[Boatanchors] HRO-50T Follow-Up.

[john fitzsimmons]

Get at it with a scope.  Look at the grds of each 6V6, if the audio amplitude isn't equal then there's something up with the phase inverter.

Positive voltage on the grid of the 6SN7 is bad indeed, if in fact that's a positive voltage.  That would mean there's leakage from the plate of the 6SJ7 to the grid of the 6SN7.


________________________________
 From: Joe Connor <joeconnor53 at yahoo.com>
To: National Radio Equipment <national at mailman.qth.net>; boatanchors mailman.qth.net <boatanchors at mailman.qth.net> 
Sent: Monday, March 3, 2014 7:53 PM
Subject: [Boatanchors] HRO-50T Follow-Up.
 

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).

What do you make of these readings? As always, thank you for your help.

Joe Connor
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