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Sun Feb 10, 2019, 10:12 PM

Best method I've seen - Schematic Demo


How to change out selenium rectifier to silicon diode in portable tube radios.

Lookit the cool schematic animation!


4 replies, 139 views

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Reply Best method I've seen - Schematic Demo (Original post)
wonderwarthog Feb 2019 OP
TheShoe Feb 2019 #1
wonderwarthog Feb 2019 #2
rampartb Feb 2019 #3
wonderwarthog Feb 2019 #4

Response to wonderwarthog (Original post)

Sun Feb 10, 2019, 11:53 PM

1. Seems a bit hueristic

But works. Good video.

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Response to TheShoe (Reply #1)

Mon Feb 11, 2019, 12:02 AM

2. Agree.


Geared for simple folk such as myself!


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Response to wonderwarthog (Original post)

Mon Feb 11, 2019, 06:54 AM

3. viltage drop across a forward biased se junction is about 1v

but the junctions were stacked leading to a drop of up to 10v.

if you are adding resistance, add 33 ohms (in this example) to to the resistance you want to add and replace that 33 ohm resistor with the new resistor. these power supply resistors tend to be large ceramic rather than carbon resistors and space should be saved. these resistors tend to be + or - 10% or 20% of the color code. maybe the factory had a batch of them and selected those closest. maybe not.

i don't remember changing any single selenium diodes as in the example, as this is normally a bridge rectifier. requiring 4 silicon diodes or a potted rectifier package whuch is really the same thing.

also, in some of those old redios that you fool with the rectifier may be a vacuum tube diode. i've never modernized one of them but it sure sounds possible.

if you are doing this much, be sure to replace any electrolytic capacitors (the big cans). after 50 years they are certain to have leaked. symptom might be hiss in output or maybe a loud kaboom and a chassis full of electrolyte and can

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Response to rampartb (Reply #3)

Mon Feb 11, 2019, 09:48 PM

4. Thanks for the great post!


And yes, some folks even replace the selenium with a vacuum tube!

Had a cap go bang in a 52 Zenith.

Fixed and soon to test, video forthcoming!

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