[Heathkit] SB-220 cooling air exhaust

[Rick Poole]

Where does the cooling air exhaust on the SB-220?  Is it out the back 
(e.g. TL-922), or out the side (e.g. 30L-1), or out the top?

I need to figure out how much space I need to leave above an SB-220 
for proper cooling at rated output.

Thanks...

Rick WA1RKT