Hot PT

[richon]

Why would a power transformer with heater consumption of just 60% of maximum heater current from transformer... And everyother voltage measuring right get HOT

I mean hot hot

Is it just about to fail?

I use 2x 6L6 and 4x 12AX7
PT gives 690v 150mA, 6.3v 5A, 5v 3A

[M Fowler]

Wound improper.

[richon]

Wound improper.

So eventually it would die (soon)??

[M Fowler]

Maybe depends on how hot it is running.

Could smoke first then take it's last dying breath.

[Structo]

Does it get so hot that the power switch and standby switch toggles are too hot to touch?

That has always been my warning sign.

Do you smell anything strange when it gets hot?

Another thing to try is a different set of tubes, maybe one or more is drawing a lot of current?

I suppose you could hook up a Ammeter in series and see how much the amp is drawing, or use a Variac so equipped.

Trying different tubes would be the easiest experiment.

On my 100w Dumble with Twin Reverb iron from Magnetic components, it gets pretty hot (although not burning hot) and I am no where near maxing it out.

Another thing you can do is put a fan in the chassis.
You can get real quiet ones like the muffin fans used in computers.
The trick is not to blow cool air on a small area of the power section as that will cause uneven heating and cooling.

[heisthl]

Measure the heater voltage to make sure it's not being pulled down somewhere. If it's alright, and your B+ also measures alright, It could be that it's normal - on our small amps the 6L6 tubes are right near the power transformer and the combined heat does make the chassis, transformer body and any switch handle in the area very hot to the touch after the amp has been running for an hour or so.

[martin manning]

150mA and 345VAC seems a little light for a 2x 6L6 amp...

[richon]

I have 458VDC in the first filter (didn't Get the "light" sentence, sorry)

[richon]

Measure the heater voltage to make sure it's not being pulled down somewhere. If it's alright, and your B+ also measures alright, It could be that it's normal - on our small amps the 6L6 tubes are right near the power transformer and the combined heat does make the chassis, transformer body and any switch handle in the area very hot to the touch after the amp has been running for an hour or so.

How much heat is still "normal" then?

Should we measure in C or F for reference?

[ToneMerc]

150mA and 345VAC seems a little light for a 2x 6L6 amp...

My thoughts exactly. It would be nice to know what exactly is " hot hot" though, is it 110 or 150 degrees.

TM

[Structo]

As a comparison, the Brown Note D'lite 44 (2x 6L6, 3x 12ax7) power transformer has these specs.

Heyboer

325-0-45-325 @ 300ma

6.3vct @ 6A

5v @ 3A

[richon]

But each 6L6 uses 38mA and each 12AX7 only 1mA

So, 150mA for B+ would ve enough , right?

[Structo]

Could be the heater current as well.

But, you really need to measure the current draw on the different circuits to figure out if one is drawing too much.

Try a different set of 6L6 to see if anything changes.

What amp is this?
4x 12ax7, does it have reverb?

[M Fowler]

Most likely something is touching the chassis causing excessive current draw.

[ToneMerc]

But each 6L6 uses 38mA and each 12AX7 only 1mA

So, 150mA for B+ would ve enough , right?

For class AB fixed bias, zero signal plate current is at least 2.5 times that much. A stock Fender Bassman PT (4-12AX7, 2-6L6) is rated typically around 240mA on the HT winding.

TM