[R-390] R-390 "non A" cap replacement list/order?

[Norman Ryan]

Hi, All,

This is a good mod for the mod-averse. Good in that it doesn't alter the receiver -- arguably not a mod at all in that you just hang the fan off the side as Roy suggests.

The 47 ohm carbon comp cathode balancing resistors tend to increase in resistance over time due to extreme heat from the 6082s.  I replaced my 47 ohm resistors with ten watt wire wound ceramics that hold their resistance better, but someone pointed out that it puts the power transformer at risk if a short circuit somewhere causes it to burn up.  It seems that the two-watt resistors act as fuses in this instance.


If I had to do this over, I would use matched NOS carbon comp two-watt 47 ohm resistors and the fan.  Even with the stronger (higher wattage) resistors, the heat is still too high not to consider Roy's fan option.

Some 220 volt fans will run sufficiently fast enough on 125 volts, thus enabling silent operation.  I suggest orienting the fan so that it pulls the warm air out of the receiver.

Norman

________________________________
From: Roy Morgan <k1lky68 at gmail.com>

My very strong recommendation is to put a fan against the chassis to cool the 6082 tubes (and replace the cathode balancing resistors at their sockets).

I’ll send to Jacques and any others interested the picture of my lashed up fan plate that holds a fan in the right place.

Roy

Roy Morgan
k1lky68 at gmail.com
K1LKY Since 1958