Toshiba 42H81 Blows Fuse at Random

C

Chris F.

Guest
This 2001 model projection set has a tough problem to track down, so I'm
hoping someone can give me some advice. Fuse F850 (5A), in the power supply,
will blow at random intervals - sometimes when trying to power up, or the
set might run fine for hours, days, or even weeks. Just thought I'd check
for any known issues with this set, before attempting what could be a long
and frustrating job.
 
Chris F. wrote:
This 2001 model projection set has a tough problem to track down, so I'm
hoping someone can give me some advice. Fuse F850 (5A), in the power supply,
will blow at random intervals - sometimes when trying to power up, or the
set might run fine for hours, days, or even weeks. Just thought I'd check
for any known issues with this set, before attempting what could be a long
and frustrating job.


Maybe you have the wrong fuse in there?
Click to expand...

Most likely requires a slow blow type..


http://webpages.charter.net/jamie_5"
 
It doesn't specify. If it always blew instantly, I would indeed suspect that
the inrush current was too much for it. But once the set is warmed up, it
shouldn't be drawing anywhere near 5 amps (at least not on the B+ supply,
which is where I assume this is). Some component must be shorting
intermittently, and finding it isn't going to be easy unless someone can
fill me in on a known issue with these sets.

"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in message
news:eda1l.18757$R43.8219@newsfe08.iad...
Chris F. wrote:
This 2001 model projection set has a tough problem to track down, so I'm
hoping someone can give me some advice. Fuse F850 (5A), in the power
supply, will blow at random intervals - sometimes when trying to power
up, or the set might run fine for hours, days, or even weeks. Just
thought I'd check for any known issues with this set, before attempting
what could be a long and frustrating job.
Maybe you have the wrong fuse in there?

Most likely requires a slow blow type..


http://webpages.charter.net/jamie_5"
Click to expand...
 
On Sun, 14 Dec 2008 10:47:36 -0800, "Chris F."
<zappyman@hotmail.com>wrote:

It doesn't specify. If it always blew instantly, I would indeed suspect that
the inrush current was too much for it. But once the set is warmed up, it
shouldn't be drawing anywhere near 5 amps (at least not on the B+ supply,
which is where I assume this is). Some component must be shorting
intermittently, and finding it isn't going to be easy unless someone can
fill me in on a known issue with these sets.
Click to expand...
Well the chance of this unfortunately is not good. Maybe you should
think more along the lines of making the part fail. I've at least once
in my 30 some years in the industry over fused an intermittent and
then looked for smoke/fire. I'm not outright suggesting you do so but
it is a last ditch consideration.




"Jamie" <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in message
news:eda1l.18757$R43.8219@newsfe08.iad...
Chris F. wrote:
This 2001 model projection set has a tough problem to track down, so I'm
hoping someone can give me some advice. Fuse F850 (5A), in the power
supply, will blow at random intervals - sometimes when trying to power
up, or the set might run fine for hours, days, or even weeks. Just
thought I'd check for any known issues with this set, before attempting
what could be a long and frustrating job.
Maybe you have the wrong fuse in there?

Most likely requires a slow blow type..


http://webpages.charter.net/jamie_5"
Click to expand...
 
"Chris F." <zappyman@hotmail.com> wrote in message
news:49452d08$0$5467$9a566e8b@news.aliant.net...
This 2001 model projection set has a tough problem to track down, so I'm
hoping someone can give me some advice. Fuse F850 (5A), in the power
supply, will blow at random intervals - sometimes when trying to power up,
or the set might run fine for hours, days, or even weeks. Just thought I'd
check for any known issues with this set, before attempting what could be
a long and frustrating job.
Click to expand...

I've come across equipment before that has the wrong fuse specified. For
various reasons the manufacturer uprated it later on. And of course, the
manufacturer might not be in a hurry to point out its mistake .......


Gareth.
 
"Chris F." <zappyman@hotmail.com> wrote in message
news:49452d08$0$5467$9a566e8b@news.aliant.net...
This 2001 model projection set has a tough problem to track down, so I'm
hoping someone can give me some advice. Fuse F850 (5A), in the power
supply, will blow at random intervals - sometimes when trying to power up,
or the set might run fine for hours, days, or even weeks. Just thought I'd
check for any known issues with this set, before attempting what could be
a long and frustrating job.
Click to expand...

What circuits does this supply line service? Monitor each circuit to see
how much each is drawing. Fuse each circuit supplied by this fuse
individually if the excessive current is intermittent. When that circuit
blows its fuse you know where the problem is.

Leonard
 
"Chris F." <zappyman@hotmail.com> wrote in message
news:49452d08$0$5467$9a566e8b@news.aliant.net...
This 2001 model projection set has a tough problem to track down, so I'm
hoping someone can give me some advice. Fuse F850 (5A), in the power
supply, will blow at random intervals - sometimes when trying to power up,
or the set might run fine for hours, days, or even weeks. Just thought I'd
check for any known issues with this set, before attempting what could be
a long and frustrating job.
Click to expand...
You could temporarily substitute an AC ammeter for the fuse and watch the
current. Alternatively, you could use a large fusible resistor, say 1 ohm at
10 watts or .1 ohm if you prefer, and monitor the voltage across the
resistor. Should give you an idea what the current is doing.

Mark Z.
 
"Mark D. Zacharias" <nonsense@nonsense.net> wrote in message
news:Izk1l.12179$ZP4.6041@nlpi067.nbdc.sbc.com...
"Chris F." <zappyman@hotmail.com> wrote in message
news:49452d08$0$5467$9a566e8b@news.aliant.net...
This 2001 model projection set has a tough problem to track down, so I'm
hoping someone can give me some advice. Fuse F850 (5A), in the power
supply, will blow at random intervals - sometimes when trying to power
up, or the set might run fine for hours, days, or even weeks. Just
thought I'd check for any known issues with this set, before attempting
what could be a long and frustrating job.


You could temporarily substitute an AC ammeter for the fuse and watch the
current. Alternatively, you could use a large fusible resistor, say 1 ohm
at 10 watts or .1 ohm if you prefer, and monitor the voltage across the
resistor. Should give you an idea what the current is doing.

Mark Z.
That's basically what I plan to do. I have a Fluke DMM that can record
Click to expand...
min/max readings, I plan to insert it at various points in the circuit and
have it record any current spikes when and if they occur. Hopefully it
should help narrow the problem down.
 
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