[TMC] SBt-1K workout

[LARRY D GODEK]

After i finished testing some 8295 tubes for a fellow the other day i shut the radio off and quit for the day.  When you test the finals of course you ahve to pull the RFA out, pull the cover, change out the tube, replace the cover (optional if you want to just pull out the top cover microswitch) push the PA back into the cabinet.  Well i figured i'd take a shortcut in order to save some time.  Satanding on concrete after a while almost puts my lower back into non-functional status.  Anyway i digress.  Instead of putting the top cover back on which would ahve closed the interlock up there and proceeded to push the RFA back into the cabinet.  Wouldn't go.  Checked the release buttons on the sliding shelves, nothing out of line there.  Tried to puh it back in again.  Not going anyplace.  Looked on tip and the cover not being in place allowed the interlock to stay in the up or neutral position.  Ahhhh ha!  Put the top cover back on and proceeded to slose things up for the afternoon.  
 
Wednesday AM i figured i'd play with the setup to see what kind of power i'd get out of this tube which was my original.  Turned on the switches and let it set till the time delay in the Med-Low voltage supply came up and cycled the relay allowing HV etc to be applied.  
 
NADA.  Didn't happen.  Played around with a variety of items to see if it was something simple.  Uh uh.  Not to be.
 
This AM i am gonna make it work or find out what happened anyway.  got out the VOM (after removing all power of course) and a good schematic showing the interlock circuitry.  Knew that had to be the problem as everything else had been working fine.  After pulling off top and bottom covers aong with the little plate that covers the base of the PA tube, checking wiring across each component and thru the PA deck interlocks i found that the troupble was with the topp interlock.  One thing about all this was that it gave me a chance to look over both the top and bottom of the RF deck.  Actually very clean.  Remember i said when i tried to push the deck back into the cabinet it wouldn't go cause it was hitting the top interlock.  Well it bent the little pushrod that activates the microswitch.  after i straightened that out (delicately of course with a small hammer!) the RF deck now perfroms as normal. 
 
Just in case anyone runs into something similar.  Chasing interlock problems is not as simple as it sounds unless you have all the necessary covers off (think Air compartment under PA for the air pressure vane).  Nice learning experience.
 
Anyone know if you can take the play out of the right angle gear drive for the tuning and loading controls which happens to be underneath the chassis?  I've got a little slop but nothing that can't be lived with and maybe that's the way it's supposed to be.
 
250W carrier at 300 ma Ip and about 37 ma if Ig.  I can run it to 600W but that's at 50 ma Ig and then on keying it kicks off the HV.  Possibly the HV overload needs to be adjusted a bit.  As an added not i do not have a means of connecting ALDC to the back of the RF deck.  There is a switch there for either internal or External and i've got mine set for internal.  The ALDV control on the front panel does indeed work.  WIth the knob turned to about the 2 olock position i do see a bit or cutback on output power.  I'm running this one just below that.  Right or wrong?
 
Now for the PA overload adjustment to get it to kick out where it should be which i higher in Ip anyway.
 
Larry
W0OGH