Since I acquired a KWS-1 and PS from the scrap pile, while restoring the unit I am considering updating some parts of the setup, with 21st Century updates. This rig is no Virgin, missing original parts and might just work better when the mods are completed. 1 of the main problems with the KWS-1 combo was the forced air cooling setup of the PA tubes. The original Collins setup has a blower motor unit consisting of a 5 1/2" diameter by 1 7/8" wide blower fan, mounted to a 115V motor. The motor I am guessing spins about 3K (?) RPM, as I can find no information on this. With 1 1/2" ID air duct being used between the blower motor and the PA cage. Even with my shoddy ME skills, it is easy to see this factory setup was lacking severally. Has anyone ever operated a KWS-1 where the PA tubes weren't frying eggs at the same time? With the 250Bs installed in the final PA cage, each tube needs 6.4 CFM of air being pushed over it's fins according to the spec sheet. With 2 tubes in the cage that comes out to 12.8 CFM to cool the tubes properly at max. With the size of the factory blower motor setup, CFM capacity of the 1 1/2" ID duct and the rather large frictional losses (90 deg elbow) in the PA tube forced cooling system, it is easy to see why the KWS-1 suffered from serve PA tube heat problems. The main cause of why the S-1's VFO isn't as stable as the A-4s are? The CFM capability of the 1 1/2" duct is under 10 CFM with the factory blower motor setup in the PS. That is with no frictional losses. The frictional loss of the 90 degree elbow, can be as much as 30% in some cases. That is 1 reason why the PA section gets mighty toasty. There is another reason why the factory forced air cooling system is inadequate. The blower motor setup is sucking in far hotter air, then the ambient air temperature is at, that resides in the PS's oven like box. Then it blows this hotter air across the tubes to cool them. If it had a ambient temperature, fresh air intake system, the PA tube's forced air cooling system would be more efficient. The blower setup can actually be moved in the PS box to the left and back. Drilling new mounting holes and tapping them out isn't much of a problem. This would help facilitate a fresh air intake system. With today's blower setups, such as the 1s being used for wood stoves, you can get more then enough CFM output to cool the 250Bs. These units are actually a little smaller in size then the original Collins factory unit and run off 115V. Using 2" ID vinyl duct hose and softening the frictional losses, with either 2 @ 45 degree elbows or a plenum chamber mounted to the outside the PA cage will help cool the tubes more efficiently also. The plenum chamber will provide a higher constant static pressure then the factory setup did, cooling the PA tubes more efficiently. The newer blower setups are rather cheap on Zoro's website. (Grainger) The vinyl duct hose is the same stuff being used a coin operated car wash vacuum setups and is very tough stuff. The purists might be wringing their hands about this mod, but if it makes the rig preform better, it's worth considering, I reckon.