[dude_500]

I have a 10 volt hammond transformer that puts out about 11.5 volts AC without load on my meter.

I was originally going to rectify it voltage doubling, then feed it into a 10,000uF capacitor, then run it into an LM317 voltage regulator. I believe I burned out the regulator, and it also got extremely hot from dumping 7 volts off my load.

Is it ok to drop the regulator, and go to a standard full-wave rectifier? This gives me 7.2 volts unloaded at the end of the capacitor. It is likely very rippled though, will that be a bad thing?

I'm building the phono amp that is on the ecp.cc website.

 

[digger945]

The 317 should be able to easily handle a 35V+ input to output difference, at the rated 1.5A load.
I assume your shooting for about 6.3V for heaters, correct?

 

[n_maher]

It would be helpful to know the current draw of the heaters you're trying to feed.

 

[dsavitsk]

Quote:

Originally Posted by n_maher /img/forum/go_quote.gif It would be helpful to know the current draw of the heaters you're trying to feed.

4x 6GK5 + 2x 6T4. About 1.2A IIRC.

Quote:

Originally Posted by dude_500 /img/forum/go_quote.gif I have a 10 volt hammond transformer that puts out about 11.5 volts AC without load on my meter. I was originally going to rectify it voltage doubling, then feed it into a 10,000uF capacitor, then run it into an LM317 voltage regulator. I believe I burned out the regulator, and it also got extremely hot from dumping 7 volts off my load.

A big heatsink is fine to use. The LM317 should be thermally cut off, so if it gets too hot, it will stop working but will generally protect itself from damage.

Under load, the transforer will run close to 10.5V I think. With a 2V diode drop, that is about 12VDC. To regulate this, you need a heatsink that can dissipate 8 to 10W. Not trivial, but not that bad, either. I usually just use the case -- assuming the case is metal and big

Quote:

Is it ok to drop the regulator, and go to a standard full-wave rectifier? This gives me 7.2 volts unloaded at the end of the capacitor. It is likely very rippled though, will that be a bad thing?

7.2V unloaded is likely going to drop quite a bit loaded. You can try it with a resistor that simulates the 6 heaters to see how much (R=V/1=6.3/1.2~5 ohms - use 12W at least). You can also use a LM317 as a CCS to simulate the current draw and see if the supply can keep up, or what sort of dropping resistor you need.

For unregulated, my guess is that you'll want at least 2x 47000uf with a small resistor in between them for decent enough ripple reduction.

Best solution here really is perhaps some voltage dropping resistors before the rectifier, a big cap, a regulator, and a big heatsink. Also, instead of the big resistors, try using 1 or 2 diodes in series to drop a few volts. Same heat, but maybe easier to do. You do need larger than 1A diodes here. 2A min, and 3A is better.

You could use a 12.6V supply and feed the two 6T4's in series and each pair of 6GK5's in series. It would cut the current draw in half. I don't think the 10V transformer will keep up, though.