KV28LS36U 11 blinks


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KV28LS36U 11 blinks

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2000DPL
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Apr 1, 2014, 4:40 PM

Post #1 of 10 (2649 views)
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KV28LS36U 11 blinks	Can't Post

About 15 months ago my Sony television (KV28LS36U on sccq52qa chassis) failed to start-up and blinked 11 flashes: a fault on the 8V jungle.

At about the same time I retired and kept the Sony with a view to learning about circuit boards and electronics in general: a sort of retirement project, and that’s what I’ve been doing for the last year or so, learning about Ohms Law and more, and replacing components on the FE-2 chassis based on messageboard research of other people’s Sony TV problems. I have now hit a brickwall and reluctantly seeking help of where to go next. I just need a pointer of where to go and look on the FE-2 board, and not a step-by-step repair guide – after all, I am on a learning adventure and quite enjoying it if the truth be told.

The symptoms are, the relay switch RY601(DLS1U-5v) clicks on and then within a full second it clicks off. Tracing the circuit back I find (unwanted) 14 volts in many components and when the relay cuts out some of the components revert to the correct 5volts or no volts. I have taken out and tested ALL switching components in the immediate circuit and there is nothing untoward.

So, the brick wall I am having is this: At the component R603 I’m getting 14 volts where 14 volts should not be; moreover, the 14 volts are coming into R603 from BOTH SIDES?

On the chip, IC601 when using my multimeter, I’m getting MINUS 14 volts (or so) to each of the 17 pins. The question is: where is the erroneous 14 volts coming from and is IC601 buggered? I don’t mind replacing small components on spec but an IC601 replacement and I think I’ll call it quits with this telly and keep it for spares to go along with my shed full of spares (or junk as my family say).

Thanks for reading and any pointers you can give me.

A link to a 'blow-up' of the schematics...

http://s1172.photobucket.com/...1&sort=1&o=0

jts1957
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Apr 1, 2014, 10:05 PM

Post #2 of 10 (2628 views)
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Re: [2000DPL] KV28LS36U 11 blinks [In reply to]	Can't Post

What DC voltage do you have across C606?

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Location: Far, Far Away

2000DPL
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Apr 2, 2014, 12:34 PM

Post #3 of 10 (2609 views)
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Re: [jts1957] KV28LS36U 11 blinks [In reply to]	Can't Post

Thanks for comment.

When the TV is switched on, RY601 clicks on (and before it clicks off due to a fault somewhere) I get 14 volts at C606. I also get 14 volts at D613, C613, R603 (and on that fused resistor the volts are coming in from each side). When RY601 cuts out after detecting the fault the aforementioned components revert to the correct 5 volts or nil volts.

At D614 at the bottom left of the schematics I get a CONSTANT 14 volts even when RY601 clicks off to close the circuit.

When using a multimeter to the following components I get a MINUS 14 volts ( reverse polarity?) to many but not all pins on the IC601, R634 and others to that side of the PCB.

My previous comment about my reluctance to replace the IC601 was due to a real risk of damaging the board and the replacement chip with my ham-fisted soldering skills: getting the board & chip too hot in the solder process. Last night I went on Youtube yet again, and noticed for the first time someone replacing a similar chip but they used a cage
to solder to the PCB. The replacement chip was then just pushed into the soldered cage. This makes perfect sense as it eliminates potential heat damage to the chip. When I finish posting this reply, I'm going to order a IC601 chip & cage. They only cost about £15 UK and it'll be good experience/practise for me. I'll keep the board posted of any developments.

jts1957
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Apr 2, 2014, 1:19 PM

Post #4 of 10 (2609 views)
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Re: [2000DPL] KV28LS36U 11 blinks [In reply to]	Can't Post

C606 is the main (raw) b plus cap. It is rated at 450 volts DC. Voltage chart says the drain of Q606 is 86.7 VDC

While relay is energized I would expect at least 86.7 VDC ACROSS that cap. You ARE using that capacitor's negative terminal as your meter negative reference?

What is VDC ACROSS C632? Also VDC ACROSS C624?

Would 'cage' also be called an 'IC Socket'?

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Location: Far, Far Away

(This post was edited by jts1957 on Apr 2, 2014, 1:20 PM)

2000DPL
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Apr 2, 2014, 9:18 PM

Post #5 of 10 (2600 views)
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Re: [jts1957] KV28LS36U 11 blinks [In reply to]	Can't Post

EDITED POST

Thanks for the reply.

With multimeter probes on the correct sides of C606, the TV is switched on, the RY601 relay clicks and the multimeter shows + 338VDC constant. When the relay clicks off the cap slowly drains.

If I use the multimeter negative and clip it to a heatsink I get +14VDC at the positive terminal of C606. When the relay RY601 clicks off it reverts to +5VDC.

C632 I'm getting +5VDC constant when the relay RY601 is on and when the relay clicks off this cap fluctuates between +4.8 and +5.2VDC without draining?

C624 I'm getting a constant +3.3VDC

The cage is indeed the ICSocket...I had to call it something.

Thanks for you help, it's much appreciated.

Post edited because I had the multimeter on the wrong setting when checking C606: 200vdc instead of the correct 600vdc and of course it sent me in a wrong direction entirely.

(This post was edited by 2000DPL on Apr 2, 2014, 10:29 PM)

jts1957
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Apr 3, 2014, 12:39 AM

Post #6 of 10 (2591 views)
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Re: [2000DPL] KV28LS36U 11 blinks [In reply to]	Can't Post

'Heat sinks' may or may NOT be at the correct ground potential, which is why I'm asking for the meters negative lead to be placed on a particular capacitor's negative terminal (and the meters positive lead on a particular capacitor's positive terminal).

Standby 3.3 & 5 volt ARE correct.

IC601 voltages will be referenced from its ground pin #5, DO NOT slip with either meter lead and create a short - even momentary! If necessary, 'sharpen probe tips, 'tack' short lengths of wires at solder joints further along THE SAME foil traces and connect meter leads to them instead of using the IC pins, etc.

Service literature should include a voltage chart of IC601 (page 30 in mine).

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Location: Far, Far Away

(This post was edited by jts1957 on Apr 3, 2014, 12:41 AM)

2000DPL
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Apr 6, 2014, 2:27 PM

Post #7 of 10 (2571 views)
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Re: [jts1957] KV28LS36U 11 blinks [In reply to]	Can't Post

Just a quick reply in acknowledgment for your SOUND advice. It seems I'm destined to make every rookie error with my multimeter.

I'm reviewing all the diagnostics on the main chassis board that I've done thus far; clearly, what data I think I have, and think what I have is right, is in fact wrong....arse and elbow come to mind.

I'll post back to this thread when I'm stuck again or how I fixed the fault...

I came here looking for a pointer of where or what to do and you gave me exactly what I was looking for, so many thanks for that.

2000DPL
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May 15, 2014, 5:42 PM

Post #8 of 10 (2487 views)
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Re: [2000DPL] KV28LS36U 11 blinks [In reply to]	Can't Post

Starting at knowledge base of near zero; 15 months later; about £80 sterling in components; some 2 billion brain cells expended, I've eventually managed to fix the damn television after making, I would assume, every possible mistake a novice could make.

There are a number of fused resistors incorporated on the main board circuits. I purchased one at just about £5 and another £5 post & package: it blew again! I purchased another two and they blew as well but not before I found the faulty capacitor shorting the circuit.

I ended up buying a load of fused resisters and a load of other components direct from China at a total cost of £23.

The FIX was replacement of all the fused resistors on the main board, replacement of the faulty capacitor (that showed no signs of defects?), soldered a few dry joints + a quick prayer and HEY PRESTO!

My thanks for the sound advise about where to put the earth probe...?

jts1957
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May 15, 2014, 9:07 PM

Post #9 of 10 (2485 views)
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Re: [2000DPL] KV28LS36U 11 blinks [In reply to]	Can't Post

That's like $134 USD. Way too much.

What 'locations' cap/resistors? (Or value/voltage).
I highly doubt that ALL fused resistors were defective - maybe after your first attempt(s). My SM part list only shows three 'fusible resistors' on the 'A' board. Also a number of low value metal film/metal oxide ones that I've heard called fusible.

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Location: Far, Far Away

(This post was edited by jts1957 on May 15, 2014, 9:22 PM)

2000DPL
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May 20, 2014, 9:28 PM

Post #10 of 10 (2442 views)
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Re: [jts1957] KV28LS36U 11 blinks [In reply to]	Can't Post

This TV repair was a HOBBY repair and the costs involved was of no consequence.

When I started off all those many months ago, I did internet searches for repairs. Based on those searches I replaced quite a number of components without really checking if my components were actually at fault. Clearly, I had no idea what I was doing and so, I went back to basics of learning: "what is a resistor/capacitor/transistor" - I missed the one on how to use a multimeter!

So, after trying everything and exhausting all the internet searches, and no idea where to look for the fault, I posted a message on here. It transpired that I was taking readings off heatsinks when I should have been taking them from a definitive/known earth point. Ergo, my search of the PCB's fault started all over again.

The last time I repaired a television I was about 8 years-old and my father told me to put a glass valve into a slot that his shovel-hands couldn't get into: it was a mono with a 12" screen.

So, once again my thanks to the people on this forum.

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