texas star 2879
 

Have a texas star 500. One of the pills (2879) gets hot as soon as
power is supplied to the amp and then blowes fuse when you key up. Can
I check this trans out of the amp with a dvm for short and what is the
procedure? Thanks, Bill

texas star 2879
 

The transistor that heats up immediately is
bad (excessive C-E leakage).

The DVM test procedure is to use the diode
check function. Imagine a transistor as
two diodes back-to-back with the base being
the common element. Test from base to emitter,
and from base to collector. You should only
get a reading in one direction on each test
(when the base is above either of the other
elements), and it should be around 600 mV.
--
bdonovan1 wrote:
Have a texas star 500. One of the pills (2879) gets hot as soon as
power is supplied to the amp and then blowes fuse when you key up. Can
I check this trans out of the amp with a dvm for short and what is the
procedure? Thanks, Bill

texas star 2879
 

Collector-Emitter leakage... LOL
What he's got is a shorted transistor. That's got nothing to do with
leakage.

Professor
www.telstar-electronics.com


Bill Eitner wrote:
The transistor that heats up immediately is
bad (excessive C-E leakage).

The DVM test procedure is to use the diode
check function. Imagine a transistor as
two diodes back-to-back with the base being
the common element. Test from base to emitter,
and from base to collector. You should only
get a reading in one direction on each test
(when the base is above either of the other
elements), and it should be around 600 mV.

texas star 2879
 

Can he put a patch on the leaks He Hee


"Professor" wrote in message
ups.com...
Collector-Emitter leakage... LOL
What he's got is a shorted transistor. That's got nothing to do with
leakage.

Professor
www.telstar-electronics.com


Bill Eitner wrote:
The transistor that heats up immediately is
bad (excessive C-E leakage).

The DVM test procedure is to use the diode
check function. Imagine a transistor as
two diodes back-to-back with the base being
the common element. Test from base to emitter,
and from base to collector. You should only
get a reading in one direction on each test
(when the base is above either of the other
elements), and it should be around 600 mV.

texas star 2879
 

If it was shorted the fuse would blow
as soon as the amp was attached to a
source of power.

Excessive C-E leakage is a partial short
(where the C-E resistance with no bias
or signal applied is significantly above
zero but well below normal).

You should have known that.

I can see some things never change.
--
Professor wrote:
Collector-Emitter leakage... LOL
What he's got is a shorted transistor. That's got nothing to do with
leakage.

Professor
www.telstar-electronics.com


Bill Eitner wrote:

The transistor that heats up immediately is
bad (excessive C-E leakage).

The DVM test procedure is to use the diode
check function. Imagine a transistor as
two diodes back-to-back with the base being
the common element. Test from base to emitter,
and from base to collector. You should only
get a reading in one direction on each test
(when the base is above either of the other
elements), and it should be around 600 mV.

texas star 2879
 

TNT wrote:
Can he put a patch on the leaks He Hee

Yes--by replacing the leaky transistor.
--

texas star 2879
 

On 19 Nov 2005 18:22:33 -0800, "Professor"
wrote in
. com:

Collector-Emitter leakage... LOL
What he's got is a shorted transistor. That's got nothing to do with
leakage.

Professor
www.telstar-electronics.com


Bill Eitner wrote:
The transistor that heats up immediately is
bad (excessive C-E leakage).
snip


........oh brother.

Hint #1: The amp doesn't blow a fuse until it's keyed. If the
transistor was shorted the fuse would blow on power-up. It's not a
shorted transistor.

Hint #2: Excessive quiescient collector current is not definitive of a
C-E leak, nor is it even a likely possibility since the gain of the
transistor would be almost nil, and keying up isn't likely going to
increase the current enough to blow the fuse.

Both of you voodoo-techs missed the obvious and most likely problem:
excessive base bias current. The cause could be a bad bias supply
and/or base shunt, or the other transistor (assuming a push-pull amp)
being blown wide open.


BTW, who let you out of your cage, Bill?









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texas star 2879
 

On Sun, 20 Nov 2005 04:00:04 GMT, Bill Eitner
wrote:


I can see some things never change.

STFU Bill and go QRM another repeater so riley will take your damn
lincense, you ****ing ignorant piece of ****...

Bill Nazdam was right about you, you ARE full of yourself.. dickheaded
asshole.

texas star 2879
 

Well, let me add or define this problem some. Amp on- transistor starts
getting real hot real quick and Will blow fuse.
Amp on and keyed, definate blown fuse. Checked biasing, all
resistors,diodes near and around problem transistor, all ok. Removed
the transistor and power up amp, no problem. Have not keyed the amp in
this state so dont know if it would blow the fuse. Tested trans with
dvm in diode check, get readings from base to emitter and base to
collector no matter how the test leads are applyed. Ill be the first to
admit I am no tech, but it seems to me its shorted internaly some how.
As I say, Im no tech, just learning. Any help I can get I can sure use.
Thanks again, Bill

texas star 2879
 

me wrote:
On Sun, 20 Nov 2005 04:00:04 GMT, Bill Eitner
wrote:


I can see some things never change.


STFU Bill and go QRM another repeater so riley will take your damn
lincense, you ****ing ignorant piece of ****...

Bill Nazdam was right about you, you ARE full of yourself.. dickheaded
asshole.

Way to go Chuck. Keep coming up with these gems you psuedo christian
whack job.

texas star 2879
 

"jim" wrote in message
...
me wrote:
On Sun, 20 Nov 2005 04:00:04 GMT, Bill Eitner
wrote:


I can see some things never change.


STFU Bill and go QRM another repeater so riley will take your damn
lincense, you ****ing ignorant piece of ****...

Bill Nazdam was right about you, you ARE full of yourself.. dickheaded
asshole.

Way to go Chuck. Keep coming up with these gems you psuedo christian whack
job.

LOL!! I was going to comment, but You put it so
eloquently.

Landshark


--
The internet is fun but it's no substitute for books, people, nature,
or direct experiences. But you think that you can get everything you
need from your computer, you are a fool.

Frank Gililland

texas star 2879
 

Frank, you're absolutely right. I was so busy laughing about Bill's
leakage that I missed the previous statement about the fuse not blowing
until the unit went into transmit. I'm in full agreement that the
transistor could not have a hard short and if the bias was excessive...
it certainly could blow the fuse instantly.

Professor
www.telstar-electronics.com


Frank Gilliland wrote:
On 19 Nov 2005 18:22:33 -0800, "Professor"
wrote in
. com:

Collector-Emitter leakage... LOL
What he's got is a shorted transistor. That's got nothing to do with
leakage.

Professor
www.telstar-electronics.com


Bill Eitner wrote:
The transistor that heats up immediately is
bad (excessive C-E leakage).
snip


.......oh brother.

Hint #1: The amp doesn't blow a fuse until it's keyed. If the
transistor was shorted the fuse would blow on power-up. It's not a
shorted transistor.

Hint #2: Excessive quiescient collector current is not definitive of a
C-E leak, nor is it even a likely possibility since the gain of the
transistor would be almost nil, and keying up isn't likely going to
increase the current enough to blow the fuse.

Both of you voodoo-techs missed the obvious and most likely problem:
excessive base bias current. The cause could be a bad bias supply
and/or base shunt, or the other transistor (assuming a push-pull amp)
being blown wide open.

texas star 2879
 

Landshark wrote:
"jim" wrote in message
...

me wrote:

On Sun, 20 Nov 2005 04:00:04 GMT, Bill Eitner
wrote:



I can see some things never change.


STFU Bill and go QRM another repeater so riley will take your damn
lincense, you ****ing ignorant piece of ****...

Bill Nazdam was right about you, you ARE full of yourself.. dickheaded
asshole.


Way to go Chuck. Keep coming up with these gems you psuedo christian whack
job.


LOL!! I was going to comment, but You put it so
eloquently.

Landshark


Its amazing the prick keeps coming back after his blathering post about
leaving for good.
Anyway Sharkie, snow up by you yet? calling for it turkey day here.

texas star 2879
 

On 20 Nov 2005 04:34:45 -0800, "bdonovan1" wrote
in om:

Well, let me add or define this problem some. Amp on- transistor starts
getting real hot real quick and Will blow fuse.
Amp on and keyed, definate blown fuse. Checked biasing, all
resistors,diodes near and around problem transistor, all ok.


Don't just check the components -- physically test your base bias
current. If there is no series resistance at the base then at least
check the base voltage. And check -both- transistors (without keying
the amp, of course).


Removed
the transistor and power up amp, no problem. Have not keyed the amp in
this state so dont know if it would blow the fuse.


Don't. Assuming it's a push-pull amp (i.e, two transistors) you do
-=NOT=- want to key the amp with only one transistor.


Tested trans with
dvm in diode check, get readings from base to emitter and base to
collector no matter how the test leads are applyed.


Sounds like you checked them in-circuit. Won't work. You have to pull
the transistors in order to test them. Ideally, you should pull -both-
transistors and compare them to each other.


Ill be the first to
admit I am no tech, but it seems to me its shorted internaly some how.
As I say, Im no tech, just learning. Any help I can get I can sure use.
Thanks again, Bill


Since you little or no experience with these things, you should be
aware that ceramic RF transistors are made with Beryllium, a very
poisonous material. If the ceramic 'pill' is damaged in any way you
could be risking your health.

Just thought you should know.....









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texas star 2879
 

"jim" wrote in message
...
LOL!! I was going to comment, but You put it so
eloquently.

Landshark


Its amazing the prick keeps coming back after his blathering post about
leaving for good.
Anyway Sharkie, snow up by you yet? calling for it turkey day here.

Nope. Month started wet with snow at Tahoe, but since then
dry and warm.

Landshark


--
My bad..the camera is mightier than the blowhard(s)..in most respects.