A close listen revealed that the unit was not totally dead, pressing the power button the unit would click on then immediately off (but nothing on the display). This could be repeated a second time but then the unit would not respond. Pulling the power lead would allow this sequence to be repeated.
So the unit was alive and intelligent.
A quick google gave me the manual to download from the excellent site, electrotanya.
http://elektrotanya.com/panasonic_sa-pt470.pdf/download.html
Panasonic / Technics manuals are absolutely superb.
I may do a post about my beautiful Technics SC-CH900 that I finally bought after 22 years ! :-) anyway..
So I opened it up and stated to take a look. Nothing obvious so decided the best plan of attack was to take the PSU out to get some proper access.
Admission: I took a stonking 360v dc hit from the main cap, Warning, always approach with caution, measure the high voltage DC caps, and discharge as appropriate.
This fault will leave the main caps charged. I usually check but got sloppy.
So nothing jumped out visually, the mains went through a hefty filter and feeds standby power section of the PSU, the main psu is switched in through a relay, the relay only stays in if the PSU behaves correctly.
I did some passive checking but again nothing jumping out.
A move not without risks but I decided the best way forwards was to bypass the relay and see what wasn't powering up, the brain was obviously not happy and shutting everything down.
Using the drawings I checked all the rails and found the 18v fan power to be absent. I checked the rectifier diode D5805 and found it short. Fitted a repalcement and all good.
Hi i have the same fault, what is the spec of the diode? and where can i buy one? many thanks in advance. great blog!
ReplyDeleteThanks for this post. I have the same issue and same question. Where can I get a replacement diode. It's marked as KS2102. Many thanks
ReplyDeleteMay I just say that on the diagram the line pointing to the diode() is in fact pointing to three diode rectifiers that reside on the heatsink unit and are labled from d5801-3. The d5805 is a bigger diode that is next to it.
ReplyDeleteI have the exact same simptom on mine but have found the d5801 two pin diode to be art fault and not the d5805. What I'm trying to say is is it possible that these two faults can cause the same symptoms as it would appear to be the case!!!
Yes my problem was the two pinned diode D5803 on the heat sink on the 18 volt line, great blog with great detail. Thank you and love the warning, those power caps do pack a punch!!
ReplyDeleteDo somebody have a replacement found for the diode 5805 D0HFRJ000012?
DeleteRegards Harold
I find the replace for any one needed FML-G12S
ReplyDeletepanasonic sa-btt270
ReplyDeleteCould anyone help me please. Given a dead player and found that if I blew cold air into it from a hairdryer it would work perfectly. The fan was working but still gave a clean out. Has anyone got any ideas. Thanks in advance
panasonic sa-btt270
ReplyDeleteCould anyone help me please. Given a dead player and found that if I blew cold air into it from a hairdryer it would work perfectly. The fan was working but still gave a clean out. Has anyone got any ideas. Thanks in advance
Just stumbled accross this pos and comments, i have similar issue and i've not been able to sort it out for 2 years plus now..The red dot light on the power button comes on but the system doesn't come on. Please can i get help here?
ReplyDeleteHello Mr LowFinger, how do i get the component replacement (or equivalent) for D5801, D5802 or D5803, because i have same symptoms like that, after checking those diodes found out that actually D5801 was broken.
ReplyDeleteWhen i check the Service Manual it said diode b0hbsm000043 which i cannot find this component on regular market.
Hi, I have just stumbled across this post, I have a SA-PT 460 where the power light comes on but the unit will not power up at all, could this be a similar power supply issue ? I haven't used the unit for some years since I moved it out of service for a bluray device,but I would now like to use this one too without a lot of expense !
ReplyDeleteThanks for the wonderful blog post!
ReplyDeleteI also have a Panasonic SA-PT470.
In your post you reported: "A close listen revealed that the unit was not totally dead, pressing the power button the unit would click on then immediately off (but nothing on the display). This could be repeated a second time but then the unit would not respond. Pulling the power lead would allow this sequence to be repeated."
I had almost the same problem. As in your case, "the unit was not totally dead, pressing the power button the unit would click on then immediately off (but nothing on the display)". However, in my case the fan is working so I heard a click and the fan starting then immediately stopping.
I found the problem to be one of the two fuse protectors that are welded directly on the SMPS P.C.B, i.e., FP2901 (1 Amp.) and FP2902 (2 Amp.), see Page 41 of the Service Manual for details. I replaced FP2902 and everything is now working fine.
Hi Franco. I have exactly the same problem you described. I feel like it’s something that’s just within my grasp of fixing if I can think back to my school days doing DT: Electronics! The trouble is, I’m not sure where to start. I can get a soldering iron easily enough but where can I get the components? Any help would be appreciated!
DeleteHello,
DeleteI am happy to read that my reply to the original blog post was useful!
In my case the problem was a broken fuse protectors, i.e., FP2901 (1 Amp.) and FP2902 (2 Amp.),
Here my suggestions (what I actually did) for solving the problem:
1) download the service manual (SM) here: http://elektrotanya.com/panasonic_sa-pt470.pdf/download.html
2) Section 9.19 (page 63 of SM) shows how to disassemble the SMPS P.C. board. disassemble it.
WARNING: approach with caution! risk of electric shock when manipulating the board! you should properly discharge the High Voltage DC capacitors.
3) Page 41 of the SM shows where the two fuses (FP2901, FP2902) are located on the SMPS P.C.B. Find them on your board.
4) You now need a multimeter with continuity check. Test both fuses. For the broken one the tester won't beep.
5) Unsolder the broken fuse. I was not able to find the original spare part. I thus used an "external" fuse holder like this one: http://www.elcart.com/it/portafusibile-volante-per-fusibili-5x20--16051
I just soldered two pieces of insulated cable on the board that connect the fuse holder.
6) check continuity after the fix. now the tester should beep when checking the two fuses.
you've done.
Hope it helps. Let me know your progress on that.
Ciao!
Franco
Thank you. The repair was successful.
ReplyDeleteNow I have a new problem: when loading a CD the I have the display "NO DISC".
What can I do?
I have exactly the same problem as Lowfinger, however, my Unit is a Panasonic SA PT 860. I have already removed the SMPS Board (almost identical to Lowfingers' model). I have replaced all Electrolytics on the SMPS, but there was no joy in doing this work. I had already tested all diodes on the heatsink with a DMM, and these all tested fine.However, it may be better to take the diodes out of circuit and then re-examine them.The large 180uF Filter Cap is the one that we should all be concerned about, and (for safety) I always take care in removing the SMPS Board, and then completely discharge the large Filter Cap (this stores 340vdc) with a 300 ohm resistor which is shorted across this Cap. If anyone could add more information with regards to Lowfingers symptoms and the resultant fix or repair, it would be of great help.Thanks.
ReplyDeleteJust an fyi for anybody looking back at this issue. There is nothing more frustrating than knowing that somebody had exactly the same problem, fixed it, wrote about it....and yet there is not enough info to proceed. We all like and need specific instructrions...."go here to print out diagram". Put multitestor on continuity....DISCHARGE CAPACITORS BEFORE KILLING YOURSELF. this happens every year when people's ac units go out. Unlike the little capacitors,on these audio machines....a capacitormin a house ac unit looks like a coke can......when it looks like a coke can that has burst from the top...it is bad. It is easy to replace for about 25$. The problem arises because people unplug the machine and dont realize that it contains enough stored electricity to kill you. It MUST BE DRAINED. GLOVES...AND INSULATED TOOLS ARE GOOD. ANYWAY, back to panasonic....nobody really explained how or where to track down parts....or where pieces they were talking about were located. Just a thought
ReplyDeleteNot like anyone dumb enough to not take caution would even try to fix it
DeleteI need block diagram for panasonic sa-btt370 pdf
ReplyDeleteHi, I have the exact same issue as you described. I checked d5805 and it looks good, not short. I also checked fuse fp2901 and fp2902, both are okay. Any idea what else could go wrong?
ReplyDeleteIf there is any problem with dc detector circuit you will get the same fault. check Q5840, Q5841,( on SMPS board)Q2909,Q2919 and Q2924 on main board. If these transistorsare OK then disconnect power supply on Audio board and using 2 pin connector give power supply to fan. If one of the Audio ICs are faulty the after switching it on display should appear. I was having the same proble.after replacing transistors and Audio ICsthe set isworkingproperly.
ReplyDeleteI finally figured this out after searching everywhere online and seeing people in similar situations but no solutions. I was getting 2 audible relay clicks but no power to the surround sound unit. After some experimenting this is what worked for me:
ReplyDeleteRemove all wires to the unit including the ac power cord, plug in all the cables you need THEN the power cable after. In my case I had a Panasonic sa-pt770, I plugged in the speakers to the respective colors, then my HDMI, then the power cable.