First Tube Amp Help

[disraeligears]

Hi,

I just finished building my first amp (Fender Champ.) My power tube won't light up. My preamp tube is all black (says "U.S. Navy/ Army 1944" on it) so I don't know what's going on in there, and the rectifier is a Sovtek Solid State plug-in.
I don't understand how the heaters couldn't be getting power; the wire leads directly from the lit-up pilot light to the heater pin, and the other heater pin is clearly wired to ground. I tried another tube and it didn't light up either. Any suggestions?

[Regis]

Check the voltages on the power tube to see what is awry.

[tubeswell]

Hi disraeligears

Welcome to the forum

have you got the fuse plugged in?

1st with all the tubes out, carefully measure the VAC voltages at your power transformer secondary windings. You should get a high voltage AC on your HT secondary (4 and 6 on your rectifier socket) with the centre tap grounded. You should get 5VAC on the rectifier filament pins (2 and 8 on the rectifier socket), and 6.3VAC on the heater winding.

Then check the heater pins on all the empty tube sockets for 6.3VAC

If you get that, then switch everything off and put your rectifier in, and now measure the DC on pin 8 of the rectifier socket. It should be high and climbing if it is working. (If it is, then switch it off before it gets too high)

Report back

[erndawg]

Since the pilot light is illuminating, you know your fuse is okay. If you are using solid core wire from the pilot light to the 6V6 socket, it might have broken inside the insulation. Also, triple check your solder joints. You should have 6.3 VAC between pins 2 and 7.

On the old 5C1, pins 1 and 7 go to ground. Note that pin 1 to ground is not really necessary. It used to be tied to the old metal 6V6s. Pin 2 goes to the pilot light, which is the 6.3 VAC high side.

The 5E1 has pins 1 and 2 tied to ground. Again, pin 1 is the metal 6V6 connection. Tie pin 7 to the 6.3 VAC high side via the pilot light.

Bottom line, you should read 6.3 VAC between pins 2 and 7 for the heater supply on the 6V6. Make certain you are reading the right pin numbers. A lot of builders make that mistake.

Your preamp tube must be a metal tube 6SJ7 if you can't see inside it. I always liked pentodes as the preamp tube in a Champ.