HOT slowly overheating

On Wed, 27 Dec 2006 08:14:42 -0700, Ken G. Has Frothed:

Take the flyback from the smashed set and swap.

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If everything else seems ok, ie, picture and deflection are ok, can you increase the heat sink size somehow? Maybe a bad design from the beginning.

H. R.(Bob) Hofmann

Ken G. wrote:

Either the heat sink is way undersized or the retrace tuning cap may be leaky. Sounds like more HS surface area is a good idea either way.

A bad design? No shit asshole.

I have worked on several of the Toshiba with the same exact heat sink and HOT and chassis and never found one till now that got hot like this The picture shows no sign of any problems .

My next step was to put in the flyback from the smashed set ... THANKS . Today i also found another 02. 9`` set that had a shorted picture tube only it had a vcr in it but same exact HOT . Fylback # ??

I thought of adding more heat sink but thats not always the best thing to do .

of course it's going to get hot. It's a HEAT SINK. What part of that don't you understand,

I love you and i want more !

Let us know what finally happens. (about the tv that is )

H. R. Hofman

Ken G. wrote:

I had some similar problems with other TV brands. Regularly the HOT was not driven properly. In one case the electrolytic capacitor to the base had lost capacity, in an other case a solenoid parallel to a resistor to the base was not soldered correctly on one end. The HOT can survive only if it really works as a switch, ie, strong input signal and short pulse rise times. Good luck, H.

Ken G. ha escrito:

did you just esr the caps in the hor drive cct or actually change them?

-B.

A properly designed and functioning HOT should not get hot.

Either a problem with the drive or the output circuit can result in excessive dissipation in the HOT.

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Sam Goldwasser ha escrito:

You haven't worked on many Samsungs , have you! ;-) they're so mean with the metal, piddling little heatsinks mean the trannys always seem to run hot but somehow they work. also some of the the newer sharps and daewoos don't even heat sink the HOT :-o

-ben

or maybe he just changing the channels too fast.

Right. Note the part about "properly designed". :)

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Looks to me like you need a ring tester for flyback (LOPT) transformers. Dick Smith makes one that we, and others, sell - if DS EVER makes any more that is (backordered for a month or two so far!). Still a ring tester is great, and is a useful tool on the TV/Monitor repair bench. You can pick up second hand ones on eBay - Sencore and the like.

We test all our monitors with a ring tester (Bob Parkers design - Dick Smith sells) before we recap them - saves a lot of trouble.

John :-#)#

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On Wed, 27 Dec 2006 08:14:42 -0700, snipped-for-privacy@webtv.net (Ken G.) put finger to keyboard and composed:

I'd look for an electrolytic cap on the primary side of the horizontal drive transformer.

- Franc Zabkar

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Ok i finally got back to this thread . I only ESR the caps , i didnt change any . I did however take the flyback off the newly found set and put it in the overheating set and the overheating stopped . I left the set on all night long and in the morning the HOT heat sink was only slightly warm .

I know these tv sets are cheaply made and all but this whole project was free accept my time and this is what people buy and want fixed so fix i will . The little set has a DVD in it and a 12 volt jack and still looks like new . Someone will like it .

Thanks for all the pointers and technical info .

On 28 Dec 2006 10:06:28 -0800, "b" put finger to keyboard and composed:

Why Do Apparently Similar or Better HOTs Sometimes Run Hot:

Typical HOT Dissipation:

Here is an excerpt from the aforementioned URL:

=============================================================== Here are some measured values for TV HOTs with optimized drive: (From: David, a Philips application engineer).

14-21", 16 kHz: About 1 W (some have the HOT running in free-air) 21-36", 16 kHz: Less than 2 W (some new large CRT's only need 9 A p-p) 25-36", 32 kHz: Less than 4 W (dissipation really is prop. to frequency) ===============================================================

- Franc Zabkar

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