SR-160 to SR-500 MOD

The SR-160 is the predecessor of the SR-500. They took the SR-160 made a few ckt changes to improve the overall performance and used different final tubes. Then they replaced the PS-150-120 power supply with the PS-500-120, PS-500-DC, P-500-DC or the P-500-AC.

The factory change used the 8236 carbon block plate tube. However the 6DQ5 is a direct replacement for the rare and expensive 8236. If you use the 6DQ5 you will absolutely need to use a fan for cooling. I use a 12 volt computer muffin fan powered by a 12v wall wart simply placed on the top of the case over the final tubes. The fan should draw hot air out not blowing cold air in. If at all possible go with the 8236, it is indestructible and will last forever. But you need a MATCHED PAIR.


PART CHANGES required for proper operation.


C11 *                                   47uuf                                  22uuf

C12 *                                   8.2uuf                                 6.8uuf

R53                                       47K                                     6.8K

C65                                       47uuf                                  150uuf

R92                                       180K                                   220K

C100                                     1000uuf                    750uuf

C104                                     470uuf                                220uuf

C107                                     1000uuf                    750uuf

R96 **                                 56K                                     delete

C119                                     680uuf                                620uuf

C120                                     430uuf                                250uuf

C121                                     510uuf                                300uuf


* These changes did not have anything to do with the PA mod. They were Factory directed changes to improve the receiver operation.


** Resistor R96 was removed for proper bias for either the 8236 or 6DQ5 final upgrade.


Making the change from the 12DQ6A to the 6DQ5 or the 8236 will require rewiring the cathode, screen and the filaments.


Best Regards, Walt WD0GOF.