TDI SL changes

[Mark-VA]

Copied this from another site regarding changing .22uf caps to 10 and was asking for a picture with actual locations of caps that can be changed.
This is a quote made by Reg



"Yes, the SAT speed is identical on the TDI, the Pro, and the SL. The only difference is in the stage just before the SAT and it is in this previous stage that there is too much filtering. This excessive filtering conflicts with later filtering which causes a depth loss if the coil is swept too fast. This previous stage is what I call the integration stage and it is the stage that adds all the sample signals together to form the target response. The TDI uses .22uf capacitors and the Pro uses .10uf capacitors. Change the TDI caps to .10uf types and you convert a TDI to a poor man's Pro.

The only other differences between the TDI and the Pro are the Pro has a vernier GB control and the volume control moved from the motherboard to an external adjustment. In other words, the TDI has an internal volume control while this control is removed off the motherboard and added as an external adjustment on the Pro. Those people who had their TDI's modified previously had the option to have the caps changed on the TDI to the values in the Pro, thus if they had this mod done, they already have a pseudo Pro, or what I call the poor man's Pro. Outside of the three mentioned differences, the TDI and the Pro are identical, component wise. THERE ARE NO OTHER MAGICAL DIFFERENCES BETWEEN THE TDI AND THE PRO.

Reg

[dbanner]

maybe this can help.

[dbanner]

just look for .22uF caps around the integration stage and change them to 100nF(there should be 4 capacitors to change from .22uf to .1uf i think)

[Seden]

Mark, since you have a TDI SL as I do you only have to chage C20+C21 from .47uf to .22uf. If your SL was made in 2015 or later you don't have any changes to make as the newer TDI SL's already have them. It's the TDI that you change C59 and C60 from .22uf to .1uf. Also on the pre-2015 SL's there are other mods that could be done. The good news is C20+21 are both through hole components. I've done all the Reg Sniff mods to my pre-2015 SL and it runs fantastic.
The kind of capacitor Reg said to use was:a quality metal film,polyester or polypropylene 50v caps. He told me to just get 50v epoxy dipped metalized film caps from ebay. When you start to work on your SL the first thing you want to do is to remove the plastic knobs. Then take all screws out and open the case VERY carefully as the lead length's of the wires from the pots to the boards are too short. You're going to use a socket wrench to unscrew the nuts around the pots while holding the base of the pots underneath. And do not use a solder sucker to remove the solder on the caps as they will leave tiny bits of solder on the board (my SL didn't work until I washed the ckt. board with isopropal alcohol and dried off as I DID make the mistake of using a solder sucker!).
Reg recommends the Miner John folded loop coils (his design) as they will quiet down the receiver and you can crank the Gain up to maximum. The folded loops are the best for the smallest of gold nuggets or whatever your after. For depth I plan on getting the 14" mono loop by Coiltek which was recommended by an Aussie nugget hunter on the White's TDI forum for the bigger Mojave Desert nuggets. Good luck!

[Geo]

Thanks Seden.
I will make the mode at my TDI.

[Mark-VA]

Sounds very interesting. I've had my SL since 2014 so some of the mods might apply the same. I don't live in gold nugget country, (southeastern Virginia) but that's not the reason I bought my PI. Most of the old locations in my area, including schools burn coal for their heat and over several decades have discarded the coal waste over many acres of adjoining property. This waste can all but shut down (limiting depth to 3-4" at best) the best VLF machines in the world, which is why I bought the SL. The continued hunch about needing the SL has really paid off because I have found some very nice gold rings and very old silver with my SL in the same areas where machines like CTX 3030, Etrac, F75 and DFX just to name a few that have hunted these same sites. The second reason I bought the SL was to beach hunt and man that is where the machine excels a regular VLF machine. Enough with my rambling I do desire to have a PI with good discrimination, for the nails and at some point in the future someone will discover how to do it efficiently even though all that I've read about say it can't be done on a regular PI. I will add, humans limit their creative discoveries when they believe something can't be done.
I'll have to look into the benefit of upgrading my SL.
Thanks for all the information.

[Jose]

Mark, since you have a TDI SL as I do you only have to chage C20+C21 from .47uf to .22uf. If your SL was made in 2015 or later you don't have any changes to make as the newer TDI SL's already have them. It's the TDI that you change C59 and C60 from .22uf to .1uf. Also on the pre-2015 SL's there are other mods that could be done. The good news is C20+21 are both through hole components. I've done all the Reg Sniff mods to my pre-2015 SL and it runs fantastic.
The kind of capacitor Reg said to use was:a quality metal film,polyester or polypropylene 50v caps. He told me to just get 50v epoxy dipped metalized film caps from ebay. When you start to work on your SL the first thing you want to do is to remove the plastic knobs. Then take all screws out and open the case VERY carefully as the lead length's of the wires from the pots to the boards are too short. You're going to use a socket wrench to unscrew the nuts around the pots while holding the base of the pots underneath. And do not use a solder sucker to remove the solder on the caps as they will leave tiny bits of solder on the board (my SL didn't work until I washed the ckt. board with isopropal alcohol and dried off as I DID make the mistake of using a solder sucker!).
Reg recommends the Miner John folded loop coils (his design) as they will quiet down the receiver and you can crank the Gain up to maximum. The folded loops are the best for the smallest of gold nuggets or whatever your after. For depth I plan on getting the 14" mono loop by Coiltek which was recommended by an Aussie nugget hunter on the White's TDI forum for the bigger Mojave Desert nuggets. Good luck!

Hello Seden
Maybe a silly question. The bent loop coils of Miner Jhon, are similar to the figure 8 coils, or it is something different.
Thank you
Jose

[Seden]

You guessed right Jose, they are the figure 8 coils folded back on itself. Fortunately the SL has lot's of gain and you actually benefit overall since it cancels all noise including ground noise so you come out ahead to find the deep small targets other machines will miss.

[Seden]

More advice from Reg

DO NOT USE TANTALUM, ELECTROLYTIC, CERAMIC MONO, ETC TYPES. Also, the value of the caps have to be matched to at least 1%! Ok I'm going to try and attach a jpeg picture of the board with arrows pointing to the above mentioned caps.

[Jose]

Seden thank you for answering, and for the mods. Very good photo.
Regards
Jose

[6666]

Hello Seden
Maybe a silly question. The bent loop coils of Miner Jhon, are similar to the figure 8 coils, or it is something different.
Thank you
Jose

Hi Jose, see picture above, also
have a look at this link for a bit of info on the PI Folded 8 mono coil, the topic wandered a bit onto DOD coils , but basicly you wind a normal round coil then gently fold part of the coil back into the middle of the coil forming a smaller inside loop like an 8, there are some pictures in the thread so you should get the idea. You can alter the ratio of the outside loop to inside loop to give different sensitivity , Regs idea dates back to 2009, and I am trying to find that thread.
http://www.findmall.com/read.php?34,2166202

[Mark-VA]

After looking at all those components that need to be replaced I'm weighing the reason for me to change them. I used to do electronic component repair back in the 90's so I'm not a stranger until it comes to surface mounts.
Now I'm not sure the risk is worth the advantages gained since I have a good working machine at present.
But very interesting to say the least.

[Jose]

Thanks 6666 for the link.
I will try to experiment a bit in the next days.
Observe in the image published by Seden, that the TDI SL, does not have the diode between the TX stage and the coil. In its place you see a bridge, I think it is a detail to take into account on that subject that was much discussed.
Jose

[Geo]

I tried the DOD and OOO coils before 2 years.
Finally i took about 10% more depth but with larger coil so i let it.
If anyone wants to give it a try, here are some posts about it.
http://www.geotech1.com/forums/showt...D-coil-for-TDI

[green]

I tried the DOD and OOO coils before 2 years.
Finally i took about 10% more depth but with larger coil so i let it.
If anyone wants to give it a try, here are some posts about it.
http://www.geotech1.com/forums/showt...D-coil-for-TDI

I tried a DOD coil awhile back also, tried to copy GPZ7000 for shape . With Rx coils adding, signal strength looked about the same as a mono coil. With Rx coils subtracting lost distance. The GPZ7000 works good, wondering if I did something wrong or maybe the GPZ7000 not being a PI has something to do with it. Maybe something else? http://www.geotech1.com/forums/showt...352#post204352