with my recent estate sale scores i have gotten around to testing xfrmrs to see how good of a deal i got. to date i have only built se. i know how to test a se ot to get an idea of output impedance. for instance i use my variac on the primary and adjust until i have 1volt on the secondary. say i have 25 volts on the primary to 1 on the sec. 25:1 which i square the 25 to get 625 and multiply times my desired load imp of 8 which gives me 625x8=5k. easy but when testing a push pull do i test from center tap to each plate wire or across the whole winding? i got this stereo 7189 push pull amp so 1 power tranny and 2 ot. when i put voltage on the primary and adjust to get 1 volt on the 8ohm tap across the whole winding i get 31.25:1 thus 31.25 squared =976.5625 times 8ohm = 7812.5 so to my thinking this is roughly an 8k push pull which should be great for a 7189 pp or a 6v6,el84 etc.
that is if i am doing this right? or am i supposed to test from center tap?
also this thing has a common as well as 4,8, 1nd 16ohm secondarys and if i am not mistaken i read using a different tap with a mismatched speaker can give you perhaps a different desired reflected load. i am a little iffy on exactly how this fits together if i want to use this with a pair of output tubes with a different load impedance. as well its always in the back of my head a lesson i was taught 30 years ago to never use a 4 ohm speaker with an 8 ohm amp you will burn up your ot and /or output tubes. so i am curious and hope some of the pros will wish to help a po' dumb boy like me get this. thank you sirs
ps. one of the reasons i ask is because i have a pair of used but good 6973s that i want to built a model 24 supro with and i am wondering since the ot required is spec a 7.5k and if i did this right i have a pair close to 7.8k can i use this ot for my supro or is the fact that it is a hi-fi stereo amp ot will it sound shite with a guitar amp?
Topic: confusion on testing a push pull ot (Read 1834 times)