Hello All,
Now that I have all the paper and electrolytic capacitors replaced, I notice that there are pretty much, no low frequencies and even when the volume controls are turned all the way down, there's still something being picked up. All the shielding seems good yet it's picking up something. Maybe it needs that small capacitor that connects to the line cord. I'll double check to see if it has one. If it doesn't I'll add it. That will take care of the shielding problem, but what's usually the problem if there's no low frequencies. There's no schematic available for this late 30s amplifier anywhere I can find.

Thanks,

Dave

Hello Again All,
I tried a 2-Way HiFi speaker and voila, the sound is fantastic from this amplifier. The old speaker I was using to test the amplifier was pretty bad sounding. I also added the line cord capacitor and it helped a bit, but there's still a little pick-up from something. I remember from a problem I had with a radio that sometimes the rivets that attach sockets, which use a terminal connected to them sometimes have a poor connection, maybe due to age. I'll check things over one last time and then give up because it works fine.
That mike input section is really sensitive. If I turn up that volume it will whistle pretty loud, with nothing connected to it and the bottom cover off. So I took the mike pre-amp tube out.

Dave
:Hello All,
: Now that I have all the paper and electrolytic capacitors replaced, I notice that there are pretty much, no low frequencies and even when the volume controls are turned all the way down, there's still something being picked up. All the shielding seems good yet it's picking up something. Maybe it needs that small capacitor that connects to the line cord. I'll double check to see if it has one. If it doesn't I'll add it. That will take care of the shielding problem, but what's usually the problem if there's no low frequencies. There's no schematic available for this late 30s amplifier anywhere I can find.
:
:Thanks,
:
:Dave
:

Normally the Mic input gets grounded out with no Mic jack plugged into it. Check the female input jack. The bottom sometimes needs to be on. It too is a shield.

Warren,
This is a very "ancient" mike jack. 3 holes in a piece of phenolic material. There's no bottom that I can find. The assembly with the bias battery is very sensitive. When I have my hand near it, without touching it, it hums loudly (Pick-up hum). If I turn up the volume with nothing attached to it it makes a very shrill loud sound that's ear piercing. So I'll keep it turned down, or I have the tube unplugged.
I'll look for that "bottom" and see if I can find it.

Thanks,

Dave
:Normally the Mic input gets grounded out with no Mic jack plugged into it. Check the female input jack. The bottom sometimes needs to be on. It too is a shield.
:

Anytime there is an open input it will pick up hum and almost anything else. This may have had a shorting plug for when Mic not in use. Ground the input to its own ground point. See if it stays quiet then.

Warren,
That could be that it had a shorting plug. Anyway,
when I put the bottom cover on the amplifier, when I turn up the mic volume it just hisses loudly. The hiss gets louder as I turn up the volume and decreases as I turn it down. At zero, there's no hiss at all. No more pick-up through the mic pre-amp. I still hear a tiny bit of something with all volumes all the way down to zero,but it's very faint.
It's pretty good now. So I'm going to leave it as it is for now.

Thanks,

Dave
:Anytime there is an open input it will pick up hum and almost anything else. This may have had a shorting plug for when Mic not in use. Ground the input to its own ground point. See if it stays quiet then.
:

My bad. I thought you said 6N7G, but you said 6N6G. I've already bought some of those and put them to use. Decent sound. I'd like to get ahold of some 6N7Gs, though. Interesting to experiment with. Not a high priority, though. Someday.

Regarding noise pick-up, purchase a couple of long tight-wound springs, or some mesh shielding. Put these over the 6J7 and 6C6 grid wires. Ground to chassis. Should remove a lot of noise. You can also do things like wrap 5 to 10 turns of insulated wire around the grid capacitor of each stage, and ground this to the chassis. Helps to shield out noise pick-up.

T.

Thomas,
There is a 6N7 in this amplifier. I think it's being used as a mixer tube. Tube line up again: 6J7, 6C5, 6N7, 6N6, 6N6, 5V4. The 6C5 is like a 6J5. The 6N7 is two triodes that have a single cathode that they share. They have separate grids and plates. The 6J7 is like a 6K7.

Dave
:My bad. I thought you said 6N7G, but you said 6N6G. I've already bought some of those and put them to use. Decent sound. I'd like to get ahold of some 6N7Gs, though. Interesting to experiment with. Not a high priority, though. Someday.
:
:Regarding noise pick-up, purchase a couple of long tight-wound springs, or some mesh shielding. Put these over the 6J7 and 6C6 grid wires. Ground to chassis. Should remove a lot of noise. You can also do things like wrap 5 to 10 turns of insulated wire around the grid capacitor of each stage, and ground this to the chassis. Helps to shield out noise pick-up.
:
:T.
:

Ya. They can be used as a driver or as an output. Since there are two separate triodes, you could use one tube for push-pull, or two for even more power. Kinda cool. I need to buy some. ...And that's why I have junk, because I always have to buy little curiosities.

I actually have an amplifier (Webster Chicago wire recorder) that uses one 6SN7 as a push-pull output, and it works fairly well, but I want to try it with a 6N7 or two, especially in G style, since they look so cool that way.

T.

:Warren,
: That could be that it had a shorting plug. Anyway,
: when I put the bottom cover on the amplifier, when I turn up the mic volume it just hisses loudly. The hiss gets louder as I turn up the volume and decreases as I turn it down. At zero, there's no hiss at all. No more pick-up through the mic pre-amp. I still hear a tiny bit of something with all volumes all the way down to zero,but it's very faint.
: It's pretty good now. So I'm going to leave it as it is for now.
:
:Thanks,
:
:Dave
::Anytime there is an open input it will pick up hum and almost anything else. This may have had a shorting plug for when Mic not in use. Ground the input to its own ground point. See if it stays quiet then.
::
:
Dave:
From my radio days, I remember some reel-to-reel tape machines that had a microphone input and preamplifier that would make all kind of noise if the mike jack wasn't loaded or shorted. We used a higher level line input that was connected to the amplifier after the mike preamp, and had all kind of trouble until we learned about unloaded microphone inputs.
Lewis

Gentlemen,

Is it possible (or impossible) that the amp may have been made for Lafayette by Gibson? I seem to recall a late Gibson guitar amp that used a couple of 6N6s in pushpull, a 6N7, 6C5 and etc. Maybe late 30's?

Clifton

::Warren,
:: That could be that it had a shorting plug. Anyway,
:: when I put the bottom cover on the amplifier, when I turn up the mic volume it just hisses loudly. The hiss gets louder as I turn up the volume and decreases as I turn it down. At zero, there's no hiss at all. No more pick-up through the mic pre-amp. I still hear a tiny bit of something with all volumes all the way down to zero,but it's very faint.
:: It's pretty good now. So I'm going to leave it as it is for now.
::
::Thanks,
::
::Dave
:::Anytime there is an open input it will pick up hum and almost anything else. This may have had a shorting plug for when Mic not in use. Ground the input to its own ground point. See if it stays quiet then.
:::
::
:Dave:
:From my radio days, I remember some reel-to-reel tape machines that had a microphone input and preamplifier that would make all kind of noise if the mike jack wasn't loaded or shorted. We used a higher level line input that was connected to the amplifier after the mike preamp, and had all kind of trouble until we learned about unloaded microphone inputs.
:Lewis
:
:

:Gentlemen,
:
:Is it possible (or impossible) that the amp may have been made for Lafayette by Gibson? I seem to recall a late Gibson guitar amp that used a couple of 6N6s in pushpull, a 6N7, 6C5 and etc. Maybe late 30's?
:
:Clifton

Gentlemen,

OOPS! Don't know how 'late' got in the message...senior moment possibly??

Clifton

:
:
:::Warren,
::: That could be that it had a shorting plug. Anyway,
::: when I put the bottom cover on the amplifier, when I turn up the mic volume it just hisses loudly. The hiss gets louder as I turn up the volume and decreases as I turn it down. At zero, there's no hiss at all. No more pick-up through the mic pre-amp. I still hear a tiny bit of something with all volumes all the way down to zero,but it's very faint.
::: It's pretty good now. So I'm going to leave it as it is for now.
:::
:::Thanks,
:::
:::Dave
::::Anytime there is an open input it will pick up hum and almost anything else. This may have had a shorting plug for when Mic not in use. Ground the input to its own ground point. See if it stays quiet then.
::::
:::
::Dave:
::From my radio days, I remember some reel-to-reel tape machines that had a microphone input and preamplifier that would make all kind of noise if the mike jack wasn't loaded or shorted. We used a higher level line input that was connected to the amplifier after the mike preamp, and had all kind of trouble until we learned about unloaded microphone inputs.
::Lewis
::
::
:
: