Pioneer plasma turns off: update

Er, make that "all are a few hundredths high"...

That might very well be the defining symptom. What is the circuit difference in the way the unit turns on and off via remote, and by flipping the switch?

When it's turned off by the switch in the back, it's really off, just as if you'd pulled the plug.

When you turn it off with the remote, some parts of the set are still on, at least enough to allow it react to the remote. This means that the power supply is still doing something, or at least trying to.

Okay, so let's go from there. What is or is not happening when the remote control is used that causes the near-instant shutoff, that is not or is happening when the main power switch is cycled?

I presume that when the remote is used, some monitoring circuit detects an out-of-spec PS voltage immediately after power-on. Using the mains switch removes power from even the monitor circuits and clears the error code.

Not really my area of expertise, but you've obviously got a cold fault. Maybe the inrush-limiting thermister?

That's plausible. So how would you troubleshoot that?

Next question -- Assuming this analysis is correct, why does the presumed out-of-spec voltage -- or its detection -- NOT occur when there's a "hard" power cycling?

There's a few connectors on the PS pcb that look like they be monitor and/or control signals. I'll scope them and see what they do (tomorrow morning -- the next possible time for an error-inducing "cold" turn-on).

I'm not sure it's due to a difference between the two power-on techniques. I think it's just the fact that it is power cycled, period. Since the remote control circuitry will not allow a power cycle until the error condition has been cleared, the only way to power cycle is to use the mains switch. If successive power-cycling were possible via the remote control, I think the unit would power up and stay powered on. And I would not be asking for help. If the only problem with the unit was that every time you turned it on for the first time in the day you had to push the remote Power button twice, well that would be a great day.

Also, I scoped the PS voltages.

Is 0.5v noise excessive? Shown is 5v supply measured at test pin on PS pcb. Others have similar noise except 139v: 12v (0.5v noise), 60v (0.5v noise),

I appreciate your thought-provoking questions.

It is part of a start up routine initiated by the remote cycling?

I'd get friendly with some Pioneer tech support types and secure a schematic.

Check the feed ins to the main controller board. Some watchdog is not getting the same rail voltage you are reading at the PS.

So, even though your PS is good, it is not making it into the board correctly.

One is a start up from a sleep mode, and the other is a hard power switch.

This is a common sense prediction. You can bet that the remote operates a relay though.

What's happening to the power supply voltages when it shuts down? Are there any error codes or does it just turn off? Once it's on and running, can you turn it off then back on with the remote?

I've seen a very similar problem with an old PC power supply that had some bad capacitors, could you have additional bad caps? I've had a few cases where a capacitor was in parallel with something else that caused the ESR meter to read good even when the cap was bad.

It may also be a thermal problem as someone else suggested, freeze spray is handy for this sort of thing, you can also use a can of that air duster stuff held upside down.

Whoops. The same noise on all but one supply sounds like a reference problem. Are you grounding your probe? This is where a schematic becomes invaluable.

Were any of the caps bulging? Perhaps electrolytic spilled on the circuit traces causing a sneak path?

No spilled caps. Just low measurement on ESR meter.

First time (ie, in the morning) it is turned on, it turns off after 5 seconds. "PD" (auto Power Down) LED lights on PS pcb. Power LED (on front panel) flashes error code = 6. (A TV tech I e-mailed with says this is frequently a PS failure code for Pioneer, but he does't have the exact service manual for this model (PDP-V401) so cannot confirm.)

During error condition, must use mains switch to power off (which clears error condition) and back on. Remote is ineffective while error condition exists.

Once this is done, can then use remote to power it on and off all day. No issues. Only after sitting off overnight will error condition occur again.

Do not know what voltages are doing when error condition occurs. I will guess that they are OK, because I get a normal picture on the screen. It's a bit time-consuming to do these V checks; I can only get an error condition once a day ( x 5 voltages...)

Thanks.

Sounds like a bad cap in the delay timing circuit that detects valleys in the voltage/Peaks in surge currents. This normally shuts down the unit in the event of a voltage sage due to an excessive unexpected load on the PS.

This problem would also cause it not to start properly if the main caps are totally discharged and there for, is taking to long on the start to charge them for what the current existing delay is at due to a faulty cap in the delay protection circuit.

This cap is normally a small type. You may want to look into that.

It's a common problem is power supply protection in many of designs..

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Turn-off after 5 seconds is a bit long for a surge or slow cap-charge error, isn't it?

Without wiring diagrams, how would one go about locating such a cap?