6 volt LT at 2 amps

[Mark Hennessy]

Depends how big it is, but if you could make the top panel from aluminium, you might not need the fan. You could bolt everything to it, including a bridge rectifier and the transformer, and the heat is conducted straight outside. Would be a neat construction...

Just make sure it (or any other metal like your grille) is firmly connected to mains earth. If there's space, a fused IEC inlet is recommended.

[unrealdave]

Well I put my own bridge together and used a new regulator.  4700uf for smoothing and it works fine.  Drops from just over 6Volts to 5.15ish when its on load so should run my American sets fine, I've got some that use DE5 triodes as well, the sets are from 1 valve up to 4, so I think I should check the load resistance as I don't really want to go with much over 5V.  I guess that's why they have filament resisters

Mark - I take your point about getting hot.  I might use another box I've got - see the pics.  Its a bit bigger and obviously constructed to shed heat!  Not sure what it originally was though - says Cambridge instruments - DC range multiplier 3000v

All in all I think a duff regulator as mike suggested - I bought a bunch of them from china and now I don't trust them very much  

[ppppenguin]

A regulator like this shouldn't drop more than a tiny fraction of a volt when loaded. Something is still not quite right.

[unrealdave]

It drops about .8v when I put 2 * 10ohm resistors in parallel across it (so 5ohm) - I thought this was normal?

[pwdrive]

What regulator are you using?

Lawrence.

[ppppenguin]

Not normal at all. Some regulators will run quite high when totally off load but once you've got a small load on it it should drop no more than a few millivolts from there to full load. So try 100R load and see what happens.

If the voltage drops significantly from 100R load to 5R load then what could have gone wrong? One likely reason is that the troughs of the input DC are dipping below the dropout voltage of the regulator. As you increase the load the troughs get deeper as the reservoir cap discharges more before it gets recharged at the next peak of the mains. The remedy is a higher voltage transformer, bigger reservoir cap or possibly using lower drop (schottky) rectifiers.

[unrealdave]

What regulator are you using?

Lawrence.

LM338T

OK Jeff I will give it a go.

I did wonder about the transformer as it was not marked which secondary to which should be connected to double the output power so I guessed

[pwdrive]

Maybe post the voltages with the 5 ohm load connected.....The regulator output voltage, the regulator input voltage and the AC voltage input to the bridge rectifier.

Lawrence.

[ppppenguin]

If you connected the secondaries in parallel the wrong way round you'd know about it soon enough

If you connected them in series the wrong way round you'd get nothing out at all. But no smoke.

[unrealdave]

If you connected the secondaries in parallel the wrong way round you'd know about it soon enough

How's that?  Also if its bad then is there a way to check which goes were?