Neovo F-419 no power.

[Rtech]

Re: Neovo F-419 no power.

Recently we have had a few cases where the problem was the 'organism' holding the probes.

PlainBill[/QUOTE]

Gave me a good start to the day,thanks Bill.

[PlainBill]

Re: Neovo F-419 no power.

Yes you labeled pin1 correct.
V- to U801 pin1 =0.9
V- to U801 pin3 = no read
V- to U801 pin6 =1.2
R821 to U801 pin3 = 0.9
did not get any reading past R821

Ps.
Is there any way to make my crapy DMM better?

The resistance readings are what I would expect. Next, let's try voltage measurements. All readings will be made with the black probe on V-. Rather than specify the voltage range to use, set the meter to the 1000 VDC range, then go to the next lower range if the reading is within that range. (For example, you measure the voltage on U801, pin3. It reads about 160 volts, Reduce the range to the 200 VDC range and measure again.)

Now plug in the power cord and carefully make these measurements.
V- to U801 pin1
V- to U801 pin3
V- to U801 pin6

The best way to make a crappy DMM better is to sell it and buy a new one. Recently we have had a few cases where the problem was the 'organism' holding the probes.

PlainBill

[playman]

Re: Neovo F-419 no power.

Yes you labeled pin1 correct.
V- to U801 pin1 =0.9
V- to U801 pin3 = no read
V- to U801 pin6 =1.2
R821 to U801 pin3 = 0.9
did not get any reading past R821

Ps.
Is there any way to make my crapy DMM better?

[PlainBill]

Re: Neovo F-419 no power.

R822=814 or 814kohm, wich is well with in the 5% tolerance.
I put it back in and checked a reading between them and got 1491kohm


I was going to say HAH you just gave me the answer earlyer, was going to say well ofcourse 470kohm,
then,
hey wait a minute what's that 0 there, so i'm guessing it's 0-1-2-3-etc..
so a 470 would give me 4.7kohm? (man I have no idea how I got that number lol)
but then as I was not 100% sure so I checked the net and 470 should be 47ohm right?

Acording to this site http://www.electronicrepairguide.com...stor-code.html
those SMD's are just like the color resistors except they use numbers instead of color code?
SMD and SMT are the same?

You are correct, it's 47 ohm. And SMD and SMT are used interchangeably, although I suppose one is preferred, I just don't know (or care) which.

This of course doesn't help explain the original problem, so lets see if we can figure out what is going on with the SMPS controller. To that end, I've crudely marked up your picture of the bottom of the power supply, labeling a few points of interest.

V- is the negative side of the rectified AC, V+ is the positive side. I believe you indicated that was 320 volts. I've also marked the rough boundaries of the hot side of the SMPS in yellow. Lastly, I've numbered the SMPS controller in orange - assuming the lower right corner is pin 1.

With AC power disconnected and the DMM on the 200 ohm range, what is the resistance between V- and U801, pin 1? Between V- and U801, pin 3? Between V- and U801, pin 6? Between the upper end of R821 and U801, pin 3?

PlainBill
Wit

[playman]

Re: Neovo F-419 no power.

Shoot!!! That indicates the resistor is good. Check R822, please.

R822=814 or 814kohm, wich is well with in the 5% tolerance.
I put it back in and checked a reading between them and got 1491kohm

Some parts are 'jelly bean' parts - available from multiple companies and interchangeable. For decades the standard resistor used in electronics was a 1/2 watt leaded carbon composition resistor with a 20% tolerance. As electronics moved away from vacuum tubes, current demands dropped, and better materials became available this evolved to the 1/4 watt metal film 5% tolerance leaded resistor. With surface mount, the standard resistor is now a 1/8 watt metal film SMT resistor.

To answer your question, all of the other components that look like R821 and have an R designation are resistors; the only difference between them would be the resistance. R821 should have the numbers 684 on the top - 68 followed by four zeros, or 680000 ohms, or 680K ohm. I'll let you tell me what a 470 ohm resistor would say.

PlainBill

I was going to say HAH you just gave me the answer earlyer, was going to say well ofcourse 470kohm,
then,
hey wait a minute what's that 0 there, so i'm guessing it's 0-1-2-3-etc..
so a 470 would give me 4.7kohm? (man I have no idea how I got that number lol)
but then as I was not 100% sure so I checked the net and 470 should be 47ohm right?

Acording to this site http://www.electronicrepairguide.com...stor-code.html
those SMD's are just like the color resistors except they use numbers instead of color code?
SMD and SMT are the same?

[PlainBill]

Re: Neovo F-419 no power.

Allright I'll keep that in mind, but after I read your reply, I relalised one thing, I only checked 200, 2000 and 20k ohm,
so I went a checked it with the remaining settings.
On 2000k ohm I got a reading of 675, wich would be 675k ohm I guess.

Shoot!!! That indicates the resistor is good. Check R822, please.

Allright now I have to ask you, what do you mean by standard SMT device?
so all R821 "look alike" chips are resistors with different stats?
I'm sorry i'm not quite understanding how to find those components
I'm just used to just read of the component and search for those numbers.

Some parts are 'jelly bean' parts - available from multiple companies and interchangeable. For decades the standard resistor used in electronics was a 1/2 watt leaded carbon composition resistor with a 20% tolerance. As electronics moved away from vacuum tubes, current demands dropped, and better materials became available this evolved to the 1/4 watt metal film 5% tolerance leaded resistor. With surface mount, the standard resistor is now a 1/8 watt metal film SMT resistor.

To answer your question, all of the other components that look like R821 and have an R designation are resistors; the only difference between them would be the resistance. R821 should have the numbers 684 on the top - 68 followed by four zeros, or 680000 ohms, or 680K ohm. I'll let you tell me what a 470 ohm resistor would say.

PlainBill

[playman]

Re: Neovo F-419 no power.

For clarity, please NEVER use 'no ohm reading' unless you qualify it with the range - 'no ohm reading on the 20 Megohm range' - as an example, 'reads open on all ranges' is better.

Allright I'll keep that in mind, but after I read your reply, I relalised one thing, I only checked 200, 2000 and 20k ohm,
so I went a checked it with the remaining settings.
On 2000k ohm I got a reading of 675, wich would be 675k ohm I guess.

R821 is a standard SMT device, Panasonic ERJ-6GEYJ684V is one choice; Digikey has over 168,000 of them at .04 each. Double check the size.

PlainBill

Allright now I have to ask you, what do you mean by standard SMT device?
so all R821 "look alike" chips are resistors with different stats?
I'm sorry i'm not quite understanding how to find those components
I'm just used to just read of the component and search for those numbers.

[PlainBill]

Re: Neovo F-419 no power.

I belive it's broken, I get no ohm reading of it

How can I search for it's datashet?
I searched for SD011680300 S RES and had no luck.

For clarity, please NEVER use 'no ohm reading' unless you qualify it with the range - 'no ohm reading on the 20 Megohm range' - as an example, 'reads open on all ranges' is better.

R821 is a standard SMT device, Panasonic ERJ-6GEYJ684V is one choice; Digikey has over 168,000 of them at .04 each. Double check the size.

PlainBill

[playman]

Re: Neovo F-419 no power.

NOW, either you are not measuring the voltages correctly, or R821 is defective. The problem is you will have to remove R821 to test it.

I belive it's broken, I get no ohm reading of it

How can I search for it's datashet?
I searched for SD011680300 S RES and had no luck.

[PlainBill]

Re: Neovo F-419 no power.

I did that soon as I had finished testing it


There you got me, i'm not sure how I would do that, could you draw a line on the picture for me? so I could se how you would figure that route out.
I did not find the IC801, did you mean U801 maybe?
Reflow, does that mean I should heat up the solder or remove it and re-solder it?
But I just went trough the whole area where we have been working on and heated the solder(wich is inside the black line)


I got 316 now, is there any possibility that I might be testing wrong joints?
Is there any reason why I should change the R822 and not R821? just asking.
what do you mean by "see if you get output voltages" talking about the P803 wires?

Sorry I wasn't clearer, I was rushing. I'm not up to marking up pictures this morning, so will refer to the schematic, then explain some terms.

If you look at the schematic, AC power comes in at P801, goes through some filters to black noise and then to BD801. Which converts it to DC. The DC is filtered by C805, and then goes through R800, a fusible resistor. The main current path is through T801, L803, Q801, and the unholy mess of R819, R819A, R820, and R820A.

Q801 is the power FET, and is controlled by U801 pin 8. While the power supply is operating, power for U801 comes from T801 pin 6, D802, R807, and is filtered by C809.

If you look at this circuit you can see that there will be voltage at pin 6 of T801 only when Q801 is switched on, and U801 must have power to do that. But U801 gets it's power from T801. How does this process start???

For that, trace the path R822, R821, U801 pin 3. When AC power is applied C805 charges up to 320 volts very quickly. The voltage is dropped across R822 and R821. Typically we see about 20-30 volts at U801 pin 3. U801 contains a switched constant current source which charges C809. When the voltage across C809 reaches 16 volts U801 starts sending pulses to Q801, U801 gets power from T801, and the constant current source is switched off.

Now R822 and R821 are in series. R822 is 820 Kohms, R821 is 680 Kohms, so the total resistance is 1.5 Megohms. They form a voltage divider, I would expect to see 20 volts at u801 pin 3 and the left end of R821, 155 volts at the right end of R821 and left end of R822, and of course, 320 volts at the right end of R822. (Left and right refer to the schematic, that corresponds to top and bottom in the picture).

NOW, either you are not measuring the voltages correctly, or R821 is defective. The problem is you will have to remove R821 to test it.

'Reflow solder' means to heat it up with a soldering iron so it will flow and hopefully fill any gaps.

If you were getting the correct voltages at R821, R822 I would have expected U801 to be working, and you should have gotten output voltages at P803.

PlainBill

[playman]

Re: Neovo F-419 no power.

1. If you haven't already done so, solder D802 back in place. It tests good.

I did that soon as I had finished testing it

2. Trace the circuit from the + lead of the large cap through R821 and R822 to IC801, pin 3. Look for bad solder joints. If you don't find any, reflow the solder on each of those pins.

There you got me, i'm not sure how I would do that, could you draw a line on the picture for me? so I could se how you would figure that route out.
I did not find the IC801, did you mean U801 maybe?
Reflow, does that mean I should heat up the solder or remove it and re-solder it?
But I just went trough the whole area where we have been working on and heated the solder(wich is inside the black line)

3. Now hook up the power cord and retest. If you get about 145 volts at the junction of R821-R822 see if you get output voltages. If you don't get 145 volts, replace R822.

I got 316 now, is there any possibility that I might be testing wrong joints?
Is there any reason why I should change the R822 and not R821? just asking.
what do you mean by "see if you get output voltages" talking about the P803 wires?

[PlainBill]

Re: Neovo F-419 no power.

D802=560 and open the other way (I belive "1" means open right?)

U801=3.80 it also was quite fluctuating sometimes showed 0.0v and upto 3.60v depending on if I moved then pin or not.

junction of R821 and R822=315v steady

Those readings indicate a problem, I'm not sure exactly where it is. R821 is 820K, R822 is 680K. (Initially I had assumed they were equal my mistake). I would expect 145 volts at the junction.

Here are some additional tests.

1. If you haven't already done so, solder D802 back in place. It tests good.

2. Trace the circuit from the + lead of the large cap through R821 and R822 to IC801, pin 3. Look for bad solder joints. If you don't find any, reflow the solder on each of those pins.

3. Now hook up the power cord and retest. If you get about 145 volts at the junction of R821-R822 see if you get output voltages. If you don't get 145 volts, replace R822.

PlainBill

[playman]

Re: Neovo F-419 no power.

D802=560 and open the other way (I belive "1" means open right?)

U801=3.80 it also was quite fluctuating sometimes showed 0.0v and upto 3.60v depending on if I moved then pin or not.

junction of R821 and R822=315v steady

[PlainBill]

Re: Neovo F-419 no power.

So if I probe red on negative and get a reading going from 100 towards the "1" signal does that mean the diode is broken?
so D980-D983 could be bad diodes?
And the D801 is also broken since it gives readings of .018v wich is under 0.4v, right?


thanks for that, reading rarely gives me the information but it can help me, but asking relative questions give me the most information,along with doing the repair or work my self.

D801 is good - you got 568 in one direction, open in the other.
D802 reads 018 in both directions. That indicates a problem.
D980-D983 are probably good. We will ignore them for now.

Earlier you had mentioned that you had 0 volts across C809. This is a problem. There are several possible causes. A bad D802 is one of them. Unsolder one end of D802 and check it. If it reads about .5 volts '500 - 600' in one direction and open in the other it is good, solder it back in. If it still reads 018, replace it.

This next test involves dangerous voltages, so be careful. Work on an insulated surface. The power supply / inverter should be disconnected from the signal card and the LCD panel. Set your DMM to the 20 volts DC range. Hook up the power cord. CAREFULLY measure the voltage from pin 1 (Gnd) to pin 3 (Vin) of U801. It should read about 16 volts. If it reads 0 volts, reset your DMM to the 200 volt range and read the voltage at the junction of R821 and R822. It should read about 160 volts. Disconnect the power cord and take a deep breath. Wait several minutes before touching the power supply.

Additional information. At this point there are three prime suspects. In order they are U801, D802, C809. U801 is notorious for failing.

PlainBill

[playman]

Re: Neovo F-419 no power.

I also checked the D980-D983 just for fun, they read,
black on negative, 215-213 all 4
Red on Negative, they go over 2000 and then the screen just show's "1"

So if I probe red on negative and get a reading going from 100 towards the "1" signal does that mean the diode is broken?
so D980-D983 could be bad diodes?
And the D801 is also broken since it gives readings of .018v wich is under 0.4v, right?

Ask away!! We all learn by different methods. I find that reading gives me the information but it fades quickly; actually using the information 'locks it in place'.

thanks for that, reading rarely gives me the information but it can help me, but asking relative questions give me the most information,along with doing the repair or work my self.

[PlainBill]

Re: Neovo F-419 no power.

( I belive that silver end of the diode or the end that goes into the black whole on the PCB is the negative)
First number is with the black probe on Negative.
D802=018 both way's
D801=568 then 0 the other way ( the LCD does not change, "1" just stay's on, so my gues it's not conducting)

I also checked the D980-D983 just for fun, they read,
black on negative, 215-213 all 4
Red on Negative, they go over 2000 and then the screen just show's "1"

TVS1=565 no reading the other way.

D842=452 then otherway it goes past 2000

what does 568 or 452 mean? 5.68V and 4.52V?

Your decimal point is off. 568 means .568 volts; a typical voltage for a standard diode. 213 would of course be .213 volts, which would indicate a schottky diode.

If the meter shows "1" on the left side, does it means that there was no conductivity in the diode mode?
(like the meeter does not know if i'm testing with it? and is that a good thing, if the probe is on negative?)

That's normal. A diode conducts electricity in only one direction. Commonly for the diode test function the meter will put out a maximum of slightly over 2 volts at low current, with the red lead positive. It displays the voltage across the leads with a maximum of 1.999 volts. In the reverse direction a good diode will not conduct, so it will act like the probes aren't touching anything.

Sorry for the questions and crude testing and testing report, I'm just trying to learn in my way,
as I have a short span (AD/HD) so reading long text's and stuff that does not directly fit to my problem description can be hard,
so I'm trying to learn by using my method. (also language differental does not help lol

Ask away!! We all learn by different methods. I find that reading gives me the information but it fades quickly; actually using the information 'locks it in place'.

PlainBill

[playman]

Re: Neovo F-419 no power.

Diodes should be measured using the diode test function on your multimeter.

A good diode read between 0.4 and 0.7V one way and "0L" or "1" ("1" on the left hand side) the other way.

So put black probe on one side and red on the other. Take reading. Now reverse probes and take another reading.

( I belive that silver end of the diode or the end that goes into the black whole on the PCB is the negative)
First number is with the black probe on Negative.
D802=018 both way's
D801=568 then 0 the other way ( the LCD does not change, "1" just stay's on, so my gues it's not conducting)

I also checked the D980-D983 just for fun, they read,
black on negative, 215-213 all 4
Red on Negative, they go over 2000 and then the screen just show's "1"

TVS1=565 no reading the other way.

D842=452 then otherway it goes past 2000

what does 568 or 452 mean? 5.68V and 4.52V?
If the meter shows "1" on the left side, does it means that there was no conductivity in the diode mode?
(like the meeter does not know if i'm testing with it? and is that a good thing, if the probe is on negative?)

Sorry for the questions and crude testing and testing report, I'm just trying to learn in my way,
as I have a short span (AD/HD) so reading long text's and stuff that does not directly fit to my problem description can be hard,
so I'm trying to learn by using my method. (also language differental does not help lol

[jetadm123]

Re: Neovo F-419 no power.

Due to the 0.8 ohm offset on your meter, I would say that R800 is probably good. Also, since you're getting a out of range reading on Q801, it's probably also good.

[retiredcaps]

Re: Neovo F-419 no power.

D801= 78.1 @ 200ohm on DMM it reads 78 for a split second then 0
D802= 17.6 @ 200ohm on DMM

Diodes should be measured using the diode test function on your multimeter.

A good diode read between 0.4 and 0.7V one way and "0L" or "1" ("1" on the left hand side) the other way.

So put black probe on one side and red on the other. Take reading. Now reverse probes and take another reading.

[retiredcaps]

Re: Neovo F-419 no power.

Many people get confused with manual multimeters and how to correctly report and intrepret the readings. From my 2 seconds to black guide ...

=== begin ====

If you have a manual ranging multimeter, set it to 200 (two hundred) ohms. Touch the black and red probe together. It should read 0.3 or 0.4 ohms. If it is higher than 1.0 ohm, there is something wrong with your multimeter.

If your multimeter reads "1" or "OL", it means the measurement is outside your chosen range. Don't confuse "1" on the left hand side of this display with 1.0 on the right hand side. The first means out of range and the second means 1.0 unit of your measurement.

=== end ===

Normally, we suggest testing for shorts using the 200 ohms scale. If it is shorted, the component will probably read less than 30 ohms. If it is not shorted, the multimeter will show a "1" on the left hand side. This "1" indicates the resistance reading is greater than 200 ohms. We don't care about the actual reading because we are only interested if it is shorted or not.

A tutorial at

http://www.sparkfun.com/tutorials/202