I have a radio the uses a 12BW4 Rectifier tube and I was wondering if there is a solid state replacement for this. It looks like the high voltage is 360.
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Rectifier change out
- Thread starter datsun66
- Start date
Two 1N5408 rectifier diodes will replace it. The banded ends of BOTH diodes go to pin 9 on the socket. One unbanded end goes to pin 1, the other to pin 7.
Trouble is, these rectifier diodes are more efficient than the original tube. The original tube would lose around 40 Volts, where the 1N5408 loses less than one Volt. This will raise the DC voltage on the power-supply filter capacitors. If they are old, this stress may cause them to fail soon. Electrolytics will get 'accustomed' to operating at whatever voltage the old 12BW4 tube was delivering. Boosting that voltage, even by 10% or so, can upset the applecart.
New filters will prevent this problem, so long as you use new ones with a high enough voltage rating.
73
Trouble is, these rectifier diodes are more efficient than the original tube. The original tube would lose around 40 Volts, where the 1N5408 loses less than one Volt. This will raise the DC voltage on the power-supply filter capacitors. If they are old, this stress may cause them to fail soon. Electrolytics will get 'accustomed' to operating at whatever voltage the old 12BW4 tube was delivering. Boosting that voltage, even by 10% or so, can upset the applecart.
New filters will prevent this problem, so long as you use new ones with a high enough voltage rating.
73
Thanks for the info, I thought there would be a way to convert but was not to sure. I was thinking about doing a total recap on the radio anyway. The diode conversion was for test proposes only and not for a permanent installation. Anytime I work on the old tube stuff I do a recap and if there not to bad I will try to reform the larger caps. This works pretty good for the most part. 
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