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Old 10th Apr 2014, 5:25 pm   #1
ComputerMuseum
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Default Museum needs help with Sony KV-29FX65

Hi All,
I wonder if you can help. We have 10 Sony KV-29FX65 TV's that we have built into a wall at The Centre for Computing History to connect retro computers and games consoles to. They have been working well but about 3 now fail after a random amount of time where the screen turns off and the power light flashes 3 times. I have looked it up here and it appears to be an over voltage fault. I am hoping that it is a case of replacing a capacitor for smoothing or something? But the question is which one. Or is it something else? I am an electronics engineer but not TV's specifically. Any help would be much appreciated. Here's the service manual : http://www.go-gddq.com/upload/2010-0...1914583174.pdf
Cheers
Jason
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Old 11th Apr 2014, 1:19 pm   #2
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Default Re: Museum needs help with Sony KV-29FX65

Hi Jason,

I think we've met before - I donated some BBC Micro stuff to the centre last year. Though I'm usually out of the UK, I'll be in Cambridge for the week after Easter and would be happy to come along and help.

I'm not a Sony TV expert, but debugging complicated electronic things is my day job. Looking at the service manual, it looks like there are a number of things which would be quite simple to check to isolate the fault - first of all, whether any of the power supply rails really are going over voltage.

I searched for 'Sony AE5 OVP' and got one useful hit which indicated that D6621 had gone leaky. There are a whole bundle of similar components in that area which could have similar troubles.

It's possible that a failing smoothing capacitor somewhere, probably C6630 on the +135V line which seems to be the one that's regulated, is causing the power supply to work hard and so the voltage on other outputs (the 10.5V seems to be sensed) is creeping up. But there could be other causes too.

Let me know if you'd like a hand with it,
Chris
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Old 14th Apr 2014, 9:29 pm   #3
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Default Re: Museum needs help with Sony KV-29FX65

Hey Chris,
That would be amazing! Thanks so much. We've put some slightly smaller screens in their place which looks terrible but at least they're working!
So as not to waste your time, please feel free to get any components we might need whatever it costs and I will fully reimburse you. In fact get more than you might need! It's always good to have spares!
I'll have tea and coffee on tap if that helps!!
I really appreciate the offer - thank you.
Just drop me an email and let me know when it might be.
Cheers!
Jason

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Old 18th Apr 2014, 2:37 pm   #4
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Default Re: Museum needs help with Sony KV-29FX65

The AE5 chassis is quite a difficult and complex chassis to work on, access can also be a problem.

The usual Sony dry joints are found anywhere and everywhere, some are hidden under the chassis support struts/frame, so a good look is always worthwhile, not forgetting that on many Sony Chassis of this era that often the heatsinks were used as part of the chassis/ground return lines, so a check on these is worthwhile.

There is also, as Cmjones01 correctly mentions, the usual electrolytic capacitor problems becoming apparent as these sets age.

One particular part of the set I would take a good look at is the stby/always 5V rail, when the capacitors fail here it causes havoc on this chassis giving a number of possible different symptoms and error codes, depending on how the set's micro interprets the fault.

Also relevant to this particular fault the above mentioned 5V rail plays a part in the error sensing control in the OVP system, the parts to check here are C6557 470uF @ 25V, C6558 and C6559 100uF @ 25V (these capacitors should preferably be replaced), also check the regulator for this rail IC6554 KA78R05, this IC is sometimes dryjointed, and I have had it faulty on the odd occasion, probably due to overheating due to the aforementioned capacitors putting excess ripple on the device.

I have also had various Silicon devices failing, as well as the very low ohms (sub 1 ohm)resistors and very high ( above 100K) resistors failing, although the silicon failures are usually obvious and permanent, as well as various other Electrolytics in other parts of the set.

I hope this helps whoever takes these sets on.
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Last edited by Red to black; 18th Apr 2014 at 2:50 pm. Reason: additional
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Old 18th Apr 2014, 6:45 pm   #5
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Default Re: Museum needs help with Sony KV-29FX65

Thanks for the tips, Red to Black - they're extremely helpful. Having looked at the circuit diagram, I can see how the standby 5V rail could cause all manner of havoc if it was grubby. I'm trying to arrange a visit with the museum to see if I can help.

Chris
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Old 18th Apr 2014, 7:19 pm   #6
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Default Re: Museum needs help with Sony KV-29FX65

Hi Cm,
I am not saying this is your fault, it could very well be that there is a genuine overvolt condition with the PSU proper, or it could be a problem in the trip/sensing circuit itself as you pointed out earlier (faulty 10.5V line and faulty zeners etc...etc..).

I should really have put "in addition to" in my post, still the points I made are worth bearing in mind, every little helps as they say.


Good luck with the sets !, access is horrendous BTW, and the way the LOP stage and E/W circuit works is very different to other sets, although Sony used a very similar system in the later AE6 and AE7 chassis.
Again, Good luck!
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Old 18th Apr 2014, 8:42 pm   #7
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Default Re: Museum needs help with Sony KV-29FX65

Hi
Thought I would just mention that a common fault on some sony set
causing tripping was dry joints on the field output ic, but careful make certain the all the electros around the Ic are discharged b4 soldering, as soldering tip of iron could discharge on of these causing the ic to go faulty(guess how I know) Regards Derrick
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Old 18th Apr 2014, 8:46 pm   #8
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Default Re: Museum needs help with Sony KV-29FX65

Head magnifier and rework All regulator joints /frame ic etc Check esr of all caps in those areas.(Electro that is).
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Old 18th Apr 2014, 9:41 pm   #9
cmjones01
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Default Re: Museum needs help with Sony KV-29FX65

Quote:
Originally Posted by Red to black View Post
I am not saying this is your fault, it could very well be that there is a genuine overvolt condition with the PSU proper, or it could be a problem in the trip/sensing circuit itself as you pointed out earlier (faulty 10.5V line and faulty zeners etc...etc..).

I should really have put "in addition to" in my post, still the points I made are worth bearing in mind, every little helps as they say.
No offence taken! Your post inspired me to think harder about the standby 5V supply. Thank you again for sharing your experience - I've never so much as opened up a modern(-ish) Sony like this so, as you rightly say, every little helps. I'll certainly report back if I get a chance to have a look at these sets.

Chris
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