Silvertone Meteor 1430 Amp

[angelodp]

Ok, its all wired up and safe.... no voltage on chassis. It sounds very good with original speaker (now repaired).

I have not slipped in the extra dropping R

Here's what I have at 110v on the Variac.

35W4 pin 7 - 132V

50C5 pin 7 - 129V

12AU6 pin 5 - 69V

So these are high especially the plate on the 12AU6

Looks like I should add that 50ohm 5watt dropping R... yes

Or, should I increase R3 to 560K?

Heaters at 110V

12AU6 14.5
50C5 51.6
35W4 38.8

Added the 5w 50ohm in series

now still 110V

12AU6 13.3
50C5 46
35W4 35.4

Seems like I need to keep going here if I want to run at wall voltage... Replace the 150 ohm setup with
300ohm 5w - a guesstimate

checking 100ohm R might be toast

[angelodp]

100 ohm Resistor is ok, its 105 ohms. I inserted the 50 ohm in line with the 100ohm at the top of that resistor, should it be at the bottom between the 100ohm and the first heater of the 35W4?

[martin manning]

Looked like it would be easiest to put it between the fuse holder and the 100Ω, and that's probably the best place for it. You could check the current using one of the dropping resistors, but you'll have to take what you get for the voltage across each tube.

[angelodp]

Martin, the 100ohm is not connected to the fuse??

[martin manning]

I'd put it where this bare wire is.

[angelodp]

The amp is not wired like that after I followed the schematic supplied by Steve. That bare wire is not there now. The layout I supplied is how its wired. I simply have the 50ohm in series with the 100ohm now

I now have on heaters

110V

35.7
46.2
13.2

120v
38.7
50
14.5

The 50C5 is a new tube the others are original, could this be where I am having a discrepancy.

[martin manning]

Could be. What is the VAC across the 50Ω? Divide that voltage by 50 to get the current. And the 50Ω should only be in series with the heaters.

[angelodp]

VAC on 50ohm is 11.37 so Current is .2274

[angelodp]

Ok so if only in series with the heaters then I need to change its position to the bottom of that 100ohm I believe.

[martin manning]

Ok, once you get that in the right place check the current through it again. You want 150 mA when the line in is 120VAC.

[sluckey]

Replace the red wire between the 100Ω resistor and pin 4 of the 35W4 tube with the 50Ω resistor. Now monitor the voltage across the 100Ω resistor. When you have 15V the filament circuit will be right. You may need to experiment with different value resistors to get the 15V across the 100Ω resistor. Do all this with the variac set for 120V into the amp power cord.

This ain't a collector's showpiece. Voltages only need to be in the ballpark.

[angelodp]

Made that change so the 50ohm is in series only to the heaters. I do think that the older tubes are drawing more current.

Here is what I have

At 110V & 120

13.2 14.9 12AU6
36.3 39.6 35W4
47.41 51.5 50C5

Not sure I can get this balanced for the older tubes as well as the 50C5

Amp sounds good and low low noise. Maybe try some newer tubes.......

thanks for the help Martin

[sluckey]

The tube filaments are in series so the same current flows through every tube. Getting the 'correct' voltage drops at every tube is not as important as setting the current to 150mA. When you get 15V across that 100Ω resistor, the filament current will be 150mA and everything will be fine. It's important to let the tubes warm up for a few minutes before measuring the 15V.

[angelodp]

At Line voltage 120V, I am seeing 16.8V across the 100ohm resistor. If I back off variac the voltage to 110 its closer to 15v. So right now I have 150ohms on the filament string, keep going?

[sluckey]

I have a good supply of power resistors so I would keep fine tuning to get 150mA. I would replace the 50Ω with a 100Ω (total of 200Ω) and see where that lands. But if I didn't have plenty of resistors to experiment with I'd probably call it done.