[R-390] 3TF7

[John B.]

Hank,

I've owned one R-390, one R-1247/GRC-129 and one R-390-A and have only
experienced one radio failure that was related to the current regulator.

The R-390 did not have a 3TF7 installed when I bought it in 1976.  In order
to get it running, I temporarily put a 43 ohm, 5w resistor in the 3TF7
socket and when I foolishly sold it in 1981, it went to the new owner with
the resistor still installed.

The R-1247 developed an intermittent frying noise that turned out to be a
5749 with an intermittent short.  Further investigation revealed that the
current regulator had been replaced incorrectly with a 3HTF4, which left the
two 5749s to divide about 18v.  No wonder the tube had problems.  Replaced
all three, the 5749s and the wrong regulator for a 3TF7 that receiver has
been playing well with occasional service from 1981 through today.

The R-390A, a Motorola, 14 Ph 56 contract had a TJ311M01 installed when I
got the receiver in the spring of 1982, and is still working fine as my
chairside monitor receiver in our den.

I'm like you, I believe most of the 3TF7 failures are man made or by extreme
vibration of a well used 3TF7 during shipment.

 My 02c worth,  John Bunting, W4NET