[Boatanchors] HRO-50T Follow-Up.

[Drew P.]

Joe Connor wrote: 

"I followed your suggestions and did some resistance and voltage measurements. I've underlined the voltage readings that seem out of line. Curiously, Rider's and Sams state different voltage readings. Please let me know what you think.?

Audio Transformer: Primary: Plate of 6V6 to center tap: 426 and 441 ohms. Secondary: 500-ohm tap to ground: 29 ohms; 8-ohm tap to ground: less than 1 ohm.

6V6: plates: 278 and 276; screen grid: 263 and 262; control grid: 262 and 262; cathode: 12 and 12

6SJ7 (1st audio): plate (pin 8) 72; cathode (pin 5) 2; screen grid (pin 6) 72. The screen grid is high. Rider's says it should be 40 (Sams says 60). The plate is a little low. Rider's says it should be 80 (Sams says 34).

6SN7 (phase inverter): grid (pin 4) 48; plate (pin 5) 206; cathode (pin 6) 65. The grid is high. Rider's says it should be 0.2 ?(Sams says it should be 30). The plate is a bit high. Rider's says it should be 165. (Sams says 190)."


Joe, if the 6V6 grids are indeed at 262 volts as you say, the voltage would be higher than that at the phase inverter plate/cathode.  Sounds like both of your 6V6's are toast, with screen grid to control grid shorts. While you are replacing them, make sure that you have replaced all of the paper capacitors in the radio if you have not already done so.

Drew