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Fusible resistor selection

R

Russ_Verdon

Jan 1, 1970
0
Hi, I just fixed a 19" monitor rescued from the kerb (LICOM N9054LP), and I
got there before the annoying man who goes aroung cutting off all the cables
from appliance did!

Horizontal but no vertical. The Vertical chip was TDA 0472 (couldn't get any
data).

The obvious fault was an overheated R501 fusible resistor probably a 1W
size. If feeds the chip with 15V as per the diagram. Its value changed quite
dramatically when you flexed the leads from about 60R to hundreds of ohms.
My problem is that the heat had caused the colour bands to change colour and
were undecipherable.
My question is what is the method for calculating a value for these
protection resistors? I assume we want to minimise Voltage drop and have the
resistor run within its rating. What base load would you run through the
resistor? I ended up with a .68ohm with .6volts dropped across it. This
seemed to restore vertical. The resistor thus dissipates .5W. IS this ok?

15V supply
______|
__| /
| \e--------^^^^^^------ pin2 /TDA0472
NPN _|_ R501 _|_
__ _ _
|__________ |
GND

Regards

Russell
 
Russel, your calculations seem close enough and your final selection of
a .68 ohm 1 Watt resistor seem to be quite plausible.
Run the television for a couple days and make frequent checks to make
certain than nothing overheats.
Nice rescue from the curb.
electricitym
..
..
 
C

Chance

Jan 1, 1970
0
Russ_Verdon said:
Hi, I just fixed a 19" monitor rescued from the kerb (LICOM N9054LP), and I
got there before the annoying man who goes aroung cutting off all the cables
from appliance did!


I'd find that guy and beat him. "Kerb" side shopping is the best, even
I can afford the prices!!!
 
D

David Nebenzahl

Jan 1, 1970
0
Russ_Verdon spake thus:
Hi, I just fixed a 19" monitor rescued from the kerb (LICOM N9054LP), and I
got there before the annoying man who goes aroung cutting off all the cables
from appliance did!

I'm curious about this part of the story: who is this guy, and why does
he go around cutting off cords from potentially good appliances? Is this
some kind of official function? or is he just an asshole? What
municipality is this?


--
Pierre, mon ami. Jetez vous une plus de Scientologiste
dans le vat de l'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"
 
3

3T39

Jan 1, 1970
0
Hello, David!
You wrote on Sat, 15 Apr 2006 11:12:37 -0700:

DN> Russ_Verdon spake thus:

DN> I'm curious about this part of the story: who is this guy, and why
DN> does
DN> he go around cutting off cords from potentially good appliances? Is
DN> this
DN> some kind of official function? or is he just an asshole? What
DN> municipality is this?



The same thing happens at the recycle centre where I salvage a lot of my
stuff, (A different man though I think, just the same job) The basic reason
is the connector wire is recycled seperately and also it makes stacking
easier ( when your dealing with dozens of TV's , VCR's etc the dozens of
wires become entangled)


With best regards, 3T39. E-mail: [email protected]
 
R

Russ_Verdon

Jan 1, 1970
0
Hi, I think this guy collects the wire for selling as scrap copper. It is
all he takes. I saw him once, he just uses a knife to hack through the
cables, be it power cords, signal cables from monitors or anythimg else.
I have lost count of how many cords I have had to attach to scavanged
equipment to test .

Regards Russell

PS I got a 21 inch monitor off the kerb today, thankfully it had an IEC
socket and separate signal cable. It even goes( just a tweak of the screen
control and focus required.)
 
T

Tom MacIntyre

Jan 1, 1970
0
Hi, I think this guy collects the wire for selling as scrap copper. It is
all he takes. I saw him once, he just uses a knife to hack through the
cables, be it power cords, signal cables from monitors or anythimg else.
I have lost count of how many cords I have had to attach to scavanged
equipment to test .

Regards Russell

PS I got a 21 inch monitor off the kerb today, thankfully it had an IEC
socket and separate signal cable. It even goes( just a tweak of the screen
control and focus required.)

It's amazing how people (even supposed technicians) have been
brainwashed into thinking that most electronics isn't worth repairing,
or cannot be repaired. It's sad, actually...

Tom
 
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