Friday, October 9, 2015

Why Y-Main and buffer boards should NOT always be replaced together

In a daily language "experts" are usually people who do something more intense and, preferably, do it for living as opposed to as a hobby or on the side.

"Specialist" is a bit better word in that context and frankly I do not want to go down to semantics as much as I'd like to separate people who develop extensive expertise in a particular area versus all others.

Without being top notch I consider myself an expert in plasma , LCD and LED TV repair due to the fact that i do it a lot and , if anything, my experience and guessing would likely be better than that of an average customer even if I happen not to be the brightest of service engineers out there.

All that said, I am often reminded how bad an expert advice can be.

A quick illustration is a blog article I came upon today, which explains why is it better to replace a plasma sustain board along with buffer boards.

The contents of the article may change after my post, so I'll copy a snippet here without author's permission. I looked for place to comment under the article to tell them what I am telling you, but there was no option to leave comments , so I am instead doing it here.

"This is actually a fairly common problem amongst Plasma TV's. The Y-Sustain Board often times go kaput and you run into the problem of "no picture but still having sound". Everything else seems to work like volume control, changing the channels, and even changing the input from one to next. No problem, you think to yourself. Just replace the Y-Sustain Board and you should be good to go, right? Hold on there, cowboy. Before you go and do that, understand for a moment that Plasma TV's, unlike LCD TV's and LED TV's, is a different type of TV technology and thus, the way it operates is also different. If and when "a part goes out," it works in a domino effect. In other words, when one board goes out, it often times takes out another board with it. 

In a Samsung HPT5054, it uses this Y-Sustain and Buffer Board set: LJ92-01490A & LJ92-01491A & LJ92-1492A. Now, inside your TV, the direction of electrical current travels from left to right and when this set is inside your TV, from where you stand with the base of the "TV Stand opening" facing towards you, it would be from the "bottom up" that the electrical current travels. And in this particular TV model, usually the "short" comes from the lower buffer board (LJ92-01492A) that ends up blowing out the Y-Sustain Board. In other words, when the lower buffer board goes bad, it usually takes out the Y-Sustain Board along with it. And before you go jumping the gun and concluding that maybe it's prudent to replace the Y-Sustain Board and just the lower buffer board without also replacing the upper buffer board as well, this is actually not a good idea. Why? Because if the lower buffer board goes bad and takes out the Y-Sustain Board along with it, it is just a matter of time before the upper board goes bad. And then you run into the same problem except this time, it will be the upper buffer board blowing out the Y-Sustain Board. In this case, it's a lot like how your mechanic recommends that when you replace your tires or shocks and/or strut assemblies, that they should be replaced in pairs, rather than individually because of the same rationale: when one goes bad, it's highly probable that the other one is on its way out even though it appears to the naked eye that nothing seems to be wrong with it. And if nothing else, replacing the Y-Sustain Board together with the Buffer Boards will sufficiently eliminate the possibility that the short was coming from the upper buffer board thus minimizing the chances that you would end up blowing out one of the two working boards that you just bought. Ultimately, it saves you time and money to replace them together as a set rather than replacing two of the three only to have one of the old boards blow out on you and taking out one of the two perfectly good board you had just bought a week ago. And these Y-Sustain Boards don't come cheap nor are they easy to find."

While there is definitely some truth to the above, there is also a fair amount of errors and misconception resulting, at the end, in an incomplete at best, and more rightfully misleading conclusion and recommendations.

Here's why:

1) The article builds a case based on one example and fails to review everyday practice for other possibilities.

Samsung HP-T5054 does have a tendency of blowing a buffer board and taking down the Y-Main board as a result, that is correct.

However I can list tens of TVs - practically all Hitachi models I know and most of the LG based ones as well - where this is NOT the case.

HP PL5060N is a 50'' plasma from about the same time when Samsung HP-T5054 was made. It tends to blow the YSUS and the ZSUS boards however rarely ever the buffer boards are affected.
And the buffer boards are practically never the source of the YSUS failure.

So the case of having to replace all 3 boards together goes down the drain from the sake of cost efficiency and even pure technical requirements.

In case of the Hitachi plasma TVs from the same time frame, buffer boards tend to fail a lot - kind of like with Samsung - but they rarely ever affect the sustain board. 1 in 100 or something to that extent.

We highly recommend that people do not replace the sustain board simply because it is not needed.

In short: Y-Main and buffer boards SHOULD NOT always be replaced together.

2) The article talks about the lower buffer board failing on HP-T5054 and specifies it as LJ92-01492A.

That is flat our wrong.

We have about 200 lower buffers L92-01492A available here, result of customers replacing the set of buffers with new ones.

The lower buffer rarely ever fails!

What is the conclusion?

Well, whoever wrote that article is not really a TV service technician. No offense meant.

For my two cents whoever composed the article is fairly intelligent as it is well written (well interpreted from other sources is my exact opinion) and it improvises a bit over the original.

But it lacks what it needs most, which is first hand experience and proper application of logic specific to the issue.

I do not mean to offend the author or the other company in any way.

I want to make a point that one should not believe everything they get from what can be perceived as an expert in a certain area.

That includes our own advices, of course :-)

Take any way you want.


Unknown said...

Yes. Absolutely agree.

No idea what an HP-T5054 is because it’s not a UK model but I do recognise the part numbers, albeit very old. In this particular case, the usual problem is one of the 2 top ICs which go s/c which knocks out the top FETs on the Y Sus. If you are lucky then replacing the FETs and the top 2 buffer ICs (both as they are interlaced and it will fail again if you don’t) will sort it but more Y Sus damage is very common.

On the wider scheme of things. Y Drives (Buffers) can usually be checked by doing a diode check across the ICs. Every tab pin to local earth should read like a diode. Around 0.7v.

There are some specific screens which do have the habit of blowing up multiple boards. We do repairs & sales of parts in the UK & Europe but only sell Y Sus & Buffers together if we know that it is a likely problem.

Here’s a Panasonic one. Sorry for the advert (probably useless in the US anyway) but thought it might be useful for you.,-txnsu1usuu,-txnsd1usuu,-y-sus-kit-md50f16c7j,-tnpa5764,-tnpa5729,-tnpa5730-detail

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