSFET's without replacing the IC at the same time.

[sdinelli]

Re: visio vx37l resistor indentity help

They are 0.22 Ohms.
For them to go open circuit or high resistance like that the MOSFETs are probably bad, or the Gate drive stuck high instead of switching.
Fusible resistor R805 which feeds the supply Voltage from the main cap to the transformer primay is still good?

both MOSFETs were blown open.
and R805 was burnt up.
Replaced all 3 and not getting voltage on the Gates, which is when i found these two resistors...

Do you think replacing these two will more than likely fix the issue or do you think the surge took out the IC601?? i was going to replace the ic with thishttp://www.st.com/content/ccc/resour...CD00001777.pdf


R623 is good and the two 20Kohm resistors connecting the gate and source are also good

[budm]

Re: visio vx37l resistor indentity help

They are 0.22 Ohms.
For them to go open circuit or high resistance like that the MOSFETs are probably bad, or the Gate drive stuck high instead of switching.
So the Fusible resistor R805 which feeds the supply Voltage from the main cap to the transformer primary is still good?

[sdinelli]

Re: visio vx37l resistor indentity help

what are these two resistors values support to be??
I pulled them and R621B tested 34.5ohms and R621A tested 1.945Mohms
From what colors i see they should be .22ohms right?

What function do these resistors perform? I see they connect the source to the ground.

[sdinelli]

Re: visio vx37l resistor indentity help

testing with the transformer removed resulted in no change.
http://html.alldatasheet.com/html-pd...3/2/L6598.html
Based on this schematic
pin 12/Vs = 10.66Vdc
pin15/HVG = is what traces to the gate. very sporadic like a short to ground but with flashs of a low voltage such as .4vdc

[sdinelli]

Re: visio vx37l resistor indentity help

ohhh right the ones attached to the heatsinks. duh

[sdinelli]

Re: visio vx37l resistor indentity help

c610 = .021uf/21.9nf ESR 80ohm
Which diodes are you referring to? the surface mount ones or the zener's on the front?

[budm]

Re: visio vx37l resistor indentity help

Those are the Gate discharge diodes. I am talking about the rectifier diodes in the cold side for this 12V/24 power supply section.

[sdinelli]

Re: visio vx37l resistor indentity help

D604 & D605 (attached to the gate of both transistors) both measure a voltage drop of.021Vdc both ways. but theyre also run parallel to a 22.1ohm resistor. which tests good.
Does this sound fishy?
both diodes labeled 5Dx