The Ten-Tec Delta has been on the bucket list for rounding out my Ten-Tec analog radio collection for quite a while. It’s a little bit hard to find these days, but I finally managed to snag the radio from a seller who could not give me a full picture of its condition. Thus, I was a little concerned that perhaps the radio might require a *lot* of work to do a restoration. Let’s face it. Forty and fifty year old radios almost always need at least a little TLC if they haven’t had much of it lately.
Fortunately, my checkout of the radio yielded some good results, as I found the transmitter PA to be doing the full 100 watts, the receiver to be working on all bands for which it had crystals, and the Cosmetics to be probably a little above par. I used it over the Easter weekend, for listening to signals on the 30m band.
Figure 2: The two empty crystal slots need to be filled to round out the upgrade for 17 meters &12 meters
As I wrote, cosmetically the Delta that came into my possession was pretty clean, but electrically it was a little unclean on both transmit and receive modes. It’s the sort of thing that happens to forty two year old radios, especially if they’ve not been stored in the best of environments for long periods of time. In my opinion, it’ll require a recapping to clean it up. Recap projects can be really involved, and they can be pretty simple. It’s a matter of the circuits, how complicated they are, and thus how many electrolytic capacitors are involved. Fortunately for me, the Delta is one of Ten Tec’s more simple rigs, and has a very manageable number of electrolytics in it.
I decided that, since I was going to make a project of it, I’d upgrade the radio to enable 17 and 12 meter band operation. It came with the crystal for 30 meters, but not the crystals for 17m or for 12m. For the Delta, the only part that need be added is the crystal itself. I have located some crystals on Mouser, but haven’t yet determined if they will adequately mimic the originals that Ten Tec supplied.
The crystal frequency that is required to enable 17 meter operation on the Delta is the frequency of the bottom of the band added to 11.5 Mhz, so it is: 18.0 + 11.5 = 29.5 Mhz. The frequency of the crystal needed to enable 12 meters on the Delta is 24.5 + 11.5 = 36.0 Mhz. Edit: Yeah, I know for legal reasons that 18.068 MHz is the bottom of the 17m band, but from Ten Tec’s circuit point of view, it is 18.0 – hihi.
Figure 3: The bottom view of the Delta shows the crystal box.
The number of electrolytic caps in the Delta is 39. This is much more manageable, relatively speaking, than the situation for the Corsair II, which has 97 electrolytic caps. The Triton IV has only 24. So, one can see from the cap count how the circuit grew from the Triton thru to the Corsair (97).
The top view of the radio is shown in the photo (above).