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91
Tubes and Hybrids / Re: Help with Hybrid Design
« Last post by phatt on December 30, 2020, 03:38:23 AM »
Agree with G1, :dbtu:
Adding;
Well the data sheet tells it as I suspected,, It's Not an *isolated 115v Tx*

It states very clearly it has 2x115v primaries and 2x 7V secondaries.

So unless I've lost it, :loco ,the only way one could get enough HT to run a valve is from one of the primary windings which means it's a death trap waiting to happen as the circuit runs off the primary. ARRRRGH!!!!
OK sure there are tons of old radio circuits that did indeed run direct from mains but most of those old units where bakalite cases and one would never come into contact with the circuit under normal use but this is an electric guitar amplifier and you ARE in direct contact with part of that circuit so if something fails you could end up Dead.
If you want to build it that is your call but I'm writing this to warm other non teck savvy folks that it's a death trap waiting to happen.

Be very careful grabbing ideas off the net some are really bad designs. 8|

To attain HT for a small valve amp there are much SAFER ways,, here is a better option for High voltage, uses back to back Tx's.
https://valveheaven.com/diy-amp-designs/the-lamington-junior/the-lamington-junior-design/

The added bonus is that it uses a 12Volt wall wart which keeps you a long way away from dangerous main voltages.
HTHelps, Phil.
92
Tubes and Hybrids / Re: Help with Hybrid Design
« Last post by g1 on December 29, 2020, 08:22:06 PM »
And if one of the secondary 7V windings is actually in series with a 115V primary winding as the drawing implies, well I don't even want to try and think about that.  ;)
93
Tubes and Hybrids / Re: Help with Hybrid Design
« Last post by g1 on December 29, 2020, 08:08:11 PM »
It should be drawn like antek draws it in the datasheet.


The two 115V windings are on the same side of the transformer, so they are not transformer (inductive) coupled.
Drawing it like they are on opposite sides of the transformer is just wrong.
I think the coupling would be very limited in terms of current, and it is just lucky that it works.
94
Tubes and Hybrids / Re: Help with Hybrid Design
« Last post by SerpentRuss on December 29, 2020, 09:37:51 AM »

Also the way in which the power Tx is drawn up in that schematic seems strange.


I agree, I would not have drawn it this way.  I would have placed the 117 VAC label under the AC source symbol and I would have put the 7 VAC symbol on the there side of the bottom transformer symbol.  Essentially those two series windings on the left side represent one pair of the 120-volt primary leads.

Here is the web page for the transformer.   Antek makes some inexpensive and interesting toroidal transformers.  I will probably use one of their tub amp models for a Rob Robinette "Deluxe Micro" project.

https://www.antekinc.com/an-0107-10va-7v-transformer/

https://robrobinette.com/Deluxe_Micro.htm

95
Tubes and Hybrids / Re: Help with Hybrid Design
« Last post by SerpentRuss on December 29, 2020, 01:04:53 AM »
This is my first amp build, but I have about 40 years of experience working with electricity all the way up to medium voltage circuits like 4160-volt motors.   I know how to work safely.

You're right, it's not an isolation transformer, but it's being used as one.   This design has a very low current draw because it is a sub-1-watt amp.  The guy who builds these has used this exact transformer in this way on several small amp builds. One primary set of leads on the transformer gets driven by the mains inducing about 120 volts on the other set.  The 7-volt secondary is dropped to 6.3 volts to run the filament on the tube.  The 6CL6 power amp doesn't require a lot of DC voltage.  I think this supply will put out about 135 volts DC.  The OT is wired using the 1/2 watt tap.
96
Schematics and Layouts / Re: Valve Tremolo - Help Wanted Please
« Last post by nodz on December 28, 2020, 08:30:26 PM »
Rightho, finally found the original doco.  Phase shift oscillator where O/P is capacitively coupled to the plate of the first stage audio amplifier.  I coupled it to the intermediate mid drive amp rather than the first stage.
97
Tubes and Hybrids / Re: Help with Hybrid Design
« Last post by phatt on December 28, 2020, 08:14:57 PM »
Hang on I just reread the 1st post and as this is your first build,, I'll assume you don't have a lot of teck skill.

Warning!!! RE this;
"The power supply for the amp I'm trying to build features an inexpensive 7-volt Antec Toroid transformer with the 120-volt coils split, making it a small isolation transformer.  The 7-volt side is used for the tube filament."

Unless I've missed something in translation,,,that tells me it is a 120/120 split *Primary* so something sounds wrong :loco

Also the way in which the power Tx is drawn up in that schematic seems strange.
Others here may know more but meantime be careful cause if I'm right as it could kill you. :police: :police:

Normally when a Tx states 120/120 split primary that means it can be wired up to either 120 mains ans 240 mains. It is most likely NOT an isolation Tx :-\
Maybe post a picture of the Tx you wish to use ideally showing the label.
Phil.
98
Tubes and Hybrids / Re: Help with Hybrid Design
« Last post by SerpentRuss on December 28, 2020, 11:11:24 AM »
Rather than screw with this design, since it's my first project, I've decided to build this as drawn as a small combo amp using a switched output jack that will allow me to use another cabinet if I want to experiment.  I will include some build photos as I go.   Wish my luck.
99
Schematics and Layouts / Re: Valve Tremolo - Help Wanted Please
« Last post by Jazz P Bass on December 27, 2020, 12:11:51 AM »
I don't think that you have it right as of yet.
The output is cathode biased not fixed as in the Fender.
Why not hook it up as I stated in my last post.
100
Schematics and Layouts / Re: Valve Tremolo - Help Wanted Please
« Last post by nodz on December 26, 2020, 05:00:20 PM »
That is why your circuit will not work.  Trem will only work if it is introduced into grid or cathode circuits.

With respect to my amp
So if I took the O/P from the trem unit (section A) after the 0.056uF coupling cap and introduced it at the junction 0.022uF (C14)  and 1M (R16) of the grid of the PI (Section D) - all well and good?

So basically free running LFO mixed with the signal from Sections A & B, without having to actually have seperate trem channels as per
http://www.valvewizard.co.uk/trem1.html

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