HAMMOND 272 JX

[Markusv]

Hi

I have a Hammond 272 JX available
I believe it may be ideal for a PT for a Liverpool Clone

Can anyone tell me if this is accurate?

I'm also confused as to how it is wired up.
Do the red leads go to the diodes and the red- and Yellow to ground via switch?

Any help, Please

Cheers,

Markus

[rhinson]

hello there, the primaries on this series of power trannies is 115v not 120v. if your wall voltage is 120 or over this will cause the resulting plate voltage on your el84's to be a good bit more than you'll want. if you use a tube rectifier (5ar4) it'll bring it down some but probably not where you want to be for this amp. actually, it would make a nice express or 50w marshall plexi power trannie. and yes the red leads are the h.v. sec. (to each diode string) and the red/yel. is it's ct. (to ground). rh

[UR12]

Hi

I have a Hammond 272 JX available
I believe it may be ideal for a PT for a Liverpool Clone

Can anyone tell me if this is accurate?

I'm also confused as to how it is wired up.
Do the red leads go to the diodes and the red- and Yellow to ground via switch?

Any help, Please

Cheers,

Markus

Marcus
The Hammond would be good except that it will probably give you a little more B+ voltage than what the El84s will take. Here is the ratings

272 JX 195 300-0-300 250ma 5V 4A+ 6.3V 8.0A+

The 300-0-300 will probaby put you in the range of about 385 - 400 volts B+. The El84s made today probably won't survive at that voltage for very long. Years ago it was common to see 400 v B+ on some amps like the AC30. This would probably limit you to NOS tubes. I am not saying it wouldn't work but if you had some way to lower the voltage to 330 - 350v it would be better IMO. Maybe use a power zener to lower the voltage. 250ma is fine as is the 8A 6.3vol heater winding. You won't need the 5.4 V 4A winding if you run SS diodes. You could use it if you plan on running a 5 volt rectifier tube like the GZ34/5AR4

Your correct about running the red wires to the diodes and you need to ground the red/yellow wire. It doesn't normally connect to a switch. The power switch will connect to the Black wires and the standby switch connects to the output of the diodes to remove B+ from the tubes.

Hope this helps!

[Markusv]

Rhinson and Dana

Thanks for both your replies.

I guess if there is a reliable way to lower the B+ voltage, Im gonna try and do that.- (I have the PT and I really want to stick with the Liverpool idea)

I have never done that though- I believe one way is to add a number of diodes backwards in series to ground?
If that's correct, how do I know which and how many?
BTW Im using a diode rectifier as in the Schematic.

Also, if my B+1 voltage is a bit high, that will mean a higher voltage for B+2 - 5, measured at each intersection of power supply caps and their respective resistors. Is that OK, or do I now have to change values elsewhere in the schem?

Thanks in advance

MarkusV

[rhinson]

hello mark, if you're determined to use this tranny you need order a 50w reverse polarity zener diode from mouser. they are nte parts and the part number i would use is 526-nte5275ak. this in theory will give a 50v drop through the power supply--in practice it'll be less---maybe 45 volts or so (it's been said to not drop any more than 50v in this fashion). i've used these before and they work great and are reliable (i've got a pal i built an amp for about 10yrs ago with one of these and he still gigs at least once a week with it). the cost is in the $10-15 range. personally i'd save this trannie for another build (because you know you'll want to build more, believe me!!) and get one of moose's power trannies and use the lower h.v.sec. taps for the liverpool. but that's me. anyway, this is the device you'll need to use the trannie----you drill a hole, bolt it to the chassis and then solder the power trans. center tap to it and that's it. anyway good luck. rh

[MarkB]

I"d save that transformer for another amp. My 270EX - 275-0-275 - puts about 360V on the plates of my 2xEL84 amp, and that's after an EZ81 rectifier drops the voltage about 25V. The 272JX is a good 2xEL34 transformer. If you try to drop that much voltage, you'll be producing a lot of heat, which is never a good thing to do in a chassis.

[Markusv]

Hi Mark B and Rhinson

Thanks for the help- much appreciated.
I know this is not my last amp, as I've already built one of the ax 84's, and I can't get enough. The wife just shakes her head and asks: "How many amps do you need?"

Perhaps I'll just get a MOOSE PT and get on with it.

You'll hear from me again soon I think

Markus

[mlp-mx6]

The wife just shakes her head and asks: "How many amps do you need?"

Answer - "Just one more..."

No matter how many times or when she asks... (grin )

[Markusv]

...and it doesn't get any headaches - just gives 'em!

Also it has an "Off" switch

[sepulchre]

The wife just shakes her head and asks: "How many amps do you need?"

Answer - "Just one more..."

No matter how many times or when she asks... (grin )

+1

Yup!

[funkmeblue]

120 volts at my house and this transformer puts out 420 volts on a pair of el34's with solid state rectifier

[sepulchre]

420V That's what I get too. (Hope it's enough for a 2204 build)

[John_P_WI]

420V That's what I get too. (Hope it's enough for a 2204 build)

In my plexi / express builds I got around 425 v using the 272 jx. You will have plenty of power for a "50 watt" build. In a few builds I had to put small power resistors in the heater string to bring the voltage down.

[jelle]

...and it doesn't get any headaches - just gives 'em!

Also it has an "Off" switch

I like 'On' switches much better! Good to see you here, BTW!

[Markusv]

Hey Jelle!!

I see this question was posted by me in 2006.
How time flies!

That transformer has long since been used, and the amp later re- built and then sold

Geez - this is a sickness

M