Transformer question

[rsumperl]

Hello everyone,
I am looking for a ~30-31v transformer to power some filaments. They seem to be few and far in between, so my next thought is a 480v-->120v transformer. With 120v on the primary I should get my ~30-31v on the secondary. I found a fairly cheap, new one on "the bay" that is rated for
100va. So, if my math is correct, if it is used as designed, the secondary will only do ~830ma. So, am I correct in saying if I need 30v @ 2a this transformer is not it?

Thanks
Ray

 

[Doz]

Can you not get a 15 - 0 - 15 out there?

 

[rsumperl]

I've looked and haven't seen any. Any suggestions besides eBay?

 

[thelenster]

Why 30V for filaments?

 

[RTF671]

Why 30V for filaments?

Series heaters. They add the overall voltages up and the current more or less stays the same. For example a 12AU7 can run 6.3v or 12.6v. You can take it further and run 4 12AU7s at 50.2v @ 150mA.

Antek is a company that puts out a variety of torodial transfomers. They have a bunch at 30 or 32v starting from 10 VA.

AnTek Transformers product index

 

[thelenster]

That's what I suspected. Why not run them in parallel @ 6V? Much more standard, easier to procure a Xfmr at desired current. Also easier to see which tube is dead if the heater burns out(rare condition). Toriod transformers are superior for coupling, but costly. Plitron, in Canada is an excellent house dealing in toriods, but there are lots of other sources.
Just went to the AnTek link. Seems interesting but just wondering if they're marketing Chinese made stuff, or a true design house.
Regards
You don't need tight coupling, or regulation for heaters

 

[rsumperl]

Actually the tubes are 31LQ6's.

 

[quikie22]

try contacting them with the specs you need. Transformers and Power Converters From Avel Lindberg, Inc.

 

[smoking-amp]

Maybe one of these:
RT-202 - TAPPED OUTPUTS: 11VDC@4A THR

or two of these:
TR-36009 - 16vac ct 2.5a, 36vac ct 300ma, prim 110v or 220v,

 

[pieter t]

Toriod transformers are superior for coupling

Yes, and that is a major drawback of the toroidal power supply transformer.
For a power supply transformer we need pure inductive coupling of the 50 - 60 Hz line voltage to the secondary voltage(s) of the transformer. Coupling of higher frequencies (line pollution) is what we do not want. Electrostatic shields between primary and secondary sections can prevent high frequency coupling but in a standard toroid this is uncommon.
Besides toroids are very sensitive to low frequency line pollution (DC like) because the highly efficient (closed loop) core of the toroid is easily saturated, especially in standard transformers already approaching max T in normal circumstances. Where toroids excel is in low stray fields, but in well designed EI or (preferably) c-core transformers this can also be achieved.

 

[Tom Bavis]

Antek has a dual 15V, dual 30V, dual 32V, all at 100VA. $18 apiece. Hammond has a toroid in 15/30V, 80 VA, but it will probably cost twice as much.

 

[Tubelab_com]

I've looked and haven't seen any. Any suggestions besides eBay?

Look again! Antek has them in several sizes. Allied has 32 and 28 volt in several sizes. 28 is common.

Just went to the AnTek link. Seems interesting but just wondering if they're marketing Chinese made stuff, or a true design house.

Chinese made stuff that seems to work pretty good. I haven't blown one up yet. Thye don't seem to understand what is really needed for a tube amp though, and their OPT's don't cut it.

try contacting them with the specs you need. Transformers and Power Converters From Avel Lindberg, Inc.

Another good choice. I got some 24 and 36 volt toroids surplus a few years ago. I use one to light up the 35LR6's.