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

[Al Parker]

Hi Dick,
	Could be the filter(s), but could be that 9.000mc isn't really what you 
want as a freq. that's supposed to be in the middle of the filters. 
This problem was much more frequent on the TR-3's filters as they aged.
	Instead of setting the 9mc osc as you did, I usually do it by listening 
to the "swoosh" as I switch between sidebands & adjust C130 to make the 
pitch of the swoosh equal.  The magnitude/loudness might be different, 
and that would be due to more loss thru one filter than the other, and 
if too much, it would indicate the need for a new filter.
	Getting that 9mc off from the middle will also make one sideband sound 
pinched and one sound bassy, usually commented on by a listener to the 
xmt sig.
	So, if you're lucky, it might not be the filter.  I had one once, a 
TR-3 I think, (I didn't have a freq. counter then), that the so-called 
9mc osc. was actually outside one of the filters completely.
	hope this is some help
73,
Al, W8UT
www.boatanchors.org
www.hammarlund.info

"There is nothing -- absolutely nothing -- half so much
worth doing as simply messing about in boats"
Ratty, to Mole

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 replaces with new ones
> (pretested).
>
> The contacts of all switches 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!
>