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Samotron or Samtron LCD Monitor model 72V S

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Samotron or Samtron LCD Monitor model 72V S

Post by ken » Sat May 14, 2016 4:16 pm

I have been given one of these. A label inside seems to suggest it was made about 2003. I was told it die after making a loud "crack". As my current monitor is a very large and heavy crt version I thought I would have a go at fixing it. When I opened it I could not see anything that had obviously gone with a bit of a pop. There was one swollen electrolytic. Then I noticed what looked like there had been a flash over to one of the legs of the TOP247F ic. On removing this it looked as if it had blown apart at this leg. Looking on the web seems to suggest that this is quite common. The heat sink compound seemed to have dried out. Other checking shows that both the two 2A 250V cylindrical pcb mounted fuses had blown. I thought if I could get the ic cheap enough I would replace it, the fuses and a couple of electrolytics and see if it worked. However, I have a couple of questions.
1. Is this likely to have taken out anything else which would make an attempt at repairing it not worthwhile?
2. I have looked for a TOP247F on the net. Radio Spares have a TOP247YN. I have looked at an on-line data sheet to look for differences. The F and the Y seem to be differences in packages ie F is TO-262-7C and Y is TO-220-7C but I don't know what the N means. Can anybody tell me if I can use the TOP247YN to replace the TOP247F and what the N means. The difference in packages look fairly easy to get round.

Regards,

Ken.

 
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Re: Samotron or Samtron LCD Monitor model 72V S

Post by Refugee » Sat May 14, 2016 4:25 pm

Those 5 pin TO220 packages have a poor reputation for flashing over.
The pin spacing is just too close.
It would have to be a valuable set for me to be bothered with a 5pin TO220 SMPSU.

 
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Re: Samotron or Samtron LCD Monitor model 72V S

Post by ken » Sat May 14, 2016 5:07 pm

Refugee wrote:It would have to be a valuable set for me to be bothered with a 5pin TO220 SMPSU.


Its not valuable as I think its about 12 yrs old. I think the N is the lead finish (Tin). The chip is not that pricey at £2.74 plus vat. There's no damage to the pcb.

Ken.

 
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Re: Samotron or Samtron LCD Monitor model 72V S

Post by Refugee » Sun May 15, 2016 12:45 am

I had a wall wart go on my computer screen and it wasted a lot of time because the spare had been lost.
I found a good quality potted transformer with smoothing that was rated at just under three times what was required. It is unregulated but a sturdy power resistor sorted out the fact that the voltage creeps up a bit. Poor regulation just varies the brightness of the backlight.

 
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Re: Samotron or Samtron LCD Monitor model 72V S

Post by ken » Sun May 15, 2016 10:41 am

Refugee wrote:I found a good quality potted transformer with smoothing that was rated at just under three times what was required. It is unregulated but a sturdy power resistor sorted out the fact that the voltage creeps up a bit. Poor regulation just varies the brightness of the backlight.

This monitor has the smps mounted on its own pcb
inside the enclosure. It doesn't have a wall wart. Is your idea to replace the smps with a separate home made one outside the case?

Ken.

 
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Re: Samotron or Samtron LCD Monitor model 72V S

Post by Refugee » Sun May 15, 2016 1:14 pm

I simply replaced the 13V 3 amp wall wart with the 8A transformer based power unit due to having got fed up with wall warts blowing up every couple of years or less,
It runs nice and cool with an output close to the rated input for the monitor. I had to chop the lead off the wall wart and re-use it on the replacement.

 
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Re: Samotron or Samtron LCD Monitor model 72V S

Post by ken » Sun May 15, 2016 3:50 pm

Thanks for that. If all else fails I might go along that road.

Regards,

Ken.

 
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Re: Samotron or Samtron LCD Monitor model 72V S

Post by ken » Fri May 27, 2016 10:52 pm

Just an update on this one. I checked around as much as I could and did not find any other obvious faults. I decided to buy the parts that I needed from RS. This included smps chip, 400v 150microF, 50V 47microF, 10V 1000microF, fuses and the zener diode. As I had to buy a number of some of the above this cost about £12. Cleaned up the pcb and resoldered a number of joints that looked as if they needed it and fitted the above. Monitor is now working.

Thanks for the help,

Ken.


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