TDI SL Mod Finished

[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.

Jim

[Jim McCulloch]

Jim, sounds interesting. Would this be a difficult conversion for the average non-techie? Were you able to discern and additional depth? Thanks for the info. HH Jim

[Jim in Idaho]

Well, it's hard to gauge people's skill, Jim. You need  a decent soldering iron with a small wedge tip, for starters. You also need some solder wick to absorb as much of the old solder as you can. It's also nice to have a really tiny drill bit, which I didn't have....the smallest I had was the one in my "number drill" kit, and it seemed it was too big, but might have been OK. (#60  .040") I ended up using a hardened steel wire, from a welding brush, heated with the soldering iron, to remove the last bit of old solder from the holes. Installing the new caps is easy, once the holes are cleaned out. The rest is just disassembly, and reassembly. A magnifying glass is a help, to check your resolder job on the new caps. The new caps need to be matched to 1%, too. The overall capacitance isn't critical, but whatever it is, they should be close to the same.

 I didn't see any difference in depth, but now wonder how much gold I've missed from sweeping too fast.

Jim

[Mark Gillespie]

I want to post and give a big thanks to Jim for all your help with my battery pack.

  All your suggestions and encouragement were much needed.

[Jim in Idaho]

Many thanks, Mark. You did a nice job on it, and will be rewarded with many years of use, not to mention the increased depth1

Jim

[Jim in Idaho]

Mark G. reminded me I hadn't posted the video link, to the comparison video, on here. So, here it is:

sweep speed comparison

[Mark Gillespie]

I believe the SL has a lot of hidden improvements if a person only knew where they were.

The increased battery pack voltage was the first major performance improvement that was made in my machine.

[Aureous]

so is this mod a variable sweep speed or just set to accept a wider range of speeds? my brother uses his tdi-sl as his primary detector due to the massive mineralization he has to cope with in his district. he will be very interested.....

[Jim in Idaho]

On 7/31/2019 at 6:32 PM, Aureous said:

so is this mod a variable sweep speed or just set to accept a wider range of speeds? my brother uses his tdi-sl as his primary detector due to the massive mineralization he has to cope with in his district. he will be very interested.....

This mod is just to accept a wider range of sweep speeds.

Jim