I have 2 .630A - federal 1267A/sarkes 759S - I would like to replace with Diodes? I do have some GE - A108 - 1 amp 600v top hats - if they will work ?

How many plates? What size plates?

Top hat diodes are nearly as old as selenium rectifiers. Get some new 1N4007s.

http://w3hwj.com/index_files/RBSelenium2.pdf

Rich
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:I have 2 .630A - federal 1267A/sarkes 759S - I would like to replace with Diodes? I do have some GE - A108 - 1 amp 600v top hats - if they will work ?

PS: Don't just replace the seleniums with diodes - your B+ will be way too high. You need to add high wattage resistors in series with each diode. For example when I restored a Raytheon B & W TV I replaced the seleniums with 1N 4007s and a 10 ohm, 10 watt resistor in series with each diode.

Lou

:How many plates? What size plates?
:
:Top hat diodes are nearly as old as selenium rectifiers. Get some new 1N4007s.
:
:http://w3hwj.com/index_files/RBSelenium2.pdf
:
:
:Rich
:++++++++++++++++++++++++++++++++++++++++++
:
:
::I have 2 .630A - federal 1267A/sarkes 759S - I would like to replace with Diodes? I do have some GE - A108 - 1 amp 600v top hats - if they will work ?

Why are you replacing them? Contrary to popular belief, selenium rectifiers don't usually hop out of equipment and attack people in their sleep.

:I have 2 .630A - federal 1267A/sarkes 759S - I would like to replace with Diodes? I do have some GE - A108 - 1 amp 600v top hats - if they will work ?

Pre-emptive parts replacement is a good philosophy if you are trying to keep critical resources online, but for most antique radio owners the failure of a selenium rectifier is a trivial and expected inconvenience, like an ignition points failure on a 1964 Mercedes. Ones world most likely won't come crashing down because either one happens.

If it ain't broke, don't fix it. To paraphrase a deceased US Senator, let selenium recifiers be selenium rectfiers. Just my two cents worth.

Just check the B+ coming out of the selenium to make sure your getting a decent DC voltage. They tend to fade in output voltage as they age. If your B+ is fine, let it be, as CV said. A slightly reduced B+ may actually be a blessing, if not too low....keeps the stress off other old components due to the higher wall current now, 125-127vac as opposed to the 110-115vac when they were designed.

My second set of two cents.

The only seleniums I have ever seen fail so far are the ones used in high current applications. The TVs of the 1950s used to take the line voltage in without a transformer and use two selenium rectifiers to get the B+ needed for the chassis. The surge current on turn on over the years just wore them out. When they are worn the forward resistance of the rectifier goes up and they get lossy.

Lou

:Just check the B+ coming out of the selenium to make sure your getting a decent DC voltage. They tend to fade in output voltage as they age. If your B+ is fine, let it be, as CV said. A slightly reduced B+ may actually be a blessing, if not too low....keeps the stress off other old components due to the higher wall current now, 125-127vac as opposed to the 110-115vac when they were designed.

:My second set of two cents.
:
:The only seleniums I have ever seen fail so far are the ones used in high current applications. The TVs of the 1950s used to take the line voltage in without a transformer and use two selenium rectifiers to get the B+ needed for the chassis. The surge current on turn on over the years just wore them out. When they are worn the forward resistance of the rectifier goes up and they get lossy.
:
:Lou
:
::Just check the B+ coming out of the selenium to make sure your getting a decent DC voltage. They tend to fade in output voltage as they age. If your B+ is fine, let it be, as CV said. A slightly reduced B+ may actually be a blessing, if not too low....keeps the stress off other old components due to the higher wall current now, 125-127vac as opposed to the 110-115vac when they were designed.

Thank you for all the info, I just wanted a back-up in case the SR fails - I also like them instead of replacement. I always run these sets with controlled voltage, not house. the 2 federal SR's are 9 plates each and measure about 2"x 2"

:Why are you replacing them? Contrary to popular belief, selenium rectifiers don't usually hop out of equipment and attack people in their sleep.

You obviously haven't seen the atrocities they've committed in Ohio . . . .