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Sony KV27S15 died

My daughter was watching our TV when she said it made a couple clicks like when you turn it off and off it went, not to come back on again. I was out of town but had them try the obvious stuff like plug into another outlet, etc.

When I got home I tried a few things, and found the fuse fine & that plugging in the set did draw a little current, although there was no response at all from the on button. I wondered if maybe the micro was getting confused by high ESR caps around it, but found none that appeared to be bad.

I searched for this problem and found some people saying to just change out the PS switchers Q601 & Q602 and R607. Some suggested also changing the HOT. I checked all solder joints under the microscope and found no bad ones.

From your experience, what would you suggest? I prefer to change parts on purpose rather than shotgun, but without a schematic, I'm not sure what voltages I should be seeing before the set powers up. At this point I'm presuming the power supply quit, but would like some opinions from those that know more about this than I do.

WT

Reply to
Wayne Tiffany
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Is this one of the sets with the separate vertically mounted power supply board?

Reply to
James Sweet

Typical repair is the HOT, switchers, and the .1 ohm resistor near the switchers, and resoldering the horizontal drive transformer and related parts to prevent recurrence.

YMMV.

Mark Z.

Reply to
Mark D. Zacharias

No, the power supply is on the main board. It does have some stand-up boards, but they are the tuner & the micro boards.

WT

Reply to
Wayne Tiffany

Typical for these symptoms enough to just order the parts and do it? It would make some sense to replace them even if that's not the problem this time in that they may be a common failure anyway.

WT

Reply to
Wayne Tiffany

Ok I can't provide any specific help on this one then. I fixed a set years ago with the separate power supply, on those there's a regulator IC that fails.

Reply to
James Sweet

The repair should really be done by a technician or at least by someone with some technical ability - there are potential pitfalls in the process of replacing the parts, and there are also safety issues, and I have no idea of your soldering ability, etc. The 2SC4834 switcher transistors are easily reversed, for example - we had a tech do this once. There are numerous fake transistors in "kits" out there which aren't really suitable. The horizontal drive transformer should be resoldered along with other parts in the area, and also the vertical output IC and 9 volt regulator should be resoldered as well. Obviously the transistors etc might not even be your problem, though I would say it's better than an 80% chance.

You can get the parts from B & D Enterprises.

800-458-6053.

You'll need to order a 2SC4927, 2 each 2SC4834, and the 0.1 ohm Micron resistor, they do have high quality kits of these. Beware of kits from anyone else.\

Mark Z.

Reply to
Mark D. Zacharias

Great, thanks.

WT

Reply to
Wayne Tiffany

Good luck with that. Be careful, and do report back and let us know.

Mark Z.

Reply to
Mark D. Zacharias

I talked with Bud there at B & D and the resistor he has in that "kit" is a

1/2 watt. The numbers that are on the resistor on my board that is labeled R607 were 2w.1, which would make me think that it's a 2 watt. He measured the one he had and it's 4.5mm dia, and 11mm long. I'm at work and my board is at home so I can't measure mine.

So, the resistor in the kit is the one that is normally replaced. Is that R607, or is there another one that should be replaced?

WT

Reply to
Wayne Tiffany

We use the .1 from B & D all the time - it's the same as the Sony, except you have to form the leads.

Mark Z.

Reply to
Mark D. Zacharias

According to Sony it is .5W. We have used .5W for years and never had a failure without a short in the set. I would assume that B&D is selling only premium parts, but verify that the transistors are N or P rank or better. Lower rank versions are likely to run hotter and vary more. Be sure to check the related caps in the circuit.

Leonard

Reply to
Leonard Caillouet

Thanks to both of you - it sounds like I have the correct parts coming. Hopefully I will have it running this weekend. I'll let you know.

WT

Reply to
Wayne Tiffany

Well, now I'm really depressed.

I received the kit with the switchers, HOT, and the .1 ohm resistor. Put them in today, and no difference. I checked the old ones and they were all bad, so I figured this was going to do it. Plugged it in, hit the power button and nothing. Tried it with the front buttonand the remote - nothing. No clicks or anything. When I plug it in I can tell there is a bit of current draw, but then no indication of activity.

Any more thoughts of what I can check without the schematics and more experience?

WT

Reply to
Wayne Tiffany

Forgot to mention that I resoldered the transformers, etc. None looked bad under the microscope, but I did them anyway.

WT

Reply to
Wayne Tiffany

Did you create a solder bridge somewhere? Are you sure you didn't leave a connector unplugged? Check to see if standby voltage is present.

Reply to
James Sweet

Ditto on the connectors - some models the front circuit board unplugs from the main board when you slide the main board out.

Mark Z.

Reply to
Mark D. Zacharias

Also it's easy to forget to plug in the power supply main connector to the main board, if this is the model I'm thinking of.

Mark Z.

Reply to
Mark D. Zacharias

I had checked all the connectors about 10 times. There are some open connectors on the vertical boards, but I'm out of cables to plug into them. :-)

I had checked for solder bridges and found none. All the stuff I resoldered was big pads, so a bridge was also less likely.

The cable from the front board with the switches was unplugged to get the main board out. But I checked again and it's plugged in.

I get about 3.7 vdc on some of the pins of the connector from the front panel, and pin 5 goes to .2 vdc when I push the power button on the front.

There isn't a main power connector other than the 110 v line. The power supply is on the main board.

I searched for a datasheet on the micro, Sony CXP80424-079S, but couldn't find one, so I don't know what pins should be supply voltage, and what pins should change with the power button, etc.

WT

Reply to
WT

Ok, I finally had a chance to work on this again. I also now have the schematics so I have more info at hand.

I measured my way up through T605, R636 & D619. Measured to chassis ground I got 9 vac in front of the diode and 13.35 vdc after the diode, which is labeled STANDBY-RECT. This line on the schematic is labeled as 14V so standby voltage is fairly close.

I then followed that standby line to the M board and found the standby 5V line out of the M board at the connector that goes to the front control panel. I measured 4.25 v at that point. I then checked the power switch pin at that connector, and with the button pushed, that pin went to about .2 v, so I know the switch is closing.

At D607 which is labeled SOFT-START, which connects to one side of the primary coil of T603, I don't get anything, which means that T603 isn't running, which means the switchers are not running. (Unless I just have it all wrong, which is a possibility.) I see several items labeled SOFT-START - what is that functionality?

So now I'm stuck due to lack of experience - I can't figure out what to check next. I see a Q604 POWER-SW and measured 12.8 v at the collector, but the schematic looks like it says that should be 0.2 v.

Thoughts? If anyone would like to call to offer some suggestions, I am home tonight. The area code here is 816, and the rest of the number is 796-9886. (I don't want the number harvested.) Thanks.

WT

Reply to
Wayne Tiffany

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