Samsung 231T, recapped, no power, no lights

[retiredcaps]

Re: green led only

I have 14 and 5 volts out of P/S to logic board, ....but then 18VDC out of logic to inverter board, of course no voltage at lamps. How did voltage get stepped up?

Is there anything on the power board (top or bottom) that indicates what the "proper" secondary output voltages should be?

If you measure the middle pin on D607 and D608, one should be 5V DC. What is the other?

[kingofcoins]

Re: green led only

The board and diagram both say 14VDC out to logic board.
Those 2 fuses, F51 and F101 on inverter both read 17.5 OHMS.
D607 and D608 can't find, and not on parts list...are you looking for switching diodes ?
Bought a Rat-shack meter, nothing special

Is there anything on the power board (top or bottom) that indicates what the "proper" secondary output voltages should be?

If you measure the middle pin on D607 and D608, one should be 5V DC. What is the other?

[jetadm123]

Re: green led only

[QUOTE=kingofcoins;141283]Update using new multimeter...I have 14 and 5 volts out of P/S to logic board, ....but then 18VDC out of logic to inverter board, of course no voltage at lamps. How did voltage get stepped up?

Question on my re-cap job (see inverter pic)...I couldn't seem to get all the cap legs thru to bottom of board so some of these are more of a surface mount, however each leg hole in the board bottom is nicely closed with solder....is this a problem > Does solder always need to on top and bottom of PCB's ?


Some boards have traces on both the top and bottom of the circuit board. Therefore, it is important that the capacitor leg go all the way through the board. You can try heating the pad on the bottom while pushing down on the side of the cap that being heated to force the lead through the hole. Do not attempt this if the problem is that the leg of the cap is too thick to fit through the hole.

Also, what are you you using as a ground reference when you measure the 18V? If you're measuring the 18V at the wiring harness, then see if there's also a ground wire on that harness and use that for your measurement.

[retiredcaps]

Re: green led only

Those 2 fuses, F51 and F101 on inverter both read 17.5 OHMS.
D607 and D608 can't find, and not on parts list...are you looking for switching diodes ?

With your new multimeter, touch the two probes together. Mine reads 0.3 ohms. If your reads the same, then the fuse reading of 17.5 ohms suggest both are open (bad). A good fuse should measure less than 1.0 ohms.

If touching the two probes on your multimeter reads 17.5 ohms, reseat the jacks in the multimeter and/or check your battery. If it still reads 17.5 ohms, go back to RadioShack and get a replacement.

D607 and D608 are the two diodes sitting on the heatsink.

[kingofcoins]

Re: green led only

Retired thanks for sticking this out. Its 2F here this AM so I; working on board. I didn't like my meter probe tips so I silver soldered some cap legs on. I get a zero ohms calibration on both the reg tips and my new pin tips. I then remeasured the components recently done:
large filter cap...156VDC at legs
voltage out of p/s ...18.5v using its ground
The IC's 101 to 106 still read the same as before
voltage into inverter board...18.5v
F51 and F101 fuses now read infinity- open
D607 and D608 one reads 5v the other 18.5v

Sorry about missing the diodes .. they didn't list the individual power supply parts.
??..>So are both diodes bad and allowing elevated voltage out and to inverter board which has blown the fuses ?

With your new multimeter, touch the two probes together. Mine reads 0.3 ohms. If your reads the same, then the fuse reading of 17.5 ohms suggest both are open (bad). A good fuse should measure less than 1.0 ohms.

If touching the two probes on your multimeter reads 17.5 ohms, reseat the jacks in the multimeter and/or check your battery. If it still reads 17.5 ohms, go back to RadioShack and get a replacement.

D607 and D608 are the two diodes sitting on the heatsink.

[retiredcaps]

Re: green led only

voltage into inverter board...18.5v
F51 and F101 fuses now read infinity- open
D607 and D608 one reads 5v the other 18.5v

??..>So are both diodes bad and allowing elevated voltage out and to inverter board which has blown the fuses ?

1) Order the fuses (maybe a couple of spares in case they blow again).

2) 5V is good.

3) If 18.5V is coming from the diode, we will assume that is good. I sometimes see 19V going to the inverter board on some designs so 18.5V DC is not too much.

[kingofcoins]

Re: Samsung 231T, recapped, no power, no lights

The 18.5vdc is common thru the circuits, even from the power out to logic where, where the board and diagram spec it at 14vdc....is that a problem?
Can I short the fuses for a sec to see what happens ? I assume they are parallel circuits so I'd only need to do one . This board had all 10 caps BAD. Any clue as to why the fuses blew ?

[retiredcaps]

Re: Samsung 231T, recapped, no power, no lights

The 18.5vdc is common thru the circuits, even from the power out to logic where, where the board and diagram spec it at 14vdc....is that a problem?

Sorry, I can't give a definitive answer.

Can I short the fuses for a sec to see what happens ? I assume they are parallel circuits so I'd only need to do one . This board had all 10 caps BAD. Any clue as to why the fuses blew ?

I'm not a fan of shorting out fuses with a wire. Fuses are there to protect the board.

One or more of the 10 bad caps could be been shorted internally and cause the fuse to blow?

[retiredcaps]

Re: Samsung 231T, recapped, no power, no lights

The 18.5vdc is common thru the circuits, even from the power out to logic where, where the board and diagram spec it at 14vdc....is that a problem?

Can we get a picture of the board where it says 14V DC? I can't see it on your existing photos. It may be covered up by the wiring?

[kingofcoins]

Re: macro pic

Here you go its marked 14V at CN 602. Also see pin 1 wire at CN101 going to inverter board is carrying that same 18.5V

Can we get a picture of the board where it says 14V DC? I can't see it on your existing photos. It may be covered up by the wiring?

[retiredcaps]

Re: macro pic

Here you go its marked 14V at CN 602. Also see pin 1 wire at CN101 going to inverter board is carrying that same 18.5V

Does it measure 14V DC at CN 602 if you have all the boards connected?

[kingofcoins]

Re: DC voltages

Today both CN 602 and CN 102 out voltages read closer to 19VDC with all boards and wires connected...no I do not get 14V.

Does it measure 14V DC at CN 602 if you have all the boards connected?

[retiredcaps]

Re: DC voltages

Today both CN 602 and CN 102 out voltages read closer to 19VDC with all boards and wires connected...no I do not get 14V.

Weird. Most logic boards don't require anything more than 5V DC. If 19V DC is present on the connector on the logic board, I have seen this rail routed to ground.

19V DC is a common voltage used on the inverter side.

I can't explain the 14V DC silkscreen.

I can't think of anything else other than getting the fuses, replace them and retest.

[kingofcoins]

Re: Samsung 231T, ..> update got led

I was able to attach test fuses to the F51 and F101 on those two open spots on the inverter board and I now I get a green led for 5 seconds and then it starts a fast blink, but no video no back lights. When the inverter board is unplugged the dc voltages to the logic board are still the 5V and 18.5v, but now when I plug in the inverter board with the temp fuses, the voltages drops way down to 1.5v and pulsates. I unplugged the CCFL's and got the same low voltage. Looks like the now closed fuse paths uncovered something worse on the inverter board.
Any ideas ? Anybody trace and solve a fast blinking Samsung green led ?

[PlainBill]

Re: Samsung 231T, ..> update got led

I was able to attach test fuses to the F51 and F101 on those two open spots on the inverter board and I now I get a green led for 5 seconds and then it starts a fast blink, but no video no back lights. When the inverter board is unplugged the dc voltages to the logic board are still the 5V and 18.5v, but now when I plug in the inverter board with the temp fuses, the voltages drops way down to 1.5v and pulsates. I unplugged the CCFL's and got the same low voltage. Looks like the now closed fuse paths uncovered something worse on the inverter board.
Any ideas ? Anybody trace and solve a fast blinking Samsung green led ?

I haven't read the entire thread, but you are obviously making progress. The latest symptoms are clear; something on the inverter is loading the power supply. As a quick guess, the sequence is going like this: Power comes up, processor on logic board starts, turns on power LED and inverter. Inverter overloads power supply, power drops, processor resets, power LED and inverter go off. Power supply restarts and the whole process repeats.

The clasic way to troubleshoot this is 'divide and conquer'. The inverter is unusual - you have two inverters on one board. It is likely the inverter won't draw power unless BOTH fuses are good, but that's the first thing to try. See if the overload problem shows up only if a particular fuse is present.

Scratch that idea. Check the two banks of driver ICs - U101, U102, U104 and U105 are one bank; U51, U52, U54, U55 (not sure about the numbers) are the other. Make sure they aren't shorted.

PlainBill

[kingofcoins]

Re: Samsung 231T, ..> IC's and fuses

Bill :
...those are exactly the driver nos, they are IC 4600's . Not sure this is what you want...but checking across legs 6 and 7 where pin 1 has a dot, all 8 read zero ohms with power off.
As for the fuses I tried removing them one at a time. They are definitely carrying a current. With just one or the other in the power didn't come on. With both out I get a steady green led that later goes to slow blink. Of course with both fuses in I got the fast blink.
Two other points of note...I put in the 4 new caps on the inverter board, on 2 of which I don't think the legs got all the way thru board although there's solder on both sides....this is between the IC's and the SMD fuses...
....the Other thing is the ccfl transformers on the U51-55 side look like heated metal blue, although they are oriented at the top of the board inside the RF shileld (heat would rise to them ), and this unit looks like its seen many hours as well.

It is likely the inverter won't draw power unless BOTH fuses are good, but that's the first thing to try. See if the overload problem shows up only if a particular fuse is present.

Scratch that idea. Check the two banks of driver ICs - U101, U102, U104 and U105 are one bank; U51, U52, U54, U55 (not sure about the numbers) are the other. Make sure they aren't shorted.
PlainBill

[bluto]

Re: Samsung 231T, recapped, no power, no lights

See other thread...

https://www.badcaps.net/forum/showth...highlight=213t

[RalphSimon]

Re: Samsung 231T, recapped, no power, no lights

Hi all - great forum.

Have replaced the 10 caps, but still no more than correct functioning of the green power LED.

Couple of questions.
What are the values for the fuses?
Can I test the FETs with the new caps installed?

[selldoor]

Re: Samsung 231T, recapped, no power, no lights

1 It is Very Very unusual for it not to say on the board what the value is for fuses.
2 Is there some reason you think you could not?


Welcome to the forum-
We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back (in the same orientation) and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed

https://www.badcaps.net/forum/attach...7&d=1280167246

https://www.badcaps.net/forum/attach...6&d=1280167246

https://www.badcaps.net/forum/attach...4&d=1280167246

It will be useful if you can say what the supposed fault was and a bit about yourself - skills tools etc.

[RalphSimon]

Re: Samsung 231T, recapped, no power, no lights

I didn't upload pictures as they would have been the same as in post #11. But can if it would help.

The fault. I did say - Have replaced the 10 caps, but still no more than correct functioning of the green power LED.
I am prone to brevity. After the hols, I switched on the 213T (used to monitor emails on a twin monitor setup) to be greeted by a dark screen. However the green power LED functions OK. No difference after replacing the caps.

I have read all the posts in all 3 threads that contain 213T.

1. No mention is made of the fuse specs.

2. In one post the following comment is made - Do yourself a favor and replace the caps on the inverter after you have replaced the MOSFETS
I do not know whether this is for convenience or need. Hence my question.

Myself. 40 years ago I qualified as a research electronics engineer. Since then I have been WAY out of the field. However in recent years (semi-retirement), primarily from a business perspective, I have been involved with a REALLY neat project called WHEELTUG. Look it up, it's fascinating.

Skills. Have always been handy & never one to chuck anything in the bin before attempting repair. Usually quite good at knowing what could be salvaged & what needs replacing. Rewired my whole house 34 years ago!

Tools (relevant only as I have a garage FULL) Weller soldering gun, miniature tools, Extech EX330 meter & a camera. Got a small soldering iron too - somewhere.....