troubleshooting TV SMPS sequence

[CapLeaker]

Re: troubleshooting TV SMPS sequence

ds3, ds5 and check those three 16V 1000uF caps. matter effect, unhook the 24V and the 12V, take your ohm meter and measure those two against GND. Probably the 12V almost measures a short.

[R_J]

Re: troubleshooting TV SMPS sequence

I would suspect a shorted diode in the 12 volt section, ds3 or ds5.
The primary circuit is working fine because the +24v is at +20v. its only a bit low because somthing in the 12 volt section is causing it to be droping a bit.
I guess you could have a shorted cap. in the +12 circuit but I doubt it.

The area in blue is the primary that drives both the +24 and the +12 and is working fine.
The area in green is working although a bit low. the area in red is where your problem is. (unless there is something connected to the +12 that is loading it down) but it does not look like it if you disconected con3 and it was still low.

[ilikesteel]

Re: troubleshooting TV SMPS sequence

thanks Capleaker. I did remove the cables from conn3, no load from TV set. still had lower voltages at the pin outs on conn3 of the PS for +12 and +24. I just can't get to the next logical step in the flow of troubleshooting it further.

ilikesteel

[CapLeaker]

Re: troubleshooting TV SMPS sequence

Look at a different way: What could be dragging the 12V down so bad?

I would disconnect everything from the PSU and force the PSU on by itself, then check the secondary voltages again. Maybe resurrect the previous thread again.

[ilikesteel]

I posted a problem with an RCA L37WD12 TV awhile ago. It's definitely has a PS problem. I've followed a logical sequence of troubleshooting and now I've run into a dilemma. I'd like to troubleshoot the problem further. here's where I'm at:

1. standby 5V good, standby LED on red.

2. PWR-ON works, PS gets AC applied to main PS, led flashes green continuously.

3. the output voltages should be +24V and +12V. the output is actually +20V and +2V respectively.

4. checked across main cap 180uf, 400V, I get 360 DC volts.

what is the next logical sequence to check voltages with DVM, I don't have access to a scope. I know there is the HOT side and COLD side with different ground references.

What would cause both DC supplies to be affected with low voltage output? that's where I need to get too.

Thanks again everyone. Budm was the last person I communicated with before the forum went off the air for about 10 days.

Thanks,

ilikesteel