Need Cross to output transistor

M

Mike

Guest
I have a peavy amp Mark V series from the 70s, and
each channel has 4 output transistors in the TO-20 or something like that
packedge,

its got the circle in the middle, and two leads comming out of the back, B
and E, and the case is C with 2 screw holes in it.

Well, I need a cross, its an RCA transistor, and it shorted. I cant find
that part number in MCM, or my datasheet site.

it says RCA, and under it says C8645, im guessing its 2SC8645? but nothing
comes up.

Above RCA, it has the serial, labled 67376-C

Any Ideas? I need 8, I might as well change all of them out preventing this
from happening in the near future. its very old amp, but it will blow the
roof off

one day, I turned it on, all the lights in the house dimmed, and blew the
fuse. again, and again.

And found 1 out of the 4 for B side shorted. I might as well change all 4,
and change the other 4 that are good just in case. you never know.

Anyway, I checked the rectifiers, and checked bias resistors, and other
resistors and so forth for aging, and drifting in value do to age, and found
none.

it just shorted between C and E, but I can get good readings from C to B,
and B to E, with about .465 for each, but .000 on C to E, indicates short, I
should have no reading here. or oL
 
Peavey part number 70467376
Field replacement is 2n5630


Bill
Christian Technology

"Mike" <mbates14@fuse.net> wrote in message
news:dpzWa.16802$dO2.3676@fe2.columbus.rr.com...
I have a peavy amp Mark V series from the 70s, and
each channel has 4 output transistors in the TO-20 or something like that
packedge,

its got the circle in the middle, and two leads comming out of the back, B
and E, and the case is C with 2 screw holes in it.

Well, I need a cross, its an RCA transistor, and it shorted. I cant find
that part number in MCM, or my datasheet site.

it says RCA, and under it says C8645, im guessing its 2SC8645? but nothing
comes up.

Above RCA, it has the serial, labled 67376-C

Any Ideas? I need 8, I might as well change all of them out preventing
this
from happening in the near future. its very old amp, but it will blow the
roof off

one day, I turned it on, all the lights in the house dimmed, and blew the
fuse. again, and again.

And found 1 out of the 4 for B side shorted. I might as well change all 4,
and change the other 4 that are good just in case. you never know.

Anyway, I checked the rectifiers, and checked bias resistors, and other
resistors and so forth for aging, and drifting in value do to age, and
found
none.

it just shorted between C and E, but I can get good readings from C to B,
and B to E, with about .465 for each, but .000 on C to E, indicates short,
I
should have no reading here. or oL
Click to expand...
 
I can Supply a Sub. Send me an Email if interested.

PS: Make sure you need 8 of the Same. Have Seen Amps where they use PNP &
NPN. 2 of Each Per channel


"Mike" <mbates14@fuse.net> wrote in message
news:dpzWa.16802$dO2.3676@fe2.columbus.rr.com...
I have a peavy amp Mark V series from the 70s, and
each channel has 4 output transistors in the TO-20 or something like that
packedge,

its got the circle in the middle, and two leads comming out of the back, B
and E, and the case is C with 2 screw holes in it.

Well, I need a cross, its an RCA transistor, and it shorted. I cant find
that part number in MCM, or my datasheet site.

it says RCA, and under it says C8645, im guessing its 2SC8645? but nothing
comes up.

Above RCA, it has the serial, labled 67376-C

Any Ideas? I need 8, I might as well change all of them out preventing
this
from happening in the near future. its very old amp, but it will blow the
roof off

one day, I turned it on, all the lights in the house dimmed, and blew the
fuse. again, and again.

And found 1 out of the 4 for B side shorted. I might as well change all 4,
and change the other 4 that are good just in case. you never know.

Anyway, I checked the rectifiers, and checked bias resistors, and other
resistors and so forth for aging, and drifting in value do to age, and
found
none.

it just shorted between C and E, but I can get good readings from C to B,
and B to E, with about .465 for each, but .000 on C to E, indicates short,
I
should have no reading here. or oL
Click to expand...
 
I only see 6 of them in Stock there. I can get you 8.

"Mike" <mbates14@fuse.net> wrote in message
news:5eEWa.32523$hc.9967@fe3.columbus.rr.com...
MCM electronics is right by here, and i needed a part number they had.



"techforce" <techforce@!~NOSPAM!~.juno.com> wrote in message
news:BuCWa.2007$jg.1007027@news1.news.adelphia.net...
I can Supply a Sub. Send me an Email if interested.

PS: Make sure you need 8 of the Same. Have Seen Amps where they use PNP
&
NPN. 2 of Each Per channel


"Mike" <mbates14@fuse.net> wrote in message
news:dpzWa.16802$dO2.3676@fe2.columbus.rr.com...
I have a peavy amp Mark V series from the 70s, and
each channel has 4 output transistors in the TO-20 or something like
that
packedge,

its got the circle in the middle, and two leads comming out of the
back,
B
and E, and the case is C with 2 screw holes in it.

Well, I need a cross, its an RCA transistor, and it shorted. I cant
find
that part number in MCM, or my datasheet site.

it says RCA, and under it says C8645, im guessing its 2SC8645? but
nothing
comes up.

Above RCA, it has the serial, labled 67376-C

Any Ideas? I need 8, I might as well change all of them out preventing
this
from happening in the near future. its very old amp, but it will blow
the
roof off

one day, I turned it on, all the lights in the house dimmed, and blew
the
fuse. again, and again.

And found 1 out of the 4 for B side shorted. I might as well change
all
4,
and change the other 4 that are good just in case. you never know.

Anyway, I checked the rectifiers, and checked bias resistors, and
other
resistors and so forth for aging, and drifting in value do to age, and
found
none.

it just shorted between C and E, but I can get good readings from C to
B,
and B to E, with about .465 for each, but .000 on C to E, indicates
short,
I
should have no reading here. or oL
Click to expand...
 
Mike: Assuming that you are using a diode checker to check the junctions,
if you get a junction from CtoB and BtoE then it is good. You can't go to E
from C without going thru B. If it is a standard bipolar transistor.
Sounds like you may have a darlington which can have strange readings,
especially if there are internal resistors. Do you get the voltage drop
across the junctions in only one direction? If it is a simple BJT (bipolar
trans) then it should block in the reverse direction. Darlingtons, which
have two transistors combined for extra gain, can give all sorts of
readings.

If all eight read the same I would look elsewhere in the circuit before
buying a bunch of transistors. MH (top post)
"Mike" <mbates14@fuse.net> wrote in message
news:dpzWa.16802$dO2.3676@fe2.columbus.rr.com...
I have a peavy amp Mark V series from the 70s, and
each channel has 4 output transistors in the TO-20 or something like that
packedge,

its got the circle in the middle, and two leads comming out of the back, B
and E, and the case is C with 2 screw holes in it.

Well, I need a cross, its an RCA transistor, and it shorted. I cant find
that part number in MCM, or my datasheet site.

it says RCA, and under it says C8645, im guessing its 2SC8645? but nothing
comes up.

Above RCA, it has the serial, labled 67376-C

Any Ideas? I need 8, I might as well change all of them out preventing
this
from happening in the near future. its very old amp, but it will blow the
roof off

one day, I turned it on, all the lights in the house dimmed, and blew the
fuse. again, and again.

And found 1 out of the 4 for B side shorted. I might as well change all 4,
and change the other 4 that are good just in case. you never know.

Anyway, I checked the rectifiers, and checked bias resistors, and other
resistors and so forth for aging, and drifting in value do to age, and
found
none.

it just shorted between C and E, but I can get good readings from C to B,
and B to E, with about .465 for each, but .000 on C to E, indicates short,
I
should have no reading here. or oL
Click to expand...
 
no, Here is how it went

what happened was all the lights in the house dimmed and it blew the fuse, I
think there was a direct short on the supply rail, especially when it blew
an 8 amp fuse.


now, there are 8 transistors, 4 per channel. every one of them have the same
marking. I know they are NPNs, I can tell by the circuit connections. Amps
are simple to me. I fix every one I run into. But, I always come here first
to get cross, or some pointers.

anyway, i pulled out every transistor, and from BtoC and BtoE reads around
..4xx on all of them, and on one of them I get .2xx both ways.

Now, here comes the tricky part. I thought all of the transistors were good,
when I read those readings.

I checked A side, and the CtoE read oL both ways, (open lead). so, thats
normal. now, on the other side, 3 of them read oL, and one of them, read
..000(short), both ways.

and that there, would ground out the supply rail, which is what is
happeneing.

and usually, when you read BtoC, or BtoE, the readings are slightly
different from each other right?

well, on the shorted one, from BtoC, and BtoE, are the same readings,
indicating CtoE short.



"Marko" <marko@vonl.com> wrote in message
news:wsqdnTaXzpyAPraiXTWJjQ@nstci.com...
Mike: Assuming that you are using a diode checker to check the junctions,
if you get a junction from CtoB and BtoE then it is good. You can't go to
E
from C without going thru B. If it is a standard bipolar transistor.
Sounds like you may have a darlington which can have strange readings,
especially if there are internal resistors. Do you get the voltage drop
across the junctions in only one direction? If it is a simple BJT
(bipolar
trans) then it should block in the reverse direction. Darlingtons, which
have two transistors combined for extra gain, can give all sorts of
readings.

If all eight read the same I would look elsewhere in the circuit before
buying a bunch of transistors. MH (top post)
"Mike" <mbates14@fuse.net> wrote in message
news:dpzWa.16802$dO2.3676@fe2.columbus.rr.com...
I have a peavy amp Mark V series from the 70s, and
each channel has 4 output transistors in the TO-20 or something like
that
packedge,

its got the circle in the middle, and two leads comming out of the back,
B
and E, and the case is C with 2 screw holes in it.

Well, I need a cross, its an RCA transistor, and it shorted. I cant find
that part number in MCM, or my datasheet site.

it says RCA, and under it says C8645, im guessing its 2SC8645? but
nothing
comes up.

Above RCA, it has the serial, labled 67376-C

Any Ideas? I need 8, I might as well change all of them out preventing
this
from happening in the near future. its very old amp, but it will blow
the
roof off

one day, I turned it on, all the lights in the house dimmed, and blew
the
fuse. again, and again.

And found 1 out of the 4 for B side shorted. I might as well change all
4,
and change the other 4 that are good just in case. you never know.

Anyway, I checked the rectifiers, and checked bias resistors, and other
resistors and so forth for aging, and drifting in value do to age, and
found
none.

it just shorted between C and E, but I can get good readings from C to
B,
and B to E, with about .465 for each, but .000 on C to E, indicates
short,
I
should have no reading here. or oL
Click to expand...
 
P.S. I have to have the red probe on Base in order to get readings. (i.e.
NPN)

except, that one transistor, i still have to have the red lead on base, but
when checking collector to emitter, it doesnt matter, I get .000 either way.



"Marko" <marko@vonl.com> wrote in message
news:wsqdnTaXzpyAPraiXTWJjQ@nstci.com...
Mike: Assuming that you are using a diode checker to check the junctions,
if you get a junction from CtoB and BtoE then it is good. You can't go to
E
from C without going thru B. If it is a standard bipolar transistor.
Sounds like you may have a darlington which can have strange readings,
especially if there are internal resistors. Do you get the voltage drop
across the junctions in only one direction? If it is a simple BJT
(bipolar
trans) then it should block in the reverse direction. Darlingtons, which
have two transistors combined for extra gain, can give all sorts of
readings.

If all eight read the same I would look elsewhere in the circuit before
buying a bunch of transistors. MH (top post)
"Mike" <mbates14@fuse.net> wrote in message
news:dpzWa.16802$dO2.3676@fe2.columbus.rr.com...
I have a peavy amp Mark V series from the 70s, and
each channel has 4 output transistors in the TO-20 or something like
that
packedge,

its got the circle in the middle, and two leads comming out of the back,
B
and E, and the case is C with 2 screw holes in it.

Well, I need a cross, its an RCA transistor, and it shorted. I cant find
that part number in MCM, or my datasheet site.

it says RCA, and under it says C8645, im guessing its 2SC8645? but
nothing
comes up.

Above RCA, it has the serial, labled 67376-C

Any Ideas? I need 8, I might as well change all of them out preventing
this
from happening in the near future. its very old amp, but it will blow
the
roof off

one day, I turned it on, all the lights in the house dimmed, and blew
the
fuse. again, and again.

And found 1 out of the 4 for B side shorted. I might as well change all
4,
and change the other 4 that are good just in case. you never know.

Anyway, I checked the rectifiers, and checked bias resistors, and other
resistors and so forth for aging, and drifting in value do to age, and
found
none.

it just shorted between C and E, but I can get good readings from C to
B,
and B to E, with about .465 for each, but .000 on C to E, indicates
short,
I
should have no reading here. or oL
Click to expand...
 
well, it sat for 20 years, and the guy just went out to run a bands sound,
and ran it full, or almost full, soo, you know what happens, when it sits in
a damp basement for 20 years, and then try to use it, it sounded great, it
was dead quiet, and then drive it really hard. and blow an xistor.

I want to get all 4, because you know, they all will be matched. Im used to
tubes. so, the more they matched, the less heat, the more quiet they are.
there is no hum, and after examining the circuit board, everythings clean,
no corrosion, no vented caps, no leaky visibly caps. so hmm.






"Marko" <marko@vonl.com> wrote in message
news:XuucnWARzbL6HLGiXTWJjw@nstci.com...
Sounds like you have only one shorted transistor. Mabey you should be
concerned with why your amp failed. Possibly your power supply is not
putting out clean d.c. If you have a scope turn your Peavy on with the
output transistors still removed and look at the voltage to the
collectors.
mabey your p/s is putting out too high of a voltage. Mabey there is some
trash in the voltage to the collectors. Unless you push it to the limit
there is usually a good reason why a transistor fails. MH
"Mike" <mbates14@fuse.net> wrote in message
news:mlQWa.33181$hc.17903@fe3.columbus.rr.com...
P.S. I have to have the red probe on Base in order to get readings.
(i.e.
NPN)

except, that one transistor, i still have to have the red lead on base,
but
when checking collector to emitter, it doesnt matter, I get .000 either
way.



"Marko" <marko@vonl.com> wrote in message
news:wsqdnTaXzpyAPraiXTWJjQ@nstci.com...
Mike: Assuming that you are using a diode checker to check the
junctions,
if you get a junction from CtoB and BtoE then it is good. You can't
go
to
E
from C without going thru B. If it is a standard bipolar transistor.
Sounds like you may have a darlington which can have strange readings,
especially if there are internal resistors. Do you get the voltage
drop
across the junctions in only one direction? If it is a simple BJT
(bipolar
trans) then it should block in the reverse direction. Darlingtons,
which
have two transistors combined for extra gain, can give all sorts of
readings.

If all eight read the same I would look elsewhere in the circuit
before
buying a bunch of transistors. MH (top post)
"Mike" <mbates14@fuse.net> wrote in message
news:dpzWa.16802$dO2.3676@fe2.columbus.rr.com...
I have a peavy amp Mark V series from the 70s, and
each channel has 4 output transistors in the TO-20 or something like
that
packedge,

its got the circle in the middle, and two leads comming out of the
back,
B
and E, and the case is C with 2 screw holes in it.

Well, I need a cross, its an RCA transistor, and it shorted. I cant
find
that part number in MCM, or my datasheet site.

it says RCA, and under it says C8645, im guessing its 2SC8645? but
nothing
comes up.

Above RCA, it has the serial, labled 67376-C

Any Ideas? I need 8, I might as well change all of them out
preventing
this
from happening in the near future. its very old amp, but it will
blow
the
roof off

one day, I turned it on, all the lights in the house dimmed, and
blew
the
fuse. again, and again.

And found 1 out of the 4 for B side shorted. I might as well change
all
4,
and change the other 4 that are good just in case. you never know.

Anyway, I checked the rectifiers, and checked bias resistors, and
other
resistors and so forth for aging, and drifting in value do to age,
and
found
none.

it just shorted between C and E, but I can get good readings from C
to
B,
and B to E, with about .465 for each, but .000 on C to E, indicates
short,
I
should have no reading here. or oL
Click to expand...
 
then again, if it blows repeatedly, then somethings wrong.



"Marko" <marko@vonl.com> wrote in message
news:XuucnWARzbL6HLGiXTWJjw@nstci.com...
Sounds like you have only one shorted transistor. Mabey you should be
concerned with why your amp failed. Possibly your power supply is not
putting out clean d.c. If you have a scope turn your Peavy on with the
output transistors still removed and look at the voltage to the
collectors.
mabey your p/s is putting out too high of a voltage. Mabey there is some
trash in the voltage to the collectors. Unless you push it to the limit
there is usually a good reason why a transistor fails. MH
"Mike" <mbates14@fuse.net> wrote in message
news:mlQWa.33181$hc.17903@fe3.columbus.rr.com...
P.S. I have to have the red probe on Base in order to get readings.
(i.e.
NPN)

except, that one transistor, i still have to have the red lead on base,
but
when checking collector to emitter, it doesnt matter, I get .000 either
way.



"Marko" <marko@vonl.com> wrote in message
news:wsqdnTaXzpyAPraiXTWJjQ@nstci.com...
Mike: Assuming that you are using a diode checker to check the
junctions,
if you get a junction from CtoB and BtoE then it is good. You can't
go
to
E
from C without going thru B. If it is a standard bipolar transistor.
Sounds like you may have a darlington which can have strange readings,
especially if there are internal resistors. Do you get the voltage
drop
across the junctions in only one direction? If it is a simple BJT
(bipolar
trans) then it should block in the reverse direction. Darlingtons,
which
have two transistors combined for extra gain, can give all sorts of
readings.

If all eight read the same I would look elsewhere in the circuit
before
buying a bunch of transistors. MH (top post)
"Mike" <mbates14@fuse.net> wrote in message
news:dpzWa.16802$dO2.3676@fe2.columbus.rr.com...
I have a peavy amp Mark V series from the 70s, and
each channel has 4 output transistors in the TO-20 or something like
that
packedge,

its got the circle in the middle, and two leads comming out of the
back,
B
and E, and the case is C with 2 screw holes in it.

Well, I need a cross, its an RCA transistor, and it shorted. I cant
find
that part number in MCM, or my datasheet site.

it says RCA, and under it says C8645, im guessing its 2SC8645? but
nothing
comes up.

Above RCA, it has the serial, labled 67376-C

Any Ideas? I need 8, I might as well change all of them out
preventing
this
from happening in the near future. its very old amp, but it will
blow
the
roof off

one day, I turned it on, all the lights in the house dimmed, and
blew
the
fuse. again, and again.

And found 1 out of the 4 for B side shorted. I might as well change
all
4,
and change the other 4 that are good just in case. you never know.

Anyway, I checked the rectifiers, and checked bias resistors, and
other
resistors and so forth for aging, and drifting in value do to age,
and
found
none.

it just shorted between C and E, but I can get good readings from C
to
B,
and B to E, with about .465 for each, but .000 on C to E, indicates
short,
I
should have no reading here. or oL
Click to expand...
 
Sounds like you have only one shorted transistor. Mabey you should be
concerned with why your amp failed. Possibly your power supply is not
putting out clean d.c. If you have a scope turn your Peavy on with the
output transistors still removed and look at the voltage to the collectors.
mabey your p/s is putting out too high of a voltage. Mabey there is some
trash in the voltage to the collectors. Unless you push it to the limit
there is usually a good reason why a transistor fails. MH
"Mike" <mbates14@fuse.net> wrote in message
news:mlQWa.33181$hc.17903@fe3.columbus.rr.com...
P.S. I have to have the red probe on Base in order to get readings. (i.e.
NPN)

except, that one transistor, i still have to have the red lead on base,
but
when checking collector to emitter, it doesnt matter, I get .000 either
way.



"Marko" <marko@vonl.com> wrote in message
news:wsqdnTaXzpyAPraiXTWJjQ@nstci.com...
Mike: Assuming that you are using a diode checker to check the
junctions,
if you get a junction from CtoB and BtoE then it is good. You can't go
to
E
from C without going thru B. If it is a standard bipolar transistor.
Sounds like you may have a darlington which can have strange readings,
especially if there are internal resistors. Do you get the voltage drop
across the junctions in only one direction? If it is a simple BJT
(bipolar
trans) then it should block in the reverse direction. Darlingtons,
which
have two transistors combined for extra gain, can give all sorts of
readings.

If all eight read the same I would look elsewhere in the circuit before
buying a bunch of transistors. MH (top post)
"Mike" <mbates14@fuse.net> wrote in message
news:dpzWa.16802$dO2.3676@fe2.columbus.rr.com...
I have a peavy amp Mark V series from the 70s, and
each channel has 4 output transistors in the TO-20 or something like
that
packedge,

its got the circle in the middle, and two leads comming out of the
back,
B
and E, and the case is C with 2 screw holes in it.

Well, I need a cross, its an RCA transistor, and it shorted. I cant
find
that part number in MCM, or my datasheet site.

it says RCA, and under it says C8645, im guessing its 2SC8645? but
nothing
comes up.

Above RCA, it has the serial, labled 67376-C

Any Ideas? I need 8, I might as well change all of them out preventing
this
from happening in the near future. its very old amp, but it will blow
the
roof off

one day, I turned it on, all the lights in the house dimmed, and blew
the
fuse. again, and again.

And found 1 out of the 4 for B side shorted. I might as well change
all
4,
and change the other 4 that are good just in case. you never know.

Anyway, I checked the rectifiers, and checked bias resistors, and
other
resistors and so forth for aging, and drifting in value do to age, and
found
none.

it just shorted between C and E, but I can get good readings from C to
B,
and B to E, with about .465 for each, but .000 on C to E, indicates
short,
I
should have no reading here. or oL
Click to expand...
 
Mike: If these are TO-3 metal can package, round with an oval flange then
they are hermetically sealed. What you are probably encountering is caps
that are leaking current. They make not be spilling their guts , but they
still leak electronically. Any electrolytic cap that has been sitting for
over 3 years is a candidate for leakage. When you first turn the unit on
they leak very badly and may recover and be fine after they 'reform'
internally over about an hour. It is the nature of the aluminum
electrolytic cap. One of the electrodes (plates) is a chemicle which falls
off of the other electrode which is metal foil. When they are suddenly
energized the current starts depositing the chemicle (aluminum oxide) back
on the foil but it takes time and they may burn out internally if the
leakage current is too high. That's when they start leaking fluid due to
vapor pressure inside.. Any how, during the first few minutes they are not
filtering properly and that is when a transistor can be damaged.
Electrolytics can be very leaky (electronically) and still not loose their
juice.

On the other hand, transistors and I.C.s which are not hermetically sealed
can absorb moisture and fail. Using electronics often heats them up and
drives the moisture out.

It's all part of the used equipment game.

I wouldn't simply replace the transistors, it will probably fail again.
Live bands need reliable equipment. I would be smart and replace all the
power supply filter caps with new ones. Not new surplus, new as in made
this year.

You may have a power supply problem. I would check the voltages. 20 years
of sitting is way too long. If your p/s filters are bad then too much a.c.
ripple may be making it through. The a.c. adds to the d.c. to give you the
peak voltage. Electrolytic caps can loose their capacitance over time, too.
Good Luck, Mark (top post)
"Mike" <mbates14@fuse.net> wrote in message
news:Kv%Wa.34685$hc.5270@fe3.columbus.rr.com...
parts just fail on there own, they fail if run over max ratings, or they
jsut fail over time. or use. if that never happend, then we wouldnt have
electronics repair. cause, shit made 50 years ago, would still work. lol.







"Marko" <marko@vonl.com> wrote in message
news:XuucnWARzbL6HLGiXTWJjw@nstci.com...
Sounds like you have only one shorted transistor. Mabey you should be
concerned with why your amp failed. Possibly your power supply is not
putting out clean d.c. If you have a scope turn your Peavy on with the
output transistors still removed and look at the voltage to the
collectors.
mabey your p/s is putting out too high of a voltage. Mabey there is
some
trash in the voltage to the collectors. Unless you push it to the limit
there is usually a good reason why a transistor fails. MH
"Mike" <mbates14@fuse.net> wrote in message
news:mlQWa.33181$hc.17903@fe3.columbus.rr.com...
P.S. I have to have the red probe on Base in order to get readings.
(i.e.
NPN)

except, that one transistor, i still have to have the red lead on
base,
but
when checking collector to emitter, it doesnt matter, I get .000
either
way.



"Marko" <marko@vonl.com> wrote in message
news:wsqdnTaXzpyAPraiXTWJjQ@nstci.com...
Mike: Assuming that you are using a diode checker to check the
junctions,
if you get a junction from CtoB and BtoE then it is good. You can't
go
to
E
from C without going thru B. If it is a standard bipolar
transistor.
Sounds like you may have a darlington which can have strange
readings,
especially if there are internal resistors. Do you get the voltage
drop
across the junctions in only one direction? If it is a simple BJT
(bipolar
trans) then it should block in the reverse direction. Darlingtons,
which
have two transistors combined for extra gain, can give all sorts of
readings.

If all eight read the same I would look elsewhere in the circuit
before
buying a bunch of transistors. MH (top post)
"Mike" <mbates14@fuse.net> wrote in message
news:dpzWa.16802$dO2.3676@fe2.columbus.rr.com...
I have a peavy amp Mark V series from the 70s, and
each channel has 4 output transistors in the TO-20 or something
like
that
packedge,

its got the circle in the middle, and two leads comming out of the
back,
B
and E, and the case is C with 2 screw holes in it.

Well, I need a cross, its an RCA transistor, and it shorted. I
cant
find
that part number in MCM, or my datasheet site.

it says RCA, and under it says C8645, im guessing its 2SC8645? but
nothing
comes up.

Above RCA, it has the serial, labled 67376-C

Any Ideas? I need 8, I might as well change all of them out
preventing
this
from happening in the near future. its very old amp, but it will
blow
the
roof off

one day, I turned it on, all the lights in the house dimmed, and
blew
the
fuse. again, and again.

And found 1 out of the 4 for B side shorted. I might as well
change
all
4,
and change the other 4 that are good just in case. you never know.

Anyway, I checked the rectifiers, and checked bias resistors, and
other
resistors and so forth for aging, and drifting in value do to age,
and
found
none.

it just shorted between C and E, but I can get good readings from
C
to
B,
and B to E, with about .465 for each, but .000 on C to E,
indicates
short,
I
should have no reading here. or oL
Click to expand...
 
true. so very true. ill check it out, that was made in the days, of raw
circuits, no green paint that goes over the connections, its just a raw
circuit. which can short out easily if the board sags from moisture, which
does happen, I didnt check that.







"Marko" <marko@vonl.com> wrote in message
news:AY6cndbTsIigIbGiXTWJkQ@nstci.com...
Mike: If these are TO-3 metal can package, round with an oval flange then
they are hermetically sealed. What you are probably encountering is caps
that are leaking current. They make not be spilling their guts , but they
still leak electronically. Any electrolytic cap that has been sitting for
over 3 years is a candidate for leakage. When you first turn the unit on
they leak very badly and may recover and be fine after they 'reform'
internally over about an hour. It is the nature of the aluminum
electrolytic cap. One of the electrodes (plates) is a chemicle which
falls
off of the other electrode which is metal foil. When they are suddenly
energized the current starts depositing the chemicle (aluminum oxide) back
on the foil but it takes time and they may burn out internally if the
leakage current is too high. That's when they start leaking fluid due to
vapor pressure inside.. Any how, during the first few minutes they are
not
filtering properly and that is when a transistor can be damaged.
Electrolytics can be very leaky (electronically) and still not loose their
juice.

On the other hand, transistors and I.C.s which are not hermetically sealed
can absorb moisture and fail. Using electronics often heats them up and
drives the moisture out.

It's all part of the used equipment game.

I wouldn't simply replace the transistors, it will probably fail again.
Live bands need reliable equipment. I would be smart and replace all the
power supply filter caps with new ones. Not new surplus, new as in made
this year.

You may have a power supply problem. I would check the voltages. 20
years
of sitting is way too long. If your p/s filters are bad then too much
a.c.
ripple may be making it through. The a.c. adds to the d.c. to give you
the
peak voltage. Electrolytic caps can loose their capacitance over time,
too.
Good Luck, Mark (top post)
"Mike" <mbates14@fuse.net> wrote in message
news:Kv%Wa.34685$hc.5270@fe3.columbus.rr.com...
parts just fail on there own, they fail if run over max ratings, or they
jsut fail over time. or use. if that never happend, then we wouldnt have
electronics repair. cause, shit made 50 years ago, would still work.
lol.







"Marko" <marko@vonl.com> wrote in message
news:XuucnWARzbL6HLGiXTWJjw@nstci.com...
Sounds like you have only one shorted transistor. Mabey you should be
concerned with why your amp failed. Possibly your power supply is not
putting out clean d.c. If you have a scope turn your Peavy on with
the
output transistors still removed and look at the voltage to the
collectors.
mabey your p/s is putting out too high of a voltage. Mabey there is
some
trash in the voltage to the collectors. Unless you push it to the
limit
there is usually a good reason why a transistor fails. MH
"Mike" <mbates14@fuse.net> wrote in message
news:mlQWa.33181$hc.17903@fe3.columbus.rr.com...
P.S. I have to have the red probe on Base in order to get readings.
(i.e.
NPN)

except, that one transistor, i still have to have the red lead on
base,
but
when checking collector to emitter, it doesnt matter, I get .000
either
way.



"Marko" <marko@vonl.com> wrote in message
news:wsqdnTaXzpyAPraiXTWJjQ@nstci.com...
Mike: Assuming that you are using a diode checker to check the
junctions,
if you get a junction from CtoB and BtoE then it is good. You
can't
go
to
E
from C without going thru B. If it is a standard bipolar
transistor.
Sounds like you may have a darlington which can have strange
readings,
especially if there are internal resistors. Do you get the
voltage
drop
across the junctions in only one direction? If it is a simple BJT
(bipolar
trans) then it should block in the reverse direction.
Darlingtons,
which
have two transistors combined for extra gain, can give all sorts
of
readings.

If all eight read the same I would look elsewhere in the circuit
before
buying a bunch of transistors. MH (top post)
"Mike" <mbates14@fuse.net> wrote in message
news:dpzWa.16802$dO2.3676@fe2.columbus.rr.com...
I have a peavy amp Mark V series from the 70s, and
each channel has 4 output transistors in the TO-20 or something
like
that
packedge,

its got the circle in the middle, and two leads comming out of
the
back,
B
and E, and the case is C with 2 screw holes in it.

Well, I need a cross, its an RCA transistor, and it shorted. I
cant
find
that part number in MCM, or my datasheet site.

it says RCA, and under it says C8645, im guessing its 2SC8645?
but
nothing
comes up.

Above RCA, it has the serial, labled 67376-C

Any Ideas? I need 8, I might as well change all of them out
preventing
this
from happening in the near future. its very old amp, but it will
blow
the
roof off

one day, I turned it on, all the lights in the house dimmed, and
blew
the
fuse. again, and again.

And found 1 out of the 4 for B side shorted. I might as well
change
all
4,
and change the other 4 that are good just in case. you never
know.

Anyway, I checked the rectifiers, and checked bias resistors,
and
other
resistors and so forth for aging, and drifting in value do to
age,
and
found
none.

it just shorted between C and E, but I can get good readings
from
C
to
B,
and B to E, with about .465 for each, but .000 on C to E,
indicates
short,
I
should have no reading here. or oL
Click to expand...
 
im not sure about vintage transistor amps, but if the filter caps, and other
go bad, Wouldnt you hear a hum, or distortion?
because, it was dead quiet. Thats what I dont get.






"Marko" <marko@vonl.com> wrote in message
news:AY6cndbTsIigIbGiXTWJkQ@nstci.com...
Mike: If these are TO-3 metal can package, round with an oval flange then
they are hermetically sealed. What you are probably encountering is caps
that are leaking current. They make not be spilling their guts , but they
still leak electronically. Any electrolytic cap that has been sitting for
over 3 years is a candidate for leakage. When you first turn the unit on
they leak very badly and may recover and be fine after they 'reform'
internally over about an hour. It is the nature of the aluminum
electrolytic cap. One of the electrodes (plates) is a chemicle which
falls
off of the other electrode which is metal foil. When they are suddenly
energized the current starts depositing the chemicle (aluminum oxide) back
on the foil but it takes time and they may burn out internally if the
leakage current is too high. That's when they start leaking fluid due to
vapor pressure inside.. Any how, during the first few minutes they are
not
filtering properly and that is when a transistor can be damaged.
Electrolytics can be very leaky (electronically) and still not loose their
juice.

On the other hand, transistors and I.C.s which are not hermetically sealed
can absorb moisture and fail. Using electronics often heats them up and
drives the moisture out.

It's all part of the used equipment game.

I wouldn't simply replace the transistors, it will probably fail again.
Live bands need reliable equipment. I would be smart and replace all the
power supply filter caps with new ones. Not new surplus, new as in made
this year.

You may have a power supply problem. I would check the voltages. 20
years
of sitting is way too long. If your p/s filters are bad then too much
a.c.
ripple may be making it through. The a.c. adds to the d.c. to give you
the
peak voltage. Electrolytic caps can loose their capacitance over time,
too.
Good Luck, Mark (top post)
"Mike" <mbates14@fuse.net> wrote in message
news:Kv%Wa.34685$hc.5270@fe3.columbus.rr.com...
parts just fail on there own, they fail if run over max ratings, or they
jsut fail over time. or use. if that never happend, then we wouldnt have
electronics repair. cause, shit made 50 years ago, would still work.
lol.







"Marko" <marko@vonl.com> wrote in message
news:XuucnWARzbL6HLGiXTWJjw@nstci.com...
Sounds like you have only one shorted transistor. Mabey you should be
concerned with why your amp failed. Possibly your power supply is not
putting out clean d.c. If you have a scope turn your Peavy on with
the
output transistors still removed and look at the voltage to the
collectors.
mabey your p/s is putting out too high of a voltage. Mabey there is
some
trash in the voltage to the collectors. Unless you push it to the
limit
there is usually a good reason why a transistor fails. MH
"Mike" <mbates14@fuse.net> wrote in message
news:mlQWa.33181$hc.17903@fe3.columbus.rr.com...
P.S. I have to have the red probe on Base in order to get readings.
(i.e.
NPN)

except, that one transistor, i still have to have the red lead on
base,
but
when checking collector to emitter, it doesnt matter, I get .000
either
way.



"Marko" <marko@vonl.com> wrote in message
news:wsqdnTaXzpyAPraiXTWJjQ@nstci.com...
Mike: Assuming that you are using a diode checker to check the
junctions,
if you get a junction from CtoB and BtoE then it is good. You
can't
go
to
E
from C without going thru B. If it is a standard bipolar
transistor.
Sounds like you may have a darlington which can have strange
readings,
especially if there are internal resistors. Do you get the
voltage
drop
across the junctions in only one direction? If it is a simple BJT
(bipolar
trans) then it should block in the reverse direction.
Darlingtons,
which
have two transistors combined for extra gain, can give all sorts
of
readings.

If all eight read the same I would look elsewhere in the circuit
before
buying a bunch of transistors. MH (top post)
"Mike" <mbates14@fuse.net> wrote in message
news:dpzWa.16802$dO2.3676@fe2.columbus.rr.com...
I have a peavy amp Mark V series from the 70s, and
each channel has 4 output transistors in the TO-20 or something
like
that
packedge,

its got the circle in the middle, and two leads comming out of
the
back,
B
and E, and the case is C with 2 screw holes in it.

Well, I need a cross, its an RCA transistor, and it shorted. I
cant
find
that part number in MCM, or my datasheet site.

it says RCA, and under it says C8645, im guessing its 2SC8645?
but
nothing
comes up.

Above RCA, it has the serial, labled 67376-C

Any Ideas? I need 8, I might as well change all of them out
preventing
this
from happening in the near future. its very old amp, but it will
blow
the
roof off

one day, I turned it on, all the lights in the house dimmed, and
blew
the
fuse. again, and again.

And found 1 out of the 4 for B side shorted. I might as well
change
all
4,
and change the other 4 that are good just in case. you never
know.

Anyway, I checked the rectifiers, and checked bias resistors,
and
other
resistors and so forth for aging, and drifting in value do to
age,
and
found
none.

it just shorted between C and E, but I can get good readings
from
C
to
B,
and B to E, with about .465 for each, but .000 on C to E,
indicates
short,
I
should have no reading here. or oL
Click to expand...
 
it does.


"Maarten A.E.Bakker" <maarten@panic.et.tudelft.nl> wrote in message
news:bgj89k$mm0$1@news.tudelft.nl...
Mike <mbates14@fuse.net> wrote:
all of these have the same number.

Make sure all of those have the 67376-C number on them, the other number,
is probably just a date code!

---
Met vriendelijke groet,

Maarten Bakker.
Click to expand...
 
Mike <mbates14@fuse.net> wrote:
all of these have the same number.
Click to expand...
Make sure all of those have the 67376-C number on them, the other number,
is probably just a date code!

---
Met vriendelijke groet,

Maarten Bakker.
 
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