HIgh Valued Traffo .. Yikes...

[fayser]

HI Folks... I have a TP40D transformer from Allen Amps and was hoping to use it for an Express build... the secondaries are 320-0-320 which seem higher than values discussed elsewhere on the forum.. would I get away it or is there anything I can do to make the secondaries fall in line with what is required
Thanks again
Tony

[FYL]

Thre's very little diff between 300 and 320V, go ahead, use your iron if the other specs are OK.

[RJ Guitars]

Fayser,

I think before I could say much about it I've got a couple questions:
1) What is the current ratings on your windings?
2) What do you want to accomplish

Question 2 probably doesn't matter if your tranny won't support a Wreck.

If you want to build an exact clone then you've got some obstacles and decisions to sort out even if the tranny is stout enough for the task.

In a Wreck build, Transformers are expensive but compared to the time and effort it takes to build a great amp, it usually doesn't pay to try to save money on the transformers.

rj

[fayser]

From the Allen site I have...
320V-0-320V at 180ma,
5V at 3A and
6.3V at 4.5A.
Supports the use of 6L6 AND EL34 power tubes Center tapped heater winding, 50V bias tap

[fayser]

Oh.. I forgot to add in terms of the second question... well I am not necessarily purist about the build however I sense from what I read that the amp is very sensitive to the build so I obviously don't want to stray to far from the beaten track for a first build I guess.

Thanks

[RJ Guitars]

Fayser,

I always enjoy watching new folks come into this hobby. Welcome to the AGF...

That tranny could be adequate although it doesn't leave much extra for a wreck build. Wrecks are sorta famous for having over-sized transformers.

Do you know if the 320 volt rating is loaded or unloaded? If your not familiar with this then unloaded simply means what voltage do you have on your B+ secondary with no load across the leads? Not all transformer companies use the same rating standards so YMMV.

Express amps generally start with 300 volts open circuit on the secondaries. In your case, you might actually load this transformer more than a typical wreck and that begins to define part of important stuff you need to consider when building an Express.

While you chew on that, there are a few ways to drop the B+ down to where you want it... I am assuming you want to try to line up the voltages with the typical Wreck build.

1) use a Zener diode on the center tap of your power transformer
2) Use big resistors in various places along the voltage string

* Note - it's likely that these practices do not meet the approval of some very well informed folks that hang out here in this forum.

rj