Repairing SMPS - DELL 1800MP - Tricky question maybee??

[ljcarballo]

Forgive my English, but it is null, all based on a translator.

Perdonar mi ingles, pero es nulo, todo a base de traductor.

[dicky96]

@ljcarbello
You are missing the point here mate.  If you have 4mA flowing through that resistor then it is more than enough to start the ML4800, which only needs 200uA to start.  The startup current path is OK.   Your problem is elsewhere because the power supply is not generating the running current for ML4800

Have you checked for short circuits on the output of the power supply as I suggested?

Rich

[tautech]

@ljcarbello
You are missing the point here mate.  If you have 4mA flowing through that resistor then it is more than enough to start the ML4800, which only needs 200uA to start.  The startup current path is OK.   Your problem is elsewhere because the power supply is not generating the running current for ML4800

Have you checked for short circuits on the output of the power supply as I suggested?

Rich

Yep, that's the bit many don't understand.....the controller might have a start supply but the rest of the SMPS must have no faults for it to start so the run supply can keep the controller going.

This is where and external supply to get the controller to a run state so the output waveforms can be checked and confirmed as correct to make the thing work. Don't try this while on mains power or the whole thing might go POP. 

[dicky96]

@tautech
 
Yep that's true mate!!  At least we have the required emoticon lol   

[ljcarballo]

Everything remains the same, I have placed a resistance of 39K but the voltage is still 10.9V, I have to start over because there is something I am jumping.
I have reviewed the two schottky diodes on plate and they are fine, there is no short. The post 5 circuit is a standard application for the LM4800, I will try to upload a small reverse engineering scheme, as well as a couple of photographs to see where the transformer and the schottky diodes are.


Todo sigue igual, he colocado una resistencia de 39K pero el voltaje sigue siendo 10,9V, tengo que empezar de nuevo porque hay algo que me estoy saltando.
He revisado los dos diodos  schottky en placa y están bien, no hay ningún corto. El circuito del post 5 es una aplicación estándar para el LM4800, voy a intentar subir un pequeño esquema de ingeniería inversa, así como un par de fotografías para ver donde se encuentra el trasformador y los diodos schottky.

[dicky96]

@ljcarballo

Ahh that's good you tested the schottky diodes.  Knowing there is no short circuit on the power supply output is a good start.

OK let's see if we can help you further.  What test equipment do you have available?

Do you have an oscilloscope?  If so is it a mains one or a portable battery one?

You said you have a bench power supply.  What are it's capabilities (or what make/model so I can look them up)? Is it a single or dual supply? 

If it is a variable dual supply is it something like 30v-0-30v or does it have two independant variable supplies 0-30V  0-30V.  Alternatively do you have two variable voltage power supplies available?

I don't suppose you have a mains isolation transformer? That would really help but we can work without one.

Also could you measure some voltages please.... place your negative meter lead on the negative end of the big 450V electrolytic capacitor,  Now measure the voltage at both ends of the large 1N5406 diode.  What do you see?

Rich

[ljcarballo]

I have a meter and oscilloscope, I have two power supplies, the one I use is ZXY6005S, the other I have to repair the intensity regulation, dual source I do not have, the isolation transformer is a project that I have in mind since I recover two transformers Same as an amplifier and I want to prepare something.
The first voltage is 315V and the second voltage is 287V

Tengo polímetro y osciloscopio, tengo dos fuentes de alimentación, la que suelo usar es ZXY6005S, en la otra tengo que reparar la regulación de intensidad, fuente dual no tengo, el trasformador de aislamiento es un proyecto que tengo en mente ya que recupere dos trasformadores iguales de un amplificador y quiero preparar algo.
El primer voltaje es 315V y el segundo 287V

[ljcarballo]

The two images are of the voltage falling on the diode.


Las dos imágenes son de la tensión que cae en el diodo.

[dicky96]

OK that sounds good amount of equipment - it is quite late in the evening here now, will reply in detail in the morning

Richard

[ljcarballo]

In post 29 in the image of the scheme I have noticed that the "P13" that goes below the resistance of 39K has been cut off


En el post 29 en la imagen del esquema me he fijado que ha quedado cortada la "P13" que va debajo de la resistencia de 39K.

[dicky96]

Ahh.....  today was definitely a day for the beach here in Gran Canaria!

OK let's do some work.  The photo of your Fluke - I assume that waveform in on the anode of the !N5106 diode? It is 100Hz so is the full wave rectified output from the bridge rectifier.  How are you powering the SMPS in this photo? Directly from mains supply or from the output of an AC transformer?

Here are a few things i would like you to try.  When you connect the SMPS to the 220V mains supply, what voltage do you read across the 100uF 450V electrolytic capacitor? 

If you then switch off the mains supply what happens to the voltage on the 450V capacitor?  Does it discharge rapidly or slowly?

Once the 450V capacitor is fully discharged connect your variable power supply as follow:
Negative of bench supply to negative end of the 450V capacitor.
Positive of bench supply to a 220R or 270R resistor. 
The other end of the 220R/270RE resistor to pin 13 on ML4800. 

Now without any 220V mains voltage supply to the SMPS, turn on your variable voltage supply and bring the voltage up to 15V or just over.

Use your oscilloscope and have a look at pins 11 and 12 of ML4800.  What do you see there?

Does the SMPS have 2 power FETs like the example circuit diagram or just one?  With the oscilloscope what do you see on the Gate pin of the Power FET(s)?

Reply back once you have done that.

Oh.... and could you tell me is your ZXY6005 powered from a step down transformer like this video? or do you have it connected in some other way?

Cheers
Rich

[ljcarballo]

OK let's do some work.  The photo of your Fluke - I assume that waveform in on the anode of the !N5106 diode? It is 100Hz so is the full wave rectified output from the bridge rectifier.  How are you powering the SMPS in this photo? Directly from mains supply or from the output of an AC transformer?
The image of the fluke are the tips in parallel with the diode IN5106
Here are a few things i would like you to try.  When you connect the SMPS to the 220V mains supply, what voltage do you read across the 100uF 450V electrolytic capacitor?
The voltage is: 315V
If you then switch off the mains supply what happens to the voltage on the 450V capacitor?  Does it discharge rapidly or slowly?
I would say slowly, from 315V to 10V it takes 45s
Use your oscilloscope and have a look at pins 11 and 12 of ML4800.  What do you see there?
Does the SMPS have 2 power FETs like the example circuit diagram or just one?  With the oscilloscope what do you see on the Gate pin of the Power FET(s)?
The oscilloscope does not mark anything either on leg 11 or 12 and on the two doors of the mofet transistors, either, the power supply is consuming 10mA (I send you an image
Does the SMPS have 2 power FETs like the example circuit diagram or just one?  With the oscilloscope what do you see on the Gate pin of the Power FET(s)?
Nothing, nor when I feed with 15V the ML4800, nor when I put the mains voltage (230V)
In this assembly the ML4800 has two mofet, although at the output has three voltages (second photograph)
Oh.... and could you tell me is your ZXY6005 powered from a step down transformer like this video?
 or do you have it connected in some other way?
 My ZXY6005S I have it connected to a switched power supply of 24V and 4.5A in one of the pictures can be seen.
The conclusion I get is that the ML4800 does not work and I will have to replace it and start over to check everything. What do you think?
Enjoy everything you can from the beach, here in Valladolid is very cold for water.


La imagen del fluke son las puntas en paralelo con el diodo IN5106
El voltaje es de: 315V
Yo diría que lentamente, de 315V a 10V tarda 45s
El osciloscopio no marca nada ni en la pata 11 ni 12  y en las dos puertas de los transistores mofet, tampoco, la fuente de alimentación esta consumiendo 10mA (te mando una imagen)
Nada, ni cuando alimento con 15V el ML4800, ni cuando meto la tensión de red(230V)
En este montaje el ML4800 tiene dos mofet, aunque a la salida tiene tres tensiones (segunda fotografia)
Mi ZXY6005S la tengo conectada a una fuente de alimentación conmutada de 24V  y 4,5A en una de las fotografías se puede ver.
A la conclusión que llego es que el ML4800 no funciona y tendré que sustituirlo y empezar otra vez a comprobar todo. ¿Qué opinas tu?
Disfruta todo lo que puedas de la playa, aquí en Valladolid hace mucho frio para el agua.

[dicky96]

OK if the ML4800 definitely has around 15V on pin 13 when feeding from your bench power supply via the 220R resistor, and you say it is drawing about 10mA which is about correct - some of those mA will be flowing through the 15V zener diode - then one likely possibility is you have a faulty ML4800

Let's just be sure of a few things before condemning it.  With the ML4800 powered from your 15v SUPPLY...

1. There is definitely 15V measured on pin 13?

2. There is definitely no signal on pin 11 or 12? 

3. Do you see any signal or voltage on pins 5,7,8 when powering the ML4800 with 15V?

4. Is there a short circuit to ground on pins 5,7 or 8?

Rich


 
rICH

[ljcarballo]

With 17V powering the ML4800 and consuming 10mA are the measures you asked me:
1. On pin 13, 14.820V
2. On pin 11 and 12 with respect to 0V we have nothing.
3. On pin 5, 0V; On pin 7, 2.632V; On pin 8, 0V.
4. There is no short circuit on pins 5.7 and 8 with respect to 0V
a greeting


Con 17V alimentando el ML4800 y consumiendo 10mA están son las medidas que me pedias:
1. En el pin 13, 14,820V
2. En  el pin 11 y 12 con respecto a 0V no tenemos nada.
3. En el pin 5, 0V; en el pin 7, 2,632V; en el pin 8, 0V.
4. No hay cortocircuito en los pines 5,7 y 8 con respecto a 0V
Un saludo

[ljcarballo]

I leave the block diagram of the ML4800.


Dejo el diagrama de bloques del ML4800.

[dicky96]

I think under those conditions the ML4800 should produce a PWM output on pin 11 so I would try replacing the ML4800

When you fit the replacement I would power up the Dell SMPS with a 60W light bulb or similar in series with the mains.  Don't connect a load to the power supply the first time you try it, and see if there is any output voltage.

I actually made little a test unit with light bulb holder, mains plug, switch and mains socket.

The switch I can either set to 'Limit' which supplies power to the device under test via the light bulb or 'Mains' which shorts out the bulb and supplies power directly.  I keep a few different bulbs of different wattage - the one I use mostly is a 220V 48W halogen bulb

At least if you connect it that way nothing bad will happen - worse case is the bulb will light up 

This is a good way to test unknown condition mains powered devices without the chance of something going BANG!

Rich

[tautech]

We know those bulb testers on the forum as Dim Bulb testers. Google returns an explanation of them and their usage.
Handy bit of kit and I use one every time there is a chance of releasing magic smoke. 
They take little effort to cobble one together.
Here's mine and link below to an old thread with description of usage.



https://www.eevblog.com/forum/repair/suggested-for-a-sticky-part-one-comments-or-additions-please/msg470686/#msg470686

[ljcarballo]

Thanks for that infinite patience that you have had with me, when I try something for the first time I also connect it to a circuit like the one you have drawn to me, it seems very practical and I avoid that if you jump the differential, my wife gets mad at me, ML4800 and I will change it to see what happens, the only thing that I have finished the rest and now it will take a little longer in the repair due to lack of time, as soon as I realize I will comment the results here. a greeting


Gracias por esa paciencia infinita que habéis tenido conmigo, cuando pruebo algo por primera vez también lo conecto a un circuito como el que me habéis dibujado, me parece muy practico y evito que si salta el diferencial mi mujer se cabree conmigo, voy a pedir el ML4800 y lo voy a cambiar a ver que sucede, lo único que se me ha acabado el descanso y ahora tardare un poco mas en la reparación por falta de tiempo, en cuanto lo realice comentare por aquí los resultados. Un saludo

[ljcarballo]

I have already removed the ML4800 now waiting to receive the spare and try to see that such.

Ya he quitado el LM4800 ahora a la espera de recibir el repuesto y probar a ver que tal.

[ljcarballo]

Bad news, already change the integrated, and everything remains the same, I still have the 10.9 V in the leg 13. I will do some reverse engineering to see that it matches the typical scheme that is in the message 5.


Malas noticias, ya cambie el integrado, y todo sigue igual, sigo teniendo los 10,9 V en la pata 13. Voy a hacer un poco de ingeniería inversa a ver que coincide con el esquema típico que esta en el mensaje 5.

[newtechnology]

Hi this theme is very old
i have problem with same power supply

i read all and make many opit
First need to work this power supply close conection for plug with name switch or solder two wire
Second need make load on 5v line if this two steps not make power not begin . i make load with 5w 12v lamp on 5 v line
  and power work fine 

[ljcarballo]

I could not solve it, the device belonged to a friend and I only had the source of feed, I asked the rest to see if having consumption behaved differently, but I bought another equipment and abandoned that and I did not leave it for see if I could solve it, a greeting and thanks for your response.

Yo no lo pude solucionar, el aparato era de un amigo y solo tenia la fuente de alimentación, le pedí el resto a ver si teniendo consumo se comportaba de otra forma, pero se compro otro equipo y abandono ese y ya no me lo dejo para ver si podía solucionarlo, un saludo y gracias por tu respuesta.