White’s TDI Battery Modifications

[Jim in Idaho]

It's been awhile since I looked at all this, but if memory serves R9 is the "flyback" resistor, and drains the coil quickly so it can start "listening" for a target response. As such, it would tend to get hot with increased current into the coil. So,I had decided ,if I ever needed to replace it, I would increases the wattage. I don't recall, offhand, the factory wattage. If you determine that pleases post it.

Jim

[CaliGold]

On 8/12/2023 at 5:50 PM, Jim in Idaho said:

It's been awhile since I looked at all this, but if memory serves R9 is the "flyback" resistor, and drains the coil quickly so it can start "listening" for a target response. As such, it would tend to get hot with increased current into the coil. So,I had decided ,if I ever needed to replace it, I would increases the wattage. I don't recall, offhand, the factory wattage. If you determine that pleases post it.

Jim

@Geotech graciously informed me to bump the 1k ohm and 680 ohm 2512 size 1 watt resistors to 2-3 watts. I did 2 watts on both and put a Q4  mosfet of same stock specification back in with a 9x9mm heat sink.  It all seems to work like normal again now. The real test will be if I can run the coiltek 14" tdi series coil on the 16v battery. (I'm not going back to 20v again). I'm gonna put a sadie coil on it for small gold on bedrock in places I go(California Motherlode and The Sierras) and may reserve more standard voltages for the coiltek 14" if it begins to misbehave with the 16v.  I butchered the logo off of and scratched the outer most plastic of the 6800 (680 ohm) resistor getting it on the pads. Seems to work ok and I have spair resistors so I hope it will hold up. Also I lifted one of the smaller mosfet pads removing the Q4 mosfet. I was able to solder the pad to the trace that goes to the next resistor well enough. This is my first solder job. I'll be testing and posting river bed performance.

[Jim in Idaho]

Thanks for the update! Looks like you did very well, for your first soldering job. Those surface-mount components are tough to work with. Have you done any of Reg Sniff's mods to your machine? I've done two, and will eventually get to a 3rd that wasn't designed by Reg. I also added vernier knobs to the Threshold and GB controls on mine. Makes razor-edged adjustments really easily. Mine will detect a 1 grain nugget at 3". Keep me updated. I've got a pair of vernier controls, with custom-made mounting hardware. They're the last pair I've got made for now. Not much demand for things for the TDI's anymore. They're $175 shipped CONUS

Jim

[Geotech]

Soldering tips:

Before removal, apply a liberal amount of lead-based solder to each pad. The lead-free stuff that's on the board is hard to reflow and adding a big mass of lead solder helps tremendously.

On the FET, bend/lift the individual pins off their pads before attacking the body.

On the resistors, crack the resistor body and then you can remove the halves easily.

A desoldering heat gun is the proper method. As cheap as $15.

[Tony]

.......and tiny dobs of flux works wonder with solder flow and good electrical joint contact. Finish with a light spray of isopropyl alcohol to clean the area.

[CaliGold]

On 8/17/2023 at 6:47 AM, Jim in Idaho said:

Thanks for the update! Looks like you did very well, for your first soldering job. Those surface-mount components are tough to work with. Have you done any of Reg Sniff's mods to your machine? I've done two, and will eventually get to a 3rd that wasn't designed by Reg. I also added vernier knobs to the Threshold and GB controls on mine. Makes razor-edged adjustments really easily. Mine will detect a 1 grain nugget at 3". Keep me updated. I've got a pair of vernier controls, with custom-made mounting hardware. They're the last pair I've got made for now. Not much demand for things for the TDI's anymore. They're $175 shipped CONUS

Jim

Jim

 

Thanks! Yes, it was tough but a good learning experience. I bought some capacitors to do the swing speed mod, but they were of different size (but same voltage) AND tolerance as I did a poor job of telling the sales guy at one of the last brick and mortar electronics stores in the area, the appropriate specs. I saw Geotech had not been crazy about that mod so put it on back burner. I'll note that ground balance on this machine with either coil I have has to be run at 7-8. The river near me isn't a gold river but upstream there were some fledgling placer and lode mines (Happy Canyon Santa Ynez) back in the day so the minerality is moderate to high probably from the volcanic rocks I see about. You can see the photo I posted of the gravel to show the sampling. That makes me reluctant to do the swing speed mod as I already have a little "chirp" here and there with minerals out here in California.  *SO you get 1 grain signals with the sadie 8x6 coile or another coil? My TDI SL SE machine was bought in 2019 so it has a couple mods done already that the earlier ones did not. I think the NF Sadie Coil is the next "move" to make this machine a real bedrock hound...

[CaliGold]

15 hours ago, Tony said:

.......and tiny dobs of flux works wonder with solder flow and good electrical joint contact. Finish with a light spray of isopropyl alcohol to clean the area.

Yes Tony, I used flux during and alcohol after to clean the board. This was my first solder job on SMD type stuff or any PCB for that matter so I made a bit of a mess but salvaged the rework luckily. Building the battery pack itself seemed daunting for a time. Good experience... Rather be on the river getting GOLD!

[Jim in Idaho]

4 hours ago, CaliGold said:

Jim

 

Thanks! Yes, it was tough but a good learning experience. I bought some capacitors to do the swing speed mod, but they were of different size (but same voltage) AND tolerance as I did a poor job of telling the sales guy at one of the last brick and mortar electronics stores in the area, the appropriate specs. I saw Geotech had not been crazy about that mod so put it on back burner. I'll note that ground balance on this machine with either coil I have has to be run at 7-8. The river near me isn't a gold river but upstream there were some fledgling placer and lode mines (Happy Canyon Santa Ynez) back in the day so the minerality is moderate to high probably from the volcanic rocks I see about. You can see the photo I posted of the gravel to show the sampling. That makes me reluctant to do the swing speed mod as I already have a little "chirp" here and there with minerals out here in California.  *SO you get 1 grain signals with the sadie 8x6 coile or another coil? My TDI SL SE machine was bought in 2019 so it has a couple mods done already that the earlier ones did not. I think the NF Sadie Coil is the next "move" to make this machine a real bedrock hound...

Yes, your machine has the second Reg mod done  by the factory. My swing speed mod made zero difference in ground noise, and I live and detect in a volcanic area with lots of iron basalt and rhyolite. Those caps need to be 1% matched and metal-film. Easy mod to do. If you do some research, there is another sensitivity mod you can do, suggested by another user. I've got it somewhere, but haven't done it yet. I think it's also pretty simple.

Jim

[CaliGold]

4 hours ago, Jim in Idaho said:

Yes, your machine has the second Reg mod done  by the factory. My swing speed mod made zero difference in ground noise, and I live and detect in a volcanic area with lots of iron basalt and rhyolite. Those caps need to be 1% matched and metal-film. Easy mod to do. If you do some research, there is another sensitivity mod you can do, suggested by another user. I've got it somewhere, but haven't done it yet. I think it's also pretty simple.

Jim

I'll probably order those matched caps as I have found good online parts place finally in my education process on all this. I'll ask again,  I assume your 1grain signal came from NF sadie coil 8x6'? I'm going to order that NF coil soon and install. I was sluicing for a couple seasons mostly and neglected to take the Tdi SL out to rivers with me but I'm gonna start bringing it along. The Sadie coil was always on my mind to get and try. They become available here and there.  I cant find the sensitivity mod you speak of but I'll keep digging, no pun. I love this detector, its light, easy to pack in to the wilderness and creeks so I'll do what I can to mod it and make it run good. ALSO, I Love Idaho, passed through a few years back on way back from looking for the Fenn treasure in W. Yellowstone area.  Took the SL up there on that one. Found some super cool old artifacts just outside the park and some even cooler Hemingrays scattered about. I found like 6 Hemingrays around an old power line that had disintegrated and returned to the earth just off the park border. Spent days surrounded by Bison and Moose etc on the madison river. Thrilling trip... 

[Jim in Idaho]

I like the Sadie, but don't find it much more sensitive than the 7 1/2" DF. Both are very good on the SL, especially with the 16v battery. I also recently bought a 5 x10 Razorback, but have yet to try it. Idaho, and the surrounding states, are really great. I feel fortunate to have spent my adult life here. Wouldn't trade it for any place else on earth.

Jim