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Search: Posts Made By: R_J
Forum: General Electronics Technical Discussion 04-12-2021, 09:22 AM
Replies: 13
Views: 593
Posted By R_J
Re: backlight tester malfunction

I would check the mosfet? near the red output plug, then check the diodes in that area. Also check for any poor solder connections.
If you only had the tester for a short time, contact the supplier...
Forum: Troubleshooting Audio Equipment 04-11-2021, 09:46 PM
Replies: 9
Views: 133
Posted By R_J
Re: Kenwood KX-56CW Duel Cassette Deck Repair

With the correct voltages, Q31 has .7v on it's base so it is already tuned on so shorting it e~c will have no effect.
It could be that Q32 is bad as it should be turned on and have the same voltage...
Forum: General Electronics Technical Discussion 04-11-2021, 09:15 PM
Replies: 13
Views: 593
Posted By R_J
Re: backlight tester malfunction

When the leads were backwards there was very little current flowing so the voltage dropped to 145v, when it was the right way around, the voltage dropped to 2.7v because there was current flowing...
Forum: Troubleshooting Power Supplies and Power Supply Design 04-11-2021, 08:45 PM
Replies: 7
Views: 397
Posted By R_J
Re: Compaq PDP-121P - Baked MOV

The two caps are in series, if the cap that has the mov across went totally open, there would be at least 300vdc across it when the other cap was conducting. The TVR 10241 is rated maximum operating...
Forum: Troubleshooting Desktop Motherboards, Graphics Cards, and PC Peripherals 04-11-2021, 07:59 PM
Replies: 9
Views: 246
Posted By R_J
Re: Installing a Cap in circuit,help

I suspect you have caused a short between the positive copper trace and the negative feedthrough. But I can't tell because your pictures are not clear, they are too out of focus (shakey) to make out...
Forum: Troubleshooting TVs and Video Sources 04-11-2021, 07:47 PM
Replies: 3
Views: 105
Posted By R_J
Re: LG 60PV450 - Replaced Z-Sus, now display has purple snow/fuzz

What about the VSC voltage? what is it and does it match the panel sticker. Try adjusting the set_up & set_dn controls, Mark there positions with a felt marker before adjusting them.
Forum: Troubleshooting Audio Equipment 04-11-2021, 06:30 PM
Replies: 2
Views: 58
Posted By R_J
Re: Yamaha YST-C10 stereo capstans run for 10 min when unit is turned on

It does sound like weak capacitors in the unit, likely in the power supply. post some pictures of the boards etc. so we can see what we are dealing with.
Here is a service manual for a YST-C11 which...
Forum: General Electronics Technical Discussion 04-11-2021, 03:53 PM
Replies: 13
Views: 593
Posted By R_J
Re: backlight tester malfunction

So what do you do? connect the tester to the led string THEN turn it on? The testers I have used, "display" a high voltage, then as soon as the string is connected the "voltage display" drops to the...
Forum: Troubleshooting Audio Equipment 04-11-2021, 03:25 PM
Replies: 9
Views: 133
Posted By R_J
Re: Kenwood KX-56CW Duel Cassette Deck Repair

I think these voltages are just measured wrong, C&B reversed. Q31 base is too low and not being turned on. To test, you can short Q31 E-C it should play at normal speed. If It does, then check the...
Forum: General Electronics Technical Discussion 04-11-2021, 12:36 PM
Replies: 13
Views: 593
Posted By R_J
Re: backlight tester malfunction

I don't think you read the whole post, He said it WAS working and supplying 300v when testing the strips and NOW only shows 17v~20v
I suspect the unit has a poor solder connection inside and that...
Forum: Troubleshooting Desktop Motherboards, Graphics Cards, and PC Peripherals 04-10-2021, 05:55 PM
Replies: 9
Views: 246
Posted By R_J
Re: Installing a Cap in circuit,help

The white half of the cap is the positive, the negative has a space between the leads feed-through (which looks destroyed) and the positive copper trace. Same on the other side, where the positive...
Forum: Troubleshooting TVs and Video Sources 04-09-2021, 07:23 PM
Replies: 4
Views: 134
Posted By R_J
Re: Samsung Model number

Ddi he burn his hands when he touched the tv? Ususlly a missing model/serial number stcker indicates the tv is hot.
Forum: Troubleshooting Computer Displays 04-09-2021, 10:53 AM
Replies: 40
Views: 2,449
Posted By R_J
Re: Samsung Syncmaster 245b BN44-00195A

Opening J808 was only to remove the vcc from the main power supply ic, you can resolder it if you like. Yes dp803 is in the gate drive circuit for the pfc mosfet. so it is ok, so it could be that the...
Forum: Troubleshooting Power Supplies and Power Supply Design 04-08-2021, 09:02 PM
Replies: 56
Views: 1,558
Posted By R_J
Re: 1300W PSU - Help with replacement mosfet

The optocouplers have numbers on them, get the datasheet and you will see how they work and how to check them. They are basically a led on one side and a photo transistor on the other, when the led...
Forum: Troubleshooting TVs and Video Sources 04-08-2021, 08:26 PM
Replies: 7
Views: 187
Posted By R_J
Re: Rca led52b45rq

The standby circuit usually supplies the vcc voltage, it is then switched and regulated by Q108, This transistor will have a zener diode (ZD102) in its base which sets the voltage (15~18v) The supply...
Forum: Troubleshooting Computer Displays 04-08-2021, 08:05 PM
Replies: 40
Views: 2,449
Posted By R_J
Re: Samsung Syncmaster 245b BN44-00195A

If the pfc ic is getting 15v for it's vcc it should be working, but it is not, so something must be wrong in that circuit. There is a low ohm resistor on the source of QP801S (pfc fet) check if it is...
Forum: Troubleshooting Computer Displays 04-08-2021, 10:24 AM
Replies: 40
Views: 2,449
Posted By R_J
Re: Samsung Syncmaster 245b BN44-00195A

Well the pfc circuit is not working. There is a small jumper wire, J808 which supplies vcc to icm801, If you lift one end of that jumper wire, then power on the board and see if the pfc voltage comes...
Forum: Troubleshooting Computer Displays 04-08-2021, 09:49 AM
Replies: 40
Views: 2,449
Posted By R_J
Re: Samsung Syncmaster 245b BN44-00195A

That 18v is still a bit low but might be ok. Check the voltage across the main filter CP801S and see if the voltage goes up when you power ON the power supply (S_B~PSON) it should increase from 317v...
Forum: Troubleshooting Computer Displays 04-07-2021, 07:03 PM
Replies: 40
Views: 2,449
Posted By R_J
Re: Samsung Syncmaster 245b BN44-00195A

Those voltages are low, The collector needs to be around +25 volts to be able to supply +18 volts on the emitter for the other ic's

I see that you have the power supply turned ON with a short...
Forum: Troubleshooting Computer Displays 04-07-2021, 01:01 PM
Replies: 40
Views: 2,449
Posted By R_J
Re: Samsung Syncmaster 245b BN44-00195A

I see what looks like a damaged trace off of one of the optocouplers, can you check this?
Forum: Troubleshooting Computer Displays 04-07-2021, 11:16 AM
Replies: 40
Views: 2,449
Posted By R_J
Re: Samsung Syncmaster 245b BN44-00195A

The schematic itself is close but the location numbers are different. When you installed the 47f/50v cap, it would have been likely seen as a short and either blew that resistor I referenced, it...
Forum: Troubleshooting Computer Displays 04-07-2021, 10:21 AM
Replies: 40
Views: 2,449
Posted By R_J
Re: Samsung Syncmaster 245b BN44-00195A

Why don't you download the schematic? I have no idea what the "left side" is. Do you mean the primary or HOT side?
You likely opened either the main fuse or the fuse resistor that supplies the...
Forum: Troubleshooting Computer Displays 04-06-2021, 04:52 PM
Replies: 40
Views: 2,449
Posted By R_J
Re: Samsung Syncmaster 245b BN44-00195A

Check that you still have 5 volt standby, installing a 50v cap in the CB806 location on your version of the board is not good as it is across the full B+ (300vdc). I was using a schematic for the...
Forum: Troubleshooting Computer Displays 04-06-2021, 10:44 AM
Replies: 40
Views: 2,449
Posted By R_J
Re: Samsung Syncmaster 245b BN44-00195A

This board must be slightly different, It was hard to read the numbers on your board. If cb806 was not populated then it must not be needed so remove it (it would not have been an electrolytic in...
Forum: Troubleshooting Game Consoles & Other Weird Devices 04-05-2021, 12:00 PM
Replies: 21
Views: 503
Posted By R_J
Re: Fluke 289 multimeter not working

I notice that the ferrite on L1 is broken, although this won't be the problem, it does seem the meter may have been dropped.
Showing results 1 to 25 of 500

 
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