[Drake] [Drakelist] TR4C weak audio and poor sensitivity

[Dick KF4NS]

Well guys, I found the trouble. I decided to try inserting a signal 
with my sig gen and started with the antenna jack, then went to the 
external antenna jack, then went to the fuse lamp socket (tested lamp 
removed) on the relay side, then to the T-9 side, VOILA! Good strong 
signal S9+5 at 50uv. I knew then that it had to be related to the 
relay. I pulled the 6EV7 relay tube V19 and it tested good. I 
substituted another 6EV7 and the trouble went away completely. I put 
the original tube back in and still no trouble !?? Socket was in good 
shape so it's a conundrum.

Hope it is not the T/R relay since I can see no way to remove the 
cover. Usually these relays are not used as a plugin so nothing to 
anchor down the base and rock the cover back and forth to pop it off.

Bottom line, the rig works great. Still no doubt that the LSB filter 
is bad. Adjusted C130 best I can. It will be good enough. Can't afford 
to buy the INRAD filter set. Will still scope it out at the CXR BAL 
and at the filters.

73, Dick KF4NS
St Petersburg, FL 33714 USA
Keep The Glow!




On 6/16/2010 7:26 PM, Dick KF4NS wrote:
> During the restoration I discovered what may be my worst nightmare. 
> The
> sensitivity and weak audio changes from band to band when I switch
> sidebands. That to me says it is likely to be one of the filters.
>
> Example: on 20M the trouble is on USB and on 15M it switches to LSB, 
> in
> other words the trouble is always when the sideband switch is in the 
> X
> position.
>
> All tubes have been tested and shorted/weak tubes replaced with new 
> ones
> (pretested).
>
> The contacts of all switches and pots have been cleaned and the 
> sideband
>switch tested for continuity.
>
> The 9mhz osc was adjusted for zero beat with C130 injecting a 
> calibrated
> signal to grid 1 of V12.
>
> I have no idea if it may be an alignment problem caused by changing
> several tubes so please clue me in if that would cause this trouble.
>
> 73, Dick KF4NS
> St Petersburg, FL 33714 USA
> Keep The Glow!
>