Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Glenn on January 11, 2022, 08:56:58 am
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Hi: I was looking at Power transformers and saw a Hammond 290cz
it has
300 0 300 taps
2 wires for 25v taps
6.3 v taps
I was wondering what is the 25v taps are used for?
I looked at AC15 schematics but can't seem to find anything about the 25v taps.
Is this PT used for a modern AC15 that might have a need for this?
any insight would be appreciated, thanks
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The 290CZ is spec'd for the "newer" AC15-C1. The 25V winding is probably there for their switching.
Here's the page for the entire line
Tube Guitar Amplifier - Power Transformers (290 Series) - Hammond Mfg. (hammfg.com) (https://www.hammfg.com/electronics/transformers/classic/290)
Take a look at the 290PX
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Hi, thanks for the link and the info.
That 290px is a better fit, with the 5v rectifier tap, if other than using the ez81 rectifier
Glenn
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I used the Hammond 270FX in my AC-15 clone.
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thanks Steve
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I used the Hammond 270FX in my AC-15 clone.
I like that it is a stand up mount.
Especially for a non-clone in a smaller chassis.
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290cz
300 0 300 taps
2 wires for 25v taps
6.3 v taps
I was wondering what is the 25v taps are used for?
For a hybrid SS/tube amp maybe :dontknow:
could use the 25v tap for bias, maybe need a voltage doubler for that depending on the bias voltage :dontknow:
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Here is another option - Hammond 270DAZ:
https://www.hammfg.com/files/parts/pdf/270DAZ.pdf
It's a laydown/horizontal "Z" type. 260-0-260 should be safe for EL84's. But, there's no 5V secondary, so you'd need to use an EZ81, or diode rectification.
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Thanks all for your input. I was only wondering what that 25v tap was used for on that PT.
Silvergun suggested that it was probably for relay switching. Which makes sense to me.
I was looking to build a Maz18 Reverb, someone here posted a schematic awhile ago, but then I saw the other day that sluckey created an ac15r schematic and it looks cool. (I think I would use a 5879 tube instead of the ef86 with a rewire)
I have an Edcor 270 0 270 ~ 6.3v Amp PT and a 15 watt Edcor OT
I was just weighing between the 2 amps as one has 5 preamp tubes and sluckey's has 4
So a 5 preamp tubes with el84's is 3.17A vs 4 preamp tubes with el84's is 2.84A current draw according to calculator I was using.
thanks again everyone
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If you're considering using the EZ81 don't forget about the 1 amp - 6.3V requirement
I was just weighing between the 2 amps as one has 5 preamp tubes and sluckey's has 4
So a 5 preamp tubes with el84's is 3.17A vs 4 preamp tubes with el84's is 2.84A current draw according to calculator I was using.
Just to keep things clear, the power tubes are not considered preamp tubes.
For sluckeys recently posted AC15 litey' lite:
2- EL84 power tubes @ .76A each = 1.52A
1- 12AX7 PI @ .3A
1- EF86 preamp tube @.2A (or your 5879 @.15A)
1- EZ81 rect @ 1A
total 3.02A @ 6.3VAC
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Hi: I was looking at Power transformers and saw a Hammond 290cz
I was wondering what is the 25v taps are used for?
Is this PT used for a modern AC15 that might have a need for this?
That's a replacement for the Vox AC15C1, a modern amp with lot's of SS circuitry. The schematic is easy to find on the net if you want to take a look.
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Thanks Silvergun.
Steve: I did google ac15 first before posting, but got the older schematics- I guess I didn't google ac15c1 for the modern ac15
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you could look at other series Hammond PTs like the 300 series https://www.hammfg.com/electronics/transformers/classic/300