heater time

[poohjangnim]

Guys please help me.How can I make the heater time of my tube amplifier be lessen. I have a push-push amplifier with (1)5881-power amp, and (2)12ax-pre-amp.Right now the heater time is almost 5 minutes. There is 270pFarad across the Stand-by switch, anyone knows what is the purpose of this capacitor?

Thanks in advance.....

[drewl]

The cap is probably there to remove any "pop" you'd hear from switching the standby switch on.
As far as increasing the speed at which the tubes warm up.....that's a new one.....nobody I know has ever complained about that problem but 5minutes is way too long.
Did you build this amp, or is it a production model?
there maybe other issues as to why it's taking so long for the tubes to warm up.

[poohjangnim]

Thanks a lot drewl.

Yes I build this amp, my friend created the design by getting the different stage from different tube schematic.I put it in a small case, for mobility purposes. It is 20W amplifier in a small box, like lunch box.
You are right maybe there are other reason.
any more ideas please......

[The Tone God]

Without more information this is going to be all guess work. Measure your heater voltage. Check your heater wiring. Have you wired any tubes in serial or at the wrong voltage ? Are you sure the transformer can handle the current for the heaters ?

Andrew

[km-r]

^ +1

heater current.

or you could use your soldering gun to aid the heating up of the tubes...

[poohjangnim]

it has a 6.3 volts across, all tube in parallel including the lamp(6.3V ac). I see choke in some tube circuit, could a choke would be a help in this case

km-r.......Bro i try the soldering iron to heat it fast but it doesn't work, don't ever try it. learn from me......hehhehehe

[DougH]

Are you sure they are not heating up? Have you tried playing your guitar through it after a minute? Or are you just watching the filament glow?

[The Tone God]

Can you measure the voltage when you first turn the amp on with the tubes cold ? If it is low does it slowly rise as the tubes warm up ?

Andrew

[poohjangnim]

I measured it, I got 6.3 volts immediately after I turn on the power.Everything is fine after five minutes. I want to make it less than five minutes for the heater time.

[petemoore]

  A funky tube comes to mind, perhaps one of the tubes heaters is somehow on the 1/2 blink ?

[R.G.]

The 12AX7 and 5881 are specified for 15 seconds warmup time at 6.3Vac on the heaters if I remember correctly.

It is very likely that there is not a full 6.3V on your heaters somehow. Measure it at the tube pins, not at the transformer.

And measure ALL of the tubes. As an amp is normally set up, any one tube coming up slow will keep them all from coming up. the 12AX7 has two heater sections and if one is not wired correctly, one side will not come up at all. For use on 6.3Vac, both sections have to be paralleled and BOTH have to have 6.3Vac across them. You didn't tie 6.3V across pins 4 and 5 and ground pin 9 did you?

[poohjangnim]

For tube 12ax, 4 and 5 is shorted, so i can measure the 6.3Vac on the across pin 4or5 and pin 9.Does it matter which one is first connected? do I have make the 12ax first then 5881 from the transformer?

[R.G.]

For tube 12ax, 4 and 5 is shorted, so i can measure the 6.3Vac on the across pin 4or5 and pin 9.Does it matter which one is first connected? do I have make the 12ax first then 5881 from the transformer?

The order of connection does not matter. Just check each tube and be sure that 6.3V is getting onto the heater windings. For the 12AX7, clip one lead to pin 9 and the other to either 4 or 5.