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Search: Posts Made By: R_J
Forum: Troubleshooting TVs and Video Sources Today, 02:36 PM
Replies: 15
Views: 210
Posted By R_J
Re: LG 47LN5700 No voltages on SMPS only standby voltage present

The ic will output a switching pulse, you would need a isolation transformer and a scope to check the ic's output
Forum: Troubleshooting Game Consoles & Other Weird Devices Today, 02:21 PM
Replies: 10
Views: 159
Posted By R_J
Re: Gardena R38li lawnrobot mainboard power issue

Based on internet pictures of the board, it kooks like the "blown something" is a mlcc (ceramic cap), the cap that was missing is a 220f/35v. Like suggested there is likely one or more shorted...
Forum: Troubleshooting TVs and Video Sources Today, 02:06 PM
Replies: 15
Views: 210
Posted By R_J
Re: LG 47LN5700 No voltages on SMPS only standby voltage present

When you short out a capacitor with 170 volts on it, you do damage. You can check zd602, if it is not shorted, start by replacing ic601.
Forum: Troubleshooting Audio Equipment 09-27-2020, 10:17 PM
Replies: 13
Views: 214
Posted By R_J
Re: troubleshooting definitive technology prosub 60

R7 is a ntc thermistor, it gets hot and the resistance goes down, thats how it works. it will not be the problem. The cold temperature is 20Ω It is just for inrush protection. they can fail open but...
Forum: Troubleshooting TVs and Video Sources 09-27-2020, 11:13 AM
Replies: 3
Views: 421
Posted By R_J
Re: Hisense - 50K3110PW

Thank you for the follow up, not many people will do this so we never know if a repair worked.
Forum: Troubleshooting TVs and Video Sources 09-27-2020, 11:01 AM
Replies: 13
Views: 102
Posted By R_J
Re: LG 50PG3000 Plasma - No Display

Have you checked the fuse on the Z-sus board? Post some pictures of the back of the tv and the boards so we can see what we are dealing with.
Have you checked the other threads on this model?
Forum: Troubleshooting TVs and Video Sources 09-27-2020, 10:39 AM
Replies: 2
Views: 90
Posted By R_J
Re: Samsung UE48JU6445K Vertical Lines

It is the cof that is defective, Not repairable without special equipment to change the cof tab.
Forum: Troubleshooting Audio Equipment 09-27-2020, 10:31 AM
Replies: 13
Views: 214
Posted By R_J
Re: troubleshooting definitive technology prosub 60

If you have a variac, that would work the best so you could increase the a/c voltage slowly. If you don't have one then you can use a lamp, but the wattage of the lamp is not that critical. It is NOT...
Forum: Troubleshooting Computer Displays 09-27-2020, 10:22 AM
Replies: 5
Views: 153
Posted By R_J
Re: Help on Samsung Syncmaster 732N LED conversion

If you lift J301, that will disable the inverter section so you can leave the blue caps in place.
Forum: Troubleshooting TVs and Video Sources 09-26-2020, 09:47 PM
Replies: 15
Views: 210
Posted By R_J
Re: LG 47LN5700 No voltages on SMPS only standby voltage present

Q501 is the vcc regulator/switch, the input (Collector) will be around 25vdc, the output (emitter) will be around 15~16vdc. Q501 is turned on by IC503 optocoupler.
Q502 is the regulator for the vcc...
Forum: Troubleshooting Audio Equipment 09-26-2020, 09:14 PM
Replies: 13
Views: 214
Posted By R_J
Re: troubleshooting definitive technology prosub 60

You can use a 60~100 watt incandescent lamp in series with the a/c input, this will limit the current and may help prevent the amp from blowing up during troubleshooting.
Forum: Troubleshooting TVs and Video Sources 09-26-2020, 08:23 PM
Replies: 10
Views: 159
Posted By R_J
Re: Vizio E55-D0 help identifying "smoked" IC on main board

The ic might be a Ti TPS54331 or TPS54231, the tps54231 has 12Vin, 3.3vout using a 10H coil? Check if the resistors are close for this voltage
Forum: Troubleshooting Audio Equipment 09-26-2020, 07:48 PM
Replies: 13
Views: 214
Posted By R_J
Re: troubleshooting definitive technology prosub 60

If Q1 & Q7 were shorted and R19 open, it is very likely the gate drive circuit is also damaged, Z1, Z4, R1, R18, Q3, Q4, Q5 etc. Z1&z4 are zener diodes and may check like a diode but zener at the...
Forum: Troubleshooting TVs and Video Sources 09-26-2020, 07:16 PM
Replies: 15
Views: 210
Posted By R_J
Re: LG 47LN5700 No voltages on SMPS only standby voltage present

You likely blew up the pfc circuit. check D601,D602,D603, but you may have damaged ic601, Q501,Q502. IC101 may not operate wit the low B+ of 172v, it needs the pfc boosted voltage which is around...
Forum: Troubleshooting TVs and Video Sources 09-26-2020, 01:39 PM
Replies: 15
Views: 210
Posted By R_J
Re: LG 47LN5700 No voltages on SMPS only standby voltage present

Yes in this case you can short stb3.3 to pwr-on, there is a 470Ω resistor already there. Have you checked F101? When you say source voltage do you mean VCC? 14~16 volts vcc is about right.
Forum: Troubleshooting TVs and Video Sources 09-26-2020, 12:45 PM
Replies: 15
Views: 210
Posted By R_J
Re: LG 47LN5700 No voltages on SMPS only standby voltage present

Disconnect the cable between the main board and power supply, and connect around a 1k resistor between standby & pwr-on, it looks like it needs a logic high, not low to turn it on
Forum: Troubleshooting Computer Displays 09-26-2020, 11:00 AM
Replies: 8
Views: 252
Posted By R_J
Re: Acer AL1916W - Two seconds to black - Voltage regulator problem?

The diodes. d504 & d507 seem to check ok, they may check different due to r523/c530. You could swap D502 or D503 for D504 and see if it makes a difference, but if you are not comfortable with...
Forum: Troubleshooting Computer Displays 09-26-2020, 09:50 AM
Replies: 5
Views: 153
Posted By R_J
Re: Help on Samsung Syncmaster 732N LED conversion

You need the information for the led board, the yellow wires are likely led on/off and led dim. The Samsung seems to have 2 dim lines, A-dim & B-dim, connecting either dim line to the led board...
Forum: General Electronics Technical Discussion 09-25-2020, 09:41 PM
Replies: 8
Views: 126
Posted By R_J
Re: Help sourcing replacement / alternative chip

If you know the logo, all you need to search is "alpha & omega 7408"
Forum: Troubleshooting Desktop Motherboards, Graphics Cards, and PC Peripherals 09-25-2020, 09:18 AM
Replies: 10
Views: 439
Posted By R_J
Forum: Troubleshooting TVs and Video Sources 09-24-2020, 09:56 PM
Replies: 20
Views: 653
Posted By R_J
Re: Samsung UN55H6203 - Power Supply BN44-00774A

M1+ is the positive supply for the led string, M5- is the return of the led string, M1- & M2+ are connected together, same goes for M2- & M3+ etc. it is basically one string between M1+ & M5- The...
Forum: General Electronics Technical Discussion 09-24-2020, 09:37 PM
Replies: 8
Views: 126
Posted By R_J
Re: Help sourcing replacement / alternative chip

It is a mosfet, Alpha & Omega AON7408
Forum: Troubleshooting Power Supplies and Power Supply Design 09-24-2020, 09:10 PM
Replies: 1
Views: 45
Posted By R_J
Re: Astec AA15990 Schematics

Got any pictures of this power supply? The only astec supplies I worked on were the old open frame ones with the 3 white connectors for the output. They had a protection scr across the +12 volt...
Forum: Troubleshooting TVs and Video Sources 09-23-2020, 05:12 PM
Replies: 39
Views: 5,348
Posted By R_J
Re: Dreambox 500s no power on

If C421 is burning It is either NOT a capacitor (maybe a resistor or inductor?) or it is shorted!
Take C421 out of the receiver and connect the 12v adaptor across it, if it burns it is bad. These...
Forum: General Electronics Technical Discussion 09-23-2020, 10:26 AM
Replies: 14
Views: 270
Posted By R_J
Re: what did i do wrong?

I use this adafruit 1497: Digikey 1528-1524-ND. and sdr-sharp software on a PC, there is also other sdr software that works well.
Showing results 1 to 25 of 500

 
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