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Search: Posts Made By: rievax_60
Forum: Troubleshooting TVs and Video Sources 07-12-2018, 09:15 AM
Replies: 140
Views: 18,414
Posted By rievax_60
Re: Sharp aquos LC-40LE810E

PNL-12V should be pin 1 of PL connector.
Forum: Troubleshooting TVs and Video Sources 07-12-2018, 06:18 AM
Replies: 140
Views: 18,414
Posted By rievax_60
Re: Sharp aquos LC-40LE810E

Pins 1 and 2 of PC7703 are on the live side. Leave them alone for now.
The schematic for the power supply can be found here,...
Forum: Troubleshooting TVs and Video Sources 07-11-2018, 10:11 AM
Replies: 140
Views: 18,414
Posted By rievax_60
Re: Sharp aquos LC-40LE810E

Those voltage readings show that the AC-DET is working properly.
There must be something else wrong, Does the voltage on pin 1 disappear after 7 seconds also?
Forum: Troubleshooting TVs and Video Sources 07-10-2018, 03:55 PM
Replies: 140
Views: 18,414
Posted By rievax_60
Re: Sharp aquos LC-40LE810E

Measure some pin voltages on the PD connector as the TV is being turned on.
Look at post 21 as an example.
I mainly want to know what happens at pins 1 and 9.
Forum: Troubleshooting TVs and Video Sources 07-10-2018, 04:50 AM
Replies: 140
Views: 18,414
Posted By rievax_60
Re: Sharp aquos LC-40LE810E

Yes, solder a 68K on top of R7019 or replace R7019 with a 33K or something a bit lower. The value is not critical. This mod increases LED current to compensate for the loss of the opto's CTR due to...
Forum: Troubleshooting TVs and Video Sources 06-28-2018, 12:17 AM
Replies: 23
Views: 9,605
Posted By rievax_60
Re: Toshiba Picture Fades To Black But Audio Continues

I have a Regza 42x3000a here which fades to black from bottom to top only when it displays video.
If I unplug the antenna or switch to an AV input in with nothing connected, the screen stays...
Forum: Troubleshooting Laptops, Portable, and Mobile Devices 05-09-2018, 05:47 PM
Replies: 79
Views: 35,197
Posted By rievax_60
Re: Toshiba L650 power problem

I'm working on an L650 with a suspect faulty MAX17435. It was totally lifeless.
The voltage on the ACIN pin is correct but ACOK stays high. The cause of this should only be because of a problem in...
Forum: Troubleshooting Audio Equipment 01-28-2018, 07:59 PM
Replies: 18
Views: 755
Posted By rievax_60
Re: Yamaha RXV595 turns off instantly

It does say "DC 18%", I'm hoping that this might mean DC protect.
I have seen false DC protect shutdowns caused by leaky diodes causing unindented interaction between Mute, I protect and DC protect...
Forum: Troubleshooting Audio Equipment 01-28-2018, 07:17 PM
Replies: 18
Views: 755
Posted By rievax_60
Re: Yamaha RXV595 turns off instantly

Also measure the voltage at the Base of one of the mute transistors to see if it ever attempts to go negative just before shutdown. It should go to -15v in a properly working receiver.
Forum: Troubleshooting Audio Equipment 01-28-2018, 07:11 PM
Replies: 18
Views: 755
Posted By rievax_60
Re: Yamaha RXV595 turns off instantly

Shutdown after 3 sec is likely to be excessive amplifier DC offset. Sometimes it can be a fault in the protection circuitry.
Measure the DC offsets.
Forum: General Electronics Technical Discussion 12-15-2017, 08:08 PM
Replies: 4
Views: 306
Posted By rievax_60
Re: TL431 question

Also, the TL431 will draw an increasing current of up to about 500ua well before the Ref pin reaches 2.5v. The TL431 needs to be allowed to draw a minimum of 1ma before any driven circuitry...
Forum: Schematic Requests ONLY! 12-04-2017, 05:29 AM
Replies: 13
Views: 499
Posted By rievax_60
Re: How to read and understand schematic diagram.

It is not really possible to directly learn to read electronic schematics. It is necessary to first understand basic electronics, then progressing to understanding how various electronics components...
Forum: General Capacitor Questions & Issues 11-21-2017, 12:47 AM
Replies: 13
Views: 501
Posted By rievax_60
Re: Is the 50% loss of energy when charging a cap from a battery a set rule in stone?

I don't think inductors are weird. They just do everything in an opposite way to capacitors.
Capacitors store energy electrostatically and cause current flow while attempting to oppose voltage...
Forum: General Capacitor Questions & Issues 11-20-2017, 11:17 PM
Replies: 13
Views: 501
Posted By rievax_60
Re: Is the 50% loss of energy when charging a cap from a battery a set rule in stone?

It is ok to have no resistance, superconductors do exist. Inductance can never be eliminated and can't always be ignored.
Forum: General Capacitor Questions & Issues 11-20-2017, 06:18 PM
Replies: 13
Views: 501
Posted By rievax_60
Re: Is the 50% loss of energy when charging a cap from a battery a set rule in stone?

"In other words, what voltage should the capacitor be when it has 14.4mJ of energy in it, which should be double or twice the amount of the 50%, if I am getting that correct at all."
The 100uf...
Forum: General Capacitor Questions & Issues 11-20-2017, 05:54 PM
Replies: 13
Views: 501
Posted By rievax_60
Re: Is the 50% loss of energy when charging a cap from a battery a set rule in stone?

The charging of the capacitor could be made more efficient by purposely placing a large inductance in series. I would expect the capacitor to be charged to close to double the supply voltage at which...
Forum: General Capacitor Questions & Issues 11-20-2017, 04:02 PM
Replies: 13
Views: 501
Posted By rievax_60
Re: Is the 50% loss of energy when charging a cap from a battery a set rule in stone?

There will be no zero resistance paradox because of the unavoidable circuit inductance. The circuit will oscillate indefinitely if every part has no resistance and no other losses.
Forum: Troubleshooting TVs and Video Sources 09-25-2017, 06:25 AM
Replies: 43
Views: 5,248
Posted By rievax_60
Re: LG 55LW5700 Service Manual

I did just that to a 42lw5700. It is working again for now. It would switch on but the back light wouldn't light up. No sound also.
I wonder what goes wrong?
Forum: Troubleshooting Audio Equipment 09-16-2017, 05:13 AM
Replies: 8
Views: 668
Posted By rievax_60
Re: Pioneer VSX- Shutdown after 1 minute- SMPS problem

It can be a fault with the TOP258. I have seen this many times with Power-Integration SMPS ICs. Or there might be high ripple on the secondary rail because of high capacitor ESR.
Forum: Troubleshooting Audio Equipment 09-15-2017, 06:57 AM
Replies: 94
Views: 8,292
Posted By rievax_60
Re: Pioneer VSX-520-K Protection problem

The 2SA684 would not have had any leakage and there was no indication that Q443 was leaky. If the PCB was charred, you should confirm it. I like things to make complete sense where possible.
It is...
Forum: Troubleshooting Audio Equipment 09-15-2017, 05:44 AM
Replies: 94
Views: 8,292
Posted By rievax_60
Re: Pioneer VSX-520-K Protection problem

I would use a small drill bit to remove the burnt paper from between the collector and emitter pads.
Forum: Troubleshooting Audio Equipment 09-15-2017, 05:38 AM
Replies: 94
Views: 8,292
Posted By rievax_60
Re: Pioneer VSX-520-K Protection problem

Did the PCB get burnt under Q444?
Forum: Troubleshooting Audio Equipment 09-15-2017, 05:35 AM
Replies: 94
Views: 8,292
Posted By rievax_60
Re: Pioneer VSX-520-K Protection problem

That was a mistake. The leakage would have to be between collector and emitter.
Forum: Troubleshooting Audio Equipment 09-15-2017, 05:21 AM
Replies: 94
Views: 8,292
Posted By rievax_60
Re: Pioneer VSX-520-K Protection problem

Ok, that helps to make sense of the voltages. The leakage has to be between collector and base pads of Q444. Try to clean it again. Do you have any information about the flux?
Forum: Troubleshooting Audio Equipment 09-15-2017, 05:11 AM
Replies: 94
Views: 8,292
Posted By rievax_60
Re: Pioneer VSX-520-K Protection problem

It still looks like high PCB leakage. The 6.3v on the base of Q444 doesnt make much sense unless D449 and D550 are missing?
Showing results 1 to 25 of 500

 
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