Greetings,

I am working on an H500 and would like to insure the rectifier is working correctly. I have never tested one before. I imagine that it should provide only DC at the output and no AC should be there? Under load tests? Standard diode tests? Any suggestions on how to test thoroughly? I have a Digital Multi Meter. I have seen test devices specifically for such rectifiers but do not own one. Thanks in advance.

Jeff W

Hi Jeff

It's best to replace the selenium rectifier with a 1N4004-1N4007 silicon diode and 47 ohm 1 watt or greater series resistor. Over time selenium rectifier have increased voltage drop. A new selenium rectifier should have a 7 volt drop under load according to Federal, manufacturer.

You don't want to have one of these burn. You will never forget the smell.

Norm

:

Greetings,
:
:I am working on an H500 and would like to insure the rectifier is working correctly. I have never tested one before. I imagine that it should provide only DC at the output and no AC should be there? Under load tests? Standard diode tests? Any suggestions on how to test thoroughly? I have a Digital Multi Meter. I have seen test devices specifically for such rectifiers but do not own one. Thanks in advance.
:
:Jeff W

Hi Jeff

It's best to replace the selenium rectifier with a 1N4004-1N4007 silicon diode and 47 ohm 1 watt or greater series resistor. Over time selenium rectifier have increased voltage drop. A new selenium rectifier should have a 7 volt drop under load according to Federal, manufacturer.

You don't want to have one of these burn. You will never forget the smell.

Norm

:

Greetings,
:
:I am working on an H500 and would like to insure the rectifier is working correctly. I have never tested one before. I imagine that it should provide only DC at the output and no AC should be there? Under load tests? Standard diode tests? Any suggestions on how to test thoroughly? I have a Digital Multi Meter. I have seen test devices specifically for such rectifiers but do not own one. Thanks in advance.
:
:Jeff W

Hi Jeff

It's best to replace the selenium rectifier with a 1N4004-1N4007 silicon diode and 47 ohm 1 watt or greater series resistor. Over time selenium rectifier have increased voltage drop. A new selenium rectifier should have a 7 volt drop under load according to Federal, manufacturer.

You don't want to have one of these burn. You will never forget the smell.

Norm

:

Greetings,
:
:I am working on an H500 and would like to insure the rectifier is working correctly. I have never tested one before. I imagine that it should provide only DC at the output and no AC should be there? Under load tests? Standard diode tests? Any suggestions on how to test thoroughly? I have a Digital Multi Meter. I have seen test devices specifically for such rectifiers but do not own one. Thanks in advance.
:
:Jeff W

:I totally agree with Norm. Don't worry about testing it, just replace it. I would go with a 1N4007 diode. The few pennies more in cost are neglible and the 1000 V. rating ensures more than enough margin.

Selenium rectifiers haven't been used in production radios for about 40 years and trying to find a working replacment selenium unit just isn't worth the trouble. When I worked for Westinghouse many years ago, we helped a customer change an electrochemical plating rectifier from selenium to silicon. We replaced a cubic yard of selenium units with a silicon unit about 25 times smaller!

Hi Jeff
:
: It's best to replace the selenium rectifier with a 1N4004-1N4007 silicon diode and 47 ohm 1 watt or greater series resistor. Over time selenium rectifier have increased voltage drop. A new selenium rectifier should have a 7 volt drop under load according to Federal, manufacturer.
:
: You don't want to have one of these burn. You will never forget the smell.
:
:Norm
:
::
:
:Greetings,
::
::I am working on an H500 and would like to insure the rectifier is working correctly. I have never tested one before. I imagine that it should provide only DC at the output and no AC should be there? Under load tests? Standard diode tests? Any suggestions on how to test thoroughly? I have a Digital Multi Meter. I have seen test devices specifically for such rectifiers but do not own one. Thanks in advance.
::
::Jeff W

Thanks to both of you. I will get a few of these for my bench stock.

I also contacted another Zenith expert and he recommended that, at the same time, I replace the 130 ohm 3w resistor with a 180-220 ohm 5 watt (He says the target is 7.6-8.4 v across the filament string) Depending upon home voltage i.e. 123-125v and he likes to "pamper" filaments so he uses a 220 ohm.
Hope this helps others.

Jeff W

::I totally agree with Norm. Don't worry about testing it, just replace it. I would go with a 1N4007 diode. The few pennies more in cost are neglible and the 1000 V. rating ensures more than enough margin.
:
:Selenium rectifiers haven't been used in production radios for about 40 years and trying to find a working replacment selenium unit just isn't worth the trouble. When I worked for Westinghouse many years ago, we helped a customer change an electrochemical plating rectifier from selenium to silicon. We replaced a cubic yard of selenium units with a silicon unit about 25 times smaller!
:
:Hi Jeff
::
:: It's best to replace the selenium rectifier with a 1N4004-1N4007 silicon diode and 47 ohm 1 watt or greater series resistor. Over time selenium rectifier have increased voltage drop. A new selenium rectifier should have a 7 volt drop under load according to Federal, manufacturer.
::
:: You don't want to have one of these burn. You will never forget the smell.
::
::Norm
::
:::
::
::Greetings,
:::
:::I am working on an H500 and would like to insure the rectifier is working correctly. I have never tested one before. I imagine that it should provide only DC at the output and no AC should be there? Under load tests? Standard diode tests? Any suggestions on how to test thoroughly? I have a Digital Multi Meter. I have seen test devices specifically for such rectifiers but do not own one. Thanks in advance.
:::
:::Jeff W

Jeff,
What your Zenith "expert" is recommending is exactly what Norm has already suggested. The only difference is that instead of adding a 47-ohm resistor in series with the silicon diode and the existing 130-ohm resistor, he is removing the original 130-ohm resistor and replacing it with a single larger one. (130 + 47 = 177 ohms, which is close to the 180 ohms he recommends.) Either way will work just fine. But going as high as 220-ohms is not always wise, for reasons mentioned below, although this depends on prevailing line voltage.

The recommendation to target 7.6 - 8.4 volts across the filament string is pretty much right. But my practice is to focus on the 1L6 converter only and target its filament for 1.4 volts, and not worry about the rest of the filament string. Two reasons for this: First, the 1L6 is an expensive tube and excessive filament voltage (1.5 volts or above) will shorten its lifespan; Second, too little voltage (below 1.3 volts) at the 1L6 will stop oscillator function. In my experience, low voltage to the oscillator section of the 1L6 is the single most common cause of T-O reception problems. If you plan to add as much as 220-ohms series resistance, depending on the line voltage at which your T-O will be operated you should check to make sure that the filament voltage at the 1L6 does not fall below 1.4 volts.

Poston

:Thanks to both of you. I will get a few of these for my bench stock.
:
:I also contacted another Zenith expert and he recommended that, at the same time, I replace the 130 ohm 3w resistor with a 180-220 ohm 5 watt (He says the target is 7.6-8.4 v across the filament string) Depending upon home voltage i.e. 123-125v and he likes to "pamper" filaments so he uses a 220 ohm.
:Hope this helps others.
:
:Jeff W
:
:
:::I totally agree with Norm. Don't worry about testing it, just replace it. I would go with a 1N4007 diode. The few pennies more in cost are neglible and the 1000 V. rating ensures more than enough margin.
::
::Selenium rectifiers haven't been used in production radios for about 40 years and trying to find a working replacment selenium unit just isn't worth the trouble. When I worked for Westinghouse many years ago, we helped a customer change an electrochemical plating rectifier from selenium to silicon. We replaced a cubic yard of selenium units with a silicon unit about 25 times smaller!
::
::Hi Jeff
:::
::: It's best to replace the selenium rectifier with a 1N4004-1N4007 silicon diode and 47 ohm 1 watt or greater series resistor. Over time selenium rectifier have increased voltage drop. A new selenium rectifier should have a 7 volt drop under load according to Federal, manufacturer.
:::
::: You don't want to have one of these burn. You will never forget the smell.
:::
:::Norm
:::
::::
:::
:::Greetings,
::::
::::I am working on an H500 and would like to insure the rectifier is working correctly. I have never tested one before. I imagine that it should provide only DC at the output and no AC should be there? Under load tests? Standard diode tests? Any suggestions on how to test thoroughly? I have a Digital Multi Meter. I have seen test devices specifically for such rectifiers but do not own one. Thanks in advance.
::::
::::Jeff W