[TenTec] Argonaut 509....the Saga Continues

[Richard Arland]

Originally I posted about the "mint" Argo 509 and some of the problems I initially encountered. 

1. RX sensitivity was way down and the LOs on each band were waaaaaay off, resulting in the dial calibration being waaaaaaaay off!

To correct this I coupled a counter to the feed thru on the back of the PTO cage to ground. By switching bands, I was able to realign the each oscillator to the exact range that T-T lists in the manual. Once this was done the RX sensitivity picked up dramatically. Prior to doing the alignment, the MDS was around -45dBM which is really pathetic. After the OSCs were aligned the MDS dropped to somewhere below -120dBM (this was all the attenuator I had on the HP gen). Not bad! 

There is still no output on 10M as that oscillator won't oscillate. I talked with Garland Jenkins at T-T and he advised it might be the band switch, a cold solder joint, or a bad coil. I tried reheating all the solder connections on the 10M coil, the bandswitch (those I could reach), but could not get the 10M osc to fire up. Alas, I have things working on all bands but 10M. Well, it was a partial "win".

2. The RF output was "squirrley". C13 on the SWR Bridge Board had been "tweaked". Once set up to original specs in the manual, my output came up to about 5-6 W max on a WM-2 meter, FS on the Argo meter shows about 3 W output on all bands (except 10M) and the SWR function now works like it shud showing 0 reflected power when termed into a 50 Ohm DL.

3. Resonate control was tightened up by physically expanding the plastic runners below the cover of the movable deck plate and retightening the screws. This provides enuff friction to hold the resonate control in palce. 

4. There are apparently 2 versions of the SSB board. One with the plug in PCB and four 9 MHz IF xtals soldered into the borad which piggy backs onto the SSB generation board and the version I have which has the four IF xtals soldered into the main PCB. Clark Turner, WA3JPG, says that this board is actually better than the piggy back version, since you can wire in four more 9MHz xtals to make an 8 pole filter that has very little blow-by. Hmmmm....I wonder if a handfull of 9 MHz computer xtals might be utilized to do this? Might make for a cheap alternative to buying an 8 pole filter. 

5. The bandswitch was purely mechanical. The rods were bent, and the set screws were lose in the plastic portion of the switches that hold the wire linkages. Once everthing was tightened up the bandswitch functioned just fine. I did use DeOxit Pro Gold quite liberally on the switches, however. 

Conclusion: I came away with a new appreciation for the T-T Argonaut 509. Everthing works except for 10 meters, and until I can solve the 10M oscillator problem, I will do without this band. RF output is good, it sounds find on an air local using a seperate receiver. The IF needs some help and I intend to pursue the additional four 9 MHz xtal idea that Clark Turner came up with. In tuning the dial up and down the band, the PTO finally took a dive so I have a PTO rebuild to do. Kits are available from T-T for about $25 to do this. So, all in all, I have a workable station that I can have some fun with. Thanks to all who took the time to write and offer suggestions. Especially Clark, who needs to contact me again and give me some particulars on how to do that filter mod. 

73 Rich K7SZ