Suitable Edcor PTs for Princeton Reverb, 5E3 Deluxe & Marshall Studio 15 builds.

[tubetone]

I'm a new member here, and this is my first post.

I need to obtain power transformers (240V primary) for building these amps:

1) Marshall Studio 15 (PT Secondaries: 300-0-300V @ 79mA & 6.3V (or is it 6.5V??) @ 1.62A - refer to the schematic at the Dr. Tube website)
2) Fender 5E3 Deluxe
3) Fender AA1164 Princeton Reverb

Based on my own research, I have narrowed down my PT choice to the following Edcor models:

5E3 & Princeton Reverb:

XPWR047 (330-0-330V @ 120mA, 6.3V @ 2.5A & 5V @ 3A)
XPWR041 (340-0-340V @120mA, 6.3V @ 4A & 5V @ 3A)

In fact, will the XPWR047 be OK for both amps ?

Studio 15:

XPWR014 (300-0-300V @ 75mA, 6.3V @ 3A & 5V @ 2A)
XPWR061 (300-0-300V @ 120mA, 6.3V @ 3A, & 5V @ 2A)

As I intend to build a "stock" version of this amp, using 6V6s, will the XPWR014 (with its HT "deficit" of 4mA) be adequate, or should I go for the XPWR061 instead ? Also, in terms of voltage regulation, is 6.3V @ 3A too high, or would a PT with a lower current rating (e.g. 2A) be better ?

I'd be grateful for any opinions that members can offer as to which of these transformers (or alternative brands/models) are suitable.

Thanks

[tubetone]

Hi,

Is anyone there ? Should I post this thread elsewhere ?

[Steve Conner]

No, nobody is here. This is the kind of question that you can answer yourself by just looking up the PT specs for the amps you're cloning, counting the tubes to determine heater current, and so on.

I'd personally go for the XPWR047 for the 5E3 and Princeton. The other transformer has too much heater current for a 5E3, maybe even too much for a Princeton (you should check this yourself though, the Princeton has more tubes since it has a reverb)

If the heater winding is underloaded, the heaters will get too much voltage, reducing tube life. You can add a low value resistor in series with the heater line to burn off the extra. I've done this when reusing PTs from old equipment.

For the Studio 15, I guess the XPWR014 would do. 4mA isn't really worth worrying about. The bigger one will run cooler, but it'll supply a higher HT voltage under load, and then the power tubes might run too hot.

If you're in the UK, have you considered Hammond transformers from Bluebell Audio?

[ThermionicScott]

I agree with Steve about the 5E3 iron. The XPWR047 would supply just enough filament current for you to play around with 6L6's, and probably give a healthier B+ for the 6V6's. It's more robust than what Fender stuck in the original PR's, too.

- Scott

[tubetone]

Hi Steve,

Thanks very much for your informative reply

Except for the Studio 15, I found it somewhat confusing to clearly define PT specs for the 5E3 and Princeton Reverb. Between PT manufacturers (MM, Hammond, Magnetic Components, Weber etc), there were wide variations in PT ratings for the "drop-in replacements" (e.g. 630 V CT to 710 V CT, and 70 to 120mA). There were similar variations at amp builder websites, and this was further complicated by references to "vintage correct" mains & B+ voltages, and the use of NOS rectifiers.

In the end, I chose the Edcor PTs, and posted this thread in order to get a "2nd opinion"

Thanks for your suggestion regarding Hammond transformers from Bluebell Audio, but I'm in Australia.

As these will be my first tube amp builds, I'll probably post some more questions later.

I really appreciate your help

[Jared Purdy]

BillM Audio and Dave Allen, of Allen Amps have Heyboer make the TO20 for the PR/PRRI. It's twice the size and weight of the stock OT in either a vintage PR or current production PRRI. They also make one for the DR/DRRI, and I beleive they have one for the 5E3. Their reputatin is quite sound.

[tubetone]

Thanks Jared. I've had a look at Allen Amps, and they sure do make excellent transformers. Unfortunately, they don't export them outside of the US

[Jared Purdy]

Wheren do you live? I ordered a TO20 from BillM Audio and had it in a week (I live in Toronto). What about Heyboer or MM??

[tubetone]

I live in Australia.

BTW, I'm only looking at power transformers for now, so I wouldn't be interested in the TO20. I had a look at BillM Audio, and although they do export internationally, I didn't see any PTs for sale. All the same, the mod kits are very interesting. Thanks for mentioning the website.

I'd consider Heyboer if I could get them for a suitably (cheap ) price, but I think MM's are too expensive. Of course, both Heyboer and MM make excellent transformers.