[Drake] PM on L4B

[Dave Edwards]

Got my L4B as a NOS leftover...about 10 years ago. 
Have not used it all that much, but made a few contacts tonight. 

Amp has pretty loud hum coming from it (not the supply).

Odd you think, what in an amp can hum??

Push on the top, and it got a bit less. Push in on the back panel, and it stopped!!
And, as the amp warms up...it pretty much goes away. 

I suspect the hum is the chassis buzzing a bit because of the fan. 

Probably, it has NEVER been oiled, and the fan has an oil opening. 

So, my question is this.....

Anyone ever do this?

I'm going to use about 4 drops of a light machine oil in there. Does anyone know if the one oil opening is the only one...or are there two?

Is it worth it to put one drop on the capacitor bearings also...or just don't fix what ain't broke?   Knobs turn just fine, I was just thinking what should be done after...what....33 years??

Thanks......Dave