[Boatanchors] HRO-50T Saga: Quick Transformer Question

[Richard Knoppow]

----- Original Message ----- 
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: Thursday, March 06, 2014 8:44 PM
Subject: [Boatanchors] HRO-50T Saga: Quick Transformer 
Question


I have a question about whether the prior owner put the 
proper replacement audio output transformer in this 
receiver. The audio is much better than it was but is still 
not as good as I would expect from push-pull 6V6s.

The replacement is a Merit A-3027, which has a 10,000-ohm CT 
primary. In looking through the Sams service material, no 
Merit replacement is listed. Further, Sams lists the primary 
impedance as 6,000 ohms CT, not 10,000 ohms.

Could this difference in impedance be giving me less than 
optimal audio output? If so, I'll probably buy a new Hammond 
(125D) and install that. What do you think?

Again, thank you for your help.

Joe Connor

     10K ohms is the correct value for plate-to-plate load 
for Class-A pentode operation with about 250 volts on plates 
and screen grids.  Sam's is wrong. Who knows why Sam's did 
not list a Merit transformer, at the time there were at 
least ten companies making audio transformers. Merit was 
considered a good brand.
     The tube handbook gives the output as 10 watts with 5% 
THD for the above conditions. Do you have the means to 
measure output power and distortion, if the transformer is 
defective this will give you a good indication.


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