[Boatanchors] HRO-50T Follow-Up.

[john fitzsimmons]

Ah, yup.  sorry, don't have the schematic in front of me but that makes sense.

In any event a scope is your friend here.




________________________________
 From: Richard Knoppow <1oldlens1 at ix.netcom.com>
To: john fitzsimmons <w3jn at yahoo.com>; Joe Connor <joeconnor53 at yahoo.com>; National Radio Equipment <national at mailman.qth.net>; boatanchors mailman.qth.net <boatanchors at mailman.qth.net> 
Sent: Monday, March 3, 2014 9:07 PM
Subject: Re: [Boatanchors] HRO-50T Follow-Up.
 


----- Original Message ----- 
From: "john fitzsimmons" <w3jn at yahoo.com>
To: "Joe Connor" <joeconnor53 at yahoo.com>; "National Radio 
Equipment" <national at mailman.qth.net>; "boatanchors 
mailman.qth.net" <boatanchors at mailman.qth.net>
Sent: Monday, March 03, 2014 5:42 PM
Subject: Re: [Boatanchors] HRO-50T Follow-Up.




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.

    The HRO-60 handbook shows plate pin-5 200V grid pin-4 
55V  cathode pin-6 60V.  I think these are correct. Note 
that the grid is connected to a tap in a voltage divider in 
the cathode and that the cathode resistance is high since it 
must develop a drive voltage equal to the plate for the 
putput tube.  The difference between the grid and cathode 
is -5 volts which is reasonable for the 6SN7 with 
effectively 140V on the plate. I think 0.3 V is an error 
copied over from National literature.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com