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I'm not sure if my SF Princeton mod/troubleshooting issues belong here, in vintage amps or mods, but, Enzo, and Bruce C, along with a cast of others, set me on the path to rightious tone, in my trouble shooting process.
Enzo suggested my popping and spike power fades in my highly modified SF Princeton might be parasitic oscillation. I tried a few things and they slowly reduced, but didn't eliminate the problem. I did a search here and found some old post comments from Bruce Collins about trimming the leads of un-used OP tranny taps, and keeping the others short and away from PI wires. One of the mods I did on my Princeton was to add a Mercury Magnetics Deluxe Reverb multi tap OP tranny. I put the 4 and 8 ohm taps on the existing jacks, and put heat shrink on the 2 ohm tap, but left it dangling around the PI wires, because I thought I might use it later (which I probably never would). I also left both the primary and secondary leads of the new OPT longer than necessary.
After reading all the suggestions, and Bruce's old posts, I shortened all the leads, and clipped the 2 ohm lead on the outside of the chassis and put heatshrink on it. That was the cure. I can now open the amp all the way with no annoying spurious power drops or popping.
I have a mission with this amp. I'm meeting up with a bunch of old rock and rollers from my high school days next month in Wisconsin for an annual jam event that is having it's 11th reunion. I haven't seen some of these guys for 35 years. So I've got this 1968 Princeton that looks stock, but is far from a stock Princeton. I'm hoping to have a "That little amp really Boogies" moment
It should be fun.
Thanks again to all those who pitched in and helped with this project.
Enzo suggested my popping and spike power fades in my highly modified SF Princeton might be parasitic oscillation. I tried a few things and they slowly reduced, but didn't eliminate the problem. I did a search here and found some old post comments from Bruce Collins about trimming the leads of un-used OP tranny taps, and keeping the others short and away from PI wires. One of the mods I did on my Princeton was to add a Mercury Magnetics Deluxe Reverb multi tap OP tranny. I put the 4 and 8 ohm taps on the existing jacks, and put heat shrink on the 2 ohm tap, but left it dangling around the PI wires, because I thought I might use it later (which I probably never would). I also left both the primary and secondary leads of the new OPT longer than necessary.
After reading all the suggestions, and Bruce's old posts, I shortened all the leads, and clipped the 2 ohm lead on the outside of the chassis and put heatshrink on it. That was the cure. I can now open the amp all the way with no annoying spurious power drops or popping.
I have a mission with this amp. I'm meeting up with a bunch of old rock and rollers from my high school days next month in Wisconsin for an annual jam event that is having it's 11th reunion. I haven't seen some of these guys for 35 years. So I've got this 1968 Princeton that looks stock, but is far from a stock Princeton. I'm hoping to have a "That little amp really Boogies" moment
It should be fun.Thanks again to all those who pitched in and helped with this project.