usp440m-42lp psu

[joehezzer]

Re: usp440m-42lp psu

i recently just did one of theese, managed to get a psu from ebay for £30 delievered, the one i had , b/r shorted and a load of mosfets ,so got another board
http://www.ebay.co.uk/itm/4004140660...84.m1497.l2649
it wasnt really worth doing but my missus likes the tv an for keeping her quiet............... priceless

ok so i gave in on trying to find out what was wrong with psu, and ordered the above psu popped it in this morning it works, for the sake of £30 with free postage i cannot moan cheers all that helped me fault find the old one, cheers paulstef

[joehezzer]

Re: usp440m-42lp psu

Ok, so if the two white resistors or one of them is open there are other component that need to be checked. First of all the bridge rectifier.

I have changed the bridge rectifier to a known working one. So will check again later after me dinner

[paulstef]

Re: usp440m-42lp psu

I measured the wrong resistors. I had the board the wrong way round, as there are 4 of them, I tested the wrong ones as I was rushing yesterday

Ok, so if the two white resistors or one of them is open there are other component that need to be checked. First of all the bridge rectifier.

[joehezzer]

Re: usp440m-42lp psu

In this post you said you have AC input voltage. So replacing anything between AC IN connector and this point won't help you. There are only the resistors between this point and the rectifier (where you measured nothing).

You said the resistors are ok. So I don't see where replacing any parts will lead you.

You are either not measuring correctly or there is something else we don't see.

When measuring resistance from one of the middle pins of the bridge rectifier to the AC input pins, what do you get?? Then from the other middle pin of the rectifier, what do you get?

I measured the wrong resistors. I had the board the wrong way round, as there are 4 of them, I tested the wrong ones as I was rushing yesterday

[paulstef]

Re: usp440m-42lp psu

Right ok test out put again and got 263v Ac atleast I have a reading this time lol

In this post you said you have AC input voltage. So replacing anything between AC IN connector and this point won't help you. There are only the resistors between this point and the rectifier (where you measured nothing).

You said the resistors are ok. So I don't see where replacing any parts will lead you.

You are either not measuring correctly or there is something else we don't see.

When measuring resistance from one of the middle pins of the bridge rectifier to the AC input pins, what do you get?? Then from the other middle pin of the rectifier, what do you get?

[joehezzer]

Re: usp440m-42lp psu

So I have decided to change the components leading to the bridge rectifier.

[joehezzer]

Re: usp440m-42lp psu

I cannot guess what you want to say. They are in parallel with the AC voltage. You only need to look at what's in series . Which component can cause an interruption from AC in to the bridge rectifier. Just follow the path. Forget the relay, it only jumpers the white resistors, which you said are ok.

Simple resistor measurement will get you there

AC OFF!!

ok, i see what you are saying, it can only be one of the components leading up to the bridge rectifier.

[paulstef]

Re: usp440m-42lp psu

Tnr101 and tnr102

I cannot guess what you want to say. They are in parallel with the AC voltage. You only need to look at what's in series . Which component can cause an interruption from AC in to the bridge rectifier. Just follow the path. Forget the relay, it only jumpers the white resistors, which you said are ok.

Simple resistor measurement will get you there

AC OFF!!

[joehezzer]

Re: usp440m-42lp psu

Tnr101 and tnr102

[paulstef]

Re: usp440m-42lp psu

Ok, look. The AC voltage that comes in goes more or less directly to the two middle pins of the bridge rectifier. You have to find out where this path is interrupted. If you cannot measure AC between the middle pins of the rectifier it should be fairly easy to find out.

[joehezzer]

Re: usp440m-42lp psu

Ok cool going to remove board as I cannot acces it

taken one out and i got the reading of 5.6ohms both are reading this

[joehezzer]

Re: usp440m-42lp psu

Ok cool going to remove board as I cannot acces it

[paulstef]

Re: usp440m-42lp psu

R106 and R105 you mean

yes.

I will only have the board for a few more days. if we can find out whats wrong today would be good.

[joehezzer]

Re: usp440m-42lp psu

R106 and R105 you mean

[paulstef]

Re: usp440m-42lp psu

disconnect AC. check the two big white resistors. they are probably open.

[joehezzer]

Re: usp440m-42lp psu

my fault lol still learning . Outter pins read 02.2v dc the inner oned read 03.5v Ac

[paulstef]

Re: usp440m-42lp psu

I don't understand.

1st measurement: Put your multimeter probes on the 2 middle pins of BD101. Measure AC. What's the voltage?

2nd measurement: Put your multimeter on the two outer pins of BD101. Measure DC. What's the voltage?

[joehezzer]

Re: usp440m-42lp psu

Voltage from cathode nothing .looking at the bridge rectifier from above the bottom pin 00.4 volts and the upper pin 00.5v dc

[paulstef]

Re: usp440m-42lp psu

BTW, leave everuything disconnected from the board apart from AC IN of course.

[paulstef]

Re: usp440m-42lp psu

Nothing from any of them. So probably need to pull off diodes and check em !!

No.

Obviously the NCP1200 (8-PIN IC) is not oscillating.

From cathode of D103 to heatsink, do you read high voltage DC?
If not what do you read from the leftmost pin to the rightmost pin of the bridge rectifier BD101?