Lifco model 1000 , need schem

[techno57]

I have an oldy , a Lifco company , model 1000 , all tube amplifier .

I want to know the 2 big tubes that goes in , because all writing on them are erased.
Only marking left is Westinghouse on it. I have all other smaller ones marking ok, except these 2.

Amp was made in Canada in early 70s.

I don't have any schem.

Any info welcome.

TIA





Gaëtan
ATV (aka: Techno Logik)
Terrebonne , Que.

[Enzo]

I don't know Lifco, maybe someone else does.

Are the mystery tubes octal based? (8 pins with the fat post in the center)

If so, my first thought would be 6L6s. SO look at the wiring. You have the two tubes - does the socket wiring look similar on both, or is one wired completely different from the other.
If there is a pair of power tubes, is there a wire from pin 3 of each running into the output transformer? Or some other pin. Is pin 8 grounded? How about pin 1? Are pins 1 and 8 wired together or is there something different going on at pin 1? If pin 8 is not grounded, then does it have something like 200-500 ohms to ground? That resistance would mean cathode bias, while grounded pin 8 means fixed bias... most likely.

If pin 8 is grounded, then with the tubes removed, is there some negative voltage on each pin 5?

Look at pin 4 of each. Is there a simple wire connecting pin 4 to the other pin 4? Or is there a resistor to each pin 4? A resistor of probably 1000 ohms or less.

Is there anything wired to pin 6?

I asked if the two large tubes were wired similar, thinking there was a pair of output tubes. But it is also possible there is a single output tube and a rectifier tube. The output tube would have wires running to the output transformer, but a rectifier tube would have four wires running directly to the power transformer. That would be a pair of probably red wires to pins 4 and 6, and a pair of probably yellow wires to pins 2 and 8.


Chances are the circuits in this amp are just like the circuits in most other amps. Large tubes are usually 6L6, especially on older amps, but the smaller 6V6 would not be uncommon. EL34 would be a lot less common in my view, but not unheard of. Outside of AMpeg, we see darn few 7027, and there are other various octal power tubes. if it is not wired for the basic 6L6 or 6V6, then the wiring would likely suggest what tubes it wants to see.

[techno57]

Yes , tubes are 8 pins with big key in center.
An older tech respond to me in another forum but this was by heart and memory , he does not have any schem , so cannot confirm 100% his reply.
He says it uses 6V6 , but all 6v6 I'm checking seems a little shorter then the one I have in the amp. It is shorter by almost 1 inch. That is why I'm not so sure of his reply.
Before buying new tubes , I want another advice.
Can we subs these tubes ?(6v6 and 6L6)
thanks

[Mark Hammer]

Check here for leads: Made In Canada

[techno57]

Thanks Enzo
I've check all about your reply and:
yes mystery tubes are octal,
yes the socket wiring is similar for both,
yes pin 3 of each runs into the output transformer,
yes pin 8 is grounded,
yes there is resistor to each pin 4 (470 ohms),
no there is nothing wired to pin 6,

Do you suggest it is a wiring for 6L6 ? or for 6V6 ?
To be certain before buying those tubes is my priority.
Thanks to confirm.


Gaëtan
ATV (aka: Techno Logik)
Terrebonne , Que.

[Enzo]

OK, turn the amp on with the power tube sockets empty. measure the B+ voltage on pins 3 and 4 of the sockets, and the bias voltage on pin 5 of each socket. That might be revealing.

Oh wait, you still have the power tubes, but don;t know what they are? Provide a photo, or measure them. 6L6s have glass that is wider than the plastic base, while 6V6 has glass the same diameter as the inside of the plastic base. 6V6 is shorter as well.

6V6


6L6