Baird x37DTV - No Power

[DJ4D]

Hi Everyone

I recently picked up a Baird X37DTV as my first project. The previous owner said that it ws working fine and then one day it just went off. They changed the fuse in the power cable and after it still didn't work they just went out and bought a new TV. So it doesn't appear as though any type of repair has been attempted previously.

I've removed some of the dust from the mains board and where the was a build up on so of the other components but that job is by no means completed, but it looks better than it did.

As outlined in this thread - https://www.badcaps.net/forum/showthread.php?t=32910 - I've removed the PSU and noticed a bulging cap which I've now replaced but unfortunately there still doesn't appear to be any power to the TV, no standby light when plugged in.

I can't see any immediate issues with any of the other caps but I've posted some photos so you can have a look.

I've picked up a multimeter as my old one was faulty. I've seen this thread - https://www.badcaps.net/forum/showpo...22&postcount=3 - and I've checked the voltage across the large cap that I replaced and the multimeter is showing 0.00.

I believe I've soldered the replacement cap into place ok. Is it likely that there is a fault elsewhere in the PSU before anythig reaches this cap, and if that is the case then where can I check please?

[tom66]

Re: Baird x37DTV - No Power

Check all outputs going to main board -- any standby voltage?
Check the mains fuse on the power board. A quite common fault with these is a blown fuse + FET + PFC IC due to bad big cap (450V one.)

[DJ4D]

Re: Baird x37DTV - No Power

Thanks for the quick reply Tom66!

Looking at my first photo showing the full board from the top, can you please point out the outputs going to the main board?

Also, can you point on the same image where the fuse, FET and PFC IC are please?

It's my first TV repair project so please be gentle

[newtothis]

Re: Baird x37DTV - No Power

As I cannot see what is what here... get the cable that fits the mainboard and see which connector it will fit on the PSU. That is the one to test.

Set DMM to 20VDC, black probe to a ground (chassis screw hole works well if you put the board back on it) and red to each pin on the connector.... you are looking for a 5v reading.

post results back like this -

pin 1 - 0v
pin 2 - 5v
etc etc

[DJ4D]

Re: Baird x37DTV - No Power

The mains lead plugs into the underside of the Tv, then there's the earth screwed to the chassis, then the blue [marked N] and brown [marked L] that plug into the mainboard.

Pin 1 [N] - 0.00v
Pin 2 [L] - -0.64 up to 0.64 and then back to -0.64

[Edit]

Sorry, I read your post wrong!

I've attached a photo of the area I think your telling me to look at.

If that's the case then I'm not getting any reading from the pins.

[/Edit]

[newtothis]

Re: Baird x37DTV - No Power

Ok just to check this.... set DMM to AC and check the N and L again for me.... Black on N and red on L

[DJ4D]

Re: Baird x37DTV - No Power

I've had a look around for the Fuse, FET and PFC IC that Tom66 suggested earlier.

I can't see anything that looks like a fuse anywhere. There are a number of FETs screwed onto the heatskins, some large, some small.

From top to bottom, left to right:-

- Large 4 pin, nothing printed on it
- Small 3 pin, CQ721G, U1560
- Small 3 pin, something printed but very faded
- Small 3 pin, IRFP460 - P728XD - MIDD
- Large 4 pin, nothing printed on it
- Small 3 pin, NXP, BYQ28E
- Small 3 pin, IRF840, 72K5
- 3 Small 3 pin, STPS2015OCT, CCOOR
- Small 3 pin [I think, bottom covered in white glue]

I am unsure what the PFC IC actually is or what it should look like. I searched on Google images and tried to find something similar and on he mainboard I could see 3 chips with 4 pins. Printed on all 3 of them is 'PC817 Sharp'.


@newtothis - I just saw your reply before I posted this. I've attached a photo of my DMM as well. Can you confirm how I need to have it configured please as I'm unsure, sorry.

Is it black probe in VmA, red probe in 10ADC, and then one of the settings on the dial?

[newtothis]

Re: Baird x37DTV - No Power

OK quick tutorial

DC is a straight line with a dotted line underneath it
AC has the symbol ~
always set your voltage to one higher than you are reading... so for 180v would be 200, 240 would be 600.... otherwise if you were to read 240VAC on 200VAC setting it would go to infinity

Com is black probe
Red to right socket (see the 600v max) other side is not fused and do not want to touch AC without fusing

so... set to V~ 600, black to (N) and red to (L) on tv

This is just to check you are getting AC into the set at the primary point

[DJ4D]

Re: Baird x37DTV - No Power

Thank you

I've done that and it floats between 241 and 242.

[newtothis]

Re: Baird x37DTV - No Power

Ok set DMM to 600v DC, leads in same sockets....

See the big capacitor, black cylinder on its side.... probe to each pin, doesn't matter which way round

[DJ4D]

Re: Baird x37DTV - No Power

Nothing unfortunately, 0.00.

[newtothis]

Re: Baird x37DTV - No Power

Sorry can you change your leads and set to 600 DC again and check capacitor again.

Keep black in com

[DJ4D]

Re: Baird x37DTV - No Power

Ok, from the back, the trace goes down and to the left slightly.

From the front, looking at L and going down and over to the right we have a component in what looks live black sleeving.

With the sleeving carefully removed it does indeed look like a fuse. It looks like it says 32S around the top. Looking inside the fuse I can' really see the filament properly, whatever is inside it looks red or brown with some wires. I'll remove it from the board and have a proper look - I work in IT and Root Cause is everything

Is this 32 amp fuse, and is it something I can pop down to Maplin for as it doesn't look like they have 32a fuses on their website - unless I'm barking up the wrong tree [which is very possible!].

Also, is the sleeving necessary when I replace it? I don't have any but I could get some and give it a gentle blow with a heatgun.

[newtothis]

Re: Baird x37DTV - No Power

set DMM to the red setting at the bottom, this is Diode and continuity test.

Touch probe to each lead of the fuse.

post back results

[DJ4D]

Re: Baird x37DTV - No Power

When I set the DMM to that setting it displays a 1 on the screen. When I probe the fuse the screen on the DMM stays at 1.

[newtothis]

Re: Baird x37DTV - No Power

When I set the DMM to that setting it displays a 1 on the screen. When I probe the fuse the screen on the DMM stays at 1.

Fuse is dead... So something blew it.

I will try finding a schematic out for the board in a little while, tom may point you straight at what needs testing though

[vinceroger69]

Re: Baird x37DTV - No Power

i would test the bridge rectifier next its screwed onto one heat sink usually has 4 legs on it.maybe behind the oblong yellow box in picture 1 can you turn board around and re take a picture of that area

[DJ4D]

Re: Baird x37DTV - No Power

Ok, [just so I understand this], the fuse is dead because of another component that is faulty so it's a case of tracking down the other faulty component[s] before swapping the fuse or putting together a shopping list?

[vinceroger69]

Re: Baird x37DTV - No Power

not very often in my opinion a fuse will blow for no reason. i recently fixed a 32in version baird slightly different psu set up there's a thread on here if i had to replace all the parts which was blown about 7 some surface mount some burnt i could not even get part ids for them i basically fitted a different psu and wired it in still works great just need a remote control to tune free view in but using a free view box so not bothered at the minute.
https://www.badcaps.net/forum/showth...ighlight=baird
whats you power supply part number?

[newtothis]

Re: Baird x37DTV - No Power

Yes as vinceroger69 said, its very rare a fuse will ever blow for no reason, they are there as protection in the case a fault occurs to minimize damage and danger.

PSU is ad301m24-4n1

Will have a better look in a while, have to go shopping so be back later