Sony KDL-S40A12U Dead...ish and flashing error 5

[tunedwolf]

Hey folks,

I have a sick sony bravia in front of me belonging to my oldest friend, it is flashing error 5 on the front led, which I hoped would be the standby 5V regulator or something equally daft, but it's sitting at 4.94V. I'm not familiar with these as I am long out the trade now, so could do with some help

Allegedly this saga began as sound, no picture, (I suspected T-Con fuse) but when he got it back from the place he took it to, it had this problem. I have no idea yet if they fixed the original issue or not.

Currently the set powers up for a couple of seconds, then back to flashing the code of 5 flashes red LED. The 17.5V rail comes up to 18.54V, the 5V comes up and I have checked the other regulators on the GE board etc, all the supplies appear to come up, with the exception of the 3.3V etc (which I'll assume is only going to come up when power good is detected), at least for the couple of seconds that it stays on. That's about as far as I have got with it, although I did obtain a manual for it today.

Any thoughts? Nigel?

 

[Nigel Goodwin]

There's a technical bulletin for 5 flashes:

SYMPTOM
No Power-on, LED blinking five times, HDMI Board defective.
SOLUTION
Check the diodes D9500 and D9501 on the P Board. Only in case these diodes are shorted, replace them as
indicated below.

However, I've never found any duff so far.

Five flashes is listed as: 'DC Alert Protection Error'

 

[tunedwolf]

Hi Nigel,

Cheers for that, they are OK unfortunately. I did notice last night that there is no obvious backlight operation, but I'm thinking that the inverters will only be fired up when the rest of the set is alive and kicking, plus I don't think it's actually powered up long enough anyway. Where to go from here? Begin subbing out boards?

Cheers for the help, it's appreciated

 

[Nigel Goodwin]

If you've got boards, then try swapping them - it's by far the best and easiest way.

Depending when the fault is being detected it's VERY likely that the inverters will never be fired up, as that wouldn't happen until all the other checks are done.

If you PM me your email address I can send you a service manual (now it's no long on encrypted DVD's I can send you a PDF - it's now on-line only).

 

[tunedwolf]

Cheers Nigel, pm sent

 

[tunedwolf]

Ok just an update, I have ordered some boards for it, regulator board, control board and main A/V board. I'll let you know how I get on with it

 

[tunedwolf]

Update:

I have replaced the main A/V board(A2E4), main Control Board(BE), Regulator Board(GE2) and T-Con board. No change in symptoms. The set is still flashing code 5 and then shutting down immediately. So I guess that leaves only the main Power Supply(G3) and the Inverters as suspects. I only replaced the T-Con board as the original symptom was allegedly sound and no picture and I chose to do it at this point as the chassis was already in bits, plus, if it was faulty, I didn't want to risk the replacement Control Board(BE).

Back to the current issue:

I am getting what I would have expected to be tolerant voltages out of the main power supply, however, the 17.5V rail when it comes up, is sitting at 18.5V. I'm now wondering if that is causing an over volt trip of the DCAlert. I would have thought it would have been up around the 20V mark, but maybe not. Anyone able to confirm this? I'll need to try and source a replacement board to test further. Does anyone have a training manual for the KDL-S40A12U/ Wax Chassis? I'm sure there will be a check voltage/ flowchart troubleshooter in it that would possibly shed more light on the issue

 

[Nigel Goodwin]

Training text emailed - but I don't think it's very thrilling.

 

[tunedwolf]

Thanks Nigel, very much appreciated. The more information I have available, the more likely a successful outcome I reckon

I'm surprised there hasn't been power supply service kit/ bulletins issued given how complex this board is, but I guess like others, Sony just replace boards now rather than component level repair them, less training/ overall cost etc. Bring back the days of the Philips G11 and Redifusion MK IV's I say where engineers were actually engineers

 

[Nigel Goodwin]

I'm surprised there hasn't been power supply service kit/ bulletins issued given how complex this board is, but I guess like others, Sony just replace boards now rather than component level repair them, less training/ overall cost etc.

That's only true on the more recent sets, sets the age of yours were repair to component level, hence the circuit diagrams in the manual. Current sets have no circuits in the manuals, and are board replacement only.

However, there's not been any PSU repair kits because Sony don't use sub-standard capacitors like Samsung and many others, so you don't often get problems.

 

[tunedwolf]

Ok, problem solved. I obtained a replacement power supply board (G3), received it today and fitted it. Nada...exact same symptom, flashing error 5.
After a few well chosen sweary words, I decided that I must have missed something, or less likely, fitted a faulty replacement board. After checking all the main supplies again, and finding nothing that jumped out at me, I started working my way back towards the power supply from the main control board.

Now I noted right from the off that some of the aux supply rails were missing, but as these come from the regulator board (G2) and have inbuilt shutdown facilities, I figured that they would only come up when the rest of the set had self tested etc. However, tonight I decided to look further into what actually switched the regulators on. This being the PWR_SW line from my reading of the schematic. Low and behold, I find a dead short on it to ground. No wonder there was no logic signal turning on the regulators for the aux supply rails. After a quick look at the schematic, I couldn't see anything obvious that could actually cause this, I checked and double checked the spare boards that I have and still couldn't see how this was possible, so it was divide and conquer time. I removed all the plugs from each board and checked again, still shorted to ground. Then I realised that the main control board and main A/V board were still connected by the flex ribbon cable. I removed it and no more short, on either board. Looking at the ribbon cable, I couldn't believe my eyes. I can only guess that the last so called engineer had no clue how the connector system works and had forced the ribbon back into the sockets. at least half the tongues were torn up and all bunched and lapped together on the main A/V side. Luckily, I had gotten a replacement ribbon with the main control board that I obtained, so after fitting it no more shorts. Voila, the set bursts into life and I'm greeted with a cracking picture. I was half expecting the replacement control board to be damaged, but it survived. This has to be a first for me to get caught out by a mangled flex ribbon rather than finding one making poor contact. but there you go, mystery solved

I'm happy it's working...time to re-sell the spare boards...

 

[Nigel Goodwin]

Nice one!

Annoying when it's something stupid like that, and not a proper 'fault' at all.