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Vintage Asylum Classic gear from yesteryear; vintage audio standing the test of time. |
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Vintage Asylum Classic gear from yesteryear; vintage audio standing the test of time. |
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In Reply to: RE: Sherwood S-5500ii power transformer woes? Bad filament secondary? posted by jamesbythebay on May 31, 2024 at 12:12:38:
I haven't worked on a Sherwood tube amp since the '70s, and I don't recall if any of those were the S-5500ii. It's not difficult to analyze the schematic to see where improvements can be made. Whether there's sufficient physical space for changes is another story. My approach to the B+ supply would be as follows:
1. Increase the value of the doubler caps from 120uF to 220uF.
2. Replace R62 33Ω with a 0.5H choke.
3. Increase the value of C62-40uF to 100uF.
4. Replace R64 470Ω with a 1H choke.
5. Add a thermistor in series with the power transformer primary.
Other revisions:
Add a 220Ω carbon comp stopper resistor to each 7868 screen grid
Add a 1Ω or 10Ω precision resistor at each 7868 cathode for measurement
I'm sure something similar has been done to these at one time or another by people who specialize in this model. Again, there are likely to be significant space limitations, especially as these are so compact. Have fun!
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Follow Ups
- RE: Sherwood S-5500ii power transformer woes? Bad filament secondary? - Triode_Kingdom 12:59:50 06/01/24 (0)
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