I have an mlt166a that shows a hot ground. 86 volts at the heatsinks on the primary side. Some of the capacitors tops show the same voltage as the heatsinks. what should I look for to try fixing this one.
Thanks, Bigbe
Thanks, Bigbe
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Re: Mlt166a Megmeet ltc2701td
When you work on the primary (hot side), you do not use chassis ground as the ground ref for voltage readings, you use the ngative leg of the main filter cap (the 450vdc rating) as the ground ref point for the meter. Also do not touch the heat sinks, it can be part of the primary circuits.
So any pictures of the board and the symptom of the problems?Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809 -
Re: Mlt166a Megmeet ltc2701td
Well Budm, The TV won't turn on just blinks red. The 5v jumps around from 4.4 to 4.9 very unstable. when connecting the 5v to the pson pin nothing happens with the 12v or 24v pins. I've changed the common caps that go bad.Comment
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Re: Mlt166a Megmeet ltc2701td
OK, at least the stanDBY 5V is kind of working but not stable, that can be due to too much load or due to bad caps such as the start up cap (22~47uF 50V) in the primary side. You can try heating the board with hairdryer to see if it becomes stable. Then we still have to find out if the PFC voltage booster circuit is working or not. When TV is plugged in but not turn on, you should have about 160~170v right at the two legs of the main 450V filter cap, when you force on the power supply on the PS_ON pin, it should jump to around 370~400VDC range on that cap, if it does not, then the 12v/24V power supply will not run.
Pictures of the boards?
SCH from tom66 web site.Last edited by budm; 12-22-2013, 06:30 PM.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
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Re: Mlt166a Megmeet ltc2701td
I'll have to get the camera out and take some snaps. give me a bit to do that, might be tomorrow.
ThanksComment
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Re: Mlt166a Megmeet ltc2701td
Budm, The SCH did the trick, I had it powered up in an hour. Z3 and the two 10 ohm surface mount resistors were the problem.
ThanksComment
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Re: Mlt166a Megmeet ltc2701td
Glad to hear, tom66 has lots of SCH.
http://www.tgohome.com/ServiceManuals/Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
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This is a warning to inexperienced and experienced techs alike:
The De-facto standard is to have the primary side heatsink live in switching power supplies.
That is the primary side heatsink is referenced to the negative of the bulk filtering capacitor.
Therefore never ever touch the heatsink if the device is plugged in.
And even if it is unplugged let the capacitor discharge first!
Another really serious concern is that the power switch also by De-facto standard is single pole.
This means it only cuts power to the phase or neutral (not both) depending...06-09-2021, 12:01 PM -
This is a warning to inexperienced and experienced techs alike:
The De-facto standard is to have the primary side heatsink live in switching power supplies.
That is the primary side heatsink is referenced to the negative of the bulk filtering capacitor.
Therefore never ever touch the heatsink if the device is plugged in.
And even if it is unplugged let the capacitor discharge first!
Another really serious concern is that the power switch also by De-facto standard is single pole.
This means it only cuts power to the phase or neutral (not both) depending... -
This is a warning to inexperienced and experienced techs alike:
The De-facto standard is to have the primary side heatsink live in switching power supplies.
That is the primary side heatsink is referenced to the negative of the bulk filtering capacitor.
Therefore never ever touch the heatsink if the device is plugged in.
And even if it is unplugged let the capacitor discharge first!
Another really serious concern is that the power switch also by De-facto standard is single pole.
This means it only cuts power to the phase or neutral (not both) depending...06-09-2021, 12:01 PM -
This one should make @Pentium4 smile
(if he is still reading BCN forums) – I got a new old stock / open box Casing Power MPT-301 PSU on eBay for $4 total. 
Yes, it’s a very generic-looking box, but the manufacturer isn’t (at least not back in the days), which is…
Macron Power Technology Co. LTD.
Let’s look at the PSU itself.
The shell/case also appears quite generic, like many “sold-with-the-PC-case” units. However, the shell is well-formed and has decent steel thickness. In terms of... -
Dear all,
I have taken out the motherboard of a Acer TravelMate P214. There is a short to ground on the main power rail (19V). I don't have the schematics or boardview for this board (DAZ8IMB1AA0 REVA). But I have found 4 MOSFETS close to the main power rail : 2 N-Channel and 2 P-Channel.
I have checked resistance across each of the 4 MOSFETS. I have the following readings:
Both N-Channel Mosfets: nothing odd
P-Channel MOSFET number 1:
source - drain : 117 kOhm
source - gate: 96 Ohm
gate - drain: 117 kOhm
P-Channel MOSFET...
Comment