I have a 1950s Stromberg Carlson PA integrated tube amp with a 2-6L6 push/pull
output. It is a three channel amp each with a Vol. control (1 meg). With the
three Vol. controls turned all the way down, a moderate signal will still pass
thru to the output on any channel. What is the cause of this? Also a signal put
into any channel will bleed thru to the other channels. There are no other
problems with the amp. Your technical help is certainly appreciated. Please
email at: Thanks

(JRUBBO770) said:

I have a 1950s Stromberg Carlson PA integrated tube amp with a 2-6L6 push/pull
output. It is a three channel amp each with a Vol. control (1 meg). With the
three Vol. controls turned all the way down, a moderate signal will still pass
thru to the output on any channel. What is the cause of this? Also a signal put
into any channel will bleed thru to the other channels. There are no other
problems with the amp. Your technical help is certainly appreciated. Please
email at: Thanks

Check the potmeters, after 50+ years they'll likely to have some
problems.
Also, check the signal ground. If necessary, rewire.

--
Sander deWaal
Vacuum Audio Consultancy

"Sander deWaal" wrote in message
news
(JRUBBO770) said:

I have a 1950s Stromberg Carlson PA integrated tube amp with a 2-6L6
push/pull
output. It is a three channel amp each with a Vol. control (1 meg).
With the
three Vol. controls turned all the way down, a moderate signal will still
pass
thru to the output on any channel. What is the cause of this? Also a
signal put
into any channel will bleed thru to the other channels. There are no
other
problems with the amp. Your technical help is certainly appreciated.
Please
email at: Thanks

Check the potmeters, after 50+ years they'll likely to have some
problems.
Also, check the signal ground. If necessary, rewire.

How about the caps on the bottom of the potentiometers?
If they're open, the pot won't function as an (AC) voltage divider.

"Prostate Cancer Man" said:

How about the caps on the bottom of the potentiometers?
If they're open, the pot won't function as an (AC) voltage divider.

Caps at the low end of volume potmeters?
That must be some design...............

Now, if this were an old AM radio, I can imagine the cold end being
connected to a cathode, thereby providing AGC in a superhet, but the
OP was clearly talking about a mixer amplifier. No RF stages in sight.

--
Sander deWaal
Vacuum Audio Consultancy

JRUBBO770 wrote:

I have a 1950s Stromberg Carlson PA integrated tube amp with a 2-6L6
push/pull output. It is a three channel amp each with a Vol. control
(1 meg). With the three Vol. controls turned all the way down, a
moderate signal will still pass thru to the output on any channel.
What is the cause of this?

Bad design
Bad grounding
Capacitance in the wiring and the potentiometers.

Also a signal put into any channel will
bleed thru to the other channels.

I presume that there is no input selector switch, and that the volume
controls make up part of an variable input mixer.

If you are using this amp with most modern sources, and even most legacy
sources, dropping the volume controls down to 100 K pots, combined with
corresponding drops in the resistors from the potentiometer outputs to the
summing point will at least partially alleviate most of these problems.