[Collins] 70K - 2 Fault

[Jim Smith]

Hi,

I have just experienced an unusual fault with a 70K-2 pto. The rig I had 
purchased arrived with the dial carefully wrapped up, the pto had obviously 
been got at - with only one of the chassis mounting crews in place. (other 
screw safely wrapped up)

I quickly set every thing back in place and switched on and on 20 m around 
14100 (my favourite check area) found the Cal and realigned the dial to 100. 
Tuning down I found the 00 cal quite a long way off. BUT on tuning up I 
could not find the 200 cal signal.

I won't waste your time further but I put a counter on the pto and found the 
pto was not going down to 2500 -hence no 200 cal.

The lowest frequency was something like 2547 and continuing the tuning to 
the actual end stop of the coil slug (a small movement) - the freq folded 
back on itself rising to about 2560. (I had of course loosened the shaft 
stop.)

I have made the quickest of fixes by adding small silver mica across that 
'adjust on final test' C 301 (as it is the easiest fix to do) which is 
across the pto assembly. The pto is back tuning 2470 and through 2700. Now I 
have my three cal points and the pto is tuning over the 2500-2700 plus a few 
khz in the usual way.

Has anyone experienced this - and what is the recommended fix - should I 
change all of the oscillator silver mica caps. Start from scratch to set it 
up again?

I feel that this pto was very close to its spec originally and age has 
pushed it outside - with no adjustment possible. The pto is pristine inside. 
It must have been the most frustrating of faults - an endless loop!!

Sorry for the long post,Norfolk island is very lonely right now - HELP - 
please reply to my email adress.

Regards

73

Jim, VK9NS
 


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