Reg Modded TDI Pulse Scan

[Steve Herschbach]

Changing coils is like changing tires on a car. It affects performance in a small way. But you still have the same engine under the hood and the TDI engine is basically a six cylinder compared to the Minelab eight cylinder engines. With any detector people look for the best coil for the situation, in general small gold means small coils and large gold means large coils. So if you have a TDI there is lots of talk about what is the best coil to use on it. But you can't make a TDI into a Minelab with coils. That requires an engine swap.

[Geotech]

As it turns out, the factory TDI coils are a major performance limitation. I've adapted an Impulse AQ coil to run on the TDI and can then reduce the minimum delay to 6us. It's still not gonna run like a Minelab, but it is a little more respectable.

 

[CaliGold]

On 8/24/2023 at 11:42 AM, Geotech said:

As it turns out, the factory TDI coils are a major performance limitation. I've adapted an Impulse AQ coil to run on the TDI and can then reduce the minimum delay to 6us. It's still not gonna run like a Minelab, but it is a little more respectable.

 

How did that sorcery come to be? lots of solder??? ha.

I installed the sadie coil with the 16.4v battery modded 2018 TDI SL of mine that I recently got back to life again. It blew the 680ohm resistor (R14) and the mosfet I suspect went south because the coil went warbly and started acting similar to when the coiltek 14" tdi series blew the resistors.... I replaced R14 with a spare 680 ohm 2 watt resistor I had on hand. I also replaced Q4 mosfet with a spare version that would had a little different specs. I put another heat sink  Below are specs.  The current mosfet installed has the specs with the lower input capacitance (1030pF @25V) and the other spec sheet shown is previous installed that matched the OEM you guys spec'd on it. Is that mosfet "better" "more durable" or have I just screwed up? Gate charge and VGS max are different on current one.  The coil runs good now. Took it to the UBER  mineralized river bed near my house and dug some nickels and lead "nugget" targets I made. Worked pretty good.  Got new headphones coming so I can run the threshold hot like I like it with volume down to get some real world depth tests done with proper threshold breaks. Old headphones volume adjustment is broken and have to run the buds hanging behind my ears near my neck so I don't go deaf... I like that little sadie coil though. Super maneuverable whens she's not blowing my machine up...

 

thanks again @Geotech 

[CaliGold]

@Jim in Idaho Made a couple test targets (.45 and .15 gram) from some gold had laying around. I rather enjoyed working with the gold after I was able to get my fire brick makeshift crucible glazed properly. The Sadie coil 8x6 on the TDI SL that I have been tinkering with picks up the .15 gram flake I produced at about 2" inches. The .45 gram sample is breaking threshold nicely at 4.5". Not bad considering I butchered this machine with my amateur solder work...

 

NOTE. I was messing around with the .45 gram gold sample to flatten it a bit and inadvertently turned it into a .33 gram gold sample nugget and it breaks threshold nicely at 100mm (4"inches) All this is with about 15.8 volts running through from mod battery. FYI I'll be using this a bedrock crevice detector mostly and waterproofing the coil with silicone and using by the river cracks and occasional up on the benches in feeder creeks and hillsides. I'll be panning any targets gold or other wise in gold producting bedrock or riverbed stretches...

[Jim in Idaho]

Id say that's not bad, at all. I think you'll be finding gold before long.

Jim

[CaliGold]

On 8/24/2023 at 11:42 AM, Geotech said:

As it turns out, the factory TDI coils are a major performance limitation. I've adapted an Impulse AQ coil to run on the TDI and can then reduce the minimum delay to 6us. It's still not gonna run like a Minelab, but it is a little more respectable.

 

Was this the TDI SL or TDI Pro? Obviously I'd love to lower the pulse delay to 8us on my SL. Is that even possible? 

[Jim in Idaho]

As far as I understand, the delay on the SL can't be lowered below 10 microseconds. The timing circuit is fixed.

Jim

[Geotech]

The AQ coil is currently on my TDI Pro, but the same can be done to the SL. For either you would need to reprogram the micro because that's what sets the timing. Only the original 200 TDIs had a timing circuit you could easily modify.

[Jim in Idaho]

I appreciate that info, Karl! I had thought it required some serious surgery to change the timing. Definitely more than I want to tackle.

Jim