Princeton w/o reverb or tremolo

[johnnyreece]

Thanks! I'm sure everyone's just riveted to hear, but here are my voltages (which are all high, but my wall voltage is usually around 122/123, so it's somewhat to be expected). Here goes:

V1a - Plate: 207; Cathode: 1.5
V1b - Plate: 201.6; Cathode: 1.6
V2a - Plate: 207.7; Cathode: 1.5
V2b - Plate: 274.1; Cathode: 80.5
V3 - Plate: 428; Screen: 431
V4 - Plate: 435; Screen: 431

Power nodes:
A-433
B-428
C-357
D-311

Filaments - 6.68

So...a few red flags. The schematic shows much lower voltages, especially on the preamp/PI. The screen being higher on V3 is also troubling. More pics incoming eventually (really)

[johnnyreece]

Okay, here are the pics, and I promise I'll shut up about it now. Cleaned up a few little things. Nothing special; hopefully nothing too ugly stands out.

[tele_player]

That looks great. Which schematic and layout did use?

Robert

[johnnyreece]

Thanks! I used the schematic from M Fowler on page 1 to create the layout on page 3. The only difference is, the cap on the boost switch was the wrong value (I fixed it in the actual build). Eventually, I'll try to fix that on the layout, and have the components drawn to scale better, and maybe show my pin jacks a little more accurately. Hoping to give it to the proud owner this weekend. Yay!

[tele_player]

Thanks! I used the schematic from M Fowler on page 1 to create the layout on page 3. The only difference is, the cap on the boost switch was the wrong value (I fixed it in the actual build). Eventually, I'll try to fix that on the layout, and have the components drawn to scale better, and maybe show my pin jacks a little more accurately. Hoping to give it to the proud owner this weekend. Yay!

Thanks, I think I'm going to build that in a vibrochamp chassis I've had lying around for years, though I'll use SS rectifier.

Robert

[johnnyreece]

Yeah, I'd hoped to give the SS option, but the voltages will be quite high...even for JJ's. Have fun with your build!

[kkregsg]

I'm working on a build with SS rectification (Thrifty Croaker from Wattkins, Champish). I like the idea because I'm basically broke, and a bit lazy, so if I'm able to save some time and extra parts that's fine with me. I'm working from a much verified schematic , and venturing into true point to point. Either adventurous, foolhardy, or both! I need to sit down and do the actual math to understand the value selection for SS vs tube rec, and move beyond just working off others' design. But I might swerve dangerously close to learning something.

[johnnyreece]

Note the voltages I'm getting are with a 5u4G and Classic Tone transformers. With diodes, I'm going to be getting awful close to 500V, which, if you run into the same, you'll want to make sure your electrolytics and tubes are rated properly.

[tele_player]

As I see it, the cost difference between SS and tube rectifier is the cost of tube+socket, minus cost of a few diodes. Probably about $15-$20 net.

My reason is mainly to avoid punching another hole in the chassis.

I'll add a resistor to get the voltage down, or maybe a zener diode.

Robert

[kkregsg]

Johnnyreece, That was my point about doing the math, so you adjust your transformer choice and other components to fit the voltages with SS rectification. Right now I'm building by rote, but ya gotta start somewhere.

Tele_player, another savings comes in the cost of your transformer if you don't need the rectifier connection, too. Maybe as I get into larger more complex amps, the tube rectifier may be something I want to play with. Right now, I'm looking to keep costs at a minimum, and get clear on what changes produce what affects.

[tele_player]

Yeah, forgot that cuz I'll be using an old vibrochamp power transformer.
Robert

[pops]

put a large choke in front of the first filter caps and you can drop quite a few volts instead of using the zener.

[tele_player]

put a large choke in front of the first filter caps and you can drop quite a few volts instead of using the zener.

That would drop too much voltage.

Robert