[Boatanchors] Ranger question

[JAMES HANLON]

I'm working on a recently acquired Johnson Ranger.  In particular I want to get it running on 160 AM and CW.  As it came to me it was modified to operate Push-to-Talk with a built-in antenna relay that switches the antenna from an outboard receiver to the transmitter.  A peculiarity about the Ranger is that it uses a clamp tube to cut the screen voltage on its 6146 final to a low value when grid drive is not applied, and it does not use any other means of cutting off the final under key-up CW conditions or drive-off AM phone conditions.

On 160, in the Phone mode which energizes the driver and thus drives the final when I close the PTT switch and which switches the transmitter output to the antenna (a Cantenna dummy load as I write this), it tunes up normally - 6146 grid current 2.5 ma, plate current 100 ma.  But when I release the PTT switch, which de-energizes the drive to the 6146 and disconnects the antenna, the 6146 goes into a TGTP oscillation.  I can kill the oscillation by detuning the driver a good bit, and I can compensate for the loss of grid drive from the driver by turning up the Drive control (driver screen voltage) and then things work OK without the final oscillating.  Or, if I load the final to about 110 ma when I tune up initially, the oscillation does not occur.

On 160 in the CW mode it works as it should (PTT closed, key controlling the driver stages).  When I open the PTT switch, the final does not oscillate, unless I close the key which energizes the driver and supplies grid drive to the final.  Then, when I let the key up, the final goes into self-oscillation.  As in the Phone case, I can kill that oscillation by detuning the driver.  `

Things are better on 80.  There is no oscillation in the Phone mode.  In CW, if I release the PTT and then hit and release the key, the final will oscillate (as it does on 160).

On 40 through 10, there is no oscillation.

This happens with two different, fairly good 6146s in the rig.

Since I've planned my control system so that I won't normally get a key closure with the PTT switch open, it looks as though I should be OK on 160 CW and on all modes on the higher frequency bands.  And I can always just detune the driver on 160 Phone, so I can really live with things there as well if I am careful.

But my question to you folks is, does anyone have a similar experience with the final in a Ranger taking off on 160 meters?

Thanks for the consult,

Jim, W8KGI