Daewoo 14V1G S (chassis CP-185G/GU) won't power up

[panoss]

Hi everybody.
I have the above mentioned crt TV.
Won't power up.
I have lost the remote control, but if I remember correctly (haven't used this tv set for 3 years now), when I opened it with the remote control, the red LED would light up and then would shut off.
I suspect the power supply.
Here is the service manual (wait about one minute till the download link gets created).
Any hints are welcome, I'm going to open it tomorrow, Saturday.

[R_J]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

The first thing I would check is the voltage at I801 pin 1, and then at pin 4. if its there check if there is any secondary voltage, especially the +13 that supplies I805 (+5 standby)
I would suspect that C834 and C832 are most likely bad. If they are bad the power supply won't run but might try, and give very low secondary voltages
Usually with the Daewoo crt tv's they had a lot of bad caps in the power supply and deflection circuits

[panoss]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

I opened it but didn't power it up, so I didn't check voltage at I801.
But I found a short circuit (B and E) in Q401.

So I removed Q401. Out of the circuit, Q401 is not shorted.
But the short on the board remains (at the pads where B and E of Q401 go).
So I removed C404, the short remains.
I checked C408, R450, D450 for short circuit, they are ok, but the short remains.
What cold be the reason for this?

I have put a red line near the parts in the attached image.

EDIT: I took a second look at the schematic, I guess the short is normal because of the ST1803dHI, right?

Should I power it up without the Q401 or is it dangerous?

[dick_barton]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

There is no short circuit between B/E. You are measuring the resistance of transformer, point 13 to ground.

[panoss]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

I checked C834 and C832, they seem ok.
I measured only capacitance as I don't have an ESR meter.
They 're not bulged.

At the PCB under R801(posistor), I see it's black colored, like having been stressed by high current.
How can I check the posistor?

[dick_barton]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

No photo's of the board so hard to guess how bad the discolouration is.

[panoss]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

I can't take a good photo, my camera is low resolution.
I found the fuse (f801) opened (open circuit).

This might mean a shorted component, right?

[dick_barton]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

Use your meter and check components in the area for short circuit.

[panoss]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

I'm checking the whole pcb (I don't know if you mean I should check in a specific area).
Still haven't found anything.

The fuse is this:

[dick_barton]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

Littlefuse Wickman available from Mouser or Digikey. Rating given on the top of the fuse.

[panoss]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

Buss SR-5
T 4A 250V ('T' means slow burn?)

This is it.

But I only have classical glass fuses, 250V 3,5A and 250V 5A.

EDIT: I also have 2A, 250V. Maybe two of them in parallel?

[dick_barton]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

T = Time delay. I would not replace the fuse until you find out what caused it to blow. Glass fuses explode and shatter glass everywhere when connected to a short circuit.
You'll need to order some replacement

http://www.digikey.co.uk/product-det...62BK-ND/103983

[panoss]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

On the pcb is written: T4AL/250V F4AH/250V, and it has holes (for a fuse holder, I suppose) and space for putting either one like the original or a glass fuse F4AH.

So maybe it could take a simple glass fuse?

[dick_barton]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

If you want to buy from amazon then try

https://www.amazon.co.uk/RADIAL-DELA...ds=bussmann+4a

[dick_barton]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

Do you know how to use a multimeter and test diodes and do resistance checks?


With the set off which of course it is. Can you check diodes D801, D802, D803, D804, D805, D806, D815, D817
What is the resistance across the two pins of C804 & also C805

[panoss]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

I checked the diodes D801, D802, D803, D804, D805, D806, D815, D817, they seem ok.
As for C804 & C805, the had the same behavior with the ohmmeter: the reading increased till infinite.

[panoss]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

I replaced the fuse with two glass fuses in parallel (they 're 250V 2A each) and did the test with the light bulb (60W incandescent).
The bulb was fully lighted, the tv didn't power up.
So, I suppose, the short circuit remains (??).

I measured voltage at pin 1 of I801, it was 25V and was not steady, it was dropping, 24, 23, 22, 21...

I don't know what this measurement means, as I have the light bulb in series with the tv.

[panoss]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

I had some progress!!!
I removed the posistor.
(with the light bulb connected)
I powered it up:
the tv seems to start up(!!), the bulb is in the beginning not lighting.
Then the light of the bulb increases and tv starts to 'fade' (like working with less and less power).

This circle continues repeatedly, the light increases - decreases.

So I guess the defective component is the posistor!

[panoss]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

I connected two lamps in parallel (60W||40W like having a light bulb of about 15W) and...it works!!!

[panoss]

Re: Daewoo 14V1G S (chassis CP-185G/GU) won't power up

I powered it up without the bulb, works fine! So definitely, the problematic part is the posistor.