Another "junk iron" question

[wireball]

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?

[eruannu]

why a verb pan on a stereo console?

[wireball]

I guess the first post here could be used as a model for why one
should never post on forums when they are more than half asleep.

My question ( the question I had on my mind in the first post )
is, how do I determine more accurately the heater current
and HV current rating of this transformer? The tubes which
the PT were powering have been added up and the current
rating is at least 392ma for the HV tap and 10.36 for the 6.3V
tap. Schematic for the amp the PT came from says 380V
after the 5U4GB, so without measuring ( have not done that yet).

380V / 1.41 = 269.5 ct

so VA / HV = current draw

and 539V(HV) X .392A(HVA) = 211.2 VA?

I lost all my data when my HD failed so I am
asking for conformation here, not for someone
to do the math for me.

is there a way to get some more accurate
numbers for the current rating?

I would like to build a fender twin R or Super R
but if the current rating of this PT is too high
I would like to know if one could build two amps
fed by the same PT?

The AA763 schematic shows 340 ct for the twin R.
Is this the correct spec for the Fender Twin Reverb amp?
got this from Antique Electronics.

Secondary: 210-0-210 V, 450 mA with 60 V bias tap

Filament winding: 6.5 V, 5.5 A

I remember seeing 10 amp FIllament for this amp somewhere
but I don't have that reference anymore.

[Arthur B.]

You said that the amp was "junk", which probably means that it's still functioning to some degree. In that case, wouldn't it be better to refurbish it, sell it off, and buy a PT that you know will do the job?

[wireball]

why a verb pan on a stereo console?


Kinda redundant with studio effects and all huh?

Marantz and other companies back in the 70's sold reverb
units for stereo too. Still see them on ebay now and then.
They don't sell for much though, which I guess means they
are not too popular.

[wireball]

You said that the amp was "junk", which probably means that it's still functioning to some degree. In that case, wouldn't it be better to refurbish it, sell it off, and buy a PT that you know will do the job?

Yes, a good point. I have two now, the first I received free also.
I put that one on ebay and had to pay for the add after no one
bid on it.

On the other hand, a working PT is not really junk if it can be re-used
right? I cannot imagine how much good re-usable stuff is rusting away
in our landfills.

I have built around ten amps from re-used parts, the amps sound great
and will be around for the next 30+ years I imagine. Stereo units may go
out of style but a nice sounding tube guitar amp will usualy be fixed and
played instead of thrown away.

And then there's the "I am not rich" thing to consider.