[TechAssist] Re: Semiconductor purchasing question
- From: Gary McCartney <gary@xxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Thu, 06 Oct 2005 10:01:07 -0400
I recently had a similar problem. I had a Hitachi 27" that I replaced
the vertical IC LA7838 and when I plugged it in, got a buzzing sound,
like the SMPS wasn't working. So I replaced some caps, only to
eventually find that pin 11 in the LA7838 was shorted to pin 12, the B+
pin, causing the SMPS to growl. Put in a new 7838 and away it went, no
problem. I got those chips at AA Electronics in Mississauga ON, run by
Chinese people.
Gary McCartney
McCartney Electronics
Guelph Ontario Canada
Est. 1984
email: gary (at) number63.ca
Premium Technologies wrote:
> Group,
> I had a Panasonic 27" in for repair today, with a not uncommon 3" high pic
> across the screen. Found three caps behind the vertical heat shield and the
> vertical IC LA7838 at fault. Replaced these and still had the problem.
> Traced and tested for about a half hour more and replaced the IC again, still
> same problem. At this point I'm fuming, going over the print, retesting up
> the circuit, ESR testing caps that I had done at least twice and looking for
> any clue as to why the IC looked as though it had failed.
> Finally I tried a third IC and to my surprise the pic was restored. I looked
> at the packaging and found that these three ICs were purchased from
> Tritronics and they didn't appear to be the cheap TT Chinese knock-offs. I'm
> at least intelligent enough to knowingly avoid those. In fact, I noted that
> I had paid almost nine bucks a piece for these.
> So, I went to order some things from Tritronics this evening and searched the
> LA7838 on their site. It came-up with several brands all using the LA7838
> and all of them a different price, ranging from a couple of bucks to eleven
> plus dollars a piece. So what denotes a knock-off from an original Sanyo
> made component when all you have is the price to go by?? None of the brands
> listed were Sanyo and most of them showed each of the brand part numbers,
> Hitachi and Toshiba for example, identifying it as a LA7838 or OEM part.
> It's probably how I ordered the last ones - middle of the road price or
> manufacturer number.
> This makes a about four times in the last month I've had to replace a
> component because it was a failure right out of the box.
> I'll be calling Tritronics tomorrow but this seems like an epidemic that
> obviously could be cured at the supplier's end. Besides, I just hate wasting
> money on such a small margin repair as this one.
> Anyone else had a similar problems lately with Tritronics parts?
> Bill
> William Rayburn, CET
> Premium Technologies
> PO Box 442
> Long Beach, WA. 98631
> 360-642-4993
>
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