On 7/14/2012 3:20 PM, Bob Grimes wrote:
I have seen the solid state replacement using the octal base for the
tube. I have a Hammarlund HQ 145XC that uses it, and it runs hot after
an hour or so. Just wondering if anyone else has used this replacement.
I found it for $9.99 on Tubedepot.com.
Thanks

Hi,

I looked at the solid-state plug in ad, but it appears
that it doesn't include a series resistor to drop the voltage
downstream to the same value as when the original 5U4 is used.
If it did, the solid state rectifier plug-in itself would run very hot.

I suggest you add a 200 Ohm 20W wirewound resistor
between pin 2 of the 5U4 tube socket and the input
to the HV filter choke/first electrolytic.
(Hammarlund might have used pin 8 for this purpose, also,
but the schematic shows pin 2).

The 5U4GB drops about 50V at its max rated current, 275mA,
per the tube data books, compared to less than a volt
for the plug-in replacement. That's why the external resistor
is required.

73,
Ed Knobloch