hello. have this PS from cisco switch.
it have V+/400V/, but dont have VCC, VG and VS. can someone lead me to repair?
it have V+/400V/, but dont have VCC, VG and VS. can someone lead me to repair?
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Last edited by ktmmotocross; 07-31-2017, 08:54 AM. -
Re: LITEON PS1211 power supply
Check R310, R318 and C306,You need at least +8 volts vcc for ic300 or you could have a faulty ic300Last edited by R_J; 07-31-2017, 10:32 AM. -
Re: LITEON PS1211 power supply
Also check C308, the 10uF, 50V small electrolytic cap. If it's bad, IC300, the 3845B PWM IC, cannot start up. If it's bad, use a Nichicon PW, Nippon Chemi-Con LXZ, or Panasonic FC series part. C308 is stressed some.PeteS in CA
Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
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To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
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Re: LITEON PS1211 power supply
hello.
Thanks for advices.
i have 8V on 7pin of IC300, but no voltage on any other pinComment
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Re: LITEON PS1211 power supply
IC300 pin 8 is zero volts? It's the 5V Reference for the IC. IC300 may be bad, or C301 may be bad. Do you have a really low resistance from IC300-8 to IC300-5?PeteS in CA
Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
****************************
To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
****************************Comment
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Re: LITEON PS1211 power supply
8 volts is at the low end (cutoff) I believe it should have a bit more voltage to start up. I would think it should be at least 10 volts when first powerd on. I might also check D304, R311 and ZD301 That part of the circuit keeps the ic running
I also think the ic300 could be badLast edited by R_J; 08-02-2017, 04:14 PM.Comment
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Re: LITEON PS1211 power supply
now i have 2 of them in the same condition, but the second have 10V Vcc, Vref ok,Comment
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Re: LITEON PS1211 power supply
what voltages must be on this chip so it must work?Comment
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Re: LITEON PS1211 power supply
If ypu have 0 volts on Vref, either the ic is defective or a component is shorted that is connected to pin 8. Did you check fet Q102, zd102,zd103 and R116? if R116 is open, q102 is bad. ZD103 needs to be checked out of circuit if R116 is good
Check R311, zd301 and d304 they supply the run voltage when the circuit is working.
Also check that D203 is not shorted on the +12VCSLast edited by R_J; 12-25-2018, 11:13 AM.Comment
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Re: LITEON PS1211 power supply
the secondone is miraccly started to working. i measure ic300 and first not working have 0.7V Vref and VCC 8.5V
Second have VCC 10V and Vref 5V
interchanged ic300 but nothing changed so ic300 is good
resistance between gnd and VCC is on working board about 15kohm and not working 13kohmComment
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Re: LITEON PS1211 power supply
If the second one had been not working and suddenly started, I'd look for bad solder joints on the primary side. That assumes that R310, R318, and C308 are good - if either resistor is open or C308 has gone high ESR the 3845B, IC300, will not start up.PeteS in CA
Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
****************************
To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
****************************Comment
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Re: LITEON PS1211 power supply
do u think i can lower one of the feeding resistor to bring vcc higher?Comment
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Re: LITEON PS1211 power supply
i measure resistance to ground on all pins of ic300 and it is nearly identicalComment
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Re: LITEON PS1211 power supply
i mean compared to good one board
even IC051 and ic101 have same pin resistance to ground on bad and working boardLast edited by ktmmotocross; 12-30-2018, 11:18 AM.Comment
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Re: LITEON PS1211 power supply
i think that come caps is bad. can anyone lead me what caps to check?Comment
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Re: LITEON PS1211 power supply
now the revived PSU died again and i notice that VCC falls from 10 to 8.5 and Vref goes to 0.8V as the bad PSU. So i think that main problem is very low VCC to start ic.
what component can be behind that voltage lowering?
every component i measure was in toleranceComment
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Re: LITEON PS1211 power supply
Do you still have pfc boost voltage +V400 volts?Comment
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Re: LITEON PS1211 power supply
where i can find "pfc boost voltage"?
+V is 415VComment
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Re: LITEON PS1211 power supply
i try tip from youtube, where guy trying to find capacitor that were little bad with hot air
so i heat some of them with hotair gun and u know what? when i heat one of them i have good output voltage :-)
VCC also rise up to cca 10V
it was C902 - 4,7uF so i check it and have this reading:
4,4uF, ESR-2,3ohm, Vloss-1,3%
i replace it and PSU now work
as i see there are some same capacitors, so i replace them allAttached FilesLast edited by ktmmotocross; 01-16-2019, 12:03 PM.Comment
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Re: LITEON PS1211 power supply
IM REALLY GETTING SICK OF THIS SHIT
replaced all small caps, but still after some time/hour or little more/ the PSU failed to start
as i said earlier after little heat from hotair station/which was a tip from youtube for finding failing caps/ in one location the PSU start
What can be bad?Attached FilesLast edited by ktmmotocross; 02-02-2019, 01:09 AM.Comment
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