Re: Fixed a ViewSonic N3260w
i replaced the optocoupler ic4. i still have weird measurements between NTC3 and EN1 of IC1. i don't understand how a i can have so many unpredicted changes in polarity across ic4 and along the feedback net???
NTC1 has to be bad. it is dropping nearly 14v. i think zd3 may be bad also. i don't have much of a clue what the values of these should be - any ideas?
12rounds
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Last Activity: 06-30-2015, 07:46 PM
Joined: 09-27-2014
Location: MERRITT ISLAND
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Last edited by 12rounds; 10-28-2014, 06:02 PM. -
Re: Fixed a ViewSonic N3260w
meter reads this one (c16) as 0.021uf
any thoughts on the ic4 question from post #109? there are some circuit changes compared to the schematic....Last edited by 12rounds; 10-23-2014, 12:55 PM.Leave a comment:
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Re: Fixed a ViewSonic N3260w
hang on... on a different page again. talking about c15 i referred to the schematic. after looking at your picture i realized that you are talking about something different! Let me pull that cap and check itLast edited by 12rounds; 10-23-2014, 11:41 AM.Leave a comment:
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Re: Fixed a ViewSonic N3260w
C15 is marked as 102k making it a 0.001uf cap. Unless i am misunderstanding the code.Leave a comment:
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Re: Fixed a ViewSonic N3260w
measured c15 in parallel with another ceramic disc which measured 0.117u. I get 0.118u, which is right on, I believe. I don't have a way to measure esr.Leave a comment:
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Re: Fixed a ViewSonic N3260w
so, i have a cap measuring 1.94u. In parallel with c15 my reading is still 1.94. i will try and find a cap tomorrow at work with a value closer to 0.022u, but is this looking like like i should replace the ceramic discs on the board? i am ready to spend the dollar!
question- the marking on the side of c15 is:
rr
102k
1kv64
doesn't that make this a 0.001uF cap?Last edited by 12rounds; 10-22-2014, 07:21 PM.Leave a comment:
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Re: Fixed a ViewSonic N3260w
tried to measure cap c15... i think i have an issue, but i don't know if it is equipment or the part. i have a fluke12 to measure capacitance. 0.022u is out of range so i figured i could connect in series with a cap of known value and read the sum and calculate. i think that the meter has the resolution to do this in the 1u range. i get a reading of 0.001u when i do this. is this a equipment problem or a bad part?Leave a comment:
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Re: Fixed a ViewSonic N3260w
Went back and re-read to re-think...
Question (may be stupid and obvious) - active high means that the voltage on a pin will always be above the threshold in normal operation, correct?
If so, my pin8 is at pretty much 0. reading the description you posted of how the comparator and EN1/2 work, i expect that something is wrong in this portion of the circuit. I went through to verify the schematic diagram and there are some differences here. I think that i have an issue with optocoupler ic4 - i see that there is 5v on p1 and 4v...Last edited by 12rounds; 10-22-2014, 11:52 AM.Leave a comment:
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Re: Fixed a ViewSonic N3260w
OK. so, i don't know where my head was at before, but even knowing that i had 2 different ground references, i must have been on the wrong one measuring CNS1 and 2.
here are the results, with respect to chassis GND:
CNS2
pin 1-4 = 0
pin 5-8 = 0
p9 = 4.8
p10 = 4.8
CNS1
pin 1-4 = 0
p 5-6 = 2.5
p 7-9 = 5
p 10 = 3.4
p 11-12 = 4.8
i have a diagram that says p12 on cns1 is over current protect and should be 0v. i did not check capacitance of c15 - mains side...Last edited by 12rounds; 10-20-2014, 06:29 PM.Leave a comment:
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Re: Fixed a ViewSonic N3260w
Will check and double check tomorrow and post results.Leave a comment:
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Re: Fixed a ViewSonic N3260w
i switched my reference. still getting the weird 65v. it doesn't make any sense.
i'm confused because in order to get anything on cns1/2 i need to see voltage on the source side of q1 or nothing is going to propagate to across to the secondary side of t1. i don't see anything on q1 source, but somehow there is still 65v.
what i really don't get is where the different voltages are coming from. i thought that t2 was only 5v. the only thing that makes me wonder is the way that the schematic is drawn to show crs1 as a part of the...Last edited by 12rounds; 10-19-2014, 06:22 PM.Leave a comment:
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Re: Fixed a ViewSonic N3260w
i am reading 65v on cns1 where i should have 12 and 24v. i don't know why....Leave a comment:
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Re: Fixed a ViewSonic N3260w
i am not getting 12 or 24v. i am getting about 65v in both of these places. there is also something wrong with q1 and q2 - possible with ic1. i get 346v on q1 drain, a pulsing low on the gate and what looks like nothing on the source. i have pretty much nothing on q2 anywhere.
i have 13.2v on p12 of ic1 so it is getting voltage. i have nothing on the EN1 line (ic1p8). i think that i have an issue with optocoupler 1c4 - i see that there is 5v on p1 and 4v on pin2, so the diode should be coming on. on the primary side of the coupler i have...Last edited by 12rounds; 10-19-2014, 05:31 PM.Leave a comment:
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Re: Fixed a ViewSonic N3260w
update:
I poster printed the available schematic and sat down for a couple hours to see if i could understand what is happening with my broken supply. I am pretty confident that my PFC circuit is functioning properly at this point - IC3 and Q3 seem to be playing nice with each other and functioning as a boost converter; I now have 346V across the main filtering cap c1.
That is the good part. the bad part is it looks like this is remaining 346V is DC across the transformer. I don't think that IC2 (smps ic) is pulsing its drive...Leave a comment:
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Re: Fixed a ViewSonic N3260w
spent some more time with this - after replacing the rest of the electro caps, the pfc ic, dead q7, and incorrect q11 the supply comes one without any more smoke. have to start looking at the schematic again and see what else is supposed to turn on now. no backlight comes on, so there is still something wrong.
I'm trying to understand how the DRV output on IC3 is supposed to work. I think i might be getting hung up on this...Last edited by 12rounds; 10-14-2014, 07:15 PM.Leave a comment:
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Re: Fixed a ViewSonic N3260w
pretty close so far. after work going to go through the pfc network and see is i can find anything wrong that would short out the ic. any ideas?Leave a comment:
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Re: Fixed a ViewSonic N3260w
you are correct - 16pin ic vcc pin is not 25ohm to gnd. pfc ic is internally short to gnd...
i just found this - it is for a different supply, but the parts that i have checked are VERY similar....Last edited by 12rounds; 10-01-2014, 09:25 AM.Leave a comment:
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Re: Fixed a ViewSonic N3260w
got wires crossed. i have the 16 pin soic as a high voltage resonant controller - for step up transformer i assume -and ic2, an 8 pin soic, as the smps controller (by part number and data sheet cross reference).
i have the 16pin ic vcc coming from q9 collector. q9 emitter is tied to vcc of pfc ic.Leave a comment:
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Re: Fixed a ViewSonic N3260w
q11 collector is not connected to smps ic vcc. it is decoupled via c32.
i have 2 of these boards - both nonfunctional. i haven't touched to other one, but it does not read 25ohhs from pri gnd to q11 collector.Leave a comment:
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Re: Fixed a ViewSonic N3260w
what is ics?Leave a comment:
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