I am trying to fix a sharp tv with a line stage which is not starting
up (140v on HOT collector Ok), there is a coil rated 4.7uH on the base
circuit of the HOT / line transistor which looks a bit tired. I only
have a 1.5uH to hand, would I cause damage by using it even just for
test purposes?

-B.

"b" wrote in message
...
I am trying to fix a sharp tv with a line stage which is not starting
up (140v on HOT collector Ok), there is a coil rated 4.7uH on the base
circuit of the HOT / line transistor which looks a bit tired. I only
have a 1.5uH to hand, would I cause damage by using it even just for
test purposes?

-B.

You might. I wouldn't normally recommend substituting values or types of
components anywhere in a HOP stage, particularly anywhere in the base
circuit of the transistor. The whole stage is a highly stressed bit of
circuitry, and any change in its operating conditions can spell instant
death to to an HOP transistor. It used to be quite common for HOP
transistors to fail because of bad components in their base circuit altering
the device's switching time, and leading to a rapid overheat and
destruction.

Arfa

yeah, I am very reluctant to modify that circuit. At the same time,
the inductance difference seems so small I was tempted - not sure the
effects of a few microHenrys difference would have. Since nobody seems
to have done this themselves and can vouch for it, probably best to
leave it alone until I order the correct spares....
-B

On Aug 26, 7:25*am, b wrote:
yeah, I am very reluctant to modify that circuit. At the same time,
the inductance difference seems so small I was tempted - not sure
the
effects of a few microHenrys difference would have. Since nobody
seems
to have done this themselves and can vouch for it, probably best to
leave it alone until I order the correct spares....
-B

Small change? You're comtemplating changing it by 3 to 1. How about
plug it into 300 volts? That's less than a 3:1 change.

G²

b wrote:
I am trying to fix a sharp tv with a line stage which is not starting
up (140v on HOT collector Ok), there is a coil rated 4.7uH on the base
circuit of the HOT / line transistor which looks a bit tired.

How do you know it's tired?
Eyes completely closed or just nodding off?

I only
have a 1.5uH to hand, would I cause damage by using it even just for
test purposes?

I've got this here 4-40 bolt. Can I use a 4-36 nut? They're both #4.

My car's outa gas. Can I use this here can of sterno?
They both burn...right???

-B.
But seriously...
Inductors don't get tired.
They get open
They get shorted turns
Cores crack.
Measure the inductance. There are many simple ways to make
the measurement...google is your friend.

If it's not open, it's unlikely that replacing the inductor
will fix it. It is possible that a bad inductor can be
the root cause and cause it to blow up again when you fix
the other broken stuff.
Inductance is not the only parameter of interest, but
if it's in a low-current part of the circuit and the
inductance is correct, it's "probably OK".

Randomly replacing components with "whatever you happen to
have" is inefficient troubleshooting.

spamme0 wrote:


Randomly replacing components with "whatever you happen to
have" is inefficient troubleshooting.

Indeed, it sounds like a quick route to insanity - you may be destroying
components faster than you're replacing them.

Sylvia