valvashon
Senior Member
Last Activity: 04-18-2024, 08:43 AM
Joined: 10-27-2020
Location: Seattle, WA
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Toshiba EM131A5C-BS microwave oven- noisy EE16 2.7 mH inductor
This poor microwave oven was purchased by my former employer in 2019 (it's a 7/2018 build) and lasted for about 3 months before making a terrible noise when in use. I determined that it was the main transformer and contacted Toshiba. They asked for a picture of the cord cut in half and the serial number, and then credited my boss' credit card. Rather than sending it to the e-waste, I bought a transformer on eBay and thought I'd try flipping it. Discovered that used microwave ovens aren't worth much but in for a penny, in for a pound as they say. It sat in my basement getting kicked and shoved...
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Repair Success! Middle Atlantic UPS2200R-IP
Yesterday I successfully repaired a Middle Atlantic UPS2200R-IP that had inadvertently been used as a surge suppressor at our transmitter site. It has already been replaced with an updated one but it's coming home with me now instead of being e-cycled. To be specific, this is the MA model that has the blue backlit display and has been discontinued, although this design may have been used in many UPS units including the smaller Middle Atlantic ones in this series.
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The FET's are marked the same as the ones that came out of there although of course they could be counterfeit. Digikey shows this part number as a "last time buy" starting in 6/2024 so fakes could already be popping up. Schematic shows the higher current ones but the lower current ones were on the board before I started shorting things out.
The set would power up and stay powered up (the first time on startup) when I had one or the other backlight connectors pulled. Dim screen during startup but then it went black. Could still hear audio; I assume that the screen going... -
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Replaced the shorted MOSFET's with eBay specials from across the ocean. Marked FDS8958A, they could of course be counterfeit but as you can see, the TV now works. Would love to now thank everybody for their help but of course the saga continues. The set will turn on and come up with a picture, but then turn off after 5-10 seconds. Subsequent turn on's will produce a flash of a screen, then turn off again. It takes 4-5 tries to actually...Leave a comment:
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...Mosfet # 1 2 3 4 Source & drain 4.4 ohm 0 ohm 4.4 ohm .3 ohm Source & gate 222 ohm 104 ohm 7.0 m ohm 5.2 k ohm Last edited by valvashon; 01-09-2024, 10:54 AM.Leave a comment:
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Insignia NS-LCD19-09 (PS OK, Inverter problem?)
For some reason I'm just not going to let this 19" TV defeat me. I guess because I have a schematic to work from I feel like I'm oh so close.
History- while adding a turn-on circuit I let a small screw roll under the power board. Worked through all of that circuitry, probably replacing a MOSFET and PWM controller that were not bad but I was following the service manual. Finally figured out that the power supply is in working order when the inverter section (for the backlights) is disconnected. When the +12 supply to the inverter is disconnected the +12 and +5 will come up... -
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The only other component that I have found that failed (besides the one MOSFET) was the common cathode dual rectifier just ahead of the MOSFETs in the circuit. One side/diode was shorted corresponding to the shorted MOSFET.
I have ordered the dual rectifier from eBay as I did not find a good cross at Digi-Key. That part number is SF10A600HPI by AUK. The Digi-Key cross was electrically compatible but in a larger case that would have required board and heat sink modification.
I did find an acceptable substitute for the MagnaChip MOSFET at Digi-Key. The part number...Leave a comment:
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I was going to check all the TO220 devices today anyway but thanks for the heads up on the problem MOSFET devices. QP802CS is the shorted one, dead short across all legs. Others check OK but I will replace its companion QP801CS. Do we know if it's the brand of the MOSFET Samsung used (MagnaChip) or is the design of the board just hard on whatever MOSFET is in there? DigiKey carries Infineon Technologies MOSFETs and I will cross to one of those and just shotgun all 4 MOSFETs on that board if the MagnaChip ones are problematic.
Again, thanks for the help!Leave a comment:
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Samsung UN65KU6290F PS board blows fuses
Samsung UN65KU6290F (May 2017); received from local Buy Nothing group. Was listed as "just went dead" and they wanted it gone. I brought it home, didn't notice anything visually wrong with the power supply board, looked up the cost of a new one and that's about as far as it went. Family was tired of tripping on the foot of the set so I decided to dig in and repair or toss.
Can't believe that I didn't check it earlier but I found the main 8 amp fuse blown. Jumped across it with a 10 amp blade style fuse and you can see that it literally exploded inside the second I plugged... -
Re: Samsung UN55FH6030: random power cycling
Thanks for the help on this one everybody. I opened the unit up and checked the voltages; they were stable. I heated up the caps and the board gently with a heat gun, no shutdowns noted. I then pulled the board and touched up a number of solder points including transformer connections and cap connections. Put the unit back together and no shutdowns noted. Wrapped the thing in a blanket, no shutdowns noted.
It's as if pulling off of the wall and taking down the hall to the shop fixed it. It's been back on the wall for close...Leave a comment:
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Samsung UN55FH6030: random power cycling
Samsung UN55FH6030, perfect size for my office and does OTA well but isn't a smart TV. That's OK because I am a TV station engineer and only need it for OTA monitoring.
About a month ago it started power cycling itself once or twice a day and now it's nearly continuous once it's been on for a few minutes. Changing channels would really start it cycling and it would take several minutes to stabilize but now it's just doing it almost non-stop without changing channels.
Once I disconnected the antenna I found that I could change channels with no issues. My guess is... -
Samsung UN19F4000AF- half chime on startup
Yet another 19" TV here in the maintenance shop. This one belongs to my 95 year old mom so I'd really like to get it fixed for her.
Samsung UN19F4000AF. Back home for a week, I found this TV in her master bathroom unplugged and not connected to anything. Would start to power up and make about half of the Samsung startup chime, then shut back down.
Brought it back home with me but after having a quick look it no longer tries to start up and does not have the red LED lit in the IR receiver/switch thing.
Power supply is good, tested it on an exact same... -
Re: Insignia NS-LCD19-09 no standby LED; (new problem)
At the risk of violating copyright for the service manual I bought (which may be different than the one that is available for free online) I'm attaching part of it. I have checked everything on the "hot" side of the power board aside from a few very small value SMT caps.
Everything checks out as having the correct value; what I have measured is highlighted in yellow. Components circled with an X are not on the board. Unless I'm missing something the High Voltage Startup chip is the likely suspect. C 906 checked...Leave a comment:
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Insignia NS-LCD19-09 no standby LED; (new problem)
Having a new problem with the 19" Insignia that I modified with one of my automatic turn on circuits. That is now completely disconnected so that is not the issue. I was doing some modifications on that circuitry and managed to short something out on the underside of the power board.
Actually found and bought the service manual (who knew it was even available?!) which brought me to the High Voltage Startup Circuit controller chip.
Looking up that chip number- LD7575APS brought me to the attached datasheet. I have marked my voltage readings on the schematic sheet (open in new... -
Re: Samsung LS23PTNSF/ZA- Erratic behavior 20 minutes after turn on
For what it's worth, I did shotgun all the caps in this power supply and the TV is now working for extended periods of time without any erratic behavior. I did test the caps once they were out but all were OK cold. I didn't measure the voltages (before replacing the caps) when the set was cold and when it was warmed up. I suppose I should have but with only a meter I wouldn't have seen what was probably some AC ripple and I don't have easy access to a scope.Leave a comment:
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Samsung LS23PTNSF/ZA- Erratic behavior 20 minutes after turn on
This smaller Samsung TV will turn on fine and work fine at first. By this I mean that it will respond properly to the remote commands with channel up and down working and volume up and down working, etc.
After the set has been on for a while- 20 to 30 minutes- it stops responding or responds erratically to commands from the remote or the front panel buttons. Remote is fine, works well with other TV's.
My guess is caps in the power supply warming up and changing value leading to the erratic behavior. TV does not act erratically unless you try to change a channel or something like... -
Re: Sharp LC19SB24U; red vertical line comes and goes
Thanks for all your help everybody but I think we are done here. I tried shimming and just made things worse. And notice how the red line is still there.
The only thing left is to figure out who gets the boards- ShopJimmy or eBay?
Val...Leave a comment:
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Re: Sharp LC19SB24U; red vertical line comes and goes
Here's what the display looks like without the T-Con board connected. Colors are reversed but the blue line is showing up where the red line was. Overview and closeup.
I'll assume that we are all done here with this set aside from parting it out, assuming anybody wants parts from a 15 year old 19" TV.
Val...Leave a comment:
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Sharp LC19SB24U; red vertical line comes and goes
Yes, this is a very old Sharp 19" but I would like to fix it if possible. As you can see from the attached picture there is a single red vertical line.
Yesterday when I turned the set on, it was there for about 30 minutes then disappeared and did not show up again (set was on for another 3 hours or so).
Today it was not there when I powered the set on, then appeared after about 15 minutes. Set has been on for about an hour and it's still there.
From what I have read I'm guessing that this might be the t-con board and not the display itself as it does come and go.
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