Seeburg MRA3-L6 voltage checks

steve_b10 · by **steve_b10** » Thu Dec 06, 2012 8:51 pm

Do all the tubes need to be installed in order to check the amp voltages listed on the schematic?

by **Ron Rich** » Thu Dec 06, 2012 9:22 pm

I assume you are speaking of DC voltages--I have always checked them with all, known good, tubes installed--but you might be able to leave out some of them if they are not directly connected to the circuit being checked--Hint: Remember, the speaker MUST be plugged in while checking---Ron Rich

steve_b10 · by **steve_b10** » Thu Dec 06, 2012 11:32 pm

Yes, DC voltages in the amp. So at least the 5U4 tube needs to be in, correct?

Also, the schematic indicates that the 5 volt AC voltage for the 5U4 is measured "across winding not to ground". Is this measured at pins 2 and 8 on the 5U4?

by **Ron Rich** » Fri Dec 07, 2012 2:25 am

Steve,
I have never attempted to read voltages without all tubes in place---and as far as the 5 vac on the 5U4, if it is lighting when the motor is running--it has five volts--Ron Rich