Sunn Sonaro head tube layout?

[mac_on_bass]

Hello all,
New to the forum, this is my first post.

Hoping to get some advice/direction about my new '69 Sunn Sonaro tube bass head.  Long have I coveted a Sunn bass head, since playing on a minty Sonaro with matching 15" JBL cab back when I was in high school (and the amp was vintage then!)... So after years of Fender, GK, Mesa Boogie, and Ampeg heads I finally landed a Sonaro off Craig's List - came with a 215SH scoop-horn cabinet too!

My question is - what is the proper rectifier tube for this amp?  Mine has a tube complement in it now that I can't seem to match up with any searches of schematics.

1 - 5U4G rectifier, 2 - 6550 power, 1 - 7199, 1 - 12ax7wa

I dated the amp by the transformer codes, so it could conceivably be any time after 1969 - maybe '70 or '71.  The 6550's are mid-'70s tung sols, and the rectifier is a '90s SED Svetlana.

So, what gives with the 5u4g?  I thought Sonaro's had GZ34 rectifiers?  Any advice would be appreciated.

[loudthud]

If your amp originally had a 7199, it's probably early 1970 or older. It was a 40W head with EL34s and a GZ34.