Premier 120

[RightLurker]

I have an old Premier 120 that I'm going to try and bring back to life. It has true point-to-point wiring, and the only schematic I can find for it doesn't match the amp, although the schematic does show the correct tube compliment (1 x 5Y3; 2 x 6V6; 1 x 12AT7; 3 x 12AX7). Right now I'm just trying to figure the circuits out. There are two potentiometers in the amp that have me stumped. I'm going to try and attach a photo (or photos) that shows the pots. One is in the upper right of the chassis, and appears to be wired into the filament circuit.

The other is in the lower left, and the shaft goes through the chassis and has an adjustment screw protruding on the tube side. The left tab of this pot goes to The center tab goes to a 6K2 resistor to ground. The right tab goes to a 4M7 resistor to pin 2 (grid) of a 12AX7. I think this 12AX7 is in the tremolo circuit.

Does anyone know what these two pots do?

[RightLurker]

Sorry, I mangled the information about the second pot in my original post. The left tab goes to pin 3 of the 12AT7. The center tab has two connections - one goes to a 6K2 resistor to ground, the other goes to a 4M7 resistor to pin 2 of a 12AX7. The right tab goes to pin 8 of the 12AT7.

[Structo]

The pictures I see show the amp on the bottom of the cab then a control panel at the top of the cab.

Do you have the whole amp?

http://uv201.com/Audio_Pages/premier_120.htm

[RightLurker]

Structo -

I have the whole amp (including the red, brown and yellow knobs!) An "umbilical cord" connects the panel to the chassis. The main chassis sits on the shelf, and the panel screws to the top. The amp in the photos you attached is a new version of the one I have, I think.

Here is my cabinet, with the chassis removed, and some other shots as well. Hope this works.

[RightLurker]

Here's the back of the cabinet.

[M Fowler]

Here is four different schematics

Mark

[RightLurker]

Thanks, Mark. The amp I have must be in there somewhere!

[Structo]

Can I see a shot of the top of the chassis.

What output tubes are in your amp?

From the little bit of reading I did on these amps, they seem to be prized by the harp players.
Cool looking retro amp.

Probably only need to replace that one cap can and then any dud tubes and you will be good to go.

Oh, also install a three prong power cord.
Is that white zip cord attached to the rectifier socket the power cord?
You will need to drill a hole and put in a strain relief and the new three prong cord.
Attach the ground wire to it's own screw and nut through the chassis.

I can't tell which one it is but there is also a .02uF death cap or two from the primary side to chassis ground.
That needs to be removed to avoid a short to the chassis in the event that fails.
A

[RightLurker]

Structo -

The amp uses two 6V6s. The amps are sought after by harp players. If I understand what I'm looking at, the input 12AX7 is grid leak biased, and that may account for the desirable "harp tone." I'm going to leave the can cap in place and put new caps in on terminal strips. I did that with a Vox Cambridge Reverb, and worked out well - and there is a lot more space in the Premier. The zip cord is indeed what someone put in as a power cord. A three prong power cord will definitely go in, and the "death caps" are coming out.

I still don't know what the two pots in the chassis do - I'll figure it out, though.

I'm posting some pictures of what I think you wanted to see - if it's not, let me know and I'll post what you'd like to see.

Many thanks.

[martin manning]

I'm going to leave the can cap in place and put new caps in on terminal strips.

You might take a look at Antique Electronic Supply and see if you can match the can cap. They are reproducing the old Mallory units.

[rhinson]

looks like the pot in the lower left is the "trem beat control" . looks like the bigger one might be a hum balance since it looks connected to the heaters. rh

[Structo]

looks like the pot in the lower left is the "trem beat control" . looks like the bigger one might be a hum balance since it looks connected to the heaters. rh

This ^^^^

Adjust beat control for best tremolo sound and the hum balance pot for lowest audible hum.

That is, once you get everything working.

[RightLurker]

Thank you both rhinson and Structo. Will do. I looked at Antique and didn't see the right cap, which is 40/10/10, although I considered using a cap with slightly higher values.

[Structo]

You could use this one and just not use one 10uF section.

Normally I would say go to the next common value like a 40, 20, 20 but if you are going to use this as a harp amp you may want to keep the low filtering to keep the same mojo.

http://www.tubesandmore.com/scripts/fox ... 0-10-10-10

[martin manning]

There are several ways to do the cap... You could get say a 20/20, parallel them together to make the 40, then put a couple of 10's on a terminal strip under the chassis. I really don't think a 40/20/20 would be out of line though, and the tolerance on those parts was typically large, note the current units are spec'd at +50%.