The Ballzz wrote:I was going by what I supposed were the voltages shown on the hand drawn, 1985 print. Luckily, a friend has a very lightly used one of these amps, still all original, including the tubes. He bought it new. I will check voltages, etc. before I make up a BOM.
The hand-drawn schematic shows the PT secondary at 300-0-300, and 70mA.
Yes, you are indeed correct sir. My concern or questions surrounded the other numbers that are near the upper right above the scren feed which appears to be 392>357, as well as some others that give two numbers. Should I assume that these are unloaded(no tubes) and loaded readings? What else might these numbers mean or signify? Just want to make sure I don't end up a tad shy on the B+ voltage.
The higher number is the DC voltage with no signal and the lower number is the voltage at clipping. Marshall 18W PT's are rated 290-0-290 at 120 to 140mA, which should be a very good match to the 300-0-300 at 79mA shown on the schematic.
martin manning wrote:The higher number is the DC voltage with no signal and the lower number is the voltage at clipping. Marshall 18W PT's are rated 290-0-290 at 120 to 140mA, which should be a very good match to the 300-0-300 at 79mA shown on the schematic.
Ahhhh, that makes sense now, thank you so much. And yes the 18w iron indeed looks to be a better match, as my friends suggestion surrounded using tube rectification as opposed to SS.
Also, any thoughts and/or comments on the reverb addition idea?
You could insert a Fender reverb circuit just before the PI input grid/470k junction. That will add a fair amount of complexity to your build, and don't forget there is no existing turret board layout for this amp; you'll have to create one of your own.
