A local picker gave me a Zenith HM2670 console stereo
and I am trying to figure out how or if it's going to become
a guitar amp PT.
The PT is powering a 4 X EL84, 2 X 6CG7, 5U4GB power amp
and a 14 tube tuner. It also has a reverb pan ( never could
understand why anyone would want that, seems redundant ).
I was looking at the Bandmaster Reverb schematic and noticed
the B+ dropping a whopping 70 volts when the standby is switched
off. I never measured a big drop like that in any of my builds. Is
there any particular reason why this would occur in one amp
and not in others? Should I consider this drop when picking a PT
secondary voltage?
Here is as close as I can get to determining the current and voltage
of this PT without some help, I need to know if there is a method
to further the accuracy that I can apply.
STANCOR PT secondary SPECS.
POWER AMP;
IH/amps IA/ma Ig2/ma
5U4GB N/A
EL84 .76 46.0 7.0
EL84 .76 46.0 7.0
EL84 .76 46.0 7.0
EL84 .76 46.0 7.0
6FQ7 .78 9.0
6FQ7 .78 9.0
IH/amps IA/ma Ig2/ma
TOTAL 1 = 4.56 202 28
TUNER SECTION;
IH/amps IA/ma Ig2/ma
6BA6 .3 11.0 4.2
6BA6 .3 11.0 4.2
6EQ7 .3 9.0 3.5
6BE6 .3 2.9 6.8
6BN6 .3 .25
6AU6 .3 5.0 2.1
6BC7 .45
6JK8 .4 10.6
6GN8 .75 57.0
6AW8A .6 17.0 3.5
6CG7 .6 9.0
6BN8 .6 1.5
12AX7A .3 2.0
12AX7A .3 2.0
-----------------------------------------------------------------------
IH/amps IA/ma Ig2/ma
TOTAL 2 = 5.8 138.25 24.3
TOTAL 1 = 4.56 202.0 28.0
Final 1&2 = 10.36 340.25 52.3
Schematic says 380V after the 5U4GB so
330V CT @ 392 ma, 6.3V @ 10.36 A ?
330 X 1.41 - 70 -18 = 377.3 ?
Seems like this PT would work for an amp
as large as a twin reverb but the heater
current is too high. Also, how do I estimate the
VA rating?
Another thing I was wondering is would it be possible to
build two separate amps with the same PT? Or would
both amps talk to each other if used at the same time?
and I am trying to figure out how or if it's going to become
a guitar amp PT.
The PT is powering a 4 X EL84, 2 X 6CG7, 5U4GB power amp
and a 14 tube tuner. It also has a reverb pan ( never could
understand why anyone would want that, seems redundant ).
I was looking at the Bandmaster Reverb schematic and noticed
the B+ dropping a whopping 70 volts when the standby is switched
off. I never measured a big drop like that in any of my builds. Is
there any particular reason why this would occur in one amp
and not in others? Should I consider this drop when picking a PT
secondary voltage?
Here is as close as I can get to determining the current and voltage
of this PT without some help, I need to know if there is a method
to further the accuracy that I can apply.
STANCOR PT secondary SPECS.
POWER AMP;
IH/amps IA/ma Ig2/ma
5U4GB N/A
EL84 .76 46.0 7.0
EL84 .76 46.0 7.0
EL84 .76 46.0 7.0
EL84 .76 46.0 7.0
6FQ7 .78 9.0
6FQ7 .78 9.0
IH/amps IA/ma Ig2/ma
TOTAL 1 = 4.56 202 28
TUNER SECTION;
IH/amps IA/ma Ig2/ma
6BA6 .3 11.0 4.2
6BA6 .3 11.0 4.2
6EQ7 .3 9.0 3.5
6BE6 .3 2.9 6.8
6BN6 .3 .25
6AU6 .3 5.0 2.1
6BC7 .45
6JK8 .4 10.6
6GN8 .75 57.0
6AW8A .6 17.0 3.5
6CG7 .6 9.0
6BN8 .6 1.5
12AX7A .3 2.0
12AX7A .3 2.0
-----------------------------------------------------------------------
IH/amps IA/ma Ig2/ma
TOTAL 2 = 5.8 138.25 24.3
TOTAL 1 = 4.56 202.0 28.0
Final 1&2 = 10.36 340.25 52.3
Schematic says 380V after the 5U4GB so
330V CT @ 392 ma, 6.3V @ 10.36 A ?
330 X 1.41 - 70 -18 = 377.3 ?
Seems like this PT would work for an amp
as large as a twin reverb but the heater
current is too high. Also, how do I estimate the
VA rating?
Another thing I was wondering is would it be possible to
build two separate amps with the same PT? Or would
both amps talk to each other if used at the same time?
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