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Old 9th Apr 2020, 7:55 pm   #1
acorn
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Default Toshiba 2879 DB

Hi all

Having some trouble with my Toshiba 28 inch TV, its developed a frame fault
the frame shrinks to about one inch top and bottom this happens intermittently
has one any idea as to the course of this fault, any help much appreciated

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Old 9th Apr 2020, 8:13 pm   #2
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Default Re: Toshiba 2879 DB

I'm not sure if the same frame circuit is employed on the 2879 as earlier Toshiba models but a very common and usually the only fault on Toshiba models is failure of the two 2.2uf 63v electrolytics. They are usually red in colour and look like the old OC81 type transistors. The circuit reference remained unchanged for years. C303 and C313.
Worth a look to see if they are fitted.
It could of course just be dry joints on the frame chip. Great receivers. I sold quite a few. John.
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Old 10th Apr 2020, 12:23 am   #3
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Default Re: Toshiba 2879 DB

If the circuit is anything like my old 2939DB then likely cracked solder on the frame chip as HKShort said. Apparently it was fairly common on those once there'd been enough heat cycles, could be similar here.
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Old 10th Apr 2020, 7:06 am   #4
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Default Re: Toshiba 2879 DB

Yes, would concur re solder round the IC. I sold mine a few years ago but checked this before it went as I didn't want it bouncing. Two years ago getting rid of crt sets was hard so I snatched at the sale. Now it seems they are becoming popular again, not surprised as LCD sets are dropping like flies.
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Old 12th Apr 2020, 10:54 am   #5
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Default Re: Toshiba 2879 DB

Thanks lads, it looks like it might be dry joints as its gone back to normal so when I have time to look at the TV I will also replace the two 2.2 uf as suggested by John

Could any one inform me as to the number on the frame ic, once again, many thanks for your help.

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Old 12th Apr 2020, 7:32 pm   #6
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Default Re: Toshiba 2879 DB

Just thinking back to my 2939DB... HKS, were C303 and 313 the ones that used to cause linearity and foldover issues? It's long gone now (sadly) but that set suffered terribly from that when cold. I never bothered repairing it though since it ran 24/7 and looked OK once warm!
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Old 12th Apr 2020, 7:49 pm   #7
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Default Re: Toshiba 2879 DB

Quote:
Originally Posted by ekjdm14 View Post
HKS, were C303 and 313 the ones that used to cause linearity and foldover issues?
They certainly did, sometimes the PCB could go leaky too due to the electrolyte leakage causing other similar problems even after they had been replaced, fortunately the board could be cleaned up with IPA and a hairdryer, sometimes this took more than one or two goes.

Depending on the set/chassis* several different field ICs were used, as HKS pointed out though Tosh used the same reference number for the caps across a few different models.
On some models one of the caps was physically nowhere near the frame output stage (one was) but rather associated with the jungle chip, or depending on the chassis an interface chip to the jungle chip.

* C5SS, C6SS, C7SS, C8SS etc. chassis plus a few other lesser models/chassis that I can't remember off-hand
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Last edited by Red to black; 12th Apr 2020 at 7:54 pm. Reason: additional info.
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Old 12th Apr 2020, 8:10 pm   #8
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Default Re: Toshiba 2879 DB

They were described in the manual as organic or something similar. I remember the leakage used to snap with a small spark, something like a mini Christmas cracker when desoldering. I used 2.2uf 100v 105 degree types and never saw them again.
Toshiba certainly manufactured great TV sets down in that old Bush factory in Plymouth.
To think only 23% of the T22 series used to work correctly on first switch on after assembly. Information obtained from paperwork discovered when Toshiba took over the factory around 1979/80.[Toshiba rep]
They managed to get this up to 99.9, a real credit to the factory. Proves we could do it if we tried. Happy days and never an unhappy moment with TOSHIBA. John.
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Old 12th Apr 2020, 8:18 pm   #9
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Default Re: Toshiba 2879 DB

Yes these Toshiba range of sets were a Joy to work on, well made and predictable for the most part, Tosh were also incredibly helpful tech wise even to non-account holders.

Were these caps called "Oscon" ? or am I thinking of Philips or Sanyo? Like you say HKS a nice little stock fault that once repaired with decent replacement 105 degree caps were never seen again for that fault.
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Last edited by Red to black; 12th Apr 2020 at 8:23 pm. Reason: punctuation
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Old 12th Apr 2020, 9:54 pm   #10
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Default Re: Toshiba 2879 DB

It's interesting to hear these stories from those who were there at the time, and heartening to see that with good management us Brits could still turn out a solid product

Now you mention it, the PCB probably did have some electrical leakage going on too on my old set, a kerbside rescue used as my main set for 8 years or so, (as well as the cold linearity issue) it used to make an occasional crack/snap like something had arced, even after repairing the cracked PCB and frame IC joints and cleaning all the dirt out (I like a clean chassis even if it doesn't make much difference to how it works, it's just "nicer" that way). Never made a difference if it was humid or dry & never affected the picture, just occasionally went crack! After I failed to find a probable cause, just decided to let the set run and see if it developed, never did...
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Old 13th Apr 2020, 12:59 pm   #11
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Default Re: Toshiba 2879 DB

It was a surprise if a Toshiba came in with anything other than a stock fault. There was obviously some reason why those capacitors were specified, but popping decent replacements in did the trick.
Toshiba were great. Although I wasn't a Toshiba dealer, they sent me CRTs for customers' sets, and replaced that DFS panel in the top of the range 32" and 36" sets for many years free of charge if the customer paid for its fitting.
I remember we did have a CRT fail after around five years on a large screen Toshiba. They sent an apologetic letter saying this shouldn't have happened so soon but they could no longer source one - I think it was made by Samsung and the neck had fallen off. Next thing a lorry arrived with a brand new set for the astounded customer. That's customer service!
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Old 13th Apr 2020, 1:43 pm   #12
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Default Re: Toshiba 2879 DB

Their LCD 3030 series were prone to corruption of the freeview firmware. Long after they were out of warranty they would send out a compact flash PCMCIA card with instructions to reflash it and return postage to any customer who requested one.

John.
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Old 13th Apr 2020, 2:51 pm   #13
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Default Re: Toshiba 2879 DB

Almost makes me feel guilty for leaving the 2939DB at my old house when I moved, it's almost certain that it would have been skipped along with the Beko as CRTs were well out of favour at the time.
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Old 13th Apr 2020, 3:05 pm   #14
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Default Re: Toshiba 2879 DB

Our old Toshiba FST set from about 1987 is still going!!! Picture isn’t the best anymore, but it’s still capable of being watched and enjoyed. Maybe I’ll stick the B&K on it to see what the emissions like after all these years, I’m not going to even attempt giving it a tickle, that would be asking for trouble. I must try and locate the caps John mentions, as the height has dropped a little in recent times.

Even more surprising is that the Toshiba’s replacement, a Sony 32” LCD set from 2006, is also still working well! Never had the back off that.

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