105*F isn't gonna hurt anything. Leave the fan off and run it for 3-4 hours at a volume of about 10:00. Check it every 1/2 hour for temp stability. If it doesn't go much higher and stabilizes after 2 hours or so, don't worry about it. It's probably NOT going to get hotter than that. But if you worry about it in the back of your mind put the fan on from the side next to the PWR X-frmr and have it blow across the unit.
This is an extreme example but shows what can be done with a "HOT RUNNING" 7591 receiver/amp.
Everyone on the Sansui Forum crams the "if you have the cover on you MUST use a fan for the 1000A", down everyone's throat! I found that the problem is not the transformers or the Output Tubes so much as it's the heat given off by the 300v drop that the large 30A resistors have to handle constantly and their location. (See illustration below). Plus anytime EH7591's are used airflow is actually restricted by the tube envelopes. As these were the only NEW plug & play 7591 replacements at the time 10 years ago it makes sense, but with the Tung-Sol's or Old Stock Westinghouse, or other brands airflow is normalized but also still somewhat restricted between the tubes and all X-frmrs but more so on the side at the pwr x-frmr. There are minimal air holes in the chassis, and the bottom has slots 1/2 way across. Old Resistors shown in Turquoise, NEW Replacement resistors in ORANGE on illustration.
I took some Solid Aluminum Hi-Wattage (50W) 12Kohm (x4) and a 600ohm 50w Dale resistors, rewired so they were spread out on the chassis, away from the transformers and output tubes. One pair was placed on the separator plate behind the P.T., but the rest (3 Total) were placed on the front cover behind the tuning string. The temps were now spread out all over the unit vs. all the heat in the back between the transformers. Temps on the PT dropped 20degF to 130*F and the output in the center dropped about 5deg DegF..
Then I installed Tung-Sol 7591 Re-Issues (Original size bottle) against the Large bottle EH's. Temps across all transformers dropped another 10-15DegF. So now with the Tung-Sol's the P.T. is running about 120-125*F and the output's are a relatively cool 105*F. There is plenty of room between the tubes, and transformers to facilitate airflow. One last thing I did was to get a roll of 3" Aluminium HVAC Seal tape (Duct Tape). This is placed on the end-bell's or winding sides directly facing the tubes. Some of the Radiant heat from the tubes is reflected back to the tubes or the air space btwn the tubes, and the transformers. Now instead of less than 1/2" of space btwn the tubes and Xfrmr's, it's over 1/2" and airflow is actually able to go thru the unit rather than being restricted some by the EH7591a tubes.
BEFORE Note how close resistors are to tubes and X-frmr Tubes are my EICO Test mules.
AFTER Note the increased room btwn the tubes and X-frmr
With Tung-Sol 7591A Re-Issues, this 1000A is now cooler than my 800c's and my 400's. NO FAN's, even with cover on top. Heat output overall is now the approx the same, but it's not concentrated at the back of the unit. Overall the cover is very warm, but it's actually cooler due to spread out sources and physical heat-sinking of the resistors where as before they depended on airflow. I normally run it naked, but when the grandkids come over, it gets the cover put on. But there is no need for a fan now.
With the 101-B, If you do add a fan, place it on the power x-frmr side and have it blow across the unit from the side, the air blowing btwn the shield and the x-frmrs. Clean up and polish the shield btwn the output tubes and X-frmrs. I don't see a need for the HVAC tape at this time. As cool as mine runs with Wall voltage to as high as 124V I don't anticipate that your's will run much different with a new transformer.