[Hammarlund] More HQ129 X Tubes??

[GARDGORE@aol.com]

Andy, I would recommending testing the tubes first and replacing only as 
necessary. If you plan a complete realignment afterwards which you should do after 
replacing all the caps anyway, then if you wanted you could replace the 
tubes. I have been fixing these for some time now and while I used to do wholesale 
tube replacements years ago experience has shown it is largely a waste of 
money. In addition the alignment can be disturbed when you change a lot of tubes. 
I would recommend testing with good mil-spec test equipment like the TV-7 or 
I-177 tube testers or good commercial mutual conductance testers such as the 
various Hickoks. If you don't have one locate a radio club near you and ask for 
assistance. Most club members have good tube testers and will be more than 
happy to help. Congratulations on your decision to own an HQ-129X. In my opinion 
they are becoming Hammarlund's best kept secret these days even though they 
sold in large numbers and were immensely popular from 1946 through the early 
Fifties. The HQ-129X was basically an updated 1946 version of the HQ-120X which 
originally replaced their aging Comet-Pro series in 1938. Though the HQ-129X 
was mostly fresh styling for the postwar market the design was very well thought 
out with excellent engineering and because they sold a lot of them they are 
not really all that scarce and bargains are out there to be found. The model is 
one where everything really came together well for them and the performance 
up to about 15mc was just excellent in my opinion. They are quite stable too, 
capable of delivering respectable performance on SSB after a reasonable warm-up 
period. Before you change all the caps bring it up slowly on a variac first 
to see if you can get anything out of it to establish a baseline. The HQ-129X 
does not have a reputation for bad caps like some of the others (SP-600) and I 
have found they often work well with the original caps. Some recommend always 
replacing all caps and they are right in many cases but not always, depending 
on the capacitor manufacturer. Some original caps were very good and still 
are. Also some caps are in critical locations and some are non-critical. All the 
caps in an HQ-129X are easy to get at so the job should go fairly quickly. If 
you decide to completely recap, again I would try to establish some kind of 
working order first and recheck after changing a few at a time to confirm still 
working. A careful realignment will be required afterwards.

Regards,
Greg Gore; WA1KBQ