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.