Ten Tec Delta Recap: Part 2


So, I’ve recapped ten boards in the Delta, and have attained a nice clean internal signal condition that looks good on a scope, and to the ear, when loading a hundred watts into a dummy load.  Also, most of the weird birdies and random noises are gone, and the rumble of the “display hiss” that was previously heard in the background, (but very noticeable), is also gone. So, I think the recapping was a success. I have a few miscellaneous caps to replace, but the priority is off for those. Of the thirty or so caps that I replaced, most were not leaky. A few were leaky, and replacing them may have been all that I needed to do. But, in-circuit tests of old electrolytics are not very effective in many cases.

All of the replaced capacitors (all thirty-something of them) – had higher ESR values than the new ones, typically double. I’m not sure that is really an issue.  For one thing – new caps do have lower ESR from the factory than the ones that -when they were new – were put into the Delta forty two years ago.

One astonishing thing is that all of the caps (except the leaky ones) – had very large increases in capacitance. Typically, a 4.7 uF cap in the 42 year old radio would now read 6.5uF or even 7 uF. Many times electrolytics are used in a fashion that allows for pretty strong changes in value, while still retaining functionality. In a few cases, this is not so. In any case, I solved that problem by replacing them. So, it wasn’t all that bad. Being retired, I have some time, and I probably devoted about a day and a half (if one doesn’t include a lot of puttering around), to the recapping project. I’d say to those thinking about doing it: go ahead. You’ll likely add some benefit to any radio that’s say – forty or fifty years old.

There remains some strong image appearances (always in the same place(s)), that I’ll need to take care of, but that’s going to be another level of investigation. I think there were some images in the Delta that couldn’t entirely be eliminated.  We’ll see. 

73’s – Ron / WB8LZR


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