05-14-2022, 06:50 AM
Hi Vydram,
I, too, wonder why 250V for the filter caps. Read on:
The TH4 is a variant of that is known in the hobby as an "AA5" Radio, a Superheterodyne using a Pentagrid Converter, Pentode IF amplifier, Duo Diode - Triode as Detector ad 1st AF Amp and a Beam Power Output Tube. The B+ on this radio is typically between 100 and 135V.
For non-electrolytic caps (capacitors) it is good to use as high a voltage rating as possible. the old paper / wax caps used in these radios typically had a maximum voltage rating between 200 and 400V. Current mylar and poly caps used by the hobby are typically rated at 630V.
However, for electrolytic caps, there is a difference. Electrolytics are rated (or used to be rated) in "Working Volts". this is because the cap is designed to work at a specific voltage. Back when I was a kid and learned this (50 years ago), if you used a cap with too high a working voltage, the capacity of the cap would drop. This may or may not be the case with current electrolytic technology.
The Working Voltage of the cap affects size and price. The 160V caps should be fine in this radio. Go to 200 if you have concerns.
Experts, please comment yay or nay to what I posted here.
I, too, wonder why 250V for the filter caps. Read on:
The TH4 is a variant of that is known in the hobby as an "AA5" Radio, a Superheterodyne using a Pentagrid Converter, Pentode IF amplifier, Duo Diode - Triode as Detector ad 1st AF Amp and a Beam Power Output Tube. The B+ on this radio is typically between 100 and 135V.
For non-electrolytic caps (capacitors) it is good to use as high a voltage rating as possible. the old paper / wax caps used in these radios typically had a maximum voltage rating between 200 and 400V. Current mylar and poly caps used by the hobby are typically rated at 630V.
However, for electrolytic caps, there is a difference. Electrolytics are rated (or used to be rated) in "Working Volts". this is because the cap is designed to work at a specific voltage. Back when I was a kid and learned this (50 years ago), if you used a cap with too high a working voltage, the capacity of the cap would drop. This may or may not be the case with current electrolytic technology.
The Working Voltage of the cap affects size and price. The 160V caps should be fine in this radio. Go to 200 if you have concerns.
Experts, please comment yay or nay to what I posted here.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards,
MrFixr55
