Panasonic SA-PT860 Stuck in Standby

[Joeyrom]

Hi, I've decided to try and take on a project. Probably not the best for a beginner but figure I might learn something.

As in the title I have a surround sound system that was stored for some time and when it was checked to see if it worked before it was given to me it would't turn on.

There is a red light indicating it has AC power but is completely unresponsive. I cracked it open to see if there was anything visually wrong with it, there was nothing I could see.

However, on the SMPS P.C.B i can here a high pitched tune/whistle coming from what I suspect is the transformer (?) with the green and purple dot on it (see attached picture.) It could be a cap further down as it's hard to pinpoint. This whistle lasts for some time after unplugging too. I'm not sure if this is completely normal behavior or not.

Just after some info so I can get a direction as to where to start problem solving.

I only have a basic electrical tester at the moment, i'll be getting a multimeter asap. Thanks in advance.

[R_J]

Re: Panasonic SA-PT860 Stuck in Standby

That is the standby transformer, it can make a bit of noise, thats normal. It is working because there is the red standy led. There is very little current drawn by the standby circuit so when you unplug the unit it takes a bit of time for the voltage (and the whistle noise) to drop off.
start by measureing the standby voltage, it should be 6 volts, if it is a lot lower that could be the problem
You can download the service manual here

[Joeyrom]

Re: Panasonic SA-PT860 Stuck in Standby

Thank you for your reply. I'm not 100 percent sure where I was supposed to test. I had a Google and a look through the manual. I tested at the switching regulator. It has 2 apparently. Both read at 0. As I was looking around I found what may be burnt connections and it appears the display screen may have burnt out too. I'd like to have your opinion on the former. I'll attach a photo. Thanks again.

[Moreno83]

Re: Panasonic SA-PT860 Stuck in Standby

That is not burned , its probably flux.

You could reflow those parts. But you need a schematic

[R_J]

Re: Panasonic SA-PT860 Stuck in Standby

on plug CN5802 Pin #2 (thats the picture in post #1) you should get 6 volts standby That is the SYS6V that supplies the micro that controls the power on PCONT line
The display circuit requires +18 volts, that comes from the main power supply which at the moment is not turned on.
The acin led does indicate that there is SYS6V but it might be too low for the unit to operate

[Joeyrom]

Re: Panasonic SA-PT860 Stuck in Standby

Thank you so much for your help so far. I tested and it has 6 volts. I assume I'd follow that line further along and see if there's a loss? I've found some other information on the Internet and will see if I find something until you get back to me with where else to look. If anything turns up that doesn't seem right I'll run it by you.

[Joeyrom]

Re: Panasonic SA-PT860 Stuck in Standby

Just to check I understand you correctly. The 6v line gives standby power to the main board which makes sure all conditions are met, such as no faults for instance. It then turns on the actual power at the power boards to run the rest of the hardware?

[Joeyrom]

Re: Panasonic SA-PT860 Stuck in Standby

Seems that the 6v is making it to the main board.

[Joeyrom]

Re: Panasonic SA-PT860 Stuck in Standby

I was wondering if there's anyway to bypass the standby? Kind of like short it somewhere so if all else is good it will start?

[Joeyrom]

Re: Panasonic SA-PT860 Stuck in Standby

I worked out the last part. On CN5802 shorting Am_BP with Sys6v resulted in coming out of standby.

[Mooikuan]

Re: Panasonic SA-PT860 Stuck in Standby

Hi Joeyrom did you finally repair your Panasonic unit ? I have the same problem and was wondering did you find out what cause the unit stuck in the standby mode? Thanks

[stevebrowndog]

Re: Panasonic SA-PT860 Stuck in Standby

Hi Joeyrom did you finally repair your Panasonic unit ? I have the same problem and was wondering did you find out what cause the unit stuck in the standby mode? Thanks

I'm with you Mooikuan. I'm in the same position. Mine wont turn on. I'm keen to open it up and have a look. I see the plug, but I'm not sure what Joeyrom is saying that he shorted. How did you go?

[Moreno83]

Re: Panasonic SA-PT860 Stuck in Standby

On that connector there are pins and one of them is a Am_BP and the other one a Sys6v.

[stevebrowndog]

Re: Panasonic SA-PT860 Stuck in Standby

On that connector there are pins and one of them is a Am_BP and the other one a Sys6v.

Thank you, I read that, but what does it mean? How does a punter identify an Am_BP or a Sys6v??

[R_J]

Re: Panasonic SA-PT860 Stuck in Standby

Plug CN5802 on smps. Pin #2=SYS6V; Pin # 11=AM_BP pins should be labeled but if not pin 11 is closer to the edge of the pc board