Re: Samsung plasma PS50A550S1F - VS voltage droop
Anyone? Would love to hear from those experienced in smps repair.
Dans2530
Member
Last Activity: 01-02-2023, 10:07 PM
Joined: 08-08-2014
Location: Wollongong, NSW
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Re: Creative Sound Blaster 16s with incorrectly capped TEA2025 amplifiers
So what you are telling me is that Doom would have sounded MORE awesome!? I had a 486 running this card through a maranz amp with some beefy speakers and it sounded good then.
Good on you for fixing something a massive company thought was "good enough" or couldn't be f'ed fixing it. If I still had that gear I would do your mods and test again.
Top work mate!Leave a comment:
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Re: has anybody used one of these testers???
I got the $16 DIY solder it yourself version of this without that fancy case direct from china. I threw it in a cheap $5 jiffy box from jaycar. It only has the two line lcd though.
It works better than you would think and it has all those functions. It also has an ESR test for electrolytics, but doesn't work in circuit and I'm not really sure of the readings, seems right but I wouldn't trust it as 100% accurate.
I use it mostly for checking transistors/mosfets for pinouts and caps to see if they are good as those tests are...Last edited by Dans2530; 09-21-2014, 01:15 AM.Leave a comment:
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Re: Multiple oscilloscope channels
I'm not a scope expert but I would assume that you could do math operations using the scope on more than one signal as a sort of differential analysis?
If someone that has a heap of scope experience could lend their opinion on this, it would be appreciated, I'm here to learn as well.Leave a comment:
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Re: Would this Oscilloscope be any good?
I have just ordered a Rigol DS1074Z after looking over heaps of different online reviews. It seems to offer the most bang for buck, especially since the hardware and options can be "upgraded" as Clutchbox & Tom66 say.
Should get it within a few days so I will let you know how I do with it. Bear in mind, my first oscilloscope is a Hantek 6022BE, so I'm no scope expert. It's not a bad scope, but my god the software is so buggy and crashy! I got by with it though.
If I broke it, it was only AU$65....Last edited by Dans2530; 09-21-2014, 12:20 AM.Leave a comment:
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Re: Samsung plasma PS50A550S1F - VS voltage droop
Update:
I have received the new power factor IC, soldered it in, and.....nothing. Same as before. Voltage sits around 340v on the main filter cap.
What an anti-climax!
The power factor controller is getting power, just no output to the totem pole transistors. If anyone has a schematic for a bn-44 00222a board or can suggest a working theory on how to fix this i will be eternally grateful. I will try anything at this point!
Cheers everyone.Leave a comment:
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Re: Samsung plasma PS50A550S1F - VS voltage droop
Update: i have checked the voltage going to the power factor controller board, all good, but not getting any output to the totem pole transistors that drive the mosfets.
I pulled the controller IC off and you can see in the picture that there looks like a burn mark on the underside near pin 20 (bottom left), which is the gate drive output according to the datasheet.
I have ordered a new IC so it will be a couple of weeks before i can see if it works. In the meantime, i have checked all the other components on that...Leave a comment:
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Re: Samsung plasma PS50A550S1F - VS voltage droop
Now we are getting somewhere!
I will update when I check out the Pfc circuit. Let's hope its something simple.
Thanks again for your time Tom!Leave a comment:
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Re: Samsung plasma PS50A550S1F - VS voltage droop
I did check the main caps voltage and it's around the 340v mark which seems kind of low, as I have read on here it should be around 380-90v or so.
Do you think the Pfc circuit is not boosting correctly under load and the vs controller is hitting max duty so the voltage starts to sag?
The controller for the PFC is the L4981AD, do they have a history of going bad?Leave a comment:
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Re: Samsung plasma PS50A550S1F - VS voltage droop
Update: i have pulled out both caps and they both test within 1nf of their 47nf capacity. I put them back in and i cranked the brightness up to full and the vs voltage started dropping again, but not as fast as it did earlier. So it may be the problem.
I am going to replace them once i find some suitable replacements.
Tom, is there anything else you can think of for me to test in the meantime, just in case that isnt the problem?
Cheers.Leave a comment:
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Re: Samsung plasma PS50A550S1F - VS voltage droop
Thanks for the tip Tom, I'll pull them out and test/replace and see if that helps.Leave a comment:
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Re: Samsung plasma PS50A550S1F - VS voltage droop
Thanks for the quick reply!
Here is my psu, would the caps you are talking about be the blue ones below the larger transformer?...Leave a comment:
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Samsung plasma PS50A550S1F - VS voltage droop
Hi everyone, I have a weird problem with a samsung plasma PS50A550S1F, the tv will operate normally, but only with the cell brightness on the lowest level. Even then, it will cut out occasionally at random.
I have checked all the voltages, all are within spec except for VS, according to the panel it is supposed to be 205. When the panel lights up it drops down to 197v and i cannot adjust it higher with the pot. It fluctuates by about +/- 2v. As i turn the brightness up it drops down further until the relay clicks out at about 191v. It is worse on a bright screen, i can restart with the... -
Re: samsung TV ps-42q97hd clicking
If this board doesn't work powered up by itself, and there isn't any cold solder or burnt out components, check the two sub boards with the MC33067 ICs. On my board that I repaired, the smd Zener diode and the totem pole transistors were busted. I replaced them and the ic as well and it worked fine after that.
On the top sub board it is diode DS823, check that for open or short (mine was open), and test transistors QS803,QS804,QS805 and QS806. If any of these aren't good, replace the lot and the ic for good measure. I used discrete...Leave a comment:
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Re: New Members - please post your introductions here
Hi, i have come to this forum to learn a bit about repairing plasmas, i have fixed one already but its alway handy to have all this knowledge at hand!
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