Newcomb P-10-A

[Blind Lemon]

Anybody got a schematic hidden away?

I found a fuzzy one that wasn't a lot of use. I am in the process of drawing it out, but a few things like the tone stack doesn't look right.

If we can't come up with one I'll post mine for the library.

BL

[sluckey]

Maybe this can help you draw an accurate schematic. Don't trust it completely though. The bottom 6V6 is missing a grid return resistor!

[Blind Lemon]

Thanks Steve, I think thats the one I found before.

[kagliostro]

This isn't much more better, may be a bit more readable



Franco

[sluckey]

Which tubes are in your amp?

Here's a similar model number but different tube compliment...

[Blind Lemon]

6v6, 6SC7, 6SQ7, 6x5GT

Kag. That is a little more readable. Thanks

[HotBluePlates]

... a few things like the tone stack doesn't look right. ...

The tone controls are probably mostly-right.

RV46 looks like your Treble tone control, and is basically the same as a tweed Fender single-knob tone control.   It looks like a 0.005µF cap to ground and 350pF/0.00035µF for brightness.

RV54 looks like your Bass tone control.  If this pot is rotated for minimum resistance, all signal is cut by the two resistors above it, except for whatever is allowed to bypass the upper resistor due to the Treble control's position.  As the Bass control's resistance is increased, the 0.01µF cap comes into play and decouples the lower resistor from ground at low frequencies. Highs can still pass through the cap and be attenuated as much as before, so overall it sounds as if bass is being increased.

I can't really make out the two resistors in the tone circuit, but might they be ~560kΩ and 18kΩ?  If so, they would cut overall signal to 1/30th the level of the input, and it would make sense that the 6SF5 (or 6SQ7) would have a gain of around 30 after the effect of being in the feedback loop...

[Blind Lemon]

The resisters in the tone stack are 56K and 39K.

[HotBluePlates]

Ah, thanks.  560kΩ (yellow band rather than orange) and 39kΩ would probably make more sense, but I can't argue those are the correct values.  Probably a good chance that if everything looks equally-old that what's in your amp is original.

[Blind Lemon]

Got it up and running. More to come.

[eleventeen]

In 1982 I moved to LA and went to work as a tech in a company called Audiotronics, North Hollywood, CA. They made those indestructible record players for schools and probably every school in the known universe had one or ten. Other makers were Califone and Newcomb. I am not sure if Newcomb ever made mechanical record players, thought they only made (electronic) amps.


Anyway, after a while I moved to a different department where worked a very old, wonderful guy whom everybody loved because he was the nicest guy in the universe. His name was Don Newcomb. I never asked if he was connected to Newcomb Electronics because I did not know of Newcomb Elec at the time.


He is definitely no longer living, and he is hard to search for since there was a famous baseball player named Don NewcombE.

Random anecdote.