hi!

i am trying to repair an old drake tr7 receiver, and found out, one of the
biasing transistors EP 487 in the power amplifier module was missing.
i cannot find this transistor anywhere on the net...:-(

are there any replacements?

cheers,

asta

Joan:

Took a look at the schematic diagram (page 2-107) and the requirements are
pretty basic. A 2N2222 or 2N3904 would probably do fine most of the time.
You can even look at the TIP series or whatever you can get your hands on.

Nominal voltages show 10 ma through one and 46 ma through the other
transistor. Worst case in a shorted output would draw 1.28 A. Input is
from a +5 V regulator so voltage rating is a non-issue.

Hope that helps.....
73 de Woody AK2F

"asta" wrote in message
.. .
hi!

i am trying to repair an old drake tr7 receiver, and found out, one of the
biasing transistors EP 487 in the power amplifier module was missing.
i cannot find this transistor anywhere on the net...:-(

are there any replacements?

cheers,

asta

Joan:

Took a look at the schematic diagram (page 2-107) and the requirements are
pretty basic. A 2N2222 or 2N3904 would probably do fine most of the time.
You can even look at the TIP series or whatever you can get your hands on.

Nominal voltages show 10 ma through one and 46 ma through the other
transistor. Worst case in a shorted output would draw 1.28 A. Input is
from a +5 V regulator so voltage rating is a non-issue.

Hope that helps.....
73 de Woody AK2F

"asta" wrote in message
.. .
hi!

i am trying to repair an old drake tr7 receiver, and found out, one of the
biasing transistors EP 487 in the power amplifier module was missing.
i cannot find this transistor anywhere on the net...:-(

are there any replacements?

cheers,

asta

Joan:

Took a look at the schematic diagram (page 2-107) and the requirements are
pretty basic. A 2N2222 or 2N3904 would probably do fine most of the time.
You can even look at the TIP series or whatever you can get your hands on.

Nominal voltages show 10 ma through one and 46 ma through the other
transistor. Worst case in a shorted output would draw 1.28 A. Input is
from a +5 V regulator so voltage rating is a non-issue.

Hope that helps.....
73 de Woody AK2F

"asta" wrote in message
.. .
hi!

i am trying to repair an old drake tr7 receiver, and found out, one of the
biasing transistors EP 487 in the power amplifier module was missing.
i cannot find this transistor anywhere on the net...:-(

are there any replacements?

cheers,

asta

Joan:

Took a look at the schematic diagram (page 2-107) and the requirements are
pretty basic. A 2N2222 or 2N3904 would probably do fine most of the time.
You can even look at the TIP series or whatever you can get your hands on.

Nominal voltages show 10 ma through one and 46 ma through the other
transistor. Worst case in a shorted output would draw 1.28 A. Input is
from a +5 V regulator so voltage rating is a non-issue.

Hope that helps.....
73 de Woody AK2F

"asta" wrote in message
.. .
hi!

i am trying to repair an old drake tr7 receiver, and found out, one of the
biasing transistors EP 487 in the power amplifier module was missing.
i cannot find this transistor anywhere on the net...:-(

are there any replacements?

cheers,

asta

hi!

thank you very much for your replay!

i am of the same opinion, the transistors ep 487 are not critical in
this biasing circuit.
the current rating behind a 1A 5V regulator is also not an issue :-)

i measured the hFE of the other one and found it to be only 22!
now i'm going to try out one of the transistors you suggested and check
for the bias.

cheers,

asta

"AK2F"
Took a look at the schematic diagram (page 2-107) and the requirements are
pretty basic. A 2N2222 or 2N3904 would probably do fine most of the time.
You can even look at the TIP series or whatever you can get your hands on.
Nominal voltages show 10 ma through one and 46 ma through the other
transistor. Worst case in a shorted output would draw 1.28 A. Input is
from a +5 V regulator so voltage rating is a non-issue.
73 de Woody AK2F

"asta"
i am trying to repair an old drake tr7 receiver, and found out, one of
the
biasing transistors EP 487 in the power amplifier module was missing.
i cannot find this transistor anywhere on the net...:-(

are there any replacements?

hi!

thank you very much for your replay!

i am of the same opinion, the transistors ep 487 are not critical in
this biasing circuit.
the current rating behind a 1A 5V regulator is also not an issue :-)

i measured the hFE of the other one and found it to be only 22!
now i'm going to try out one of the transistors you suggested and check
for the bias.

cheers,

asta

"AK2F"
Took a look at the schematic diagram (page 2-107) and the requirements are
pretty basic. A 2N2222 or 2N3904 would probably do fine most of the time.
You can even look at the TIP series or whatever you can get your hands on.
Nominal voltages show 10 ma through one and 46 ma through the other
transistor. Worst case in a shorted output would draw 1.28 A. Input is
from a +5 V regulator so voltage rating is a non-issue.
73 de Woody AK2F

"asta"
i am trying to repair an old drake tr7 receiver, and found out, one of
the
biasing transistors EP 487 in the power amplifier module was missing.
i cannot find this transistor anywhere on the net...:-(

are there any replacements?