Filament Voltages

[shagual]

Hi,

I guess this my first post. First I want to thank all the members on this board for your valuable input, it was a great help building my 5E3.

I've got 2 question for you guys.

I've been using 2 zeners & 1 NOS rectifier to drop B+ voltages to around 360DC, that is ok. Bias is 40mA.

I've been checking the filament voltages and i'm around 5.9 AC, I used 2 100ohm resisitors from the pilot light to ground. I just followed the schematic I had.

5.9 on the filaments is maybe a bit low, will removing the 2 resistors higher the filament voltages?

I guess , I'm not sure.

Thanks a lot guys.

[MWJB]

5.9VAC is low for the filaments.

The 100ohm resistors should not be loading down the filament circuit, so removing them will just make the amp hum.

40mA at 360v, perfectly feasible but out of interest, what value cathode resistor do you have at the 6V6s?

What PT primary taps do you have, what's actual wall AC?

[shagual]

We are getting around 234 AC from the wall, I connected the PT on the 240tab.

Connecting it to the 230tab will raise the filament voltage, but will impact the B+ as well.

So connecting the PT to the 230 Tab and adding another Zener will give me better voltages on the heathers and keeping the B+ around the same?

I'm using the 270ohm 5watt on the cathodes, might replace it with a 250 ohm.

[MWJB]

270ohms will be fine.

Yes, try the 230VAC tap & correct B+ with another zener if necessary (e.g. if you're getting well over 380vdc, to ground, at the 6V6 plates.)

A 5E3 slightly over voltage at the B+ will still sound "ball-park", a 5E3 with nice low B+ but undervoltage heaters will not.

[shagual]

Thanks MWJB,

I'm now measuring 6.3 on the heathers.

These are my last measurements with 230ac from the wall, normally these go up to 235ac.

b+: 358dc
b+1: 325dc
b+2: 232dc

V2 12AX7
pin 1: 140
pin 3: 1.23
pin 6: 180.

Bias measured with biasmaster: 39.3 and 40.4. That's 97.2% matching.

Values are well within range comparing to the customshop 57.