[AMPS] SB-220 cooling/filaments

[Pete Smith]

Recently, thinking to help keep my SB-220 cool under contest conditions, I
added a small 110v muffin fan pulling air from the top front of the tube
compartment -- my thought was to enhance the overall flow of cooling air.
The added fan is just sitting on top of the cabinet near the front edge,
and subjective the cabinet does seem to be staying a bit cooler.

Tonight, when I turned on the amplifier, I see only one filament lighting.
My immediate thought is that I have melted the solder in the filament pins
on that side from excessive heat.  Is it plausible that the "helper" fan
could have upset the normal flow sufficiently to have caused this?  Or is
it likely just a coincidence?  

I will be opening the amp up in the morning, checking for loose socket pins
and DC continuity in the filament -- anything else to look for in particular?

Thanks... 

73, Pete N4ZR






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