Did the TDI SL sweep speed mod this morning

[Jim in Idaho]

Bit the bullet and did the sweep speed mod this morning. Made a huge difference in the acceptable SS. I ran the 1 grain gold bar past the 8 x 6 Sadie coil before doing the mod, and there was a relatively slow, specific sweep speed that gave the best signal. Too fast, and the signal completely disappeared. After the mod, the SS made almost no difference. Fast, slow, the signal was steady. No change in indicated depth in the air test. Threshold was still smooth. I'll post a video of the before/after tests later on. I changed the filter caps (C20, 21) from .47ufd, to ,22ufd. A friend in Florida, who is a civilian tech working for the Navy, was kind enough to send me a few matched pairs of the caps. Without his encouragement, and help, I probably never would have tackled this. Now I'm really glad I did. One tool I'm glad I had was my fly-tying magnifying light. My eyes don't focus like they did when I was young, and that magnification allowed me to see the soldered spots, to be sure I had done a thorough job.
I posted a video showing a "before and after" comparison of the sweep speeds.


Jim

 

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[AllenJ]

It appears to have made a big difference, thank you for posting the video.

 

[Arizona Law]

Just picked up a new in box TDI SL then the stick in the battery door shows 2018. Would this mod still need to be done to increase sweep speed And if so, how difficult to do?

 

[Jim in Idaho]

No TDI SL's had the sweep speed mod done by the factory. The second mod, which increased sensitivity, was adopted by the factory from 2015 on. The sweep speed mod is fairy easy. You remove two large capacitors and replace them with two of half the value (go from 47mfd to 23 mfd.) You don't even have to remove the old caps...just cut them off, leaving the leads as long as possible, and solder the new caps to the leads. The new caps much be a matched-pair within 1% if I remember right. Doing it that way eliminates having to get to the bottom side of the board. You can find the instructions on the 'net. I'm probably not supposed to mention other forums on here.
Jim