The AM Forum

Good morning. A few years ago I picked up a small box of solid state rectifier tube replacements at an estate sale. I can find some references to them on the web but nothing about the internals or specs. They might be nice to use to get some load off of old power transformers and also some heat out of the cabinets.

Here they are:

IR ST-1    7 pin small tube
IR ST-2     Octal
IR ST 3     Octal
IR ST 7     Octal
1N40 US Navy Octal
1N1239     Octal
Sarkes Tarzian #S5019  2A
ST 5343 4 pin base like #80 plus top cap
ST 5018    Octal
IRC 1N 2389 Octal (pencilled with replaces 5Y3)
Raytheon CK719A  C-40919A 6435 Short octal like 6H6

These are potted and heavy.
So, what is inside? 2 semiconductor diodes? Dropping resistor?

The downside as I see it is higher B+ and sharp HV rise when turned on.

Any input would be appreciated.

Thanks, Rich

See this:
http://amfone.net/Amforum/index.php?action=dlattach;topic=42518.0;attach=54711

All SS diodes/rectifiers have a lower internal Vdrop compared to tubes.
Tubes will generally be in the 10s of volts in drop. Diodes in the 0.6vdc drop range. So this makes
the resulting voltage higher.

Since there is no filament, the B+ comes on instantly.
In many cases people use some means to reduce "inrush" current, and so diminish the
bounce in voltage when it turns on.

Means include things like a relay that bypasses a series resistor after a few seconds, and the
"Varistor" or Voltage Dependent Resistor which is placed in series with the primary (or AC line) typically.

                  _-_-

Great info. Thanks for the responses!

Rich

Another issue to be cautious about when replacing hollow state rectifiers with solid state.  I only recommend going to solid state if the radio (RX or TX) can have the heaters fully on and hot before engaging the power supply.  Electrolytic caps are sensitive to 3 things as a rule, polarity, temp and voltage.  The latter is the issue here.

If the power supply is energized before the tubes have had time to heat to temp (many seconds), the PS will be looking into a no load scenario and the PS output voltage will go sky high, likely far exceeding the rating of the filter caps.  This will result, at best, in a shortened life for the cap if not a failure.  Ask me how I know this  8) 8).

Some receivers have a PS switch labeled send/receive which could be used as a HV switch.  Some TXmitters have a separate heater and HV switch.  If you want to go solid state and enjoy the benefits of modern silicon rectifiers, make sure you pay attention to this.

My .02....

Peter
~PS

       Dont sweat it Man,

               Your AC line voltage exceeds whatever the rig was designed
for and has been stressing your rig for years any way.. Rip out those
5R4/5u4 and use the 5 volt winding to Buck the AC line.. 


/Dan