[Drake] TR-7 - Part two

[Ernie]

The output of the TR-7 did normally drop off on 10 meters. You could 
pump out 170 watts on 80 meters but some units only would put out 80 to 
90 on 10 meters. Sometimes you could not get the ALC light to light on 
10 meters on certain radios.

But your description of the high current drain indicates you may have a 
problem somewhere. If there has been a nearby lightning strike, the PIN 
diodes could be bad. Or your low pass filter might have a bad capacitor 
in it. These items could cause the high current drain.

Check to make sure your internal grounds are proper. Your description of 
the self oscillation on 80 meters may be caused by missing ground 
straps. There are a lot of ground straps and copper spring grounds in 
this radio. There is also a heavy spring wire that grounds out the band 
switch bar at the panel between the low pass filter section and the high 
pass filter section. If this is missing, all sorts of strange things 
happen.

W8EH


GGLL wrote:
>     Well, I've further checked the final amplifier; its components 
> read within tolerance; with the exception of idle currents, 400 mA for 
> drivers, 130 mA for finals. I've reset them to 200 mA and 600 mA 
> respectively.
>
>     Anyway, 10 mtr. band still is way down in my wattmeter scale 
> relative to the other bands, 40..50 watts at most, and this when 
> predriver adj. is set for full gain (but in this situation, 80 Mtr. 
> self oscillate).
>
>     Final transistors tested ok in "diode" test mode, but, they have 
> small inverse leakage  from both enitter and collector to base (500 
> Kohms) when tested with analog multimeter (R * 1K). Bases are left 
> open, unsoldered.
>
>     Any opinion, tip, etc. is surely welcome.
>
> Thanks in advance
>
> Regards
> Guillermo - LU8EYW.
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