Okay, I'm the guy who posted the "Need help, Blues Junior died a slow
death" message last month. Thanks for all the replies in the original
thread - I never got the time to reply in the original thread as I was
pretty busy with other stuff at the time. Anyway, I thought I'd have
another crack at fixing the amp and I've been learning a bit more
about valves etc. in the meantime. Here are some observations
(slightly more informed than last time) about the amp and its
continued state of non-workingness:

* The heaters in the power valves don't light up when you turn the amp
on, but the ones in the preamp valves do.
* I put a different pair of EL84s in just in case, and get the same
result.
* I went all around the small valve circuit board with a multimeter
and can't find any breaks or shorts in the heater circuit.
* The sockets are fine too.
* The heater filaments inside the EL84s themselves seem OK - in one
pair, they have a DC resistance of 2.5 ohms (cold), and 1.5 ohms in
the other, so no shorts or breaks.
* Not sure what the DC resistance of the heater transformer windings
should be (haven't learned that much yet), but it's pretty much zero.

That's all I know for the moment, don't want to start measuring with
the power on unless I have to. I live in the middle of nowhere and
don't have a clue where the nearest place I could get it repaired is,
so I'd like to fix it myself if I could.

"Scanty" wrote in message
m...
Okay, I'm the guy who posted the "Need help, Blues Junior died a slow
death" message last month. Thanks for all the replies in the original
thread - I never got the time to reply in the original thread as I was
pretty busy with other stuff at the time. Anyway, I thought I'd have
another crack at fixing the amp and I've been learning a bit more
about valves etc. in the meantime. Here are some observations
(slightly more informed than last time) about the amp and its
continued state of non-workingness:

* The heaters in the power valves don't light up when you turn the amp
on, but the ones in the preamp valves do.
* I put a different pair of EL84s in just in case, and get the same
result.
* I went all around the small valve circuit board with a multimeter
and can't find any breaks or shorts in the heater circuit.
* The sockets are fine too.
* The heater filaments inside the EL84s themselves seem OK - in one
pair, they have a DC resistance of 2.5 ohms (cold), and 1.5 ohms in
the other, so no shorts or breaks.
* Not sure what the DC resistance of the heater transformer windings
should be (haven't learned that much yet), but it's pretty much zero.

That's all I know for the moment, don't want to start measuring with
the power on unless I have to. I live in the middle of nowhere and
don't have a clue where the nearest place I could get it repaired is,
so I'd like to fix it myself if I could.



** PVs normaly have fuses in the heater supply - have you find one in
your amp ?





............... Phil

"Scanty" wrote in message
m...

That's all I know for the moment, don't want to start measuring with
the power on unless I have to. I live in the middle of nowhere and
don't have a clue where the nearest place I could get it repaired is,
so I'd like to fix it myself if I could.

Should read:

" I don't want to start measuring with the power on unless I have to. I live in
the middle of nowhere and don't have a clue where the nearest place I could get
myself repaired if I electrocute myself".

;-)

I took a look to Your amp's schematics. All heaters should be connected in
parallel, with the power valves derived upstream of the signal valves
(coming from the transformer). If it is really so (i mean, Your amp has not
been tweaked in some strange fashion) and the power valves do not light up
while the 12AX7 seem to work, there must be a broken connection somewhere or
a current loss due to some short to ground.
I suppose You'll have to check the filament voltage with "live" circuit: the
12AX7 only needs 0.15A and You can see the cathode turning red even if it's
not really hot enough, but the EL84 needs some 7 times mo if there's some
loss somewhere they will not light up.
Quick fix: get another 0-6.3V/3A transformer and connect it directly to
pins 4&5 (heaters), disconnecting the filament connections of the main
transformer You already have.
Or pack it all up in a solid case and ship it to a technician, to our fellow
Lord Valve maybe. He's not very well mannered but I guess he knows his job.

Ciao

Fabio



"Scanty" ha scritto nel messaggio
m...
Okay, I'm the guy who posted the "Need help, Blues Junior died a slow
death" message last month. Thanks for all the replies in the original
thread - I never got the time to reply in the original thread as I was
pretty busy with other stuff at the time. Anyway, I thought I'd have
another crack at fixing the amp and I've been learning a bit more
about valves etc. in the meantime. Here are some observations
(slightly more informed than last time) about the amp and its
continued state of non-workingness:

* The heaters in the power valves don't light up when you turn the amp
on, but the ones in the preamp valves do.
* I put a different pair of EL84s in just in case, and get the same
result.
* I went all around the small valve circuit board with a multimeter
and can't find any breaks or shorts in the heater circuit.
* The sockets are fine too.
* The heater filaments inside the EL84s themselves seem OK - in one
pair, they have a DC resistance of 2.5 ohms (cold), and 1.5 ohms in
the other, so no shorts or breaks.
* Not sure what the DC resistance of the heater transformer windings
should be (haven't learned that much yet), but it's pretty much zero.

That's all I know for the moment, don't want to start measuring with
the power on unless I have to. I live in the middle of nowhere and
don't have a clue where the nearest place I could get it repaired is,
so I'd like to fix it myself if I could.

"Scanty" wrote in
message
m...
Okay, I'm the guy who posted the "Need help,
Blues Junior died a slow
death" message last month. Thanks for all the
replies in the original
thread - I never got the time to reply in the
original thread as I was
pretty busy with other stuff at the time.
Anyway, I thought I'd have
another crack at fixing the amp and I've been
learning a bit more
about valves etc. in the meantime. Here are some
observations
(slightly more informed than last time) about
the amp and its
continued state of non-workingness:

* The heaters in the power valves don't light up
when you turn the amp
on, but the ones in the preamp valves do.
* I put a different pair of EL84s in just in
case, and get the same
result.
* I went all around the small valve circuit
board with a multimeter
and can't find any breaks or shorts in the
heater circuit.
* The sockets are fine too.
* The heater filaments inside the EL84s
themselves seem OK - in one
pair, they have a DC resistance of 2.5 ohms
(cold), and 1.5 ohms in
the other, so no shorts or breaks.
* Not sure what the DC resistance of the heater
transformer windings
should be (haven't learned that much yet), but
it's pretty much zero.

That's all I know for the moment, don't want to
start measuring with
the power on unless I have to. I live in the
middle of nowhere and
don't have a clue where the nearest place I
could get it repaired is,
so I'd like to fix it myself if I could.

The heater supply for your amp travels on
a parallel bus across the power tube/preamp tube
circuit board with the entry point being at either
P5/P6 or WJ6/WJ7 (depending on the age of amp).
This point is found next to the last power tube
and
the connection to the bus is made with wires that
jump
from this pc board to the main (big) board.
Since you've verified that the preamp tube heaters
have power, and that there is no issue with the
power
tubes themselves, the trouble can really only be
related
to a connection between the power tube sockets and
one side
of the heater supply. Connections between the
heater
bus and sockets sometimes requires the use of
small jumpers to allow the circuit to be routed
'over' another trace- much like a bridge over a
highway.

It is quite likely that one of these jumpers has a
bad connection
and is the reason that the power tube heaters are
not powered.

Pull [all] of the tubes and taking a resistance
reading between
pins 4 & 5 of a [power tube] socket. In your case,
you should find an open circuit. Then,
systematically measure between the same pins
and the heater entry point (see above). You find
that one pin has
continuity to the heater winding a while another
doesn't.
From that point, relax. Put on some music, get a
fresh cup of coffee
and start looking for the open connection that
should reveal itself
somewhere in a 2 1/2 x 4 inch. section of the
board on the power tube
side.

Don't get shocked.

bk

Hi,
Unfortunately Peavey uses these chintzy circuit boards which love to
have foil crack. You have a broken section in the foil trace leading to
your output tube sockets. Since your output tubes pull a lot more
filament current then the 12AX7's there is a chance that the
circuit board foil trace just gave up the ghost. This is an easy fix for
someone familiar with guitar amps and tube circuits as well as
soldering. If you are not even comfortable doing voltage tests with the
power on, you might want to leave this repair to a friend or technician
who is more familiar with electronics. First off, this amp has voltages
as high as 400 volts when powered up. These voltages are lethal. the
next thing to consider is that amps that use circuit boards are a little
harder to service and figure out without a full wiring diagram. Also,
circuit boards require a certain finesse to repair so as not to do even
more dammage then was there to begin with.
Bill B.


Scanty wrote:

Okay, I'm the guy who posted the "Need help, Blues Junior died a slow
death" message last month. Thanks for all the replies in the original
thread - I never got the time to reply in the original thread as I was
pretty busy with other stuff at the time. Anyway, I thought I'd have
another crack at fixing the amp and I've been learning a bit more
about valves etc. in the meantime. Here are some observations
(slightly more informed than last time) about the amp and its
continued state of non-workingness:

* The heaters in the power valves don't light up when you turn the amp
on, but the ones in the preamp valves do.
* I put a different pair of EL84s in just in case, and get the same
result.
* I went all around the small valve circuit board with a multimeter
and can't find any breaks or shorts in the heater circuit.
* The sockets are fine too.
* The heater filaments inside the EL84s themselves seem OK - in one
pair, they have a DC resistance of 2.5 ohms (cold), and 1.5 ohms in
the other, so no shorts or breaks.
* Not sure what the DC resistance of the heater transformer windings
should be (haven't learned that much yet), but it's pretty much zero.

That's all I know for the moment, don't want to start measuring with
the power on unless I have to. I live in the middle of nowhere and
don't have a clue where the nearest place I could get it repaired is,
so I'd like to fix it myself if I could.