Tube newbie problem

[Calamaro]

Just assembled a MD X10 clone kit.
Circuit is designed for 6DJ8/6922/ECC88 but I have two russian 6N1P. I know they require higher current: transformer in power supply is 12VAC, 45w.
When I switch on the buffer, led is ok, tubes became hot but I see no light from them. If I connect the buffer to my amp I can hear just a hum.
I really can't understand if I did something wrong in assembling parts (but it was very easy and clear), if tubes are wrong or they doesn't work at all.
Sorry for my dull question but please help

[SY]

A schematic or link to one would be helpful.

[pjp]

wired the heaters in series instead of parallel ?

[Calamaro]

Schematics.

[Calamaro]

This was an unpopulated ready pcb.
Please see attached picture for populated pcb, with power supply, connectors and case.

[Calamaro]

Finished preamp. I like it so... I can't accept it doesn't work!
The good, heavy metal case comes from an old device: I made new front and back panels. Cover is white spray painted.
Tube covers are half tea filters

[SY]

Measure the heater voltages, the B+ and B- (carefully!) and the voltages at plates and cathodes. If both channels are nonfunctional, it's most likely a power supply issue.

[netbug]

I'm also very new to tube amps, so I may be missing something. But I don't see how a 12vac supply is going to get anywhere near the voltage to power a 6DJ8 (90volts) let alone a 6N1P (250volts).

[leadbelly]

Originally posted by netbug
I'm also very new to tube amps, so I may be missing something. But I don't see how a 12vac supply is going to get anywhere near the voltage to power a 6DJ8 (90volts) let alone a 6N1P (250volts).

1) The ECC88/6922's have been reported to work OK at lower voltages.

2) It probably uses voltage doubling to get a half-decent B+. My Scott Nixon TubeDAC uses the same technique.

[ChrisA]

Originally posted by netbug
I'm also very new to tube amps, so I may be missing something. But I don't see how a 12vac supply is going to get anywhere near the voltage to power a 6DJ8 (90volts) let alone a 6N1P (250volts).

It looks like there are two voltage doublers on the power supply. It might be running the tubes between +24 and -24 for a 48V total. But I wonder why when there is AC mains available it is so easy to get all the power you'd need. OK, "Why" is not the question.

What's wrong it? My guess is you don't have the clean DC power you need. Check the outputs from both of the voltage doublers and see if there is ripple. You can pull out the tubes and check at the tube socket with an AC voltmeter or scope. A bad solder joint on a filter cap or a bad cap or a bad or poorly solders diode can cause this.