Jubilee

[dcribbs1412]

Starting a 100 watt Jubilee build.
Looking for suggestions for 100 watt Jubilee iron.
Thinking a 190-0-190 PT would give around 470V on plates?
any suggestions are greatly appreciated.

Darin

[alvarezh]

Hi Darin.

It looks like the 190-0-190 is right for the job. I have a 2550 which is the 50 watter so my OT & PT numbers are not going to help you. I bought my PT from MetroAmp. The OT is a Mercury Magnetics.

All the best.

[dcribbs1412]

Thanks alvarezh
I was suggested the Mag Comp 40-18024 or 40-18053 with M6
by Chad at Triode. They are "clones of the original T4145 PT that was used in the original 2555 Jubilee's."
Which is what I'm looking for.
Just wondering the math used to calculate the voltages.
Not sure the 350x1.4= 490V applies with a bridge rectifier?


Darin

[Bob S]

Yes Darin vac*1.4 applies for bridge rectifiers.
Should put you around 490 @ the reservoir.
Bob

[dcribbs1412]

Yes Darin vac*1.4 applies for bridge rectifiers.
Should put you around 490 @ the reservoir.
Bob

Thanks Bob
hoping that transfers to around 470V at the plates.
I need to do more reading about calculations.

Darin

[alvarezh]

Attached is the Hammond PS design guide, keep it handy.

All the best.

[dcribbs1412]

Attached is the Hammond PS design guide, keep it handy.

All the best.

Thanks!
I have seen this before didn't realize it was from Hammond

Darin

[John_P_WI]

Darin, concerning your original post, is your 190-0-190 not going to be a little low?

190+190 x 0.707 = 268 v peak, seems low unless I'm missing something.

Me thinks 350-0-350 is more in order, 500 ma... hehe just my thinking....

[alvarezh]

John, the amp has a "full wave bridge capacitor input", not a "full wave capacitor input" rectifier.

Check the Hammond PS design PDF, above.

190-0-190 volt PT is the correct one as per the Bob & Darin's calculations.

All the best.

[dcribbs1412]

I am little confused my self in some of the transformer math.
The 1.4 x Sec 350= 490V or so I understand( Mag Comp PT)
I am a little cornfused at the math involved in the 190-0-190(Marstran PT) transformer
190+190x1.4=532V ?
Some info I found of plate voltages on the 2555
was around 470V on the plates. Which I was making my target voltage.
Just wondering how much the voltages will drop loaded with tubes?
I'm guessing a lot of variables come into play. I'm hoping for
20-25V drop or so?


BTW pic of the preamp board so far

Darin

[alvarezh]

Pretty work Darin.

Follow my (ugly) arrow on the attached layout.

Cheers!

[John_P_WI]

Darin,

The Marstran is rated that way using a voltage doubler (the center tap is connected between the reservoir caps in series) or using a full wave bridge without using the center tap. I had a brain puke yesterday - was testing in an environmental and vibe lab all day - so damn noisy I couldn't think.

John

[dcribbs1412]

Thanks guys
alvarezh...I am using that layout along with some schems I found
I understand the 190x2 HT taps using no CT.
My question is using a 350V (Mag Comp)PT no CT. Would this be
175x2 no CT...which would be 20-25V lower voltages?
Sorry to drag this out. Want to make sure I get the right voltages in the end.

Darin

[alvarezh]

Thanks guys
alvarezh...I am using that layout along with some schems I found
I understand the 190x2 HT taps using no CT.
My question is using a 350V (Mag Comp)PT no CT. Would this be
175x2 no CT...which would be 20-25V lower voltages?
Sorry to drag this out. Want to make sure I get the right voltages in the end.

Darin

If you mean 175-0-175, sure, it works at a lower voltage (30 volts lower would be my guess). Just make sure the PT produces enough current and, as you stated, leave the CT unconnected.

All the best.

[dcribbs1412]

Thanks alvarezh
The Mag Comp is a 350V PT....175-0-175
My searching has shown original 2555 owners to have 460-470V on the plates loaded.
so I'm thinking about the Marstran PT (190-0-190)or equivalent which would deliver 490V to the plates unloaded as opposed to the Mag Comp which would be 470V to the plates unloaded.
This is assuming 20-25 V lower with tubes loaded?

Darin