Mesa B+ and Power Switching

[Buck455]

Hi all,

I'm trying to find the right power transformer for my current build (modified Mesa Lonestar Classic/Fender Twin), and I have a few questions about the power switching Mesa uses (i.e. Bold/Spongy).

I assume the 6.3V and 5.0V heater supplies, 12V ACC supply, and 345V B+ I see on the lonestar schematic corresponds to the 120V AC fed into the lower winding (Bold) primary. If that's the case, the heater and Acc voltages would be reduce by the same percentage as the B+ when switched to spongy. Obviously Mesa is selling a good product, but what would you all consider the acceptable range of heater supplies for the 6.3V and 5.0V.

On a related note, can anybody tell me the B+ voltages they see on a Dual Rectifier or Lonestar Classic in both "Spongy" and "Bold" power levels? Just trying to get a feel for what I'll get if I order a stock replacement or Mercury replacement power trans for these. I did talk to Mercury and got the specs, but I only have the wiring diagrams, not the turns ratios.

Thanks in advance!

Buck

[GainFreak]

According to their patent in Spongy mode you have 25% reduction of mains voltage which is beyond the +/-10% range for heaters.
If you read the forums you'll learn it's barely used, even Mesa advises to use Bold most of the time.

[GainFreak]

Here's what I found in a forum about Triple rectifier:

My Triple Rectifier's plate voltage is usually in the 465 area while in the Bold/Silicon Diode mode and the Bias will be right at 25 mA w/ Mesa spec tubes. If I switch it from Bold to Spongy and keep the Silicon Diodes, the plate voltage drops to around 420 and the bias will drop down to about 18 mA. If I swap back to Bold, but I option for the Tube Rectifiers, the plate voltage will be in the 395 to 400 area and the bias will be at about 15 mA. If I swap down to the Tube Rectifiers, while still in Spongy, the plate voltage will drop to it's lowest point to about 350 to 360 and the bias will be at about 9 or 10 mA.

You loose power and headroom if you take the course I described above. If you go in the opposite direction, you gain more power and headroom.

Bold/Silicon Diode - Highest Power
Spongy/Silicon Diode
Bold/Tube
Spongy/Tube - Lowest Power