• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Is this the selenium rectifier?

Steelman

Steelman

Super Member
Started the recap on my Scott 340-B :banana:

I have replaced all the .1, .022 and .027 caps :D

My question is...is the picture the selenium rectifier?
If so, is there something I can replace it with that Radio Shack sells?
 
Last edited:
Register to hide this ad
Steelman said:
Started the recap on my Scott 340-B :banana:

I have replaced all the .1, .022 and .027 caps :D

My question is...is the picture the selenium rectifier?
If so, is there something I can replace it with that Radio Shack sells?
Click to expand...

Looks like one. A bridged rectifier of the appropriate voltage and current will do.
 
avionic said:
Looks like one. A bridged rectifier of the appropriate voltage and current will do.
Click to expand...

Found an old thread where someone used a 8A/400V Full-wave Bridge Rectifier Radio Shack model#276-1181...Catalog#276-1181

Will this wire up just as the old one is removed?...

Sorry for the dumb question...I'm a bit dense on this...
 
Check your B+ voltages. You may need a dropping resistor in between the + lead on the new rectifier and the first cap to drop things back down. Silcon has a much lower voltage drop than selenium does.
 
Try a 50 ohm 5W resistor in series with the B+ output before it connects the first filter cap. Adjust up or down to get the B+ closer to the desired value. The circuits may be happy with higher B+ anyway, as long as the filter caps don't get overvoltaged.
 
I believe that this bridge was replacing the Siemens Selenium bridge that supplies the negative DC bias voltage for the output tubes and the filtered DC for the pre-amp tubes which are connected in series. Depending on the circuit, I find that if the first resistor after the bridge is an 18 ohm, 1-watt, the replacement is usually a 33 ohm, 5-wat wire wound which is easy to find. If the voltages are correct after replacing the bridge, you are good to go, if not, just adjust the value of the first resistor... UNLESS it is one of those STANDEE tall ceramic resistors. Then, more investigation. I have not looked at the schematic yet. I know that Scott changed the bias circuit in the last few amp/receivers.
 
I just checked both early and late schematics for the 340B. First resistor is a 10 ohm, 2-watt. You may try a 27 ohm, 5-watt and see how it goes. Just make sure the voltage is not too high. The silicon bridge is more efficient (less voltage drop) than selenium and therefore will output slightly higher voltage.
 
You must log in or register to reply here.
Back
Top Bottom