Vox UL715 Transformers

[NickS185]

Building a clone of the Vox Ul715 and I am having a bit of trouble figuring out how to select transformers for it. Any help is appreciated.

[shooter]

start with tube filament current from tube datasheets for ALL tubes used, add all the values.
since you have the secondary voltages from the schematic, guessing you know primary side 

now go "power transformers for tube amps" and match up the values, post what you found with #'s and a link n we can probably verify your finds before you spend $$$'s

[sluckey]

Gonna be difficult or even impossible to find that PT. Probably need to get a separate low voltage transformer for that +25V supply. If you decide to use a separate low voltage transformer then you could use Hammond transformers for Vox AC-15 or even Marshall 18W combo.

What's your attraction to this short lived hybrid amp? You're the only person I've ever heard mention it.

[shooter]

that +25V supply

to early, missed that 

kinda like how the PA ground rail is -25vdc 

[kagliostro]

I don't know which will be the consumption on that 25v line (I'm not able to find a complete UL715 schematic), but the OA200 diodes used on the FWB are rated for max 160mA, so I can guess a current disposable around 100mA (may be)

Find a PT among Hammond's or other brand that has a little excess of current on the 6.3v winding, using a quadrupler you can have a raw voltage around 28-29v, then use an LM7824 with a diode connected as ground reference to drop the voltage to around 24.7v

remember that to have 100mA at the output of the quadrupler it requires 400mA at the input

Franco

[NickS185]

start with tube filament current from tube datasheets for ALL tubes used, add all the values.
since you have the secondary voltages from the schematic, guessing you know primary side 

now go "power transformers for tube amps" and match up the values, post what you found with #'s and a link n we can probably verify your finds before you spend $$$'s

I've found that the 2A is required for the 6.3v filament circuit while the B+ requires 138mA

https://www.edcorusa.com/xpwr121

Would this transformer be suitable for what I need?

[Willabe]

What's your attraction to this short lived hybrid amp? You're the only person I've ever heard mention it.

Yes, why this amp?

I've never heard of it either. 

[Willabe]

https://www.edcorusa.com/xpwr121

Would this transformer be suitable for what I need?

No, not if you live in the USA or Europe. It has a 100acv primary, and no secondary wind for the 25dcv.   

 

[NickS185]

https://www.edcorusa.com/xpwr121

No, not if you live in the USA or Europe. It has a 100acv primary, and no secondary wind for the 25dcv.   
 

Dang. Guess I better move.

[PRR]

It can't be that hard. It is an "18W" tube amp transformer plus a 24VAC tranny which you might find in the furnace-parts section of the hardware store.

(The 24VAC will make 35V of DC, but today regulators are cheap.)

[NickS185]

It can't be that hard. It is an "18W" tube amp transformer plus a 24VAC tranny which you might find in the furnace-parts section of the hardware store.

(The 24VAC will make 35V of DC, but today regulators are cheap.)

So could I use something like this and get a 24VAC transformer?

http://www.classictone.net/40-18056.html

[Willabe]

https://www.edcorusa.com/xpwr121

No, not if you live in the USA or Europe. It has a 100acv primary, and no secondary wind for the 25dcv.   
 

Dang. Guess I better move.

Yeah, maybe you should.

We have members from all over the world, I have no idea where you live.

Japan is the only nation that has 100acv mains. Their are a couple of handfuls of nations that have 110acv, that PT would probably work fine with.   

We have no idea how much or how little you know. You have 4 posts here and did not give any clue as to if you've built an amp before.

The spec sheet for that PT clearly shows an input wall acv of 100acv. Not much to figure out if you could use that PT in the country you live in, before even considering if it has the secondary current and acv's you need for that amp.

That is why I said no if you live in the US or Europe.

[SoundmasterG]

What's your attraction to this short lived hybrid amp? You're the only person I've ever heard mention it.

Yes, why this amp?

I've never heard of it either.

These were the sound of the Beatles "Revolver" and "Sgt. Pepper's". Well technically Revolver was the 7120, but they are very similar to each other. They had a solid state preamp and a tube power amp. Nothing really sounds like them though one guy has a pedal that is somewhat close. Here is a video of a 7120 and a 730, which are similar to the UL715 but more power. They all used the same solid state preamp section. R.G. Keen from Geofex makes a preamp board, and the guy in this video makes clones for sale out of the UK. Its probably not "THE" sound that everyone would want for their only amp, but it is a useful sound to have in your toolbox.


https://www.youtube.com/watch?v=cAtupA4jyro&list=FL5mD20W75hVSAvA6OdQ95fw&index=80&t=0s

Greg

[sluckey]

So could I use something like this and get a 24VAC transformer?

http://www.classictone.net/40-18056.html

That'll work just fine.

[Willabe]

These were the sound of the Beatles "Revolver" and "Sgt. Pepper's". Well technically Revolver was the 7120, but they are very similar to each other. .........

Thank you Greg.