Fuse problems

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cheapNdisgusting
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Fuse problems

Post by cheapNdisgusting » Wed Sep 07, 2005 5:24 pm

I realize this is grasping at a straw but during a power company low voltage spurt, my TV blew the fuse on the low voltage side of the power supply. It is a Zenith model #C32V22. It's a 32". I tried the Zenith web site and couldn't get into the schematic because of the $45 membership.
The fuse (glass tube)is soldered in and has no visible markings. I want to TRY another fuse but have no clue as to the correct value.
Anybody got a clue what size?<p>Thanks in advance
cNd

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Chris Smith
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Re: Fuse problems

Post by Chris Smith » Wed Sep 07, 2005 5:31 pm

A lot of fuses are in a “end cap” holder that is a push in type of holder and solder the leads type of situation. See if your fuse is supported by little end cap cups that have leads on them, and simple unsolder these caps, and then pull out the fuse from the cup. <p>Then you can read the value. <p>If not unsolder the fuse and use a magnifying glass because fuses are marked almost invisible, and failing that a lot of circuit boards are marked/ stenciled at the fuse for their value.

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cheapNdisgusting
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Re: Fuse problems

Post by cheapNdisgusting » Wed Sep 07, 2005 5:56 pm

You described it perfectly. But all I can see on it is tiny marks that are parts of letters or numbers. Like it was a soft stamp job. Even with a mag glass I can't make anything out. I have a real good source of the glass tube fuses and would rather give it a try instead of just buying another TV.<p>Thanks for the reply.
cNd

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Chris Smith
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Re: Fuse problems

Post by Chris Smith » Wed Sep 07, 2005 6:19 pm

You can always start out small and build up the fuse rating, if it blows too easily. Use .250 amp steps.

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Re: Fuse problems

Post by rshayes » Wed Sep 07, 2005 6:22 pm

The letters usually indicate the fuse type and the number would indicate the rating in amperes. A 1 amp fuse might be labeled AGC 1. The AGC fuse was encased in a glass tube about 1/4 inch in diameter by 1 1/4 inch long. Lower currents than 1 ampere were described as fractions of an amp, such as 1/2, 1/4, etc. The AGC type of fuse used to be very common and there is a similar but smaller type that is standard in Europe.<p>Two major fuse manufacturers were Bussmann and Littlefuse. They may have on line catalogs that describe the numbering system.

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cheapNdisgusting
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Re: Fuse problems

Post by cheapNdisgusting » Wed Sep 07, 2005 6:44 pm

Unfortunatly, the number (or letters) are unreadable. I have a bunch of glass fuses and thought about the "swap up till they don't blow" method (one of my personal favorites) but wasn't sure if a regular fuse was the right kind, meaning - fast blow, slo blow, or current limiting, ect.<p>Thanks for the replies.
cNd

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Edd
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Re: Fuse problems

Post by Edd » Wed Sep 07, 2005 7:26 pm

cheapNdisgusting:<p>It sounds like in your dilemma that you might be like Red Ryders compatriot, Little Beaver…..”me heap gusdusted”.<p>The first thing to know about that fuse is the visual internal condition, is its link/or internal pieces still visible? If vaporized/silvered and/or blackened internally you would have had a “hard” blow and placing another fuse in circuit would typically serve to only create further meltdown of power component(s) into yet a bigger blob! <p>What I might suggest for a non destructive analysis technique is this. Get a set of test clip leads that can bite onto the end clips of the pig tail fuse, and not snap off. If alligator clips, this can be enacted by taking a pair of needle nose pliers to the center of each jaw and twisting inward so that they close with a better griping action at the very tips to each other. Then get either a drop cord/trouble light with its incandescent lamp on the end, or commandeer a small table lamp. You will want a minimum of a 100 watt lamp in the unit and 150 watt would be a bit better (easy if the lamp is a 3-way…right?). The lamp is plugged in and tested as being switched on and in an illuminative state and then its AC plug prongs are connected to each of the vacant clip leads respectively.
If the TV power cord is then plugged in and the front power switch button pressed the lamp should quickly come up in brightness and then diminish back to a glow. Typically there is inadequate power passage to operate the tv set at the restrained power level permitted to pass….BUT… what you really want to know by this test is if any of the TV sets power supply raw DC rectifier diodes/ or/ bridge junctions were crunched…or very rarely the raw DC electrolytic, that they feed or very commonly the SMPS power IC is punched out if they fail. You will be aware of this by the fact that the lamp will be very bright at turn on and stay that way…not diminishing in its luminance.
I will check our LRC later and check schemas to research your fuses value later, I am expecting 4-5A slo-blo…..and yes, the “furrin” original solder capped micro fuses (3/16 x ¾ in) usually do not have markings, as Little and Buss do… it may be days on my comeback…. I been one busy little bunny this year.<p>73's de Edd
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;) ;) <p>I saw a woman wearing a sweat shirt with "Guess" displayed on it.
So I said, "Implants?" ........She slapped me !
<p>[ September 08, 2005: Message edited by: Edd Whatley ]</p>

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Re: Fuse problems

Post by terri » Wed Sep 07, 2005 7:44 pm

Damn, you're good. Whatley.<p>I cited your article back in March on Ungar Solder Stations for one of our questioners who wanted spare parts for his station on the theory that your article would point him in the "repair" direction rather than the "remove and replace" direction. He may be contacting you on whether you might have the parts he needs.<p>No need to respond to this particular warm fuzzy.<p>Damn, you're good.<p>[ September 07, 2005: Message edited by: terri ]</p>
terri wd0edw

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cheapNdisgusting
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Re: Fuse problems

Post by cheapNdisgusting » Wed Sep 07, 2005 7:54 pm

Thanks, and waiting patiently.
cNd

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Edd
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Re: Fuse problems

Post by Edd » Wed Sep 07, 2005 8:15 pm

Whut you talkin’ ‘bout Willis?…………a la Gary Coleman/ Diff’rent Strokes.<p>Soooo…..does that mean that you have already subjected the set to the prescribed procedure and it passes?….therefore, it only then being safe for a fuse replacement.<p>73's de Edd
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Re: Fuse problems

Post by Externet » Thu Sep 08, 2005 8:09 am

Hi.<p>The television for sure has a label with the Watt rating.
Divide that figure into 120V and that should be a very near value for the fuse.<p>Interesting, Murphy's law did not apply for you: "Expensive electronic equipment blows itself to protect the fuse"<p>Miguel
- Abolish the deciBel ! -

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Re: Fuse problems

Post by dacflyer » Thu Sep 08, 2005 11:11 am

i have worked on many of these big sets, and 99% of the time the fuze is a 4 amp fast blow fuze.
a few were 4 amp slo-blo. hope this will help ya..<p>EDD >> i love your funnys at the end of yer komments,,keep em comming {:>D

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Re: Fuse problems

Post by Will » Thu Sep 08, 2005 12:27 pm

At the risk of ridicule - why wouldn't you just switch on the TV with a multimeter switched to current (10A ?) range - note start up from cold current etc, high volume currents, then choose a fuse size ?
BB

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Edd
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Re: Fuse problems

Post by Edd » Thu Sep 08, 2005 3:33 pm

Welllll... to get express action on your info, I opted instead to utilize a collegiate library aide via telephone(y)....along with some degree of telepathy......being involved in the schematics interpretation.
I was able to find one year prior to your units production, and like mass manufactured products they stick with some design for a time unless they have problems or the need for technical upgrading.
The AC line fuse should have an item designator/identifier of FX3401 silk screened on the PCB adjunct to it. The same type I mentioned previously, and yes, it is a 4 amp "blow slowly" type as I also had mentioned....for repetitively taking AC current surge inrush upon initial cold set power up.
And yes the unit did use a plastic encased full wave bridge in lieu of the typical 4 discrete diodes, for raw DC rectification, its item designator is DX3401. To confirm that the SMPS design is the same, find the SMPS transformer (TX3404) and its associated sheet alum heat sink aside and confirm the large plastic power IC's markings is of the STR53041 family. That unit looks like a very large/wide power transistor on steroids with 5 buss leads coming out its bottom.
I don't really think that you peeked behind the SMPS xformer, but there is another micro 3 amp SB PT fuse in its terminal 4 AC leg feeding to the sets derived 15/9/5 VDC supplies, probably not of any relation to YOUR problem.
So, if your set passed my initially described analysis and you are very lucky, you might be flying again with a mere fuse replacement. Ergo...'' rots o ruck''.<p>Hmmmmm...now back to that beleagured aide.....I know that I didn't hear a final extollation of ''I'M QUEEN OF THE WORLD!''...but I certainly was catching aside snippets of conversation with her associates in the effect of ....Egyptian ......tombs...... walls ......Alexandria......cuneiform… Sarcapogus
.........Hieroglyphs ..........

Will:
That’s a 50/50 chance….. if being in the dark on the integrity of the sets PS. That 10A metering current shunt wire would afford nil in any limiting to the power supply circuitry. <p>terri:
Thank 'yuh very much.......Thank 'yuh very much...........a la Elvis(esque)<p>Would you believe that I have never had Ungar since waaaaaay back to the days of "wood burner" style of units and their selectable wattage and associated tiplet choices. I did have one of the later and upgraded turqoise Imperial series , but it
was stolen from me. Therefore I am not up on their controlled temp units, however seeing a few of their tiplets at Hamfests flea markets reveals a similar “pellet” design.
Oy...oy...Xuan loi…...I DO have one of their de-soldering stations with its vacuum pump assisted solder removal to a quartz glass reservoir...and on its side there is mounted a 40-60 w soldering iron, I will have to pull it out and see how it is
designed.<p>73's de Edd
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;) ;) <p>Most people don't know what they are doing, and a lot of them are really good at it !. <p>Addenda:
Para Senor Miguel:
“Whut it wuz”… dyslexia kicking in , or the utilization of ‘smho’ Law instead ?
Let’s see now , that 89 watts consumption goes into 120 Vac… ….how much…..’bout 1.3 amps?
Pee Ess, are you gonna revamp your LM3909 equivalent wordamatic / schematamatic up for us ?……..pleeeeeeeeeassse
(o por un gran favorisimo).<p>My secret tip for fishermen:
I do my best fishing whenever it starts to rain by moving over under a bridge.
The fish keep crowding in to get out of the wet.
<p>[ September 08, 2005: Message edited by: Edd Whatley ]</p>

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Re: Fuse problems

Post by Robert Reed » Thu Sep 08, 2005 4:43 pm

EDD
"I did have one of the later and upgraded turqoise Imperial series , but it
was stolen from me."<p>
Ahhhh- the Torquoise Imperials, the finest soldering iron ever made. Handles like a sports car. I own three of them with various size tips installed and I guard them with my life.

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