I have a question for the Marantz 8B users here, or really anyone with
knowledge on this subject. I need to replace the two 6CG7 tubes on my
8B. According to the 8B instructions, Marantz suggests that the a.c.
balance may need to be readjusted if the 6CG7 tubes are replaced. I
don't have the signal generator necessary to do this adjustment. So my
question is: have you found that you really needed to readjust the
a.c. balance when you replaced the 6CG7 tubes? Or is this readjustment
usually only necessary if the two triode section measurements in each
tube are quite different from each other?

Thanks,
Brian

if you don't have siggene,just put CG in and enjoy.

--
--
.................................................. ........................
Choky
Prodanovic Aleksandar
YU

"don't use force, "don't use force,
use a larger hammer" use a larger tube
- Choky and IST"
- ZM
.................................................. ...........................
"BRIAN J" wrote in message
om...
I have a question for the Marantz 8B users here, or really anyone with
knowledge on this subject. I need to replace the two 6CG7 tubes on my
8B. According to the 8B instructions, Marantz suggests that the a.c.
balance may need to be readjusted if the 6CG7 tubes are replaced. I
don't have the signal generator necessary to do this adjustment. So my
question is: have you found that you really needed to readjust the
a.c. balance when you replaced the 6CG7 tubes? Or is this readjustment
usually only necessary if the two triode section measurements in each
tube are quite different from each other?

Thanks,
Brian

My Scott adjustment guide says the ac balance may be fine at center
position for regular listening if the necessary equipment is not
available. It is primarily for near-maximum signal, where the
different tubes may have more of a difference in gain.

Bob

(BRIAN J) wrote:

I have a question for the Marantz 8B users here, or really anyone with
knowledge on this subject. I need to replace the two 6CG7 tubes on my
8B. According to the 8B instructions, Marantz suggests that the a.c.
balance may need to be readjusted if the 6CG7 tubes are replaced. I
don't have the signal generator necessary to do this adjustment. So my
question is: have you found that you really needed to readjust the
a.c. balance when you replaced the 6CG7 tubes? Or is this readjustment
usually only necessary if the two triode section measurements in each
tube are quite different from each other?

Thanks,
Brian

Bob H.

Just grab that plate in one hand, the chassis in the other,
and FEEL the power of tube audio!!!
(not literally, of course, just kidding. DON'T DO THAT!)

BRIAN J wrote:
I have a question for the Marantz 8B users here, or really anyone with
knowledge on this subject. I need to replace the two 6CG7 tubes on my
8B. According to the 8B instructions, Marantz suggests that the a.c.
balance may need to be readjusted if the 6CG7 tubes are replaced. I
don't have the signal generator necessary to do this adjustment. So my
question is: have you found that you really needed to readjust the
a.c. balance when you replaced the 6CG7 tubes? Or is this readjustment
usually only necessary if the two triode section measurements in each
tube are quite different from each other?

Realistically, you'll probably be OK without the adjustment.

However, if you want to check the balance anyway, you could use a test CD
(like from Stereophile) to generate a 1000Hz tone at a reasonable level.
Measure the AC with a voltage meter from plate to plate. Since the
signals are out-of-phase, the voltage should measure close to zero when
in balance.

Hi:

You stated:

snip

Measure the AC with a voltage meter from plate to plate. Since the
signals are out-of-phase, the voltage should measure close to zero when
in balance.

This is not the case at all. Since the signals are 180 deg out of phase,
you'll measure TWICE the voltage betw plates that you would betw plate and
ground, NOT zero voltage. If you want to balance it this way you would look
for EQUAL voltage at each plate, measured betw plate and ground. The
voltages will be 180 deg out of phase with each other but your meter won't
tell you that bit of info.

Note that with a properly operating 8B, setting balance does not require an
external meter because it uses the bias meter for phase inverter balance
adjustment. It measures the output tube current increase while being driven
rather hard.

--
Steve

YIKES! Steve is totally right. You can set the DC balance this way, but
not the AC. To do AC you have to measure each plate individually and
compare.

SORRY!

Steve O'Neill wrote:
Hi:

You stated:

snip

Measure the AC with a voltage meter from plate to plate. Since the
signals are out-of-phase, the voltage should measure close to zero when
in balance.

This is not the case at all. Since the signals are 180 deg out of phase,
you'll measure TWICE the voltage betw plates that you would betw plate and
ground, NOT zero voltage. If you want to balance it this way you would look
for EQUAL voltage at each plate, measured betw plate and ground. The
voltages will be 180 deg out of phase with each other but your meter won't
tell you that bit of info.

Note that with a properly operating 8B, setting balance does not require an
external meter because it uses the bias meter for phase inverter balance
adjustment. It measures the output tube current increase while being driven
rather hard.

Hi (again):

"Paul D. Spiegel" wrote in message
...
YIKES! Steve is totally right. You can set the DC balance this way, but
not the AC. To do AC you have to measure each plate individually and
compare.

SORRY!

No need for sorrow, however...

With the 8B you set the output tube bias using the bias meter and you also
set the phase inverter AC balance (yes, AC balance) using that same meter
measuring the same output tube plate/g2 current. The plan is to drive the
output stage into the "B" portion of AB where output tube current will
increase and use the phase inverter balance pot to set equal (increased
compared to rest bias) plate current to each output tube. The 8B meter has
a second dot on its scale at a higher current level as the specified current
for proper balance. This method accounts for not only the phase inverter
balance but also the AC balance of the output tubes at a high drive level.
Theoretically the OPT sees a truly balanced signal instead of a signal that
is balanced at the output tube control grids but not necessarily at the
plates.

--
Steve